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USER MANUAL SWAN Cycle III version 40.51

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1. Default itest 1 SWAN writes a message name of subroutine to the PRINT file at the first itrace entries of each subroutine Default itrace 0 if this option is used the user instructs SWAN to produce detailed print output during the computational process for a grid point of the computational grid Output at a maximum of 50 grid points is possible This option can be used only after the bathymetry has been read see command READINP BOTTOM the test points are defined by means of grid indices grid indices of a test point values of i range between 0 and mxc see command CGRID values of j between 0 and myc inclusive the test points are defined terms of problem coordinates SWAN will determine the nearest grid points Output will be made for this selected grid point coordinates of a test point problem coordinates in m in case of Cartesian coordinates or longitude and latitude in degrees in case of spherical coordinates see command COORD integral parameters for test points are written HSIGN RTMO1 see Appendix A for definitions and Swind Swcap Ssurf Sfric Snl3 and Snl4 which are the integrals over frequency and direction of the respective source terms wind input whitecapping depth induced breaking bottom friction absolute value of the triad wave wave interactions and absolute value of the quadruplet wave wave interactions if the keyword S1D appears variance densities and 6 source terms see en
2. 19920517 2000 0 9 6 5 95 28 The structure of the files containing 1D or 2D spectra is described in Appendix D there is no relation with the definition of the boundary file generated by WAM or WAVEWATCH III 1D and 2D files can be used for stationary and non stationary boundary conditions and for one or more than one location The spectral frequencies and directions in the case of a 2D spectrum do not have to coincide with the frequencies and directions used in the present SWAN run in a nested run SWAN will interpolate to thes frequencies and directions The coordinates of locations in the 1D and 2D files are ignored when SWAN reads this file SWAN uses the geographical information in this BOUNDSPEC command instead gt fname name of the file containing the boundary condition seq identification number of geographic location in the file see Appendix D useful for files which contain spectra for more than one location Default seq 1 Note a TPAR file always contains only one location so in this case seq must always be 1 gt CLOSed BOUNdnesti NEST fname lt gt OPEN With this optional command a nested SWAN run can be carried out with the boundary conditions obtained from a coarse grid SWAN run generated in that previous SWAN run with command NESTOUT not to be confused with option NEST in this command BOUNDNEST1 For this nested SWAN run the user has to give the CGRID command to define the comp
3. titlel title3 same as titlel SET level nor depmin maxmes maxerr grav rho amp NAUTical inrhog hsrerr lt gt pwtail froudmax printf prtest gt CARTesian With this optional command the user assigns values to various general pa rameters level increase in water level that is constant in space and time can be given with thi option level is the value of this increase in m For a variable water level reference is made to the commands INPGRID and READINP Default level 0 nor direction of North with respect to the z axis measured counter clockwise default nor 90 i e z axis of the problem coordinate system points East When spherical coordinates are used see command COORD the value of nor may not be modified depmin threshold depth in m In the computation any positive depth smaller than depmin is made equal to depmin Default depmin 0 05 naxmes maximum number of error messages not necessarily the number of errors during the computation at which the computation is terminated During the computational process messages are written to the print file Default maxmes 200 maxerr during pre processing SWAN checks input data Depending on the severity of the errors encountered during this pre processing SWAN does not start computations The user can influence the error level above which SWAN will not start computations at the level
4. 1375 1569 1791 2045 2334 2664 3040 3470 3961 4522 5161 25891 6724 7675 8761 0000 OR OO OR OE OO On OO OO OO OO OOO OOO 42 c gt Z 3 number of quantities in table VaDens variance densities in m2 Hz m2 Hz unit 0 9900E 02 exception value CDIR average Cartesian direction in degr degr DSP 0 9990E 03 RDEGR degr 0 9000E 01 Spectrum files input and output 119 19680606 030000 LOC oO OO OO OO OO OO OO On OO OO OOO One 9 LOC 0 0 0 0 0 ATION 1 3772E 03 1039E 02 2281E 02 3812E 02 4255E 02 2867E 02 1177E 02 3892E 03 8007E 03 6016E 02 1990E 01 3698E 01 3874E 01 2704E 01 1672E 01 1066E 01 5939E 02 3247E 02 1697E 02 8803E 03 4541E 03 2339E 03 1197E 03 6129E 04 3062E 04 ATION 2 7129E 02 3503E 01 1299E 00 5623E 00 1521E 01 190 190 190 190 190 190 189 192 244 251 251 249 248 246 247 247 247 246 245 245 245 245 245 245 245 67 67 68 69 71 C2 g1014 5 O10 C1 0 4 O Lr qcCO0OoO i 0100 0000 hN2nr BNDNM ON O10 0000 Oo 41Oo0100 rn OOo o ciorn xd0o0oocdugt 600000417d 10O0 0 22 11 11 10 12 13 13 13 14 14 14 15 15 15 15 15 15 25 21 19 18 18 OONN unit exception value directional spreading unit exception value date and time 120 O0oO0o0000000000000000O0O 32
5. 51 58 63 67 68 77 diffusion 59 61 78 81 dissipation 22 50 51 53 58 74 86 BOUNDNESTI 44 BOUNDNEST2 45 nara 33 35 61 BOUNDNEST3 47 He 7 87 CO BOUNDSPEC 41 FRAME 63 BREAKING 52 breaking 10 16 17 22 50 52 54 58 74 80 86 frequency 4 7 14 15 26 30 31 40 43 49 50 52 54 58 60 61 63 68 69 73 74 77 79 80 Cartesian 3 7 21 26 27 29 34 83 84 102 103 40 42 44 46 49 56 63 65 FRICTION 53 67 69 70 73 79 84 87 100 fiction 8 10 12 16 17 19 21 22 102 103 24 33 37 50 53 74 80 86 CGRID 28 Froude 26 37 coastal 3 4 15 garden sprinkler 59 COMPUTE 80 GENI 49 convergence 5 6 60 GEN2 50 COORDINATES 27 GEN3 50 Courant 13 GROUP 64 current 3 6 8 10 12 13 16 19 21 26 33 37 43 50 61 64 74 HOTFILE 81 128 INITIAL 48 initial 8 10 13 22 40 48 49 81 82 INPGRID 32 island 5 10 ISOLINE 66 Jonswap 37 latitude 7 27 79 102 LIMITER 54 limiter 5 6 54 61 longitude 7 27 47 48 79 102 MODE 27 nautical 7 102 103 NESTOUT 78 NGRID 66 NUMERIC 59 OBSTACLE 54 obstacle 16 22 55 56 ocean 3 5 28 OFF 57 OUTPUT 70 POINTS 66 PROJECT 24 PROP 58 propagation 5 6 11 22 55 57 59 QUADRUPL 51 quadruplets 14 16 22 52 54 QUANTITY 68 RAY 65 READGRID 31 READINP 36 reflection 55 56 refraction 5 6 10 58 61 65 129 SET 25 set up 4 6
6. component and 7 component are to be read from one ar the same file with one READINP command With this option SWAN reads firs all x components components and then all y component r component see below The components and 7 are taken along the directions of the gric lines of the curvi linear grid If the wind is constant see command WIND SWAN multiplies all values that are read from file with fac For instance if the bottom levels are given in unit decimeter one should make fac 0 1 tc obtain levels in m To change sign of bottom level use a negative value of fac Note that fac 0 is not allowed Default fac 1 name of the file with the values of the variable with this option only for MODE NONSTATIONARY the user indicates that the names of the files containing the nonstationary variable s are located in a separate file with name fname2 see below name of file that contains the names of the files where the variables are given These names are to be given in proper time sequence SWAN reads the next file when the previous file end has been encountered In these files the input should be given in the same format as in the above file fname1 that implies that a file should start with the start of an input time step prescribes the order in which the values of bottom levels and other fields should be given in the file 1 SWAN reads the map from left to right starting in the upper left hand
7. corner of the map it is assumed that the x axis of the grid is pointing to the right and the y axis upwards A new line in the map should start on a new line in the file The lay out is as follows 1 myc i 2 mycti et mxc i myc 1 1 myc 2 myc zT mxc i myc 1 1 2 1 hos mxcti 1 nhedf nhedt nhedvec Description of commands 45 2 as idla 1 but a new line in the map need not start on a new line in the file 3 SWAN reads the map from left to right starting in the lower left hand corner of the map A new line in the map should start on a new line in the file The lay out is as follows 1 1 2 1 z mxc 1 1 1 2 2 2 xk mxcti 2 1 myc 1 2 myc 1 M mxc i myc 1 4 as idla 3 but a new line in the map need not start on a new line in the file 5 SWAN reads the map from top to bottom starting in the lower left hand corner of the map new column in the map should start on a new line in the file The lay out is as follows 1 1 1 2 m 1 myc i 2 1 2 2 2 myctl mxcti 1 mxcti 2 3 mxc i myc 1 6 as idla 5 but a new column in the map need not start on a new line in the file Default idla 1 is the number of header lines at the start of the file The text in the header lines is reproduced in the print file created by SWAN see Section 3 3 The file may start with more header lines than nhedf because the start of the file is often also the start of a time step and possibly also of a vector variable
8. e g for text to appear in a plot Example command scheme KEYword City data command file KEY Amsterdam data e Copy the name of the variable without the quotes literally followed by an sign and a name at the users discretion between quotes SWAN interprets the copied name in the command file as a keyword with all the characteristics of a keyword such as ending a sequence of optional data see below As with other keywords the name of the variable is case insensitive Example command scheme KEYword City data command file KEY city Amsterdam data As a rule an error message will result if numerical data is given where char acter data should be given Command syntax 107 Numerical data are simple numbers e g 15 or 7 integer data or 13 7 or 0 8E 4 real data Whether or not integer number or real number should be given by the user is indicated in the description of the command scheme Note that a decimal point is not permitted in an integer number On the other hand an integer number is accepted by SWAN where a real number should be given In a command scheme the number is always indicated with a name which is placed between square brackets In the command file such a name can be entered in two ways e Replace the name by a number not between square brackets Example command scheme KEYword nnn command file KEY 314 e Copy the name of the variable without the quotes literally
9. each having header lines see below nhedt and nhedvec Default nhedf 0 only if variable is time dependent number of header lines in the file at the start of each time level A time step may start with more header lines than nhedt because the variable may be a vector variable which has its own header lines see below nhedvec Default nhedt 0 for each vector variable number of header lines in the file at the start of 46 FREE FORMAT form 8 UNFORMATTED Chapter 4 each component e g x or y component Default nhedvec 0 With this option the user indicates that the values are to be read with free format Free format is a standard of the computer programming language FORTRAN The free format conventions in reading from a file are almost the same as the conventions for the command syntax given elsewhere in this manu the most important differences are 1 There are no continuation marks reading continues until the required number of data has been read or until a slash is encountered 2 Input lines can be longer than 80 characters depending on the operating system of the computer 3 Comment is not allowed With free format empty fields repetition factors and closure of a line by a slas can be used with this option the user indicates that fixed format FORTRAN convention i to be used when reading the values from file The format can be defined in one of two ways by g
10. of the maxima of the orbital motion near the bottom Uy V2U rns 102 TMBOT LEAK TIME TSEC SETUP Cartesian convention Nautical convention Appendix A Bottom wave period in s defined as the ratio of the bottom excursion amplitude to the bottom orbital velocity Numerical loss of energy equal to c amp E w 0 across boundaries 0 dir1 and 05 dir2 of a directional sector see command CGRID Full date time string Time in seconds with respect to a reference time see command QUANTI The elevation of mean water level relative to still water level induced the gradient of the radiation stresses of the waves The direction is the angle between the vector and the positive x axis measured counter clockwise In other words the direction where the waves are going to or where the wind is blowing to The direction 180 of the vector from geographic North measured clockwise In other words the direction where the waves are coming from or where the wind is blowing from Appendix B Command syntax B 1 Commands and command schemes The actual commands of the user to SWAN must be given in one file con taining all commands This file is called the command file It must be presented to SWAN in ASCII It is important to make a distinction between the description of the commands in this User Manual and the actual com mands in the command file The descriptions of the commands in this User Manual are called command sche
11. see Technical documentation 4 5 3 Boundary and initial conditions gt JONswap gamma gt PEAK BOUNd SHAPespec lt PM gt lt gt amp MEAN GAUSs sigfr BIN gt POWer DSPR lt gt DEGRees This command BOUND SHAPESPEC defines the shape of the spectra both in frequency and direction at the boundary of the computational grid in case of parametric spectral input see command BOUNDSPEC JONSWAP JONSWAP spectrum will be used This is default gamma peak enhancement parameter of the JONSWAP spectrum Default gamma 3 3 PM Pierson Moskowitz spectrum will be used 48 GAUSS BIN sigfr PEAK MEAN DSPR POWER DEGREES Chapter 4 a Gaussian shaped frequency spectrum will be used energy is located in one frequency bin the frequency bin closest to the per value of command BOUNDSPEC width of the Gaussian frequency spectrum expressed as a standard deviation ir Default the peak period for definition see Appendix A is used as characteris wave period This is default Tmo for definition see Appendix A is used as the characteristic wave period option for expressing the width of the directional distribution the distribution function itself is cos 0 Opeak the directional width is expressed with the power m itself this option is defaul note that the directional resolution should accommodate the directional widtl command CGRID the directional
12. see command SET Xp hexp 100 for simulations of lab experiments Hs excv 9 to change the exception value for H Hswell fswell 0 08 to change the value of fswe11 Per short Tm 1 0 power 0 to redefine average wave period Transp Frame to obtain vector components and direction with respect to the frame OUTPut OPTIons comment TABle field BLOck ndec len SPEC ndec Description of commands 83 This command enables the user to influence the format of block table and spectral output comment a comment character is used in comment lines in the output Default comment field length of one data field in a table Minimum is 8 and maximum is 16 Default field 12 ndec number of decimals in block if appearing after keyword BLOCK or spectral output if appearing after keyword SPEC Maximum is 9 Default ndec 4 in both cases len number of data on one line of output Maximum is 9999 Default len 6 gt HEADer BLOck sname lt gt fname LAYout idla NOHEADer HSign HSWE11 DIR PDIR TDIR TMO1 RTMO1 RTP TPS 84 PER RPER TMM10 RTMM10 TMO2 FSPR DSPR DEPth WATLev BOTLev VEL FRCoef WIND DISSip QB TRAnsp FORce UBOT URMS Chapter 4 gt unit gt OUTput tbegblk deltblk gt Sec MIn HR DAy Description of commands 85 TMBOT WLENgth STEEpness DHSign DRTMO1 LEAK XP YP DIST SETUP CANNOT BE USED IN 1D MODE W
13. 0 2 urslim the lower threshold for Ursell number if the actual Ursell number is below urslim triad interactions will not be computed Default urslim 0 01 LIMiter ursell qb With this command the user can de activate permamently the quadruplets when the actual Ursell number exceeds ursell Moreover as soon as the actual fraction of breaking waves exceeds qb then the limiter will not be used in case of decreasing action density urse11 the upper threshold for Ursell number Default urse11 10 0 qb the threshold for fraction of breaking waves Default qb 1 0 TRANSm trcoef OBSTacle lt DAM hgt alpha beta RSPEC REFL reflc lt gt LINe xp yp gt RDIFF pows powd Kdif NOT FOR 1D MODE With this optional command the user provides the characteristics of a line of sub grid obstacle s through which waves are transmitted or against which waves are reflected possibly both at the same time The obstacle is sub grid in the sense that it is narrow compared to the spatial meshes its length Description of commands 65 should be at least one mesh length The location of the obstacle is defined by a sequence of corner points of a line The obstacles interrupt the propagation of the waves from one grid point to the next wherever this obstacle line is located between two neighbouring grid points of the computational grid the resolution of the obstac
14. 15 30 00 3 as in Lahey compiler 05 30 87 15 30 00 4 15 30 00 5 87 05 30 15 30 00 6 as in WAM 8705301530 This format is installation dependent See Implementation Manual or ask the person who installed SWAN on your computer Default is ISO notation a nonstationary computation is to be made the start date and time of the nonstationary computation format see time Default the time read from a hotfile see command INIT HOTSTART or the end time tendc of the previous non stationary computation or the time of the previous stationary computation in the same SWAN run if any the time step of the non stationary computation the unit is indicated in the next option SEC unit seconds MIN unit minutes HR unit hours DAY unit days the end time of the non stationary computation format see time 96 Chapter 4 HOTFile fname This command can be used to write the entire wave field at the end of a computation to an initialization file e g to be used as initial condition in a subsequent SWAN run see command INITIAL HOTSTART This command must be entered immediately after a COMPUTE command The format of the initialization file is identical to the format of the files written by the SPECOUT command option SPEC2D gt fname name of the file to which the wave field is written STOP This required command marks the end of the commands in the command file Note that the command STOP may be the last comman
15. 16 17 22 28 57 61 SETUP 57 shoaling 18 SORDUP 59 SPECOUT 77 specular 56 spherical 3 4 77 9 21 25 27 29 31 34 35 43 46 48 56 57 63 65 67 79 97 102 stability 13 59 stationary 3 6 8 13 16 18 20 21 26 27 33 35 37 43 44 48 49 51 59 61 73 80 81 97 100 102 103 steepness 22 51 74 86 STOP 82 swell 11 14 15 53 69 70 73 83 TABLE 75 TEST 79 TRIAD 54 triads 16 54 WAM 3 4 6 9 14 15 18 22 35 36 44 48 52 75 18 81 WAVEWATCH 3 4 6 9 14 22 44 47 48 WCAPPING 51 whitecapping 6 16 22 50 51 58 74 80 86 WIND 39 wind 3 4 6 17 19 21 26 33 34 37 39 40 49 51 53 58 61 74 79 81 88
16. 2 Sequence of commands SWAN executes the above command blocks a j in the above sequence except f i and j The commands of the blocks f and i may appear anywhere before block j except that TEST POINTS must come after READINP BOTTOM The commands of block j may appear anywhere in the command file all commands after COMPUTE are ignored by SWAN except HOTFILE and STOP A sequence of commands of block g is permitted all commands will be executed without overriding Also a sequence of commands of block h is permitted all commands will be executed without overriding Within the blocks the following sequence is to be used In block a no prescribed sequence in block In block b READGRID after CGRID In block c READINP after INPGRID repeat both in this sequence for each quantity In block d BOUND SHAPE before BOUNDSPEC otherwise no prescribed sequence in block In block e use only one GEN command use command OFF only after a GEN command note that GEN3 is default In block f no prescribed sequence in block In block g ISOLINE after RAY ISOLINE and RAY can be repeated independently In block h no prescribed sequence in block In block i no prescribed sequence in block In block j HOTFILE immediately after COMPUTE STOP after COMPUTE It must be noted that a repetition of a command may override an earlier occurrence of that command Many commands provide the user with the
17. Default cfw 0 015 Note that cfw is allowed to vary over the computational region in that case use the commands INPGRID FRICTION and READINP FRICTION to define and read the friction data The command FRICTION is still required to define the type of friction expression The value of cfw in this command is then not required it will be ignored indicates that the expression of Madsen et al 1988 should be activated equivalent roughness length scale of the bottom in m Default kn 0 05 Note that kn is allowed to vary over the computational region in that case use the commands INPGRID FRICTION and READINP FRICTION to define and read the friction data This command FRICTION is still required to define the type of friction expression The value of kn in this command is then not required it will be ignored TRIad trfac cutfr urcrit urslim With this command the user can activate the triad wave wave interactions using the LTA method in the SWAN model If this command is not used SWAN will not account for triads trfac cutfr the value of the proportionality coefficient agp Default trfac 0 1 controls the maximum frequency that is considered in the triad computations The value of cutfr is the ratio of this maximum frequency over the mean frequency Default cutfr 5 0 64 Chapter 4 urcrit the critical Ursell number appearing in the expression for the biphase Default urcrit
18. SWAN nested grid and optionally also distributed between the corner points of the SWAN nested grid the boundary of the WAVEWATCH III nested grid need not be closed and may cover land The locations should be output by WAVEWATCH III in sequence going along the nest boundary clock wise or counter clock wise Note that SWAN will accept output of a WAVEWATCH III output location only if the SWAN grid point on the nest boundary lies within a rectangle between two consecutive WAVEWATCH III output locations with a width equal to 0 1 times the distance between these output locations on either side of the line between these WAVEWATCH III output locations This BOUNDNEST command is not available for 1D computations A nested SWAN run may use either Cartesian or spherical coordinates A curvi linear grid may be used in the nested grid but the boundaries of this nest should conform to the rectangular course grid nest boundaries gt fname the name of the file that contains the spectra computed by WAVEWATCH III CLOSED the boundary condition represented in the file is defined on a closed rectangle OPEN the curve on which the boundary condition is given is not closed xgc if SWAN is used with Cartesian coordinates longitude of south west corner of SWAN computational grid in degrees if the south west corner of the nest in the WAM computation is on land this value is required Description of commands 57 If SWAN is used with spherical coo
