USER MANUAL SWAN Cycle III version 40.72A

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56 Chapter 4 [cfw] MADSEN [kn] Collins bottom friction coefficient. 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] the value of the proportionality coefficient α EB . Default: [trfac] = 0.05. [cutfr] 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] = 2.5. [urcrit] the critical Ursell number appearing in the expression for the biphase. Default: [urcrit] = 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 permanently 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.
Description of commands 57 [ursell] [qb] the upper threshold for Ursell number. Default: [ursell] = 10.0. the threshold for fraction of breaking waves. Default: [qb] = 1.0. | TRANSm [trcoef] | OBSTacle < | | | -> GODA [hgt] [alpha] [beta] > & | DAM < | | DANGremond [hgt] [slope] [Bk] | | -> RSPEC | (REFL [reflc] < > ) LINe | RDIFF [pown] | CANNOT BE USED IN 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 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 obstacle 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 handled 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 coordinates 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.
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SWAN USER MANUAL SWAN Cycle III ver
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Contents 1 Introduction 1 2 General
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TABLE . . . . . . . . . . . . . . .
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Chapter 1 Introduction The informat
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Chapter 2 General definitions and r
Page 13 and 14: General definitions and remarks 5 r
Page 15 and 16: General definitions and remarks 7 I
Page 17 and 18: which SWAN performs the computation
Page 19 and 20: General definitions and remarks 11
Page 27 and 28: Chapter 3 Input and output files 3.
Page 29 and 30: Chapter 4 Description of commands 4
Page 31 and 32: (h) Commands to write or plot outpu
Page 33 and 34: Description of commands 25 ’name
Page 35 and 36: Description of commands 27 Default:
Page 37 and 38: Description of commands 29 mesh. Th
Page 39 and 40: ⎛ ∆f = ⎝−1 + Description of
Page 41 and 42: Description of commands 33 • Easy
Page 43 and 44: Description of commands 35 grids ca
Page 45 and 46: Description of commands 37 y ′
Page 47 and 48: Description of commands 39 [fac]
Page 49 and 50: Description of commands 41 ’(10X,
Page 51 and 52: Description of commands 43 | | East
Page 53 and 54: Description of commands 45 CONSTANT
Page 55 and 56: Description of commands 47 points o
Page 57 and 58: Description of commands 49 CRAY WKS
Page 59 and 60: Description of commands 51 This com
Page 61 and 62: Description of commands 53 | JANSse
Page 63: Description of commands 55 [Csh3] c
Page 67 and 68: Description of commands 59 [slope]
Page 69 and 70: Description of commands 61 [cgmod]
Page 71 and 72: Description of commands 63 < > [lim
Page 73 and 74: Description of commands 65 SIGIMPL
Page 75 and 76: Description of commands 67 ’sname
Page 77 and 78: Description of commands 69 (see bel
Page 79 and 80: Description of commands 71 [alpn] d
Page 81 and 82: Description of commands 73 ‘long
Page 83 and 84: | HSign | | | | HSWEll | | | | DIR
Page 85 and 86: Description of commands 77 | WLENgt
Page 87 and 88: Description of commands 79 QP DEPTH
Page 89 and 90: Description of commands 81 [tbegblk
Page 91 and 92: Description of commands 83 OUTput [
Page 93 and 94: Description of commands 85 If SWAN
Page 95 and 96: Description of commands 87 ACCUR MX
Page 97 and 98: Appendix A Definitions of variables
Page 99 and 100: Definitions of variables 91 RPER co
Page 101 and 102: Definitions of variables 93 WLEN Th
Page 103 and 104: Appendix B Command syntax B.1 Comma
Page 105 and 106: Repetitions of keywords and/or othe
Page 107 and 108: Required data and optional data Com
Page 109 and 110: Appendix C File swan.edt Below the
Page 111 and 112: File swan.edt 103 ! | -> DEFault !
Page 113 and 114: File swan.edt 105 ! FRAME ’sname
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Appendix D Spectrum files, input an
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0.3892E-03 192.0 15.2 0.8007E-03 24
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Spectrum files, input and output 11
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Spectrum files, input and output 11
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Bibliography [1] SWAN - Implementat
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117 longitude, 8, 27, 49, 50, 85, 1
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USER MANUAL SWAN Cycle III version 40.72A

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