19. TABLE output for the last time step of the computation begin time of the first field of the variable the format is 1 ISO notation 19870530 153000 2 as in HP compiler 380 May 87 15 30 00 3 as in Lahey compiler 05 30 87 15 30 00 90 Chapter 4 4 15 30 00 5 87 05 30 15 30 00 6 as in WAM 8705301530 This format is installation dependent See Implementation Manual or ask the person who installed SWAN on your computer Default is ISO notation delttbl time interval between fields the unit is indicated in the next option SEC unit seconds MIN unit minutes HR unit hours DAY unit days Otherwise see command BLOCK except that the x and y components of the vectorial quantities VEL FORCE and TRANSPORT are always given with respect to the problem coordinate system The number of decimals in the table varies for the output parameters it depends on the value of hexp given in the command QUANTITY SPEC1D gt ABSolute SPECout sname lt gt lt gt fname amp gt SPEC2D RELative gt Sec OUTput tbegspc deltspc lt MIn gt HR DAy With this optional command the user indicates that for each location of the output location set sname see commands POINTS CURVE FRAME or GROUP the ID or 2D variance energy see command SET density spectrum either the relative frequency or the absolute frequency spectrum is to be written to a data file The name
20. The minimum number of frequencies is 4 The value of msc depends on the frequency resolution Af that the user requ Since the frequency distribution on the frequency axis is logarithmic the relationship is 7 fhigh 1 nsc m T flow f Vice versa if the user chooses the value of A f f y 1 then the value of msc is given by msc log fhigh flow log 1 Af f In this respect it must be observed that the DIA approximation of the quadru interactions see command GEN3 is based on a frequency resolution of Af f and hence y 1 1 The actual resolution in the computations should therefor not deviate too much from this Alternatively the user may only specifies one the following possibilities e flow and msc SWAN will compute fhigh such that y 1 1 and write it to the PRINT file Description of commands 37 e fhigh and msc SWAN will compute flow such that y 1 1 and write it to the PRINT file e flow and fhigh SWAN will compute msc such that y 1 1 and write it to the PRINT file For illustration of a regular grid with its dimensions see Figure 4 1 problem coordinates mxc myc yp axis Xc axis 0 myc computational grid mxc 0 INS pee PF ges xpe roblem xp axis P Coordinates P Figure 4 1 Coordinates of the origin xpc and ypc the orientation alpc and the grid point numbering of the computational grid with re spect to th
21. a finer grid for a smaller region The compu tation on the fine grid uses boundary conditions that are generated by the computation on the coarse grid Nesting can be repeated on ever decreasing scales using the same type of coordinates for the coarse computations and the nested computations Cartesian or spherical Note that curvilinear grids can be used for nested computations but the boundaries should always be rectangular Furthermore suggestions are given that should help the user to choose among 4 Chapter 2 the many options conditions and in which mode to run SWAN first second or third generation mode stationary or non stationary and 1D or 2D It must be pointed out that the application of SWAN on ocean scales is not recommended from an efficiency point of view The WAM model and the WAVEWATCH III model which have been designed specifically for ocean applications are probably one order of magnitude more efficient than SWAN SWAN can be run on large scales much larger than coastal scales but this option is mainly intended for the transition from ocean scales to coastal scales transitions where non stationarity is an issue and spherical coordinates are convenient for nesting A general suggestion is start simple SWAN helps in this with default op tions 2 2 Limitations Diffraction is modelled in a restrict sense so the model should be used in areas where variations in wave height are large within a horizontal scale
22. command COORD int SWAN will generate output at int 1 equidistant locations between two xp yp RAY rname subsequent corner points of the curve including the two corner points of the c problem coordinates of a corner point of the curve Repeat the group int xp yp in proper order if there are more corner points are on the cv xpi yp1 xqi yqi lt int xp yp xq yq gt Description of commands 77T CANNOT BE USED IN 1D MODE With this optional command the user provides SWAN with information to de termine output locations along the depth contour line s defined subsequently in command ISOLINE see below The locations are determined by SWAN as the intersections of the depth contour line s and the set of straight rays defined in this command RAY These rays are characterized by a set of master rays defined by their start and end positions xp Lyp and xq yq Between each pair of se quential master rays thus defined SWAN generates int 1 intermediate rays by linear interpolation of the start and end positions Note that the rays thus defined have nothing in common with wave rays e g as obtained from conventional refraction computations rname name of the set of rays defined by this command xp1 yp1 problem coordinates of the begin and end points of the first master ray xq1 yq1 if Cartesian coordinates are used in m if spherical coordinates are used in degr
23. different from each other If a curvi linear computational spatial grid is chosen in SWAN then each input grid should be either uniform rectangular or identical to the used curvi linear grid or staggered with respect to the curvi linear computational grid SWAN has the option to make computations that are nested in coarse SWAN WAM or WAVEWATCH III In such runs SWAN interpolates the spatial boundary of the SWAN WAM or WAVEWATCH III grid to the user provided grid of SWAN that needs to nearly coincide along the grid lines of WAM or WAVEWATCH III or the output nest grid boundaries of SWAN Since the computational grids of WAM and WAVEWATCH III are in spherical coordinates it is recommended to use spherical coordinates in a nested SWAN when nesting in WAM or WAVEWATCH III General definitions and remarks 11 Nesting from a 2D model to a 1D model is possible although is should not be done by using the commands NGRID and NEST Instead define the boundary point of the 1D model as an output point using command POINTS and write the spectra for that point using the command SPECout In the 1D model this spectra is used as boundary condition using the BOUNDSPEC command Similarly the wind fields may be available in different time windows than the current and water level fields and the computations may need to be carried out at other times than these input fields For these reasons SWAN operates with different time windows with different
24. direction of the problem coordinate system must be defined by the user see the SET north command by default the positive x axis points East see description of len below these option are only effective if the option VARIABLE is used see below is used if SIDE is not used i e either the boundary segment goes around a corner of the grid or the segment is only part of one side of the grid The distance along the segment see len below is measured from the first point of the segment see XY or IJ the segment is defined by means of a series of points in terms of problem coordinates these points do not have to coincide with grid points The straight line connecting two points must be close to grid lines of the computational grid the maximum distance is one hundredth of the length of the straight line This option is default problem coordinates of a point of the boundary segment see command COORD the segment is defined by means of a series of computational grid points given in terms of grid indices origin at 0 0 not all grid points on the segment have to be mentioned If two points are on the same grid line intermediate points are assumed to be on the segment as well grid indices of a point of the segment values of i range between 0 and mxc see command CGRID values of j between 0 and myc inclusive with this option the wave spectra are constant along the side or segment with this option the wave spectra can
25. easiest if the boundary is one full side of the com putational grid although it should not be used for curvi linear grids The second SEGMENT can be used if the boundary segment goes around the cor ner of the grid or if the segment is only part of one side of the grid This BOUNDSPEC command can be given a number of times i e to define incident wave fields on various sides or segments of the boundary One BOUNDSPEC command can be used for only one side or one contiguous seg ment gt SIDE the boundary is one full side of the computational grid in 1D cases either NORTH of the two ends of the 1D grid SHOULD NOT BE USED IN CASE OF CURVI LINEAR GRIDS indicates on which side the boundary condition is applied N means the boundary is the north edge if present of the computational area likewise for W is west S is south E is east NW is northwest NE is northeast SW is southwest and SE is southeast The side does not have to face exactly the given direction the nearest direction of the normal to the side is taken this direction is determined as the normal to the sum of the vectors joining the grid points on the boundary there is an interruption in the boundary due to the occurrence of exception values then this interruption is ignored 50 CCW CLOCKWISE SEGMENT XY x Ly IJ i j CONSTANT VARIABLE PAR hs per Chapter 4 in the summation Note in case of Cartesian coordinates the
26. file created by a previous SWAN run the present SWAN run is a nested run The spectral frequencies and directions in the case of a 2D spectrum of the previous run do not have to coincide with the frequencies and directions used in the present SWAN run see command CGRID SWAN will interpolate the energy densities to these frequencies and directions see Section 2 6 3 name of the file containing the boundary conditions for the present run created by the previous SWAN coarse grid run This file is structured according to the rules given in Appendix D for 2D spectra the boundary represented in the file is a closed rectangle this is always the case if the NESTOUT command was used to generate the boundary condition file the boundary represented in the file is not a closed rectangle gt CRAY UNFormatted lt gt WKstat WAMNest fname lt gt xgc ygcl 54 Chapter 4 FREE With this optional command not fully tested a nested SWAN run can be carried out with the boundary conditions obtained from a coarse grid WAM run WAM Cycle 3 and 4 source code as distributed by the Max Planck Institute in Hamburg For this nested SWAN run the user has to give the CGRID command to define the computational grid before this BOUNDNEST2 command The computational grid for SWAN in geographic space is the area bounded by the WAM coarse run nest WAM boundary points of the nest This implies that the boundari
27. fname is required in this command gt sname name of the set of POINTS CURVE FRAME or GROUP SPEC2D means that 2D frequency direction spectra are written to file according to th format described in Appendix D Note that this output file can be used for Description of commands 91 defining boundary conditions for subsequent SWAN runs command BOUNDSPEC SPEC1D means that 1D frequency spectra are written to file according to the format described in Appendix D Note that this output file can be used for defining boundary conditions for subsequent SWAN runs command BOUNDSPEC ABS means that spectra are computed as function of absolute frequency i e the frequency as measured in a fixed point REL means that spectra are computed as function of relative frequency i e the frequency as measured when moving with the current gt fname name of the data file where the output is written to OUTPUT the user requests output at various times If the user does not use this option the program will give SPECOUT output for the last time step of the computation tbegspc begin time of the first field of the variable the format is 1 ISO notation 19870530 153000 2 as in HP compiler 30 May 87 15 30 00 3 as in Lahey compiler 05 30 87 15 30 00 4 15 30 00 59 87 05 30 15 30 00 6 asin WAM 8705301530 This format is installation dependent See Implementation Manual or ask the person who installed SWAN on you
28. for the linear solver Default niter 20 in case of SIP and niter 1000 in case of SOR 4 6 Output There are two categories of output commands 1 Locations commands defining sets of output locations at which the user requires output Each set is indicated with a name sname in this manual which must be unique and not more than 8 characters long Types of sets of output points FRAME to define a set of output locations on a regular grid GROUP to define a set of output locations on a regular or curvi linear grid CURVE to define a set of output locations along a curve RAY to define a set of output locations along a depth or bottom contour line with ISOLINE ISOLINE to define a set of output locations along a depth or bottom contour line with RAY POINTS to define a set of isolated output locations NGRID to define a set of output locations for a nested grid to be used in a subsequent SWAN run Commands FRAME GROUP RAY ISOLINE and NGRID cannot BE USED IN 1D MODE If one gives one name for two sets of output locations the first set is lost first in the sequence in the command file Two special names BOTTGRID and COMPGRID are reserved for use by SWAN see below The user may not define sets with these names 74 Chapter 4 2 Write plot commands defining data file output write at the above defined set s of output locations BLOCK write spatial distributions only for FRAMEs and GROUPs TABLE write
29. from the computational grid to the output grid If the input computational and output grids are identical then no interpolation errors occur In the regions where the output grid does not cover the computational grid SWAN assumes output values equal to the corresponding exception value For example the default exception value for the significant wave height is 9 The exception values of output quantities can be changed by means of the QUANTITY command In non stationary computations output can be requested at regular intervals starting at a given time always at computational times 2 7 Activation of physical processes SWAN contains a number of physical processes see Technical documenta tion that add or withdraw wave energy to or from the wave field The processes included are wind input whitecapping bottom friction depth induced wave breaking obstacle transmission nonlinear wave wave interac tions quadruplets and triads and wave induced set up SWAN can run in several modes indicating the level of parameterization SWAN can op erate in first second and third generation mode The first and second generation modes are essentially those of Holthuijsen and De Boer 1988 first generation with a constant Phillips constant of 0 0081 and second generation with a variable Phillips constant An overview of the options is given in Table below The processes are activated as follows e Wind input is activated by comman
30. grid In case of a curvi linear grid option CURVILINEAR in the INPGRID command the current and wind vectors are defined with the r and y component of the current or wind vector with respect to the r axis of the problem coordinate system For wind velocity and friction coefficient it is also possi ble to use a constant value over the computational field see commands WIND and FRICTION No grid definition for wind and friction is then required 40 Chapter 4 Note that in case of BOTTOM only stationary input field is allowed See Section 2 6 for more information on grids BOTTOM WLEV CURRENT VX VY FRICTION WIND WX WY REGULAR CURVILINEAR defines the input grid of the bottom level For the definition of the bottom level see command READINP water level relative to datum level positive upward in m defines the input grid of the current field same grid for z and y component defines the input grid of the zx component of the current field different grid than y component but same orientation defines input grid of the y component of the current field different grid than x component but same orientation defines input grid of the bottom friction coefficient defined in command FRICTION not to be confused with this option FRICTION defines input grid of the wind field same grid for x and y component If neither of the commands WIND and READINP WIND is used it is assumed
31. hotfile will be generated depending on the number of processors Hence for the present run the same number of processors must be chosen name of the file containing the initial wave field 4 5 4 Physics GEN1 cf10 cf20 cf30 cf40 edmlpm cdrag umin cfpm With this command the user indicates that SWAN should run in first generation mode see Technical documentation cf 10 cf20 cf30 cf40 controls the linear wave growth Default cf10 188 controls the exponential wave growth Default cf20 0 59 controls the exponential wave growth Default cf30 0 12 controls the dissipation rate i e the time decay scale Default cf40 250 Description of commands 59 edmlpm maximum non dimensionless energy density of the wind sea part of the spectrum according to Pierson Moskowitz Default edmlpm 0 0036 cdrag drag coefficient Default cdrag 0 0012 umin minimum wind velocity relative to current all wind speeds are taken at 10m above sea level Default umin 1 cfpm coefficient which determines the Pierson Moskowitz frequency apm 27g lcfpm Uio Default cfpm 0 13 GEN2 cf10 cf20 cf30 cf40 cf50 cf60 edmlpm cdrag umin cfpm With this command the user indicates that SWAN should run in second generation mode see Technical documentation The variables are identical to those in the GEN1 command except that cf50 and cf60 are ad
32. indicated the computations will continue grav rho inrhog hsrerr NAUTICAL CARTESIAN pwtail Description of commands 31 The error level naxerr is coded as follows l warnings 2 errors possibly automatically repaired or repairable by SWAN 3 Severe errors Default naxerr 1 is the gravitational acceleration in m s Default grav 9 81 is the water density p in kg m Default rho 1025 to indicate whether the user requires output based on variance or based on true energy see Section 2 5 inrhog 0 output based on variance inrhog 1 output based on true energy Default inrhog 0 the relative difference between the user imposed significant wave height and the significant wave height computed by SWAN anywhere along the computational grid boundary above which a warning will be given This relative difference is the difference normalized with the user provided significant wave height This warning will be given for each boundary grid point where the problem occurs with its z and y index number of the computational grid The cause of the difference is explained in Section 2 6 3 To supress these warnings in particular for non stationary computations set hsrerr at a very high value or use command OFF BNDCHK Default hsrerr 0 10 indicates that the Nautical convention for wind and wave direction SWAN input and output will be used inst
33. opportunity to assign values to coefficients of SWAN e g the bottom friction coefficient If the user does not use such option SWAN will use a default value Some commands cannot be used in 1D mode see individual command de scriptions below Description of commands 29 4 3 Command syntax and input output lim itations The command syntax is given in Appendix B Limitations e The maximum length of the input lines is 120 characters e The maximum length of the file names is 36 characters e The maximum length of the plot titles is 36 characters e The maximum number of file names is 99 This can be extended edit the file swaninit to change highest unit number of 99 to a higher number 4 4 Start up PROJect name nr gt titlel gt title2 title3 With this required command the user defines a number of strings to identify the SWAN run project name e g an engineering project in the print and plot file name is the name of the project at most 16 characters long Default blanks nr is the run identification to be provided as a character string e g the run number to distinguish this run among other runs for the same project it is at most 4 characters long It is the only required information in this command 30 Chapter 4 titles is a string of at most 72 characters provided by the user to appear in the outpi of the program for the user s convenience Default blanks title2 same as
34. output for set of output location s SPECOUT write to data file the variance energy see command SET density spectrum for set of output location s NESTOUT write to data file two dimensional action density spectra relative frequen along the boundary of a nested grid see command NGRID to be used in subsequent SWAN run Commands BLOCK and NESTOUT cannot BE USED IN 1D MODE 4 6 1 Output locations FRAme sname xpfr ypfr alpfr xlenfr ylenfr mxfr myfrl CANNOT BE USED IN 1D MODE With this optional command the user defines output on a rectangular uniform grid in a regular frame If the set of output locations is identical to a part of the computational grid then the user can use the alternative command GROUP sname name of the frame defined by this command xpfr x coordinate of the origin of the frame in problem coordinates if Cartesian coordinates are used in m if spherical coordinates are used in degrees see command COORD ypfr y coordinate of the origin of the frame in problem coordinates if Cartesian coordinates are used in m if spherical coordinates are used in degrees see command COORD alpfr direction of the z axis of the frame in degrees Cartesian convention must be 0 in case of spherical coordinates Description of commands 75 xlenfr length of the frame in x direction if Cartesian coordinates are used in m if spherical coordinates are used in degrees
35. proper value Default if HEADER is selected value is written as a 5 position integer SWAN takes unit such that the largest number occurring in the block can be printed If NOHEADER is selected values are printed in floating point format unit 1 OUTPUT the user requests output at various times If the user does not use this option program will give BLOCK output for the last time step of the computation tbegblk begin time of the first field of the variable the format is 1 ISO notation 19870530 153000 2 as in HP compiler 380 May 87 15 30 00 3 as in Lahey compiler 05 30 87 15 30 00 4 15 30 00 E 87 05 30 15 30 00 6 asin WAM 8705301530 This format is installation dependent See Implementation Manual or ask the person who installed SWAN on your computer Default is ISO notation deltblk time interval between fields the unit is indicated in the next option SEC unit seconds MIN unit minutes HR unit hours DAY unit days gt HEADer TABle sname lt NOHEADer gt fname amp INDexed e Meas gt Sec Description of commands 89 lt gt gt OUTput tbegtbl delttbl lt MIn gt m HR DAy With this optional command the user indicates that for each location of the output location set sname see commands POINTS CURVE FRAME or GROUP one or more variables should be written to a file The keywords HEADER and NOHEADER determine the app
36. see commands CGRID INPUT GRID and FRAME respectively 34 Chapter 4 4 5 Model description 4 5 1 Computational grid gt CGRID lt lt REGular xpc ypc alpc xlenc ylenc mxc myc gt amp CURVilinear mxc myc EXCeption xexc yexc gt CIRcle gt mdc flow fhigh msc SECtor diri dir2 With this required command the user defines the geographic location size resolution and orientation of the computational grid in the problem coordi nate system see Section 2 6 3 in case of a uniform recti linear computa tional grid or the size in case of a curvi linear grid see Section 2 5 The origin of the grid and the direction of the positive z axis of this grid can be chosen arbitrary by the user Must be used for nested runs Note that in a nested case the geographic and spectral range directional sector inclusive and resolution may differ from the previous run outside these ranges zero s are used REGULAR CURVILINEAR xpc ypc alpc this option indicates that the computational grid is to be taken as uniform anc rectangular this option indicates that the computational grid is to be taken as curvi linear The user must provide the coordinates of the grid points with command READGRID geographic location of the origin of the computational grid in the problem coordinate system x coordinate in m See command COORD Default xpc 0 0 Cartesi
37. see note for 1D spectra above the quantities appear in the order in which they appear in this description Spectrum files input and output 125 For nonstationary computations repeat from VVV 126 Bibliography 1 SWAN Implementation manual Delft University of Technol ogy Environmental Fluid Mechanics Section available from http www fluidmechanics tudelft nl swan index htmhttp www fluidmechanics tudelft nl swan Version 40 51 August 2006 SWAN Programming rules Delft University of Technol ogy Environmental Fluid Mechanics Section available from http www fluidmechanics tudelft nl swan index htmhttp www fluidmechanics tudelft nl swan Version 1 3 August 2006 SWAN System documentation Delft University of Technology Envi ronmental Fluid Mechanics Section to be available SWAN Technical documentation Delft University of Tech nology Environmental Fluid Mechanics Section available from http www fluidmechanics tudelft nl swan index htmhttp www fluidmechanics tudelft nl swan Version 40 51 August 2006 127 Index ambient 5 77 84 CURVE 64 bathymetry 5 9 10 61 79 curvi linear 8 12 13 16 21 22 28 BLOCK 70 29 32 34 37 42 45 46 48 bottom 3 7 10 12 13 16 17 19 62 64 21 22 24 33 35 38 50 53 56 62 64 66 74 80 86 87 dam 4 6 92 BOUND SHAPE 40 DIFFRACTION 57 boundary 1 3 5 13 22 26 28 30 diffraction 4 22 57 40 49
38. spectrum is prescribed Note these points do no have to coincide with grid points of the computational grid len is the distance in m or degrees in the case of spherical coordinates not in grid steps The values of len should be given in ascending order The length along a SIDE is measured in clockwise or counterclockwise direction depending on the options CCW or CLOCKWISE see above The option CCW is default In case of a SEGMENT the length is measured from the indicated begin point of the segment means that the incoming wave data are read from a file There are three types of files e TPAR files containing non stationary wave parameters e files containing stationary or non stationary 1D spectra usually from measurements e files containing stationary or non stationary 2D spectra from other computer programs or other SWAN runs A TPAR file is for only one location it has the string TPAR on the first line of the file and a number of lines which each contain 5 numbers i e Time ISO notation Hs Period average or peak period depending on the choice given in command BOUND SHAPE Peak Direction Nautical or Cartesian depending on command SET Directional spread in degrees or as power of cos depending on the choice given in command BOUND SHAPE Example of a TPAR file TPAR 19920516 1300 4 2 12 110 22 19920516 1800 4 2 12 110 22 52 Chapter 4 19920517 0000 1 2 8 110 22 19920517 1200 1 4 8 5 80 26
39. such a case it may even be better to deactivate the refraction computations if refraction is irrelevant for the problem at hand e g because the refracted waves will run into the coast anyway and one is not interested in that part of the coast In such cases the ridges are vitally important to obtain good SWAN results at sea the waves are clipped by depth induced breaking over the ridges which must therefore represented in SWAN computation This requires not only that these ridges should be well represented on the input grid but also after interpolation on the computational grid This can be achieved by choosing the grid lines of the input grid along the ridges even if this may require some slight shift ing of the ridges and choosing the computational grid to be identical to the input grid otherwise the ridge may be lost in the interpolation from the bottom input grid to the computational grid In SWAN the bathymetry current water level wind and bottom friction may be time varying In that case they need to be provided to SWAN in General definitions and remarks 13 so called input time windows they need not be identical with the computa tional output or other input windows It is best to make an input window larger than the computational time window SWAN assumes zero values at times before the earliest begin time of the input parameters which may be the begin time of any input parameter such as wind SWAN assumes constant v
40. the case of spherical coordinates SWAN operates either in a Cartesian coordinate system or in a spherical co ordinate system i e in a flat plane or on a spherical Earth In the Cartesian General definitions and remarks 9 system all geographic locations and orientations in SWAN e g for the bot tom grid or for output points are defined in one common Cartesian coordi nate system with origin 0 0 by definition This geographic origin may be chosen totally arbitrarily by In the spherical system all geographic locations and orientations in SWAN e g for the bottom grid or for output points are defined in geographic lon gitude and latitude Both coordinate systems are designated in this manual as the problem coordinate system In the input and output of SWAN the direction of wind and waves are de fined according to either e the Cartesian convention i e the direction to where the vector points measured counterclockwise from the positive x axis of this system in degrees or e a nautical convention there are more such conventions i e the direc tion where the wind or the waves come from measured clockwise from geographic North All other directions such as orientation of grids are according to the Carte sian convention For regular grids i e uniform and rectangular Figure 4 1 in Section 4 5 shows how the locations of the various grids are determined with respect to the problem coordinates Al
41. time steps each may have a different start and end time and time step e one computational time window in which SWAN performs the compu tations e one or more input time window s in which the bottom current field water level bottom friction and wind field if present are given by the user each input window may differ form the others and e one or more output time window s in which the user requires output of SWAN SWAN has the option to make computations that are nested in SWAN WAM or WAVEWATCH III SWAN searches the boundary conditions in the rel evant output file of the previous SWAN WAM or WAVEWATCH III runs to take the boundary conditions at the start time of the nested run It will not take the initial condition i e over the entire computational grid for the nested run from the previous SWAN WAM or WAVEWATCH III run During the computations SWAN obtains bottom current water level wind and bottom friction information by tri linear interpolation from the given input grid s and time window s The output is in turn obtained in SWAN by bi linear interpolation in space from the computational grid there is no interpolation in time the output time is shifted to the nearest computa tional time level Interpolation errors can be reduced by taking the grids and windows as much as equal to one another as possible preferably identi cal It is recommended to choose output times such that they coincide with comp
42. vary along the side or segment The incident wave field is prescribed at a number of points of the side or segment these points are characterized by their distance from the begin point of the side or segment The wave spectra for grid points on the boundary of the computational grid are calculated by SWAN by the spectral interpolation technique described in Section 2 6 3 the wave spectra are defined by means of the following spectral parameters see command BOUND SHAPE for spectral shape the significant wave height in m the characteristic period of the energy spectrum relative frequency which is equal to absolute frequency in the absence of currents per is the value of the peak period in s if option PEAK is chosen in command BOUND SHAPE or dir dd len FILE Description of commands 51 per is the value of the mean period if option MEAN was chosen in command BOUND SHAPE the peak wave direction Opeak direction in degrees constant over frequencies coefficient of directional spreading a cos 0 distribution is assumed dd is interpreted as the directional standard deviation in degrees if the option DEGREES is chosen in the command BOUND SHAPE Default dd 30 dd is interpreted as the power m if the option POWER is chosen in the command BOUND SHAPE Default dd 2 is the distance from the first point of the side or segment to the point along the side or segment for which the incident wave
43. width is expressed in terms of the directional standard deviatio of the cos 0 Osca distribution for definition see Appendix A Note that the directional resolution should accommodate the directional widt see command CGRID If this command is not used the JONSWAP option will be used by SWAN with gamma 3 3 BOUNdspec and POWER for the directional width North NW West SW gt CCW gt SIDE lt South gt lt gt SE CLOCKWise East NE gt XY lt xl y gt SEGMent lt gt IJ lt i j gt PAR hs per dir dd CONstant lt Description of commands 49 FILE fname seq lt PAR lt len hs per dir dd gt VARiable lt FILE lt len fname seq gt This command BOUNDSPEC defines parametric spectra at the boundary It consists of two parts the first part defines the boundary side or segment where the spectra will be given the second part defines the spectral param eters of these spectra Note that in fact only the incoming wave components of these spectra are used by SWAN The fact that complete spectra are cal culated at the model boundaries from the spectral parameters should not be misinterpreted Only the incoming components are effective in the compu tation There are two ways to define the part of the boundary at which the spectra are imposed The first SIDE is
44. 0 over one spatial grid step controls the accuracy of computing the frequency shifting and the stopping cri and amount of output for the SIP solver used in the computations in the pres of currents or time varying depth controls the stopping criterion and amount of output for the SOR solver in the computation of the wave induced set up A value of css 0 corresponds to a central scheme and has the largest accuracy diffusion z 0 but the computation may more easily generate spurious fluctuations A value of css 1 corresponds to an first order upwin scheme and it is more diffusive and therefore preferable if strong gradients in depth or current are present Default css 0 5 Relative stopping criterion to terminate the linear solver SIP or SOR The criterion for the SIP solver is based on AN b eps2 b where A is a matrix N is the action density vector b is the right hand vector and k is the iteration number The criterion for the SOR solver is based on 7 ill eps2 where 7 is the set up Default eps2 1 e 4 in case of SIP and eps2 1 e 6 in case of SOR output for the iterative solver 0 no output Description of commands 73 1 additional information about the iteration process is written to the PRINT file 2 gives a maximal amount of output concerning the iteration process 3 summary of the iteration process Default outp 0 niter maximum number of iterations
45. 89E 01 4983E 01 4T4TE 01 2322E 01 1899E 01 1900E 01 6038E 01 8575E 01 4155E 01 1109E 01 T494E 00 4937E 00 2953E 00 1661E 00 9788E 01 5766E 01 3397E 01 2001E 01 1179E 01 6944E 02 74 TT 79 79 341 314 324 326 325 322 323 323 323 323 323 323 324 324 324 324 NO lr DOAN DOWrRKrRWrFRFrRWOOrFHRON CO 18 20 22 30 56 39 31 31 30 32 33 33 33 34 33 33 33 33 33 33 NCco0d 0O10 000 10 C00 cO O1 Oo tO 4 Icd OW OO Appendix D Example of a 2D stationary Cartesian coordinates file SWAN 1 Data produced by SWAN version 40 51 Project projname LOCATIONS 1 22222 22 RFREQ 25 0 0418 0477 0545 0622 0710 0810 0924 o0oo0oo0oo0oo oO 0 00 3 run number Swan standard spectral file version runnum locations in x y space number of locations relative frequencies in Hz number of frequencies Oo0o0000000 000000O0OO CDIR 12 30 60 90 120 150 180 210 240 270 300 330 360 QUANT 1 VaDens m2 Hz 0 9900E 02 FACTOR 1055 1204 1375 1569 1791 2045 2334 2664 3040 3470 3961 4522 5161 5891 6724 7675 8761 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 degr Spectrum files input and output 121 Spectral Cartesian directions in degr number of directions number of quantit
46. ID should precede this command GROUP The subgrid contains those points ix iy of the computational grid for which ix1 lt ix lt ix2 and iyi lt iy 3y2 76 Chapter 4 For convenience the size of the group the corner coordinates and the an gle with the problem coordinate system are written to PRINT file The origin of the computational grid is ix 0 iy 0 gt sname name of the set of output locations defined by this command ixi lowest grid index of subgrid in terms of computational grid in ix direction iyi lowest grid index of subgrid in terms of computational grid in iy direction ix2 highest grid index of subgrid in terms of computational grid in ix direction iy2 highest grid index of subgrid in terms of computational grid in iy direction Limitations ix1 20 ix2 mxc iy1 gt 0 iy2 myc mxc and myc as de fined in the command CGRID CURve sname xpi yp1 lt int xp yp gt With this optional command the user defines output along a curved line Actually this curve is a broken line defined by the user with its corner points The values of the output quantities along the curve are interpolated from the computational grid This command may be used more than once to define more curves gt sname name of the curve xp1 yp1 problem coordinates of the first point of the curve if Cartesian coordinates are used in m if spherical coordinates are used in degrees see
47. LL Description of commands 81 PROBLEMcoord lt gt For directions DIR TDIR PDIR FRAME and vectors FORCE WIND VELOCITY TRANSPORT With this command the user can influence e the naming of output quantities e the accuracy of writing output quantities e the definition of some output quantities and e reference direction for vectors lt gt the output parameters are the same as given in command BLOCK short user preferred short name of the output quantity e g the name appearing in the heading of a table written by SWAN If this option is not used SWAN will use a realistic name long long name of the output quantity e g the name appearing in the heading of a block output written by SWAN If this option is not used SWAN will use a realistic name lexp lowest expected value of the output quantity hexp highest expected value of the output quantity the highest expected value is used by SWAN to determine the number of decimals in a table with heading So the QUANTITY command can be used in case the default number of decimals in a table is unsatisfactory excv in case there is no valid value e g wave height in a dry point this exception value of the output quantity is written in a table or block output The following data are accepted only in combination with selected output quantities power power p appearing in the definition of PER RPER and WLEN see Appendix A Note that th
48. P with a cos directional distribution options are available see command BOUND SHAPE ZERO The initial spectral densities are all 0 note that if waves are generated in the model only by wind waves can become non zero only by the presence of the A term in the growth model see the keyword AGROW in command GEN3 58 PAR hs per dir dd HOTSTART fname Chapter 4 the spectra in the entire computational area are generated from integral param hs etc in the same way as done for the boundary using the command BOUNI the significant wave height characteristic wave period of the energy spectrum either peak or mean period determined by the options PEAK and MEAN in the command BOUND SHAPE the peak wave direction direction in degrees Nautical or Cartesian convention see command SET the coefficient of directional spreading a cos 0 distribution is assumed See the options DEGREES and POWER in the command BOUND SHAPE initial wave field is read from file this file was generated in a previous SWAN run by means of the HOTFILE command If the previous run was non stationar time found on the file will be assumed to be the initial time of computation It can also be used for stationary computation as first guess The computational both in geographical space and in spectral space must be identical to the one the run in which the initial wave field was computed Note for MPI parallel runs more than one
49. STout sname fname OUTput tbeg delt SECIMIN HR DAY gt IJ lt i j gt X TEST itest itrace POINTS lt gt PAR fname KY lt x y gt S1D fname S2D fname STATionary time COMPute gt gt Sec tbegc deltc lt MIn gt tendc HR DAy HOTFile fname STOP Ferre eS Appendix D Spectrum files input and output This appendix described the format of the files for spectral input command BOUNdspec and output commands SPECout and NESTout by SWAN The files are recognized by SWAN or another reading program by the presence of the keyword SWAN and a version number on the first line of the file This description is valid for version number 1 These files contain the following information e coordinates of locations e frequencies directions if used for 2D time if time dependent e spectral energy or variance densities and average direction and direc tion spreading if 1D Example of a 1D non stationary spherical coordinates file SWAN 1 Swan standard spectral file version Data produced by SWAN version 40 51 Project projname run number runnum TIME time dependent data 117 118 Appendix D 1 time coding option LONLAT locations in spherical coordinates 2 number of locations RFREQ relative frequencies in Hz 25 number of frequencies 0 0418 0477 0545 0622 0710 0810 0924 1055 1204
50. SWAN USER MANUAL SWAN Cycle III version 40 51 SWAN USER MANUAL by The SWAN team mail address Delft University of Technology Faculty of Civil Engineering and Geosciences Environmental Fluid Mechanics Section P O Box 5048 2600 GA Delft The Netherlands e mail swan info citg tudelft nl home page Attp www fluidmechanics tudelft nl swan index htmhttp www fluidmechanics tu Copyright c 2006 Delft University of Technology Permission is granted to copy distribute and or modify this document under the terms of the GNU Free Documentation License Version 1 2 or any later version published by the Free Software Foundation with no Invariant Sec tions no Front Cover Texts and no Back Cover Texts A copy of the license is available at http www gnu org licenses fdl html TOC thttp www gnu org licenses fdl html ZZ TO iv Contents 1 Introduction 2 General definitions and remarks 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 Tntr d ctione d eius i he wh aia a a a E ao Sn AORA Limitations sh het Sa a Bak RD LE RR A Internal scenarios limiters shortcomings and coding bugs Relation to WAM WAVEWATCH III and others Units and coordinate systems Choice of grids time windows and boundary initial first guess conditions 2 4 erae mes aos 5 do rd ep i SS 2 6 1 Introduction s S ur e X cedem oh tede gas eodem e xg 2 6 2 Input grid s and time window s 2 6 3 Computational g
51. Spelling of keywords Required and optional keywords Repetitions of keywords and or other data B 2 2 Data Character data and numerical data Spelling of data Required data and optional data B 3 Command file and comments B 4 End of line or continuation C File swan edt vil 74 75 76 76 TT 78 78 80 80 82 83 88 90 91 92 92 94 94 95 96 97 103 103 103 103 104 104 105 105 106 106 107 108 109 111 viii D Spectrum files input and output 117 Bibliography 127 Index 128 Chapter 1 Introduction The information about the SWAN package is distributed over five different documents This User Manual describes the complete input and usage of the SWAN package The Implementation Manual explains the installation procedure of SWAN on a single or multi processor machine with shared or distributed memory The System documentation outlines the internals of the program and discusses program maintenance The Programming rules is meant for programmers who want to develop SWAN The Technical doc umentation discusses the mathematical details and the discretizations that are used in the SWAN program The mapping of these numerical techniques in SWAN code is also discussed In Chapter 2 some general definitions and remarks concerning the usage of SWAN the treatment of grids boundary conditions etc is given It is ad vised to
52. ain general parameters MODE requests a stationary non stationary or 1D mode 2D mode of SWAN COORD to choose between Cartesian and spherical coordinates Commands for model description b Commands for computational grid CGRID defines dimension of computational grid READGRID reads a curvi linear computational grid c Commands for input fields 25 26 Chapter 4 INPGRID defines dimension of bottom water level current and friction grids READINP reads input fields WIND activates constant wind option d Commands for boundary and initial conditions BOUND defines the shape of the spectra at the boundary of geographic grid BOUNDSPEC defines parametric spectra at the boundary of geographic grid BOUNDNEST1 defines boundary conditions obtained from coarse SWAN run BOUNDNEST2 defines boundary conditions obtained from WAM run BOUNDNEST3 defines boundary conditions obtained from WAVEWATCH III run INITIAL specifies an initial wave field e Commands for physics GEN1 SWAN runs in first generation mode GEN2 SWAN runs in second generation mode GEN3 SWAN runs in third generation mode WCAPPING activates cumulative steepness method for whitecapping QUAD controls the computation of quadruplets BREAKING activates dissipation by depth induced wave breaking FRICTION activates dissipation by bottom friction TRIAD activates three wave wave interactions LIMITER de actives quadruplets if a certain Ursell number exceeds OBSTACLE
53. alue is required If SWAN is used with spherical coordinates then ygc is ignored by SWAN Default the location of the first spectrum encountered in the nest file CLOSed WWIII fname lt xgc ygc OPEN With this optional command not fully tested a nested SWAN run can be carried out with the boundary conditions obtained from a coarse grid WAVE WATCH III run For this nested SWAN run the user has to give the CGRID command to define the computational grid before this BOUNDNEST3 command The computational grid for SWAN in geographic space is the area bounded 56 Chapter 4 by the WAVEWATCH III nest WAVEWATCH III boundary points of the nest This implies that the boundaries of the WAVEWATCH III nest and the boundaries of the SWAN computational area should be nearly identical see below The spectral frequencies and directions of the coarse grid run do not have to coincide with the frequencies and directions used in the nested SWAN run as defined in the CGRID command SWAN will interpolate to these frequencies and directions in the nested run see Section 2 6 3 The output files of WAVEWATCH III version 1 18 as distributed by NOAA have to be created with the post processor of WAVEWATCH III as output transfer files with WW_3 OUTP output type 1 sub type 3 at the locations along the nest boundary i e computational grid points in WAVEWATCH III These locations are equal to the corner points of the
54. alues the last values at times after the end time of each input parameter The input windows should start early enough so that the initial state of SWAN has propagated through the computational area before reli able output of SWAN is expected One should use a time step that is small enough that time variations in the bathymetry current water level wind and bottom friction are well resolved 2 6 3 Computational grids and boundary initial first guess conditions The computational spatial grid must be defined by the user The orien tation direction can be chosen arbitrarily The boundaries of the computational spatial grid in SWAN are either land or water In the case of land there is no problem the land does not generate waves and in SWAN it absorbs all incoming wave energy But in the case of a water boundary there may be a problem Often no wave conditions are known along such a boundary and SWAN then assumes that no waves enter the area and that waves can leave the area freely These assumptions obviously contain errors which propagate into the model These boundaries must therefore be chosen sufficiently far away from the area where reliable computations are needed so that they do not affect the computational results there This is best established by varying the location of these boundaries and inspect the effect on the results Sometimes the waves at these bound aries can be estimated with a certain degree of reliability This i
55. ame reference level as for bottom etc use a negative value if the top is below that reference level If this command is used this value is required coefficient determining the transmission coefficient for Goda s transmission fori Default alpha 2 6 another coefficient determining the transmission coefficient for Goda s transmi formula Default beta 0 15 if this keyword is present the obstacle will reflect wave energy possibly in combination with transmission Reflections will be computed only if the spect directions cover the full 360 i e if in the command CGRID the option CIRCLE is activated constant reflection coefficient formulated in terms of wave height i e ratio of reflected significant wave height over incoming significant wave height Restriction 0 reflc lt 1 Default reflc 1 if the keyword REFL is present NOTE before calculation the program checks if the criterion 0 lt reflc trcoef lt 1 is fulfilled indicates specular reflection which is the default T he angle of reflection equals the angle of incidence indicates diffuse and scattered reflection in which the angle of reflection does not equal the angle of incidence power of cosine in scattered reflection powd Kdif LINE xpl Lypl Description of commands 67 Default pows 1 power of cosine in diffuse reflection Default powd 1 fraction of energy that is reflected in a diffuse way Restr
56. an adjacent parallel wet link is removed e each wet computational grid point that is linked to only one other wet computational grid point is removed and e each wet computational grid point that has no wet links is removed The effect of this filter is that if exception values are used for the depth grid or the curvi linear computational grid one dimensional water features are ig nored in the SWAN computations results at these locations with a width of about one grid step may be unrealistic If no exception values are used the above described filter will not be applied As a consequence one dimensional features may appear or disappear due to changing water levels flooding may create them drying may reduce two dimensional features to one dimensional features It must be noted that for parallel runs using MPI the user must indicate an exception value when reading the bottom levels by means of command INPGRID BOTTOM EXCEPTION in order to obtain good load balancing The computational time window must be defined by the user in case of non stationary runs The computational window in time must start at a time that is early enough that the initial state of SWAN has propagated through the computational area before reliable output of SWAN is expected Before this time the output may not be reliable since usually the initial state is not known and only either no waves or some very young sea state is assumed for the initial state This is
57. an be nested in WAM or WAVEWATCH III In such runs SWAN interpolates the spectral grid of WAM or WAVEWATCH III to the user provided spectral grid of SWAN The WAM Cycle 4 source term in SWAN has been retuned for a highest prognostic frequency that is explicitly computed by SWAN of 1 Hz It is therefore recommended that for cases where wind generation is important and WAM Cycle 4 formulations are chosen the highest prognostic frequency is about 1 Hz In directional space the directional range is the full 360 unless the user specifies a limited directional range This may be convenient less computer time and or memory space for example when waves travel towards a coast within a limited sector of 180 The directional resolution is determined by the number of discrete directions that is provided by the user For wind seas with a directional spreading of typically 30 on either side of the mean wave direction a resolution of 10 seems enough whereas for swell with a direc tional spreading of less than 10 a resolution of 2 or less may be required If the user is confident that no energy will occur outside a certain directional sector or is willing to ignore this amount of energy then the computations by SWAN can be limited to the directional sector that does contain energy This may often be the case of waves propagating to shore within a sector of 180 around some mean wave direction It is recommended to use the following discretizat
58. an coordinates In case of spherical coordinates there is no default the user must give a value geographic location of the origin of the computational grid in the problem coordinate system y coordinate in m See command COORD Default ypc 0 0 Cartesian coordinates In case of spherical coordinates there is no default the user must give a value direction of the positive z axis of the computational grid in degrees Cartesia xlenc ylenc nxc nyc EXCEPTION xexc yexc CIRCLE SECTOR Description of commands 35 convention In 1D mode alpc should be equal to the direction alpinp see command INPGRID Default alpc 0 0 length of the computational grid in z direction in m In case of spherical coordinates xlenc is in degrees length of the computational grid in y direction in m In 1D mode ylenc should be 0 In case of spherical coordinates ylenc is in degrees number of meshes in computational grid in z direction for a uniform recti linear grid or direction for a curvi linear grid this number is one less than the number of grid points in this domain number of meshes in computational grid in y direction for a uniform recti linear grid or rj direction for a curvi linear grid this number is one less than the number of grid points in this domain In 1D mode myc should be 0 only available in the case of a curvi linear grid If certain grid points ar
59. and SETUP For the first SWAN runs it is strongly advised to use the default values of the model coefficients First it should be determined whether or not a certain physical process is relevant to the result If this cannot be decided by means of a simple hand computation one can perform a SWAN computation without and with the physical process included in the computations in the latter case using the standard values chosen in SWAN After it has been established that a certain physical process is important it may be worthwhile to modify coefficients In the case of wind input one may at first try to vary the wind velocity Concerning the bottom friction the best coefficients to vary are the friction coefficient Switching off the depth induced breaking term is usually unwise since this may lead to unacceptably high wave heights near beaches the computed wave heights explode due to shoaling effects 2 8 Time and date notation SWAN can run for dates i e non stationary mode e between the years 0 and 9999 if ISO notation is used in the input recommended or e between the years 1911 and 2010 if two digit code for years is used formats 2 6 in every command that contains moments in time Be careful when nesting SWAN in WAM since WAM does not use ISO notation Chapter 3 Input and output files 3 1 General SWAN is one single computer program The names of the files provided by the user should comply with the rules of
60. as with the abovementioned second command scheme key1 KEY2 data may appear in the command file In the command file e a keyword is closed by a blank or one of the following characters or e a keyword is not enclosed by square brackets or quotes e a keyword followed by a comma is interpreted as a keyword followed by an empty data field see below Required and optional keywords All keywords in a command are required except when an option is available Optional keywords are indicated in the command scheme with the following signs enclosing the keywords concerned KEYiword data 2 lt gt KEY2word data For the above example it may appear as Command syntax 105 KEY2word data KEYiword lt gt KEY3word data In case the user does not indicate an option in a command SWAN chooses the alternative indicated with an arrow gt appearing in the command scheme the default option In the above example it may appear as KEY2word data KEYiword lt gt gt KEY3word data where KEY3WORD is the default option Repetitions of keywords and or other data The use of keywords is sometimes repetitive e g in a sequence of data and keywords containing many locations in x y space In such a case the command scheme indicates this repetitive nature by placing the keywords and data concerned between angle brackets For instance KEYiword data KEY2word data In
61. ault is ISO notation deltnst time interval between fields the unit is indicated in the next option SEC unit seconds MIN unit minutes HR unit hours DAY unit days 4 6 3 Write or plot intermediate results gt IJ lt i j gt TEST itest itrace POINTS lt gt amp XY lt x y gt PAR fname S1D fname S2D fname If SWAN produces unexpected results this optional command can be used to instruct the program to produce intermediate results during a SWAN run test output A TEST command may change between commands in the file to change the level of test output during a SWAN run This change occurs during the execution of the run A TEST command controls the test output Description of commands 93 until the next TEST command Such a next TEST command may have level 0 thus stopping test output itest itrace POINTS IJ i j XY x y PAR 51D fname the level of test output For values under 100 the amount is usually reasonable for values above 200 it can be very large For values of itest up to 50 the test output can be interpreted by the user For higher values of itest the test output can only be interpreted by those who have the program source listing at their disposal Note that for sequential or parallel runs it might be interesting to print the timings both wall clock and CPU times in seconds in the PRINT file for this itest should be set to 1
62. be in the PRINT file prtest unit reference number of the test output file As default prtest is equal to If it is changed to 6 all test output will be written to the screen This is useful if test print output is lost due to abnormal end of the program while information about the reason is expected to be in the test output file gt STATionary gt TWODimensional MODE lt gt lt gt NONSTationary ONEDimensional With this optional command the user indicates that the run will be ei ther stationary or non stationary and one dimensional 1D mode or two dimensional 2D mode Non stationary means either see command COMPUTE a one non stationary computations or b a sequence of stationary computations or c a mix of a and b The default option is STATIONARY TWODIMENSIONAL CARTesian COORDINATES lt gt CCM gt REPeating SPHErical lt QC Description of commands 33 Command to choose between Cartesian and spherical coordinates A nested SWAN run must use the same coordinate system as the coarse grid SWAN run CARTESIAN all locations and distances are in m Coordinates are given with respect to r and y axes chosen by the user in the various commands SPHERICAL all coordinates of locations and geographical grid sizes are given in degrees x is longitude with x 0 being the Greenwich meridian and x gt 0 is East of this meridian y is latitude with y gt 0 being
63. ber of meshes in z direction of the input grid this number is one less than the number of grid points in this direction number of meshes in y direction of the input grid this number is one less than the number of grid points in this direction In 1D mode myinp should be 0 mesh size in x direction of the input grid in m in case of Cartesian coordinates or in degrees if spherical coordinates are used see command COORD mesh size in y direction of the input grid in m in case of Cartesian coordinates or in degrees if spherical coordinates are used see command COORD In 1D mode dyinp may have any value Default dyinp dxinpl For a CURVILINEAR input not fully tested for spherical coordinates mxinp myinp stagrx stagry EXCEPTION number of meshes in direction of the input grid this number is one less than the number of grid points in this direction Default mxinp mxc number of meshes in 7 direction of the input grid this number is one less than the number of grid points in this direction Default myinp myc staggered x direction with respect to computational grid default 0 Note e g stagrx 0 5 means that the grid points are shifted a half step in x direction in many flow models z velocities are defined in points shifted a half step in direction staggered y direction with respect to computational grid default 0 Note
64. bove the results may look realistic but they may locally not be accurate Any change in these scenarios limiters or shortcomings in particular newly discovered coding bugs and their fixes are published on the SWAN web site and implemented in new releases of SWAN 2 4 Relation to WAM WAVEWATCH III and others The basic scientific philosophy of SWAN is identical to that of WAM Cy cle 3 and 4 SWAN is a third generation wave model and it uses the same formulations for the source terms although SWAN uses the adapted code for the DIA technique On the other hand SWAN contains some addi tional formulations primarily for shallow water Moreover the numerical techniques are very different WAVEWATCH III not only uses different nu merical techniques but also different formulations for the wind input and the whitecapping This close similarity can be exploited in the sense that 8 Chapter 2 e scientific findings with one model can be shared with the others and e SWAN can be readily nested in WAM and WAVEWATCH III the formulations of WAVEWATCH III have not yet been implemented in SWAN When SWAN is nested in WAM or WAVEWATCH III it must be noted that the boundary conditions for SWAN provided by WAM or WAVEWATCH III may not be model consistent even if the same physics are used The potential reasons are manifold such as differences in numerical techniques employed and implementation for the geographic area spatial and spectral res
65. compiler 30 May 87 15 30 00 3 as in Lahey compiler 05 30 87 15 30 00 4 15 30 00 5 87 05 30 15 30 00 6 as in WAM 8705301530 This format is installation dependent See Implementation Manual or ask the person who installed SWAN on your computer Default is ISO notation BOTtom WLEVel CURrent READinp lt Description of commands 43 fnamel WInd gt fac lt gt idla amp SERIes fname2 FRiction gt FREe form nhedf nhedt nhedvec lt FORmat lt gt gt idfm UNFormatted With this required command the user controls the reading of values of the in dicated variables from file This command READINP must follow a command INPGRID Note that for each stationary or nonstationary field one combination of INPGRID and READINP suffices if one has more than one COMPUTE command in a run If the variables are in one file then the READINP commands should be given in the same sequence as the sequence in which the variables appear in the file BOTTOM WLEV CURRENT with this option the user indicates that bottom levels m are to be read from file bottom level positive downward relative to an arbitrary horizontal datum level The sign of the input can be changed with option fac 1 see below with this option the user indicates that water levels m are to be read from file water level positive up
66. d from a file option FILE gt sname name of the points xp yp problem coordinates of one output location if Cartesian coordinates are used in m if spherical coordinates are used in degrees see command COORD NGRid sname xpn ypn alpn xlenn ylenn mxn myn CANNOT BE USED IN 1D MODE If the user wishes to carry out nested SWAN run s a separate coarse grid SWAN run is required With this optional command NGRID the user defines in the present coarse grid run a set of output locations along the boundary of the subsequent nested computational grid The set of output locations thus defined is of the type NGRID Command NESTOUT is required after this command NGRID to generate some Description of commands 79 data for the subsequent nested run not with command BLOCK because a set of locations of the type NGRID does not represent a geographic region but only its outline sname xpn ypn alpn xlenn ylenn mxn myn name of the set of output locations along the boundaries of the following nested computational grid defined by this command geographic location of the origin of the computational grid of this coarse grid run in the problem coordinate system x coordinate if Cartesian coordinates are used in m if spherical coordinates are used in degrees see command COORD geographic location of the origin of the computational grid of this coarse grid run in the probl
67. d in the input file any information in the input file beyond this command is ignored Appendix A Definitions of variables In SWAN a number of variables are used in input and output Most of them are related to waves The definitions of these variables are mostly conventional HSIGN HSWELL TMM10 TMO1 Significant wave height denoted as H in meters and defined as H AJ f J E w 0 dud6 where E w 0 is the variance density spectrum and w is the absolute radian frequency determined by the Doppler shifted dispersion relation Significant wave height associated with the low frequency part of the spectrum denoted as H swe in meters and defined as H swell 4 ee ling E w 0 dwd0 with wswell 27 fewen and fowen 0 1 Hz by default this can be changed with the command QUANTITY Mean absolute wave period in s of E w 0 defined as w iE c0 ded oq J S 9 EW 6 dodo opd Lm EX 2m J J E c 0 dcd6 J J F 0 dwde Mean absolute wave period in s of E w 0 defined as E f eB o 0 doao T ff eB w 0 dwao Tmoi 27 J J E e 9 dcd0 2m J E o 6 acdo 97 98 TM02 DIR PDIR TDIR RTMM10 RTMO1 RTP PER Appendix A Mean absolute wave period in s of E w defined as 7 J Ebda TP 2 E o 6 dodoN T Lmoz 20 J E o 0 4od0 2m J E o 6 acdo Mean wave direction in Cartesian or Nautical convention as defined by see Kuik et al 1988 DIR arctan ly
68. d of this list of options as computed will be printed as 1D spectral frequency output The definition of this file is given in Appendix D This output will be made after every iteration in the case of MODE STATIONARY and after every time step in the case MODE NONSTATIONARY see command MODE name of the file to which the output is written default filename SWSRC1D 94 Chapter 4 S2D if the keyword S2D appears variance densities and 6 source terms see end of this list of options as computed will be printed as 2D frequency and directior spectral output The format of this file is defined in Appendix D This output be made after every iteration in the case of MODE STATIONARY and after every time step in the case MODE NONSTATIONARY see command MODE fname name of the file to which the output is written default filename SWSRC2D Note that the keywords PAR S1D and S2D need to be given in that order The source terms written due to the presence of the keyword S1D or S2D are source terms of variance density The 6 source terms are wind input whitecapping bottom friction breaking 3 wave interactions and 4 wave in teractions When a number maxmes of error messages see command SET have been written to the PRINT file the computation will stop If necessary make maxmes larger using command SET and rerun the program 4 7 Lock up STATionary time COMPute lt gt gt Sec gt NONSTat tbegc
69. ded cf50 controls the spectral energy scale of the limit spectrum Default c 50 0 0023 cf60 controls the spectral energy scale of the limit spectrum Default cf60 0 223 JANSsen cdsi1 delta GEN3 lt KOMen cds2 stpm gt AGROW a WESTHuysen With this command the user indicates that SWAN should run in third generation mode for wind input quadruplet interactions and whitecapping Triads bottom friction and depth induced breaking are not activated by this command See the Technical documentation for more information The op tion GEN3 KOMEN is default 60 JANSSEN cds1 delta KOMEN cds2 stpm WESTH AGROW a Chapter 4 linear growth Cavaleri and Malanotte Rizzoli 1981 activated only if the keyword AGROW is present see below exponential growth Janssen 1989 1991 coefficient for determining the rate of whitecapping dissipation C4 5 Default cds1 4 5 coefficient which determines the dependency of the whitecapping on wave num mix with Komen et al formulation Default delta 0 5 linear growth Cavaleri and Malanotte Rizzoli 1981 activated only if the keyword AGROW is present see below exponential growth Komen et al 1984 coefficient for determining the rate of whitecapping dissipation C4 Default cds2 2 36e 5 value of the wave steepness for a Pierson Moskowitz spectrum 32 Default stpm 3 02
70. defines characteristics of sub grid obstacles SETUP activates the computation of the wave induced set up DIFFRAC activates diffraction OFF de activates certain physical processes f Commands for numerics PROP to choose the numerical propagation scheme NUMERIC sets some of the numerical properties of SWAN Description of commands 21 Output commands g Commands for output locations FRAME GROUP CURVE RAY ISOLINE POINTS NGRID defines an output frame a regular grid defines an output group for regular and curvi linear grids defines an output curve defines a set of straight output lines rays defines a depth or bottom contour for output along that contour defines a set of individual output points defines a nested grid h Commands to write or plot output quantities QUANTITY OUTPUT BLOCK TABLE SPECOUT NESTOUT defines properties of output quantities influence format of block table and or spectral output requests a block output geographic distribution requests a table output set of locations requests a spectral output requests a spectral output for subsequent nested computations i Commands to write or plot intermediate results TEST requests an output of intermediate results for testing purposes Lock up commands j Commands to lock up the input file COMPUTE HOTFILE STOP starts a computation stores results for subsequent SWAN run end of user s input 28 Chapter 4 4
71. deltc lt MIn gt tendc HR DAy This command orders SWAN to start the computation s If the SWAN mode is stationary see command MODE then only the com mand COMPUTE should be given here no options If the SWAN mode is non stationary see command MODE then the compu tation can be e cither stationary at the specified time option STATIONARY here or e non stationary over the specified period of time tbegc etc Description of commands 95 To verify input to SWAN e g all input fields such as water depth wind fields etc SWAN can be run without computations that is zero iterations by using command NUM ACCUR MXITST 0 In the case MODE NONSTATIONARY several commands COMPUTE can appear where the wave state at the end of one computation is used as initial state for the next one unless a command INIT appears in between the two COMPUTE commands This enables the user to make a stationary computation to ob tain the initial state for a non stationary computation and or to change the computational time step during a computation to change a boundary con dition etc This also has the advantage of not using a hotfile since it can be very large in size STATIONARY time NONSTATION tbegc deltc tendc a stationary computation is to be made time level for which the stationary run is to be made the format is 1 ISO notation 19870530 153000 2 as in HP compiler 30 May 87
72. ds GEN1 GEN2 or GEN3 lactive by default can be deactivated with command OFF General definitions and remarks 21 Table 2 1 Overview of physical processes and generation mode in SWAN process authors generation mode 1st 2nd 3rd Linear wind growth Cavaleri and Malanotte Rizzoli 1981 x x modified Cavaleri and Malanotte Rizzoli 1981 x Exponential wind growth Snyder et al 1981 modified x x Snyder et al 1981 x Janssen 1989 1991 x Whitecapping Holthuijsen and De Boer 1988 x X Komen et al 1984 x Janssen 1991 x Quadruplets Hasselmann et al 1985 x Triads Eldeberky 1996 x x x Depth induced breaking Battjes and Janssen 1978 x x x Bottom friction JONSWAP 1973 x x x Collins 1972 x x x Madsen et al 1988 x x X Obstacle transmission Seelig 1979 x x x Wave induced set up x x x Whitecapping is activated by commands GEN1 GEN2 or GEN3 Quadruplets is activated by command GEN3 Triads is activated by command TRIAD Bottom friction is activated by command FRICTION Depth induced breaking is activated by command BREAKING Obstacle transmission is activated by command OBSTACLES active by default can be deactivated with command OFF 3 active by default can be deactivated with command OFF 4active by default can be deactivated with command OFF 22 Chapter 2 e Wave induced set up is activated by comm
73. e 3 nonlinear saturation based whitecapping combined with wind input of Yan 19 if this keyword is used the wave growth term of Cavaleri and Malanotte 1981 activated if this keyword is NOT used the wave growth term of Cavaleri and Malanotte is NOT activated Note that in non stationary runs SWAN start with INIT ZERO see command wave energy remains zero unless wave energy penetrates over the boundary or is activated In case of stationary runs however SWAN will start with a first if the wave growth term of Cavaleri and Malanotte 1981 is activated a is the proportionality coefficient in that term Default a 0 0015 WCAPping CSM cst pow With this command the user wants to choose the Cumulative Steepness Method CSM for approximating whitecapping see Technical documen tation and not the formulation of Komen et al 1984 and not Janssen 1991a cst the tuneable coefficient C s pow Description of commands 61 Default cst 4 0 power m Default pow 2 0 Note that the CSM method in SWAN is still in its experimental phase Its results are promising but the method still suffers some numerical problems QUADrupl iquad lambda Cn14 Csh1 Csh2 Csh3 With this option the user can influence the computation of nonlinear quadru plet wave interactions Default the quadruplets are included in the compu tations Can be de activated with command OFF QUAD Note that the DIA approximat
74. e g stagry 0 5 means that the grid points are shifted a half step in i direction in many flow models y velocities are defined in points shifted a half step in y direction if land points remain dry during the computations no flooding then these points can be ignored during the computations saving computer time and memory To do this give bottom level values in these 42 excval NONSTATION tbeginp deltinp tendinp Chapter 4 grid points that are equal to excval NOT FOR 1D MODE exception value required if this option EXCEPTION is used see option EXCEPTII For parallel runs using MPI this exception value should be prescribed in order to have a good load balancing the variable is non stationary given in a time sequence of fields NOT FOR 1D MODE begin time of the first field of the variable the format is 1 ISO notation 19870530 153000 2 as in HP compiler 30 May 87 15 30 00 3 as in Lahey compiler 05 30 87 15 30 00 ANS 15 30 00 5 87 05 30 15 30 00 6 asin WAM 8705301530 This format is installation dependent See Implementation Manual or ask the person who installed SWAN on your computer Default is ISO notation time interval between fields the unit is indicated in the next option SEC unit seconds MIN unit minutes HR unit hours DAY unit days end time of the last field of the variable the format is 1 ISO notation 19870530 153000 2 as in HP
75. e problem coordinates system Note that in case of spherical coordinates the zc and xp axes both point East READgrid COORdinates fac fname idla nhedf nhedvec amp gt FREe form lt FORmat lt gt gt idfm 38 Chapter 4 UNFormatted With this command required if the computational grid is curvi linear not allowed for a regular grid the user controls the reading of the coordinates of the computational grid points These coordinates must be read from a file as a vector x coordinate y coordinate of each single grid point This command READGRID must follow a command CGRID CURVILINEAR See command READINP for the description of the options in this command READGRID This command cannot be used in 1D mode SWAN will check whether all angles in the grid are gt 0 and lt 180 degrees If not it will print an error message giving the coordinates of the grid points involved It is recommended to use grids with angles between 45 and 135 degrees 4 5 2 Input grids and data BOTtom WLEVel CURrent lt I VX VY INPgrid lt gt FRiction WInd lt WX WY gt REGular xpinp ypinp alpinp mxinp myinp dxinp dyinp lt CURVilinear stagrx stagry mxinp myinp Description of commands 39 EXCeption excval amp gt Sec NONSTATionary tbeginp deltinp
76. e second derivative or curvature of the iteration curve of the significant wave height As the solution of a simulation approaches full convergence the curvature of the iteration curve will tend to zero SWAN stops the process if the absolute change in the local significant wave height H from one iteration to the next is less than dabs or the relative change in the local significant wave height from one iteration to the next is less than drel and the curvature of the iteration curve of H normalized with H is less than curvat Default dabs 0 00 Default dre1 0 02 Default dhoval 0 02 Default dtoval 0 02 Default curvat 0 005 Default npnts 98 the maximum number of iterations in a stationary computation the maximum number of iterations for stationary computations The computation stops when this number is exceeded Default mxitst 15 Note that mxitst can be set to 0 if one wants to check the input to the model without making computations proportionality constant used in the frequency dependent under relaxation technique Default alfa 0 00 NOT MEANINGFUL FOR NONSTATIONARY COMPUTATIONS the maximum number of iterations per time step in a non stationary computation the maximum number of iterations per time step for non stationary computations The computation moves to the next time step when this number is exceeded Default mxitns 1 Note that mxitns can be set to 0
77. e to be ignored during the computations e g land points that remain dry i e no flooding saving computer time and memory then this can be indicated by identifying these grid points in the file containing the grid point coordinates see command READGRID For an alternative see command INPGRID BOTTOM the value which the user uses to indicate that a grid point is to be ignored in the computations this value is provided by the user at the location of the x coordinate considered in the file of the x coordinates see command READGRID Required if this option EXCEPTION is used the value which the user uses to indicate that a grid point is to be ignored in the computations this value is provided by the user at the location of the y coordinate considered in the file of the y coordinates see command READGRID Required if this option EXCEPTION is used Default yexc xexc this option indicates that the spectral directions cover the full circle This option is default this option means that only spectral wave directions in a limited directional sector are considered the range of this sector is given by diri and dir2 It must be noted that if the quadruplet interactions are to be computed see command GEN3 then the SECTOR should be 30 wider on each side than the directional sector occupied by the spectrum everywhere in the computational grid If not then these computations are inaccurate If the directional distribut
78. e value for power given for PER affects also the value of RPER the power for WLEN is independent of that of PER or RPER 82 ref fswell Chapter 4 Default power 1 reference time used for the quantity TSEC Default value starting time of the first computation except in cases where this is later than the time of the earliest input In these cases the time of the earliest input is used upper limit of frequency range used for computing the quantity HSWELL see Appendix A Default fswell 0 1 Hz PROBLEMCOORD vector components are relative to the z and y axes of the problem FRAME Examples QUANTITY QUANTITY QUANTITY QUANTITY QUANTITY coordinate system see command COORD directions are counter clock wise relative to the positive x axis of the problem coordinate system if Cartesian direction convention is used see command SET directions are relative to North clockwise if Nautical direction convention is used see command SET If output is requested on sets created by command FRAME or automatically COMPGRID or BOTTGRID vector components are relative to the z and y axes of the frame coordinate system see command COORD directions are counter clock wise relative to the positive z axis of the frame coordinate system if Cartesian direction convention is used see command SET directions are relative to North clockwise if Nautical direction convention is used
79. ea The spatial resolution of the computational grid should be sufficient to re General definitions and remarks 15 yp axis PA mean wave direction 2 Q non zero wave boundary 2 wave direction Figure 2 1 Disturbed regions in the computational grid due to erroneous boundary conditions are indicated with shaded areas Xp axis solve relevant details of the wave field Usually a good choice is to take the resolution of the computational grid approximately equal to that of the input bottom current grid SWAN may not use the entire user provided computational grid if the user defines exception values on the depth grid see command INPGRID BOTTOM or on the curvi linear computational grid see command CGRID In such a case a computational grid point is either e wet ie the grid point is included in the computations since it repre sents water this may vary with time dependent or wave induced water levels or e dry ie the grid point is excluded from the computations since it represents land which may vary with time dependent or wave induced water levels or e exceptional i e the grid point is permanently excluded from the com putations since it is so defined by the user 16 Chapter 2 If exceptional grid points occur in the computational grid then SWAN filters the entire computational grid as follows e each grid line between two adjacent wet computational grid points a wet link without
80. ead in free format i e with at least a blank or comma between numbers Note that the format of time and date that can be accepted by SWAN is YYMMDDHHMMSS i e include seconds fname UNFORMATTED CRAY WKSTAT FREE xgc ygc BOUNdnest3 Description of commands 55 a file name that contains all the names of WAM files containing the nested boundary conditions in time sequence usually one file per day For example the contents of fname can look like CBO9212010000 CBO9212020000 CBO9212030000 SWAN will read the boundary data from these WAM files one after the other the user indicates that the WAM files are binary input will be read from file created by the CRAY version of WAM input will be read from file created by the WORKSTATION version of WAM the user indicates that the WAM files can be read with free format these files are not generated standard by WAM if SWAN is used with Cartesian coordinates longitude of south west corner of SWAN computational grid in degrees if the south west corner of the nest in the WAM computation is on land this value is required If SWAN is used with spherical coordinates then xgc is ignored by SWAN Default the location of the first spectrum encountered in the nest file if SWAN is used with Cartesian coordinates longitude of south west corner of SWAN computational grid in degrees if the south west corner of the nest in the WAM computation is on land this v
81. ead of the default Cartesian convention For definition see Section 2 5 or Appendix A indicates that the Cartesian convention for wind and wave direction SWAN input and output will be used For definition see Section 2 5 or Appendix A power of high frequency tail defines the shape of the spectral tail above the highest prognostic frequency fhigh see command CGRID The energy density is assumed to be proportional to frequency to the power pwtail Default values depend on formulations of physics command GEN1 pwtail 5 command GEN2 pwtail 5 command GEN3 KOMEN pwtail 4 command GEN3 JANSEN pwtail 5 If the user wishes to use another value then this SET command should be 32 Chapter 4 located in the command file after the GEN1 GEN 2 or GEN3 command these will override the SET command with respect to pwtail froudmax is the maximum Froude number U 4 gd with U the current and d the water d The currents taken from a circulation model may mismatch with given water d in the sense that the Froude number becomes larger than 1 For this the curre velocities will be maximized by Froude number times ygd Default froudmax 0 8 printf unit reference number of the PRINT file As default printf is equal to 4 If it is changed to 6 all print output will be written to the screen This is useful if print output is lost due to abnormal end of the program while information about the reason is expected to
82. earance of the table the filename determines the destination of the data sname HEADer NOHEADer INDexed fname OUTPUT tbegtb1 name of the set of POINTS CURVE FRAME or GROUP output is written in fixed format to file with headers giving name of variable and unit per column A disadvantage of this option is that the data are written in fixed format numbers too large to be written will be shown as Number of header lines is 4 output is written in floating point format to file and has no headers it is intended primarily for processing by other programs With some spreadsheet programs however the HEADER option works better a table on file is produced which can be used directly without editing as input to ARCVIEW ARCINFO etc The user should give two TABLE commands one to produce one file with XP and YP as output quantities the other with HS RTMO1 or other output quantities such as one wishes to process in ARCVIEW or ARCINFO The first column of each file produced by SWAN with this command is the sequence number of the output point The last line of each file is the word END name of the data file where the output is to be written to Default for option HEADER is output to the PRINT file In case of NOHEADER the filename is required the output parameters are the same as given in command BLOCK the user requests output at various times If the user does not use this option the program will give
83. ees see command COORD int number of subdivisions between the previous master ray and the following master ray defined by the following data number of subdivisions is one more than the number of interpolated rays xp yp problem coordinates of the begin and end points of each subsequent master ray xq yq if Cartesian coordinates are used in m if spherical coordinates are used in degrees see command COORD gt DEPth ISOline sname rname lt gt dep BOTtom CANNOT BE USED IN 1D MODE With this optional command the user defines a set of output locations along one depth or bottom level contour line in combination with command RAY 78 Chapter 4 gt sname name of the set of output locations defined by this command rname name of the set of rays as defined in command RAY dep the depth in m of the depth contour line along which output locations are generated by SWAN If the keyword DEPTH appears in front of the value the true depth is used if the keyword BOTTOM appears the water level is ignored ie the depth with respect to datum level is used The set of output locations along the depth contour lines created with this command is of the type CURVE lt xp yp gt POINts sname lt gt FILE fname With this optional command the user defines a set of individual output lo cations points The coordinates of these points are given in the command itself or rea
84. em coordinate system y coordinate if Cartesian coordinates are used in m if spherical coordinates are used in degrees see command COORD direction of the positive r axis of the computational grid of this coarse grid run in degrees Cartesian convention length in the z direction of the nested grid if Cartesian coordinates are used in m if spherical coordinates are used in degrees see command COORD length in the y direction of the nested grid if Cartesian coordinates are used in m if spherical coordinates are used in degrees see command COORD number of meshes of the output grid in the z direction of this grid this number is one less than the number of grid points in this direction mxn does not have to be equal to the number of meshes in the nested computation SWAN will interpolate the required information Default mxn is chosen such that the mesh size of the output grid is roughly equal to the mesh size of the coarse grid but at least 1 number of meshes of the output grid in the y direction of this grid this number is one less than the number of grid points in this direction myn does not have to be equal to the number of meshes in the nested computation SWAN will interpolate the required information Default myn is chosen such that the mesh size of the output grid is roughly equal to the mesh size of the coarse grid but at least 1 80 Chapter 4 4 6 2 Write or plot computed quanti
85. eriod in s mean relative wave period in s mean absolute wave period in s mean relative wave period in s mean absolute zero crossing period in s FSPR DSPR DEPTH WATLEV BOTLEV VEL FRCOEF WIND DISSIP QB TRANSP FORCE UBOT URMS TMBOT WLEN STEEPNESS DHSIGN DRTMO1 LEAK XP YP DIST Description of commands 87 the normalized width of the frequency spectrum directional spreading of the waves in degrees water depth in m not the bottom level water level in m bottom level in m current velocity in m s friction coefficient equal to cfw or kn in command FRICTION wind velocity in m s energy dissipation due to bottom friction wave breaking and whitecapping in W m or m s depending on command SET fraction of breaking waves due to depth induced breaking transport of energy vector W m or m s depending on command SET wave induced force per unit surface area vector in N m the rms value of the maxima of the orbital velocity near the bottom in m s Output only if command FRICTION is used If one wants to output UBOT but friction is to be neglected in the computations then one should use the command FRICTION with the value of the friction set at zero FRICTION COLLINS 0 the rms value of the of the orbital velocity near the bottom in m s If one wants to output URMS but friction is to be neglected in the computations then one should use the comma
86. es of the WAM nest and the boundaries of the SWAN computational area should be nearly identical see below The spectral frequencies and directions of the coarse grid run do not have to coincide with the frequencies and directions used in the nested SWAN run as defined in the CGRID command SWAN will interpolate to these frequencies and directions in the nested run see Section 2 6 3 Note that SWAN will accept output of a WAM output location only if the SWAN grid point on the nest boundary lies within a rectangle between two consecutive WAM output locations with a width equal to 0 1 times the dis tance between these output locations on either side of the line between these WAM output locations This BOUNDNEST command is not available for 1D computations A nested SWAN run may use either Cartesian or spherical coordinates A curvi linear grid may be used in the nested grid but the boundaries of this nest should conform to the rectangular course grid nest boundaries WAM output files are unformatted binary this usually implies that WAM and SWAN have to run on the same computer For those cases where WAM and SWAN run on different types of machines binary files do not transfer properly the option FREE is available in this command The distributed version of WAM does not support the required free format nesting output WAM users who modify WAM such that it can make formatted output must modify WAM such that the files made by WAM can be r
87. f breakers in expression of Battjes and Janssen 1978 Energy transport with components P pg f f c E c 0 dod0 and P pg J f c E c 0 dad0 with x and y the problem coordinate system except in the case of output with BLOCK command in combination with command FRAME where x and y relate to the z axis and y axis of the output frame Current velocity components in x and y direction of the problem coordinate system except in the case of output with BLOCK command in combination with command FRAME where x and y relate to the x axis and y axis of the output frame Wind velocity components in x and y direction of the problem coordinate sytem except in the case of output with BLOCK command in combination with command FRAME where x and y relate to the z axis and y axis of the output frame Wave induced force per unit surface area gradient of radiation stresses with x and y the problem coordinate system except in the case of output with BLOCK command in combination with command FRAME where x and y relate to the x axis and y axis of the output frame F Ox Oy _ Sys _ Syy Fy Ox Oy where S is the radiation stress tensor as given by 4 pg n cos 0 n 1 Edod0 Sry Sy pg J nsin0 cos 0Edod0 Syy pg J nsin 0 n 1 Edod0 and n is the group velocity over the phase velocity Root mean square value in m s of the orbital motion near the bottom Ums VLU S Root mean square value in m s
88. file identification of the computer sys tem on which SWAN is run In addition SWAN does not permit file names longer than 36 characters Moreover the maximum length of the lines in the input files for SWAN is 120 positions The user should provide SWAN with a number of files input files with the following information e a file containing the instructions of the user to SWAN the command file e file s containing bottom current friction and wind if relevant and e file s containing the wave field at the model boundaries if relevant 3 2 Input output facilities To assist in making the command file an edit file is available to the user see Appendix C In its original form this file consists only of comments all lines begin with exclamation mark In the file all commands as given in this User Manual Chapter 4 are reproduced as mnemonics for making the final command file Hence the user does not need to consult the User Manual every time to check the correct spelling of keywords order of data etc The 23 24 Chapter 3 user is advised to first copy the edit file the copy file should have a different name and then start typing commands between the comment lines of the edit file SWAN is fairly flexible with respect to output processing Output is avail able for many different wave parameters and wave related parameters e g wave induced stresses and bottom orbital motion However the general rule is
89. followed by an sign and the number not between square brackets SWAN interprets the copied name in the command file as a keyword with all the characteristics of a keyword such as ending a sequence of optional data see below As with other keywords the name of the variable is case insensitive Example command scheme KEYword nnn command file KEY nnn 314 Required data and optional data All data must be given by the user in the command file in the same order as they appear in the command scheme They are separated by blanks or comma s Required data indicated in the description of each individual command must be given explicitly as character string or numbers Optional data are indicated a in the text of each individual command or 108 Appendix B b for sets of data in parenthesis around the data concerned data For example KEYiword KEY2word name nnn mmm zzz or c some optional data are indicate in the same way as optional keywords are indicated Optional data of the kind a or b may be omitted by giving blanks be tween comma s SWAN then substitutes reasonable default values If after a required datum all data is optional till the next keyword or the next end of line then the comma s may be omitted too Optional data of the kind c are to be treated in the same way as optional keywords B 3 Command file and comments All text after one or between two signs on one l
90. frequency resolution It seems to work reasonably in many cases but it is a poor approximation for frequency resolutions with ratios very different from 10 see command CGRID This is a fundamental problem that SWAN shares with other third generation wave models such as WAM and WAVE WATCH III SWAN can be used on any scale relevant for wind generated surface gravity waves However SWAN is specifically designed for coastal applications that should actually not require such flexibility in scale The reasons for providing SWAN with such flexibility are e to allow SWAN to be used from laboratory conditions to shelf seas and e to nest SWAN in the WAM model or the WAVEWATCH III model which are formulated in terms of spherical coordinates Nevertheless these facilities are not meant to support the use of SWAN on oceanic scales because SWAN is less efficient on oceanic scales than WAVE WATCH III and probably also less efficient than WAM 2 3 Internal scenarios limiters shortcomings and coding bugs Sometimes the user input to SWAN is such that SWAN produces unreli able and sometimes even unrealistic results This may be the case if the bathymetry or the wave field is not well resolved Be aware here that the grid on which the computations are performed interpolates from the grids on which the input is provided different resolutions for these grids which are allowed can therefore create unexpected interpolation patterns on the com putati
91. given in Figure 2 1 For this reason the lateral boundaries should be sufficiently far away from the area of interest to avoid the propagation of this error into this area Such problems do not occur if the lateral boundaries contain proper wave information over their entire length e g obtained from a previous SWAN computation or if the lateral boundaries are coast When output is requested along a boundary of the computational grid it may occur that this output differs from the boundary conditions that are im posed by the user The reason is that SWAN accepts only the user imposed incoming wave components and that it replaces the user imposed outgoing wave components with computed outgoing components propagating to the boundary from the interior region Moreover SWAN has an option to only compute within a pre set directional sector pre set by the user Wave com ponents outside this sector are totally ignored by SWAN no replacements either The user is informed by means of a WARNING in the output when the computed significant wave height differs more than 10 say 10 is default from the user imposed significant wave height command BOUND The actual value of this difference can be set by the user see the SET com mand If the computational grid extends outside the input grid the reader is re ferred to Section 2 6 to find the assumptions of SWAN on depth current water level wind bottom friction in the non overlapping ar
92. iction 0 lt Kdif lt 1 with this required keyword the user defines the location of the obstacle s coordinates of a corner point of the line that defines the location of the obstacle s in problem coordinates if Cartesian coordinates are used in m or if spherical coordinates are used in degrees see command COORD At least two corner points must be provided SETUP supcor If this optional command is given the wave induced set up is computed and accounted for in the wave computations during the computation it is added to the depth that is obtained from the READ BOTTOM and READ WLEVEL commands Note that set up is not computed correctly with spherical coor dinates Note that set up is not supported in case of parallel runs using MPI and aslo not tested with OpenMP supcor by default the wave induced set up is computed with a constant added such that the set up is zero in the deepest point in the computational grid The user can modify this constant by the value of supcor The user can thus impose a set up in any one point and only one in the computational grid by first running SWAN then reading the set up in that point and adding or subtracting the required value of supcor in m positive if the set up has to rise Default supcor 0 DIFFRACtion idiffr smpar smnum cgmod If this optional command is given the diffraction is included in the wave computation 68 Chapter 4 idiffr indicates the
93. ies in table variance densities in m2 Hz degr unit exception value 122 0 675611E 06 51 129 273 665 1302 2328 3365 3426 2027 672 n e urs OOOooo0ooo0oocoo coOO OoO ON 242 610 1287 3152 6159 10989 15922 16230 9612 3178 479 11 o OOo ooo ooooococo 574 1443 3054 7463 14608 26020 37712 38440 22730 7538 1135 N O o0o0o0o000000000O O 956 Appendix D 1288 1482 1481 1286 2402 3238 3725 3724 3234 5084 6846 7872 7869 6837 12402 24275 43341 62733 63939 37790 12535 16712 32688 58358 84492 86109 50909 16892 19229 37618 67109 97150 99010 58529 19440 19221 37603 67080 97110 98969 58505 19432 16690 32644 58281 84380 85995 50841 16870 1890 2542 2924 2923 2539 D w o0oo0o0o00000000Ore O1 N o0oo0o0o00000000Ore o o o0Oo0o0o00000000OO re o o OOo o ooooocoococococonuc ol OOo o ooooocoococococonuc 957 579 2406 1454 5091 3076 12419 7518 24309 14716 43401 26213 62820 37991 64027 38724 37843 22898 12552 7594 1892 1144 NN w N O 0o0o0o00000000Ore o0oo0o0o00000000O0O 244 613 1295 3172 6198 11058 16021 16331 9672 3198 482 11 o o0oo0oo0o0o000000O 0O O Note that the true variance or energy densities are obtained by multiplying each number with the factor given under the keyword FACTOR Formal description of the 1D and 2D spectral file This description refers to either write
94. if one wants to check the input to the model without making computations determines in both stationary and non stationary runs the maximum change per iteration of the energy density per spectral o bin given in terms of a fraction of the omni directional Phillips level see Technical documentation zl in case of ACCUR and drel 0 01 in case of STOPC 72 DIRIMPL cdd cdlim SIGIMPL SETUP css eps2 outp Chapter 4 Default limiter 0 1 this option is used to influence the numerical scheme for refraction A value of cdd 0 corresponds to a central scheme and has the largest accuracy diffusion z 0 but the computation may more easily generate spurious fluctuations A value of cdd 1 corresponds to an first order upwind scheme and it is more diffusive and therefore preferable if strong gradients in depth or current are present Default cdd 0 5 If the spatial discretization of the bathymetry or the flow currents is too coarse the waves may turn too far more than 90 degrees say over one spatial grid st The computational results will then be very inaccurate In such a case SWAN limit the maximum turning of the waves over one spatial grid to 90 degrees to obtain robust but not necessarily correct results cdlim lt 0 then no limiter is used this is default cdlim 0 refraction is off same effect as command OFF REFRAC cdlim 4 waves turning limited to about 9
95. ig msc 111 g 112 Appendix C INPgrid GRID amp BOTtom WLEVel CURrent VX VY FRiction WInd WX WY amp REG xpinp ypinp alpinp mxinp myinp dxinp dyinp lt gt amp CURVilinear stagrx stagry mxinp myinp NONSTATionary tbeginp deltinp SECIMINIHRIDAY tendinp READinp BOTtom WLevel CURrent FRiction WInd COORdinates amp fac fnamei1 X SERIES fname2 idla nhedf nhedt nhedvec amp FREE FORMAT form idfm UNFORMATTED WIND vel dir l l l l l l l l l l l l l l l l l JONswap gamma BOUNd SHAPespec PM lt GAUSs sigfr gt PEAK MEAN DSPR_ POWerlDEGRe BIN l l l l l l l l l l l l l l l l l gt SIDE North NW West SW South SE East NE CCWICLOCKWise BOUNdspec lt SEGment gt XY lt x y gt IJ lt i j gt UNIForm PAR hs per dir dd lt FILE fname seq XV VARiable PAR lt len hs per dir dd gt FILE lt len fname seq gt BOUNdnesti NEST fname CLOSed OPEN BOUNdnest2 WAMNest fname UNFormatted CRAY WKstat FREE xgcl L ygc BOUNdnest3 WWIII fname CLOSed OPEN xgc ygc File swan edt 113 gt DEFault INITial lt ZERO GEN1 GEN2 GEN3 lt WCAP lt PAR hs per dir dd HOTStart fname cf10 cf20 cf30 cf40 edmlpm cdrag umi
96. in shallow water in the SWAN model If this command is not used SWAN will account for wave breaking anyhow with default options and values If the user wants to specifically ignore wave breaking he should use the command OFF BREAKING CONSTANT indicates that a constant breaker parameter is to be used alpha proportionality coefficient of the rate of dissipation Default alpha 1 0 gamma the ratio of maximum individual wave height over depth Default gamma 0 73 gt JONswap cfjon FRICTION COLLins cfw MADsen kn With this optional command the user can activate bottom friction If this command is not used SWAN will not account for bottom friction In SWAN three different formulations are available i e that of Hasselmann et al 1973 JONSWAP Collins 1972 and Madsen et al 1988 The default option is JONSWAP JONSWAP cf jon COLLINS cfw MADSEN kn Description of commands 63 indicates that the semi empirical expression derived from the JONSWAP results for bottom friction dissipation Hasselmann et al 1973 JONSWAP should be activated This option is default coefficient of the JONSWAP formulation cfjon is equal to 0 038m s for swell conditions Hasselmann et al 1973 and equal to 0 067 m s for wind sea conditions Default cf jon 0 067 indicates that the expression of Collins 1972 should be activated Collins bottom friction coefficient
97. ine in the command file is ignored by SWAN as comment Such comments may be important to the user e g to clarify the meaning of the commands used In fact this option has been used to create the edit file swan edt see Appendix C Anything appearing after two signs is not interpreted as comment but again as data to be processed possibly interrupted again by or two signs Since version 40 20 the exclamation mark can be used as comment sign Everthing behind a is interpreted as comment also if or are in that part of the input line Command syntax 109 B 4 End of line or continuation A command in the command file may be continued on the next line if the previous line terminates with a continuation mark amp or _ underscore 110 Appendix B Appendix C File swan edt Below the file swan edt is presented in which all the commands that can be used with SWAN are specified PROJECT name nr title1 title2 title3 SET level nor depmin maxmes maxerr grav rho inrhog hsrerr CARTesian NAUTical pwtail froudmax printf prtest DYNAMIC ONEDimensional COORDinates gt CARTesian NV REPeating X SPHErical CCMIQC CGRID REGular xpc ypc alpc xlenc ylenc mxc myc CURVilinear mxc myc excval CIRcle MODE STATIONARY TWODimensional X SECtor diri dir2 mdc flow fh
98. ion in SWAN for applica tions in coastal areas direction resolution for wind sea A 15 10 direction resolution for swell A0 5 2 frequency range 0 04 lt f lt 1 00 Hz spatial resolution Az Ay 50 1000 m The numerical schemes in the SWAN model require a minimum number of discrete grid points in each spatial directions of 2 The minimum number of directional bins is 3 per directional quadrant and the minimum number of frequencies should be 4 General definitions and remarks 19 Interpolation of spectra The interpolation of spectra in SWAN both in space and time is a slight modification of the procedure used in WAM This procedure is not a simple spectral bin by bin interpolation because that would cause reduction of the spectral peak if the peaks of the original spectra do not coincide It is an interpolation where the spectra are first normalized by average frequency and direction then interpolated and then transformed back The average frequencies of the two origin spectra are determined using the frequency moments of the spectra mi f N o 0 a dod0 with i 1 2 the two origin spectra and k 0 1 the zero and first frequency moments of these spectra Then F m 1 m 9 The average frequency for the interpolated spectrum is calculated as amp wm wom wimi o wom o where w is the relative distance in space or time from the interpolated spectrum to the first origin spectrum N i c 0 a
99. ion of the spectrum is symmetric around the centre of the SECTOR then the computed quadruplet wave wave interactions are effectively zero in the 30 range on either end of the SECTOR The problem can be avoided by not activating 36 diri dir2 mdc flow fhigh msc Chapter 4 the quadruplet wave wave interactions use command GEN1 or GEN2 or if activated with command GEN3 by subsequently de activating them with command OFF QUAD the direction of the right hand boundary of the sector when looking outward fr the sector required for option SECTOR in degrees the direction of the left hand boundary of the sector when looking outward fro the sector required for option SECTOR in degrees number of meshes in 0 space In the case of CIRCLE this is the number of subdivisions of the 360 degrees of a circle so A0 360 madc is the spectra directional resolution In the case of SECTOR A0 dir2 dir1 mdc The minimum number of directional bins is 3 per directional quadrant lowest discrete frequency that is used in the calculation in Hz highest discrete frequency that is used in the calculation in Hz one less than the number of frequencies This defines the grid resolution in frequency space between the lowest discrete frequency flow and the highe discrete frequency fhigh This resolution is not constant since the frequenc are distributed logarithmical f yf with y is a constant
100. ion of the quadruplet interactions is a poor approximation for long crested waves and frequency resolutions very different from 1096 see command CGRID iquad lambda Cn14 Csh1 Csh2 the quadruplets can be integrated by four different numerical procedures semi implicit computation of the nonlinear transfer with DIA per sweep 2 fully explicit computation of the nonlinear transfer with DIA per sweep 3 fully explicit computation of the nonlinear transfer with DIA per iteration 8 fully explicit computation of the nonlinear transfer with DIA per iteration but neighbouring interactions are interpolated in piecewise constant manner other techniques for the computation of quadruplets are 4 Multiple DIA 6 FD RIAM 51 XNL deep water transfer 52 XNL deep water transfer with WAM depth scaling 53 XNL finite depth transfer Default iquad 2 coefficient for quadruplet configuration in case of DIA Default 1ambda 0 25 proportionality coefficient for quadruplet interactions in case of DIA Default Cn14 3 x 10 coefficient for shallow water scaling in case of DIA Default Csh1 5 5 coefficient for shallow water scaling in case of DIA 62 Chapter 4 Default Csh2 6 7 Csh3 coefficient for shallow water scaling in case of DIA Default Csh3 1 25 BREaking CONSTANT alpha gamma With this command the user can influence depth induced wave breaking
101. ith this optional command the user indicates that one or more spatial distributions should be written to a file sname HEADER NOHEADER fname LAY OUT name of frame or group see commands FRAME or GROUP with this option the user indicates that the output should be written to a file with header lines The text of the header indicates run identification see command PROJECT time frame name or group name sname variable and unit The number of header lines is 8 with this option the user indicates that the output should be written to a file without header lines name of the data file where the output is to be written to Default for option HEADER is the PRINT file In case of NOHEADER the filename is required Note that when the extension is mat a binary MATLAB file will be generated automatically This file requires less space on your computer and can be loaded in MATLAB much faster than ASCII file with this option the user can prescribe the lay out of the output to file with the value of idla 86 idla Chapter 4 see command READINP options are idla 1 3 4 Option 4 is recommende for postprocessing by MATLAB however in case of a generated binary MATL file option 3 is recommended Default idla 1 For definitions of the output quantities see Appendix A Note that the wave parameters in the output of SWAN are computed from the wave spectrum over the prognostic part of
102. iving the format number idfm or the format string form a user specified format string according to Fortran convention e g 10X 12F5 0 Format according to BODKAR convention a standard of the Ministry of Transport and Public Works in the Netherlands Format string 10X 12F5 0 Format 16F5 0 i e an input line consists of 16 fields of 5 places each Format 12F6 0 i e an input line consists of 12 fields of 6 places each Format 10F8 0 i e an input line consists of 10 fields of 8 places each is a form of reading without conversion binary files Not recommended for ordinary use If the file does not contain a sufficient number of data i e less than the number of grid points of the input grid SWAN will write an error message to the PRINT file and if itest gt 0 see command TEST it will reproduce the data in the PRINT file using the lay out according to idla 1 This echo of the data to print file is also made if the READINP command is embedded between two TEST commands in the command file as follows TEST 120 READINP TEST O Description of commands 47 WIND vel dir With this optional command the user indicates that the wind is constant vel wind velocity at 10 m elevation m s dir wind direction at 10 m elevation in degrees Cartesian or Nautical convention see command SET Both quantities are required if this command is used Note that SWAN converts Uio to U
103. l grid points of a curvi linear grid are relative to the problem coordinate system 2 6 Choice of grids time windows and bound ary initial first guess conditions 2 6 1 Introduction Several types of grids and time window s need to be defined a spec tral grid b spatial geographic grids and time window s in case of non stationary computations The spectral grid that need to be defined by the user is a computational spectral grid on which SWAN performs the computations 10 Chapter 2 SWAN has the option to make computations that can be nested in coarse SWAN WAM or WAVEWATCH III In such cases the spectral grid need not be equal to the spectral grid in the coarse SWAN WAM or WAVE WATCH III run The spatial grids that need to be defined by the user are if required e a computational spatial grid on which SWAN performs the computa tions e one or more spatial input grid s for the bottom current field water level bottom friction and wind each input grid may differ from the others and e one or more spatial output grid s on which the user requires output of SWAN The wind and bottom friction do not require a grid if they are uniform over the area of interest For one dimensional situations ie O Oy 0 SWAN can be run in 1D mode If a uniform rectangular computational spatial grid is chosen in SWAN then all input and output grids must be uniform and rectangular too but they may all be
104. l spreading or directional standard deviation in defined as DSPR 18 f 2sin 955 D 9 d0 and computed as conventionally for pitch and roll buoy data Kuik e al 1988 this is the standard definition for WAVEC buoys integrated over all frequencies DSPR i 2 1 os gl Beate gy J coser a 1 As input to SWAN with the commands BOUNDPAR and BOUNDSPEC the directional distribution of incident wave energy is given by D 0 A cos 0 for all frequencies The parameter m is indicated as MS in SWAN and is not necessarily an integer number This number is related to the one sided directional spread of the waves DSPR as follows 100 Appendix A Table A 1 Directional distribution MS DSPR in 1 37 5 2 31 5 3 27 6 4 24 9 5 22 9 6 21 2 7 19 9 8 18 8 9 17 9 10 17 1 15 14 2 20 12 4 30 10 2 40 8 9 50 8 0 60 7 3 70 6 8 80 6 4 90 6 0 100 5 7 200 4 0 400 2 9 800 2 0 DISSIP Energy dissipation per unit time due to the sum of bottom friction whitecapping and depth induced wave breaking in W m or m s depending on the command SET WLEN The mean wavelength defined as f kP E c 0 dodo c WLEN 2m Gs As default p 1 see command QUANTITY i e WLEN is based on Tmo2 using linear dispersion relation STEEPNESS QB TRANSP VEL WIND FORCE URMS UBOT Definitions of variables 101 Wave steepness computed as HSIG WLEN Fraction o
105. le is therefore equal to the computational grid spacing This implies that an obstacle to be effective must be located such that it crosses at least one grid line This is always the case when an obstacle is larger than one mesh length 1 If a straight line is defined with more than two points then the sum of the reflection of the parts may differ from the situation when you define it with just two points This is due to the way obstacles are han dled numerically in SWAN It defines from computational grid point to its neighbor whether there is a crossing with an obstacle In defining which directions of the wave spectrum should be reflected i e which directions are pointed towards the obstacle it uses the obstacle coordi nates as defined by the user to define the angle of inclusion This angle will be smaller if more points are defined and so the reflected energy will be less for the computational grid point This problem becomes smaller if the computational grid points are closer to the obstacle So the advise is to define obstacles with the least amount of points possible 2 In case of sharp angles in the obstacles it is very likely that there are more than one crossing between two computational grid points In this case SWAN does not give correct reflection results e Avoid sharp angles in the obstacle definition e If necessary put corner point of the sharp edge exactly on line between two computational grid points but not e
106. lt MIn gt _ tendinp HR DAy OPTION CURVILINEAR NOT FOR 1D MODE With this required command the user defines the geographic location size and orientation of an input grid and also the time characteristics of the vari able if it is not stationary If this is the case the variable is not stationary the variable should be given in a sequence of fields one for each time step deltinp The actual reading of values of bottom levels currents etc from file is controlled by the command READINP This command INPGRID must precede the following commatd There can be different grids for bottom level BOTTOM flow current CURRENT bottom friction coefficient FRICTION and wind velocity WIND If the cur rent velocity components are available on different grids then option VX VY can define these different grids for the z and y component of the current respectively but the grids must have identical orientation Different grids for VX and VY may be useful if the data are generated by a circulation model using a staggered grid The same holds for the wind velocity components If the command INPGRID is given without any of the keywords BOTTOM WIND etc it is assumed that all the input grids are the same In the case of a regular grid option REGULAR in the INPGRID command the current and wind vectors are defined with the x and y component of the current or wind vector with respect to the z axis of the input
107. mes Each such command scheme includes a diagram and a description explaining the structure of the command and the meaning of the keyword s and of the data in the command The proper sequence of the commands is given in Section 4 2 B 2 Command B 2 1 Keywords Each command instructs SWAN to carry out a certain action which SWAN executes before it reads the next command A command must always start with a keyword which is also the name of the command which indicates the primary function of that command see list in Section 4 1 A simple command may appear in its command scheme as KEYword data A command may contain more than one keyword which refines the instruc tions to SWAN e g 103 104 Appendix B KEYi1word KEY2word data where KEY2word is the second keyword Spelling of keywords In every command scheme keywords appear as words in both lower and upper case letters When typing the command or keyword in the command file the user must at least copy literally the part with upper case letters SWAN reads only this part and SWAN is case insensitive except for one instance character strings see below When typing the keyword in the command file any extension of the part with upper case letters is at the users discretion as long as the extension is limited to letters or digits as well as the characters and _ So in the first command outlined above one may write KEY or KEYW or KEY word or keyhole etc where
108. n cf10 cf20 cf30 cf40 cf50 cf60 edmlpm cdrag umin JANSSEN cds1 delta gt KOMEN cds2 stpm gt AGROW a YAN WESTHuysen K0Men cds2 stpm powst delta powk JANSsen cdsi delta pwtail LHIG cflhig BJ bjstp bjalf gt KBJ bjstp bjalf kconv CSM cst pow AB cds2 br pO powst powk QUADrupl iquad limiter lambda cn14 cshi csh2 csh3 CNL4 lt cn14 gt MDIA LAMbda lt lambda gt lt gt CNL4_12 cnl4 1 cnl4 2 gt 114 Appendix C BREaking CONSTANT alpha gamma FRICTION JONSWAP cfjon COLLINS cfw MADSEN kn TRIAD trfac cutfr urcrit urslim LIMiter ursell qb TRANSm trcoef OBSTacle lt gt amp DAM hgt alpha beta RSPEC REFLec reflc gt amp RDIFF POWS POWD Kdif LINe lt xp yp gt SETUP supcor DIFFRac idiffr smpar smnum cgmod OFF WINDGrowth QUADrupl WCAPping BREaking REFrac FSHift BNDCHR PROP BSBT GSE waveage SECIMIN HR DAY gt ACCUR drel dhoval dtoval npnts NUMeric gt amp STOPC dabs drel curvat npnts gt STAT mxitst alfa lt gt limiter amp NONSTat mxitns DIRimpl cdd cdlim amp File swan edt 115 SIGIMpl css eps2 outp niter amp SETUP eps2 outp niter FRAME sname xpfr
109. nd FRICTION with the value of the friction set at zero FRICTION COLLINS 0 the bottom wave period in s average wavelength in m average wave steepness dimensionless the difference in significant wave height as computed in the last two iterations This is not the difference between the computed values and the final limit of the iteration process at most an indication of this difference the difference in average wave period RTMO1 as computed in the last two iterations This is not the difference between the computed values and the final limit of the iteration process at most an indication of this difference numerical loss of energy equal to cgE w across boundaries 0 diri and 0 dir2 of a directional sector see command CGRID user instructs SWAN to write the x coordinate in the problem coordinate system of the output location user instructs SWAN to write the y coordinate in the problem coordinate system of the output location if output has been requested along a curve see command CURVE then the distance 88 Chapter 4 along the curve can be obtained with this command TABLE DIST is the distanc along the curve measured from the first point on the curve to the output locat on the curve in m SETUP Set up due to waves in m unit this controls the scaling of output The program divides computed values by before writing to file so the user should multiply the written value by unit obtain the
110. nd we is the same for the second origin spectrum N2 0 0 Obviously w we 1 The average directions of the two origin spectra are determined using direc tional moments of the spectra Miz J Nio 0 cos 0 do d0 2 1 and Miy J Nio 0 sin 0 dod0 2 2 with i 1 2 The average direction is then 0 atan m mj The average direction of the interpolated spectrum is calculated as 0 atan wym y wam y wm z wams 2 3 Finally the interpolated spectrum is calculated as follows N o 0 w Ni o1o 0 0 0 064 waNo 050 0 0 0 65 2 4 2 6 4 Output grids SWAN can provide output on uniform recti linear spatial grids that are independent from the input grids and from the computational grid In the computation with a curvi linear computational grid curvi linear output grids 20 Chapter 2 are available in SWAN An output grid has to be specified by the user with an arbitrary resolution but it is of course wise to choose a resolution that is fine enough to show relevant spatial details It must be pointed out that the information on an output grid is obtained from the computational grid by bi linear interpolation output always at computational time level This implies that some inaccuracies are introduced by this interpolation It also implies that bottom or current information on an output plot has been obtained by interpolating twice once from the input grid to the computational grid and once
111. npnts gt STAT mxitst alfa gt limiter amp NONSTAT mxitns DIRimpl cdd cdlim amp SIGIMpl css eps2 outp niter amp SETUP eps2 outp niter With this optional command the user can influence some of the numerical properties of ACCUR SWAN With this option the user can influence the criterion for terminating the iterati procedure in the SWAN computations both stationary and non stationary mo SWAN stops the iterations if a the change in the local significant wave height H from one iteration to the next is less than 1 fraction drel of that height or 2 fraction dhoval of the average significant wave height average over all wet grid points and b the change in the local mean wave period 75 91 from one iteration to the next is less than 1 fraction drel of that period or 2 fraction dtoval of the average mean wave period average over all we grid points and STOPC dabs drel dhoval dtoval curvat npnts STAT nxitst alfa NONSTAT nxitns limiter Description of commands 71 c conditions a and b are fulfilled in more than fraction npnts of all wet grid points With this alternative option the user can influence the criterion for terminating the iterative procedure in the SWAN computations both stationary and nonstationary This criterion is solely based on the significant wave height Furthermore the criterion make use of th
112. of a few wave lengths However the computation of diffraction in arbitrary geophysical conditions is rather complicated and requires considerable com puting effort To avoid this a phase decoupled approach is employed so that same qualitative behaviour of spatial redistribution and changes in wave di rection is obtained SWAN does not calculate wave induced currents If relevant such cur rents should be provided as input to SWAN e g from a circulation model which can be driven by waves from SWAN in an iteration procedure As an option SWAN computes wave induced set up In one dimensional cases the computations are based on exact equations In 2D cases the com putations are based on approximate equations the effects of wave induced currents are ignored in 1D cases they do not exist The LTA approximation for the triad wave wave interactions depends on the width of the directional distribution of the wave spectrum The present tuning in SWAN the default settings see command TRIAD seems to work reasonably in many cases but it has been obtained from observations in a General definitions and remarks 5 narrow wave flume long crested waves The DIA approximation for the quadruplet wave wave interactions de pends on the width of the directional distribution of the wave spectrum It seems to work reasonably in many cases but it is a poor approximation for long crested waves narrow directional distribution It also depends on the
113. olutions coefficients etc Generally the deep water boundary of the SWAN nest must be located in WAM or WAVEWATCH III where shallow water effects do not dominate to avoid too large discontinuities between the two models Also the spatial and spectral resolutions should not differ more than a factor two or three If a finer resolution is required a second or third nesting may be needed 2 5 Units and coordinate systems SWAN expects all quantities that are given by the user to be expressed in S I units m kg s and composites of these with accepted compounds such as Newton N and Watt W Consequently the wave height and water depth are in m wave period in s etc For wind and wave direction both the Cartesian and a nautical convention can be used see below Directions and spherical coordinates are in degrees and not in radians For the output of wave energy the user can choose between variance m or energy spatial density Joule m i e energy per unit sea surface and the equivalents in case of energy transport m s or W m i e energy transport per unit length and spectral energy density m Hz Degr or Js m rad ie energy per unit frequency and direction per unit sea surface area The wave induced stress components obtained as spatial derivatives of wave induced radiation stress are always expressed in N m even if the wave en ergy is in terms of variance Note that the energy density is also in Joule m in
114. onal grid In such cases SWAN may invoke some internal scenarios or limiters instead of terminating the computations The reasons for this model policy is that Chapter 2 e SWAN needs to be robust and e the problem may be only very local or e the problem needs to be fully computed before it can be diagnosed Examples are The user can request that refraction over one spatial grid step is limited to about 90 see command NUMERIC This may be relevant when the depth varies considerably over one spatial grid step e g at the edge of oceans or near oceanic islands with only one or two grid steps to go from oceanic depths to a shallow coast This implies inaccurate re fraction computations in such grid steps This may be acceptable when refraction has only local effects that can be ignored but depending on the topography the inaccurately computed effects may radiate far into the computational area SWAN cannot handle wave propagation on super critical current flow If such flow is encountered during SWAN computations the current is locally reduced to sub critical flow If the water depth is less than some user provided limit the depth is set at that limit default is 0 05 m see command SET The user imposed wave boundary conditions may not be reproduced by SWAN as SWAN replaces the imposed waves at the boundaries that propagate into the computational area with the computed waves that move out of the computational area at the b
115. or read energy variance density spec tra to or from the file The description of the file to write or read source terms is identical to this description except that the quantities obviously differ The format that is used by SWAN or should be used by the user when of fering the file to SWAN is free format FORTRAN convention except that 51 128 271 662 1296 2317 3349 3410 2018 669 101 0oOo0o0o0000000000O N Spectrum files input and output 123 all keywords and names of quantities see below should start on the first position of the line on which they appear see Appendix B for the syntax of keywords This format implies that all information on each line after the required input for SWAN is ignored by SWAN This can be used to enter user s information at the discretion of the user First line the keyword SWAN followed by version number Then Then Then Then Then Then if non stationary computation the keyword TIME if stationary computation not present if non stationary computation time coding option ISO notation 1 is recommended if stationary computation not present e the description of the locations if Cartesian coordinates the keyword LOCATIONS if spherical coordinates the keyword LONLAT e number of locations e for each location if Cartesian coordinates r and y coordinate in m problem coordinates if spherical coordinates longitude and latitude Note that if the file is used for in
116. oundaries SWAN may have convergence problems There are three iteration pro cesses in SWAN 1 an iteration process for the spatial propagation of the waves 2 if ambient currents are present an iteration process for spectral propagation current induced refraction and frequency shift and 3 if wave induced set up is requested by the user an iteration pro cess for solving the set up equation General definitions and remarks 7 ad 1 For spatial propagation the change of the wave field over one iter ation is limited to some realistic value usually several iterations for stationary conditions or one iteration or upgrade per time step for nonstationary conditions see command NUMERIC This is a common problem for all third generation wave models such as WAM WAVEWATCH III and also SWAN It does not seem to affect the result seriously in many cases but sometimes SWAN fails to converge properly ad 2 For spectral propagation but only current induced refraction and frequency shift SWAN may also not converge ad 3 For the wave induced set up SWAN may also not converge Information on the actual convergence of a particular SWAN run is provided in the PRINT file see SWAN Implementation Manual Some other problems which the SWAN user may encounter are due to more fundamental shortcomings of SWAN which may or may not be typical for third generation wave models and unintentional coding bugs Because of the issues described a
117. put for SWAN but not generated by SWAN and the user so desires the names of locations can be written behind the two coordinates these names are ignored by SWAN when reading the file see remark on format above the frequency data for 1D and 2D spectra e the keyword AFREQ or RFREQ to distinguish between absolute and relative frequencies e number of frequencies e a column with frequencies always in Hz each on a new line the direction data only for 2D spectra e the keyword NDIR or CDIR to distinguish between nautical and Cartesian direction e number of directions e a column with directions always in degrees each on a new line the group describing the quantities in the tables of this file see the above examples e the keyword QUANT e number of quantities for each quantity e name of the quantity e unit of the quantity e exception value of the quantity i e the value that is written 124 Then VVV Appendix D instead of a computed value if that is undefined Note for 1D spectra the number of quantities is always 3 and the quantities are always energy or variance density average direction CDIR for Cartesian direction or NDIR for nautical direction and directional spreading DSPR in terms of DEGREES SWAN write the keyword DSPRDEGR SWAN reads the keyword DSPRD or DEGR in case of option DEGREES or the keywords DSPRP or POWER in case of option POWER in command BOUND SHAPE The quantities appear in the order in
118. quency and the frequency resolution which is proportional to the frequency itself i e logarithmic e g Af 0 1 f The frequency domain may be specified as follows see command CGRID e The lowest frequency the highest frequency and the number of frequen cies can be chosen e Only the lowest frequency and the number of frequencies can be cho sen The highest frequency will be computed by SWAN such that Af 0 1 f This resolution is required by the DIA method for the approximation of nonlinear 4 wave interactions the so called quadru plets e Only the highest frequency and the number of frequencies can be cho sen The lowest frequency will be computed by SWAN such that Af 0 1 f This resolution is required by the DIA method for the approximation of nonlinear 4 wave interactions e Only the lowest frequency and the highest frequency can be chosen The number of frequencies will be computed by SWAN such that Af 0 1 f This resolution is required by the DIA method for the approximation of nonlinear 4 wave interactions The value of lowest frequency must be somewhat smaller than 0 7 times the value of the lowest peak frequency expected The value of highest frequency 18 Chapter 2 must be at least 2 5 to 3 times the highest peak frequency expected For the XNL approach however this should be 6 times the highest peak frequency Usually it is chosen less than or equal to 1 Hz SWAN has the option to make computations that c
119. r computer Default is ISO notation deltspc time interval between fields the unit is indicated in the next option SEC unit seconds MIN unit minutes HR unit hours DAY unit days gt Sec NESTout sname fname OUTput tbegnst deltnst lt MIn gt HR DAy CANNOT BE USED IN 1D MODE With this optional command the user indicates that the spectra along a nest boundary sname see command NGRID should be written to a data file with name fname This name is required in this command 92 Chapter 4 gt sname name of the set of output locations as defined in a command NGRID gt fname name of the data file where the output is written to The file is structured according to the description in Appendix D i e also the information about th location of the boundary are written to this file SWAN will use this as a checl for the subsequent nested run OUTPUT the user requests output at various times If the user does not use this option the program will give NESTOUT output for the last time step of the computatiot tbegnst begin time of the first field of the variable the format is 1 ISO notation 19870530 153000 2 as in HP compiler 30 May 87 15 30 00 3 as in Lahey compiler 05 30 87 15 30 00 ANS 15 30 00 5 87 05 30 15 30 00 6 asin WAM 8705301530 This format is installation dependent See Implementation Manual or ask the person who installed SWAN on your computer Def
120. rdinates then xgc is ignored by SWAN Default the location of the first spectrum encountered in the nest file ygc if SWAN is used with Cartesian coordinates longitude of south west corner of SWAN computational grid in degrees if the south west corner of the nest in the WAM computation is on land this value is required If SWAN is used with spherical coordinates then ygc is ignored by SWAN Default the location of the first spectrum encountered in the nest file Note that xgc and ygc are ignored if SWAN is used with spherical coordinates if SWAN is used with Cartesian coordinates the values must be provided by the user DEFault ZERO INITial lt gt PAR hs per dir dd HOTStart fname This command can be used to specify the initial values for a stationary INITIAL HOTSTART only or non stationary computation The initial values thus specified override the default initialization see Section 2 6 3 Note that it is possible to obtain an initial state by carrying out a previous stationary or non stationary computation DEFAULT the initial spectra are computed from the local wind velocities using the deep water growth curve of Kahma and Calkoen 1992 cut off at values of significant wave height and peak frequency from Pierson and Moskowitz 1964 The average over the model area spatial step size is used as fetch with local wind The shape of the spectrum is default JONSWA
121. read these definitions and remarks before consulting the rest of the manual Chapter 3 gives some remarks concerning the input and output files of SWAN Chapter 4 describes the complete set of commands of the program SWAN It is strongly advised that users who are not so experienced in the use of SWAN first read Chapters 2 and 3 This Manual also contains some appendices In Appendix A definitions of several output parameters are given Appendix B outlines the syntax of the command file or input file A complete set of all the commands use in SWAN can be found in Appendix C Appendix D described the format of the files for spectral input and output by SWAN 1 Chapter 1 Chapter 2 General definitions and remarks 2 1 Introduction The purpose of this chapter is to give some general advice in choosing the basic input for SWAN computations SWAN is a third generation wave model for obtaining realistic estimates of wave parameters in coastal areas lakes and estuaries from given wind bottom and current conditions However SWAN can be used on any scale relevant for wind generated surface gravity waves The model is based on the wave action balance equation with sources and sinks An important question addressed is how to choose various grids in SWAN resolution orientation etc including nesting only for uniform recti linear grid The idea of nesting is to first compute the waves on a coarse grid for a larger region and then on
122. rids and boundary initial first guess conditions a des eue bet ares le cui dee ae hs 2 6 4 Output grids t4 ed a eee Be ek Activation of physical processes 04 4 Time and date notation a de eke ed ae Ye BY 3 Input and output files 3 1 3 2 3 3 4 1 4 2 4 3 4 4 General e eame d oso Y bac bao db erae d ena red Input output facilities oe eus d edel EN add ees Print file and error messages luem dew IRE EROR Description of commands List of availablecommands 005 Sequence of commands ek eg ceu bees We eo RS Command syntax and input output limitations USN AA pee es lt a teeters edd ec m Eg Sel tne eme es dl Ve ep Mens vi PROJECTS cat da cage aa ed AS ae ip el a ig debe 29 SE ene wk ale ani as eee ae eg E uds 30 I MIE soe 85 es nats ee smack he ae ah Ea de Se ek oe ie 32 COORDINATES 23 4 aacra diaaa a ht ade RE ua 32 4 5 Model description a acy cte koh a 34 4 5 1 Computational grid 2a v eoe RR x 34 CGRID 21x oe Yh ee ae en he bed x 34 READGRID dre ane hg eS Cae Neg A Sessa 37 4 5 2 Input grids and data Se he e a See ee 38 ipei 38 TED 122 uino to SI bus 0 m Prec t M ur d RIO Sees 42 WIND a i gaua gee es este eke or atti a a a 47 4 5 3 Boundary and initial conditions 47 BOUND SHAPE ose ete eS aS eS DAH a RL 5 47 BOUNDSPBSG terin Side BAP OG m Eo eh 48 BOUNDNESTI 3 imc ox eoe Se Dese cec ey 52 BOUNDNES T2 eL tm rumen p be ad PUR
123. s the case if a results of another model run are available nested computations or b observations are available If model results are available along the boundaries of the computational spatial grid they are usually from a coarser resolution than the computational spatial grid under consideration This implies that this coarseness of the boundary propagates into the computational grid The problem is therefore essentially the same as if no waves are assumed along the boundary except that now the error may be more acceptable or the 14 Chapter 2 boundaries are permitted to be closer to the area of interest If observations are available they can be used as input at the boundaries However this usually covers only part of the boundaries so that the rest of the boundaries suffer from the same error as above A special case occurs near the coast Here it is often possible to identify an up wave boundary with proper wave information and two lateral bound aries with no or partial wave information The affected areas with errors are typically regions with the apex at the corners of the water boundary with wave information spreading towards shore at an angle of 30 to 45 for wind sea conditions to either side of the imposed mean wave direction less for swell conditions the angle is essentially the one sided width of the direc tional distribution of wave energy For propagation of short crested waves wind sea condtions an example is
124. see command COORD ylenfr length of the frame in y direction if Cartesian coordinates are used in m if spherical coordinates are used in degrees see command COORD mxfr number of meshes in z direction of the rectangular grid in the frame one less than the number of grid points in this direction Default mxfr 20 myfr number of meshes in y direction of the rectangular grid in the frame one less than the number of grid points in this direction Default nyfr 20 Some output may be required on a frame that is identical with the input bottom current grid or with the computational grid e g for test purposes or to avoid interpolation errors in the output These frames need not be de fined by the user with this command FRAME the frames are always generated automatically by SWAN under the names sname BOTTGRID for the bottom current grid and sname COMPGRID for the computational grid GROUP sname SUBGrid ixi ix2 iy1 iy2 CANNOT BE USED IN 1D MODE With this optional command the user defines a group of output locations on a rectangular or curvi linear grid that is identical with part of the computational grid recti linear or curvi linear Such a group may be con venient for the user to obtain output that is not affected by interpolation errors which would occur when an output grid is used that is not identical with part of the computational grid Command CGR
125. sin 0E 0 0 dod0 J cos0B c 0 dod0 This direction is the direction normal to the wave crests Peak direction of E 0 f E w 0 dw f E c 0 da in Cartesian or Nautical convention Direction of energy transport in Cartesian or Nautical convention Note that if currents are present TDIR is different from the mean wave direction DIR Mean relative wave period in s of E c 0 defined as f o7 E c 0 dcd0 TN BI ao 2n f J E o 6 aod0 This is equal to TMM10 in the absence of currents Mean relative wave period in s of E c 0 defined as 7 f oB 0 0 doao 1 RTmor 2n J J E o 6 4od0 This is equal to TMO01 in the absence of currents Relative peak period in s of E c equal to absolute peak period in the absence of currents Average absolute period in s defined as f 971 E c 0 dcd0 Tm pip 27 J eo E o 0 dodd The power p can be chosen by the user by means of the QUANTITY command If p 1 the default value PER is identical to TMO1 and RPER FSPR DSPR MS Definitions of variables 99 if p 0 PER TMM10 Average relative period in s defined as oP f f E o 0 dod0 oP f B c 0 dod0 FU pA 2m Here if p 1 RPER RTMOI and if p 0 RPER RTMM10 The normalized frequency width of the spectrum frequency spreading as defined by Battjes and Van Vledder 1984 fo E ei 7de Erot 2 FSPR for T Tmo2 The one sided directional width of the spectrum directiona
126. that output is produced by SWAN only at the user s request The instructions of the user to control output are separated into three categories e Definitions of the geographic location s of the output The output locations may be either on a regular geographic grid or along user specified lines e g a given depth contour line or at individual output locations e Times for which the output is requested only in non stationary runs e Type of output quantities wave parameters currents or related quan tities 3 9 Print file and error messages SWAN always creates a print file Usually the name of this file is identical to the name of the command file of the computations with the extension SWN replaced with PRT Otherwise it depends on the batch file that is used by the user Consult the Implementation Manual for more information The print file contains an echo of the command file and error messages These messages are usually self explanatory if not users may address the SWAN forum page on the SWAN homepage The print file also contains computational results if the user so requests with command BLOCK or TABLE Chapter 4 Description of commands 4 1 List of available commands The following commands are available to users of SWAN to look for the commands quickly see table of contents and index Start up commands a Start up commands PROJECT title of the problem to be computed SET sets values of cert
127. that there is no wind defines input grid of the z component of the wind field different grid than x component but same orientation defines input grid of the y component of the wind field different grid than y component but same orientation means that the input grid is uniform and rectangular means that the input grid is curvi linear this option is available only if the computational grid is curvi linear as well The input grid is identical which is default to the computational grid or it is staggered in x and or 3j direction NOT FOR 1D MODE For a REGULAR grid xpinp Lypinp geographic location coordinate of the origin of the input grid in problem coordinates in m if Cartesian coordinates are used or in degrees if spherical coordinates are use see command COORD Default xpinp 0 In case of spherical coordinates there is no default the user must give a value geographic location y coordinate of the origin of the input grid in problem coordinates in m if Cartesian coordinates are used or in degrees if spherical coordinates are use see command COORD alpinp mxinp myinp dxinp dyinp Description of commands 41 Default ypinp 0 In case of spherical coordinates there is no default the user must give a value direction of the positive z axis of the input grid in degrees Cartesian convention See command COORD Default alpinp 0 num
128. the Northern hemisphere Input and output grids have to be oriented with their x axis to the East mesh sizes are in degrees All other distances are in m CCM defines the projection method in case of spherical coordinates CCM means central conformal Mercator The horizontal and vertical scales are uniform in terms of cm degree over the area shown In the centre of the scale is identical to that of the conventional Mercator projection but only at that centre The area in the projection centre is therefore exactly conformal QC the projection method is quasi cartesian i e the horizontal and vertical scales are equal to one another in terms of cm degree REPEATING this option is only for academic cases It means that wave energy leaving at one end of the domain in computational z direction enter at the other side it is as if the wave field repeats itself in z direction with the length of the domain in x direction This option cannot be used in combination with computation of set up see command SETUP This option is available only with regular grids Note that spherical coordinates can also be used for relatively small areas say 10 or 20 km horizontal dimension This may be useful if one obtains the boundary conditions by nesting in an oceanic model which is naturally formulated in spherical coordinates Note that in case of spherical coordinates regular grids must always be ori ented E W N S ie alpc 0 alpinp 0 alpfr 0
129. the actual command in the command file the user must give such a se quence It ends with either e end of line e keyword other than the ones mentioned in the repetition group e the character or If more than one line is required for a command the user may continue on the next line as described in Section B 4 The repetition may consist of one instance in fact no repetition at all B 2 2 Data Most commands contain data either character data or numerical data 106 Appendix B Character data and numerical data Character data character strings are represented in the command schemes by names enclosed in quotes Numerical data are represented in the command schemes by names enclosed in square brackets As a rule an error message will result if numerical data is given where char acter data should be given Spelling of data Character data are represented as character strings sequence of characters and blanks between quotes in the command scheme and in the command file SWAN interprets an end of line as an end quote a character data field can therefore never extend over more than one line In a command scheme the character string is always a name which is placed between quotes as indicated In the command file such a name can be entered in two ways e Replace the name by another character string at the users discretion between quotes this is the only occurrence where SWAN is case sen sitive
130. the spectrum with the diagnostic tail added Their value may therefore deviate slightly from values computed by the user from the output spectrum of SWAN which does not contain the diagnostic tail TIME HSIGN HSWELL DIR PDIR TDIR TMO1 RTMO1 RTP TPS PER RPER TMM10 RTMM10 TMO2 time for which the values on the same line are valid Useful only in case of nonstationary computations significant wave height in m swell wave height in m mean wave direction Cartesian or Nautical convention see command SET for Cartesian convention relative to x axis of the problem coordinate system counter clockwise possible exception in the case of output with BLOCK comn in combination with command FRAME see command QUANTITY peak wave direction in degrees for Cartesian convention relative to x axis of the problem coordinate system counter clockwise possible exception in the case of output with BLOCK comn in combination with command FRAME see command QUANTITY direction of energy transport in degrees for Cartesian convention relative to x axis of the problem coordinate system counter clockwise possible exception in the case of output with BLOCK comn in combination with command FRAME see command QUANTITY mean absolute wave period in s mean relative wave period in s peak period in s of the variance density spectrum relative frequency spectru smoothed peak period in s mean absolute wave p
131. ties For definitions of output parameters see Appendix A WARNING When integral parameters are computed by the user from the output spec trum of SWAN differences with the SWAN computed parameters may occur The reasons are e SWAN accepts at the boundaries of the computational grid only the user imposed incoming wave components and it replaces the user imposed outgoing wave components with computed components propagating to the boundary from the interior region e during the computation of the parameters SWAN adds an analytical diagnostic high frequency tail to the discrete spectrum e SWAN has an option to only compute within a pre set directional sector pre set by the user Wave components outside this sector are totally ignored by SWAN no additions or replacements This is particularly relevant along the boundaries of SWAN where the user imposed integral parameters boundary conditions may differ from the SWAN computed parameters The user is informed by means of a warning in the output PRINT file when the computed significant wave height differs more than 10 say from the user imposed significant wave height command BOUNDSPEC The actual value of this difference can be set by the user see the SET command Section 4 4 QUANTity lt gt short long lexp hexp excv MEISTE power For output quantities PER RPER and WLEN ref For output quantity TSEC swe11 For output quantity HSWE
132. ts 53 BOUNDNESL s tous dni ee Yrs eel be 55 INPDLATIS uin om eius edes dem det doter mes 57 aur PHYSICS 50th etre e tbe beu dea uie e N 58 GENTI adeo txt Sate AE AS xe Ch e te ee ig 58 GENZ va sae s Ba es gf Wubi quee ae a 59 GENS uk Red ee ge RU dud 59 WCOAPRPING au So dodo eni brodo rede Se e DECR 60 QU ADBULDL 75 Stoeb qlee ek a RS utem SO RS 61 BREAKING fone rA Sala abate e uo SP 62 PRICTION crs ah nasn 3 4 e 2 8 e eae ap 62 TRIAD RECEN E RED RUE EINE 63 LIMITER Gti othe Qa bu att Sat Ot 2 eat oot 2 Ge 2 ANS 64 OBSTACLE xt ni do ate Rhe ca Se ge ERE ct ey 64 SETUP nerd a Arcu dc ciui o uh Mei 67 DIFFRACTION 42 ssh 608 eg amp Me ede s 67 ORP a ee S erat e AUR ME Lu Mod ess 68 Z5 0 Numers aL t6 ac M UBND t6 nc i Trendi rures He Dees 69 PROP S on Lu REO e Rui BSE OOo we ee 69 NUMERIC o reta a datiuo BA due rato Bato Ree es 70 AOs UNS diio Sie eg siete YO CR T6 do OR Wee t m A 73 4 6 1 Output locations 6 esa Ao Aloe Ee AXIS E EE 74 ISOLINE POINTS NGRID 4 202 4 6 2 Write or plot computed quantities QUANTITY OUTPUT BLOGR xa TABLE 12a SPECOUT NESTOUT 4 6 3 Write or plot intermediate results TESI 3 6 5 oA 4 7 Lock up gt x od ke oh Glo de SH COMPUTE HOTFILE STOP us e m us A Definitions of variables B Command syntax B 1 Commands and command schemes B 2 Command i i vae B 2 1 Keywords
133. undary of the computational grid see also command SET 4 5 5 Numerics PROP lt BSBT Sec GSE waveage lt MIn gt HR DAy Command to choose e the BSBT scheme stationary and non stationary instead of the default S amp L scheme in case of non stationary cases or the default SORDUP scheme in case of stationary cases or e the wave age for the default non stationary S amp L scheme BSBT GSE waveage the BSBT scheme will be used in the computations garden sprinkler effect is to be counteracted in the S amp L propagation scheme default for non stationary computations by adding a diffusion term to the basic equation This may affect the numerical stability of SWAN see Technical documentation the time interval used to determine the diffusion which counteracts the so called garden sprinkler effect The default value of waveage is zero i e no added diffusion The value of waveage should correspond to the travel time of the waves over the computational region 70 Chapter 4 Note All schemes can be used in combination with curvilinear grids With the higher order schemes S amp L and SORDUP it is important to use a grad ually varying transitions in NUMeric lt grid otherwise there may be a severe loss of accuracy If sharp the grid cannot be avoided it is safer to use the BSBT scheme gt ACCUR drel dhoval dtoval npnts STOPC dabs drel curvat
134. use of diffraction If idiffr 0 then no diffraction is taken into account Default idiffr 1 smpar smoothing parameter for the calculation of V Ex During every smoothing step all grid points exchange smpar times the energy with their neighbours Default smpar 0 smnum number of smoothing steps It should be approximately equal to s Default smnum 0 cgmod adaption of propagation velocities in geographic space due to diffraction If cgmod 0 then no adaption Default cgmod 1 WINDGrowth QUADrupl WCAPping OFF gt BREaking REFrac FSHift BNDCHK With this optional command the user can change the default inclusion of various physical processes e g for research purposes This command is not recommended for operational use WINDGROWTH QUADRUPL WCAPPING BREAKING switches off wind growth in commands GEN1 GEN2 and GEN3 switches off quadruplet wave wave interactions in command GEN3 switches off whitecapping in command GEN3 switches off depth induced breaking dissipation Caution wave heights may REFRAC FSHIFT BNDCHK Description of commands 69 diverge in very shallow water switches off refraction action transport in 0 direction switches off frequency shifting in frequency space action transport in o space switches off the checking of the difference between imposed and computed significant wave height at the bo
135. utational grid before this BOUNDNEST1 command The computational grid for SWAN in geographic space is the area bounded by the SWAN coarse run nest SWAN boundary points of the nest This implies that the boundaries of the SWAN coarse run nest and the boundaries of the SWAN nested computational area should be nearly identical see below The spectral frequencies and directions of the coarse grid run do not have to coincide with the frequencies and directions Description of commands 53 used in the nested SWAN run as defined in the CGRID command SWAN will interpolate to these frequencies and directions in the nested run see Section 2 6 3 To generate the nest boundary in the coarse grid run use command NGRID For the nested run use the command CGRID with identical geographical in formation except the number of meshes which will be much higher for the nested run This BOUNDNEST command is not available for 1D computations in such cases the commands SPECOUT and BOUNDSPEC can be used for the same purpose To define the computational grid use command CGRID A nested SWAN run must use the same coordinate system as the coarse grid SWAN run For a curvi linear grid it is advised to use the commands CURVE and SPECOUT instead of NGRID and BOUNDNEST NEST fname CLOSED OPEN BOUNdnest2 with this option the user indicates that the boundary conditions all four sides of the computational grid are to be retrieved from a
136. utational time levels 12 Chapter 2 2 6 2 Input grid s and time window s The bathymetry current water level bottom friction and wind if spatially variable need to be provided to SWAN on so called input grids It is best to make an input grid so large that it completely covers the computational grid In the region outside the input grid SWAN assumes that the bottom level the water level and bottom friction are identical to those at the nearest boundary of the input grid lateral shift of that boundary In the regions not covered by this lateral shift i e in the outside quadrants of the corners of the input grid a constant field equal to the value at the nearest corner point of the input grid is taken For the current and wind velocity SWAN takes 0 m s for points outside the input grid One should choose the spatial resolution for the input grids such that rel evant spatial details in the bathymetry currents bottom friction and wind are properly resolved Special care is required in cases with sharp and shal low ridges sand bars shoals in the sea bottom and extremely steep bottom slopes Very inaccurate bathymetry can result in very inaccurate refraction computations the results of which can propagate into areas where refrac tion as such is not significant the results may appear to be unstable For instance waves skirting an island that is poorly resolved may propagate be yond the island with entirely wrong directions In
137. very often erroneous and this erroneous initial state is propagated into the computational area The computational time step must be given by the user in case of non stationary runs Since SWAN is based on implicit numerical schemes it is not limited by the Courant stability criterion which couples time and space steps In this sense the time step in SWAN is not restricted However the accuracy of the results of SWAN are obviously affected by the time step Generally the time step in SWAN should be small enough to resolve the General definitions and remarks 17 time variations of computed wave field itself Usually it is enough to con sider the time variations of the driving fields wind currents water depth wave boundary conditions But be careful relatively small time varia tions in depth e g by tide can result in relatively large variations in the wave field As default the first guess conditions of a stationary run of SWAN are de termined with the 2 generation mode of SWAN The initial condition of a non stationary run of SWAN is by default a JONSWAP spectrum with a cos 0 directional distribution centred around the local wind direction A quasi stationary approach can be employed with stationary SWAN com putations in a time varying sequence of stationary conditions The computational spectral grid needs to be provided by the user In frequency space it is simply defined by a minimum and a maximum fre
138. ward relative to the same datum level as used in option BOTTOM Sign of input can be changed with option fac 1 If the water level is constant in space and time the user can use the command SET to add this water level to the water depth recti linear curvi linear input grid with this option the user indicates that the r and y component and 7 component are to be read from one and the same file with one READINP command With this option SWAN reads first all x components components and then all y components 7 components see below The firs component r or component is always eastward oriented and the second one y or 7 component is always northwise oriented The components and 7 are taken along the directions of the grid lines 44 FRICTION WIND fac gt fnamei SERIES fname2 idla Chapter 4 of the curvi linear grid If the current velocity is relatively large i e the Froude number U gd is larger than 0 8 it will be reduced such that the Froude number becomes equal to 0 8 with this option the user indicates that friction coefficient is to be read from file for Collins cfw and for Madsen kn no space or time variable coefficient for the Jonswap expression see command FRICTION If the coefficients are constant in space and time see command FRICTION recti linear curvi linear input grid with this option the user indicates that the r and y
139. which they appear in this description Note for 2D spectra the number of quantities is always 1 the quantity is always energy or variance density EnDens is the short name of true energy densities VaDens for variance densities the group with the tables of the quantities e date and time not present for stationary computation for each location if 2D spectrum e the keyword FACTOR This keyword is replaced by the keyword ZERO if the spectrum is identical 0 or it is replaced by NODATA if the spectrum is undefined not computed e g on land no numbers follow e the factor to multiply the values in the following table e scaled energy variance densities truncated by SWAN to integer valu for compact writing SWAN accepts these values as reals when reading this file other programs e g for postprocessing should also accept the values as reals the values should be multiplied by the factor to get the proper values of the densities else if 1D spectrum e the keyword LOCATION followed by the index of the location on the same line This is replaced by the keyword NODATA if the spectrum is undefined not computed e g on land no numbers follow e a table containing three columns the 3 quantities per frequency energy or variance density average direction CDIR for Cartesian direction and NDIR for nautical direction and directional spreading DSPR in terms of DEGREES writing or reading the file or POWER only reading the file
140. xactly on the grid point 3 At the boundaries of the computational area the reflected spectrum is not taken into account This can only be resolved by a different treatment of the boundaries in the program Until this time it is recommended to place obstacles at the inner area of the computational grid not at or through the boundaries 66 Chapter 4 The computation of transmission and reflection is problematic if an obstacle runs exactly through one or more grid points of the computational grid SWAN will move the obstacle over a small distance 0 01 of the mesh size if this occurs The reflection results are incorrect if more than one obstacle crosses the same grid line between two neighbouring grid points SWAN is not able to detect this so the user must check if his model fulfills this condition TRANSM trcoef DAM hgt alpha beta REFL reflc RSPEC RDIFF pows with this option the user indicates that the transmission coefficient is a constai constant transmission coefficient formulated in terms of wave height i e ratio of transmitted significant wave height over incoming significant wave height Default trcoef 0 0 no transmission complete blockage with this option the user indicates that the transmission coefficient depends on the incident wave conditions at the obstacle and on the obstacle height which may be submerged the elevation of the top of the obstacle above reference level s
141. ypfr alpfr xlenfr ylenfr mxfr myfr GROUP sname SUBGRID ixi ix2 iy1 iy2 CURVE sname xpi ypi int xp yp gt RAY rname xpi ypi xq1 yq1 amp lt int xp yp xq yq gt ISOLINE sname rname DEPTH BOTTOM dep POINTS sname lt xp yp gt FILE fname NGRID sname xpn ypn alpn xlenn ylenn mxn myn PA QUANTity lt gt short long lexp hexp exc amp EA power ref fswell amp PROBLEMcoord FRAME OUTPut OPTIons comment TABle field BLOck mdec len amp SPEC ndec BLOCK sname HEADER NOHEADER fname LAY OUT idla DSPR HSIGN DIR PDIR TDIR TMO1 RTMO1 RTP TM02 FSPR DEPTH VEL FRCOEFF WIND DISSIP QB TRANSP FORCE UBOT URMS WLEN STEEPNESS DHSIGN DRTMO1 LEAK XP YP DIST SETUP TMM10 RTMM10 TMBOT WATLEV BOTLEVITPS gt unit OUTPUT tbegblk deltblk SEC MIN HR DAY F 89 8 amp 8 8 Appendix C TABLE sname HEADER NOHEADER INDEXED fname lt DSPR HSIGN DIR PDIR TDIR TMO1 RTMO1 RTP TMO2 FSPR DEPTH VEL FRCOEFF WIND DISSIP QB TRANSP FORCE UBOT URMS WLEN STEEPNESS DHSIGN DRTMO1 LEAK XP YP DIST SETUP TMM10 RTMM10 TMBOT WATLEV BOTLEVITPS gt unit OUTPUT tbegtbl delttbl SEC MIN HR DAY SPECout sname SPEC1D SPEC2D ABS REL fname OUTput tbeg delt SECIMIN HR DAY NE

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