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## Initial and boundary conditions

          | -> CONstant [wlev] [vx] [vy] [tke] [epsilon]
|
INITial  <   ZERO
|


This command can be used to specify the initial values for flow variables.

 CONSTANT the initial flow and turbulence quantities are set to a constant. [wlev] the water level. [vx] the u -component of velocity. [vy] the v -component of velocity. [tke] the turbulent kinetic energy. [epsilon] the dissipation rate of turbulent kinetic energy. ZERO Both the initial water level and velocity components are set to zero. STEADY If this option is specified, the initial velocities will be derived from the water levels using the Chezy formula for steady flow. This can shorten the spin-up time of the SWASH run and can be meaningful in the case of quasi-steady flow condition (e.g. flow in a river).

                   |    PM                |
|                      |    | -> SIG |    | -> PEAK  |
BOUnd SHAPespec   <  -> JONswap  [gamma]   >  <          >  <            >   &
|                      |    |    RMS |    |    MEAN  |
|    TMA               |

| -> POWer      |
DSPR   <                 >
|    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 BOUNDCOND).

 PM Pierson-Moskowitz spectrum will be used. JONSWAP JONSWAP spectrum will be used. This is default. [gamma] peak enhancement parameter of the JONSWAP spectrum. Default: [gamma]=3.3 TMA A modified JONSWAP spectrum for finite depth will be used. SIG The significant wave height (for definition, see Appendix A) is used as the characteristic wave height. This is default. RMS The RMS wave height (for definition, see Appendix A) is used as the characteristic wave height. PEAK The peak period is used as the characteristic wave period. This is default. MEAN Tm01 (for definition, see Appendix A) is used as the characteristic wave period. DSPR option for expressing the width of the directional distribution; the distribution function itself is cosm(). POWER the directional width is expressed with the power m itself. This option is default. DEGREES the directional width is expressed in terms of the directional standard deviation of the cosm() distribution (for definition, see Appendix A).

If this command is not used, the JONSWAP option will be used by SWASH with [gamma]=3.3 and POWER for the directional width.

                       | North |
| NW    |
| West  |
| SW    |   | -> CCW     |
| -> SIDE  <  South  > <              >          |
|           | SE    |   | CLOCKWise  |           |
|           | East  |                            |
|           | NE    |                            |
|                                                |
BOUndcond <                                                  >                    &
|                                                |
|                                                |
|              | -> XY  <  [x]  [y]  >  |        |
|    SEGMent  <                          >
|    IJ  <  [i]  [j]  >  |

BTYPe WLEV|VEL|DISCH|RIEMann|LRIEmann|WEAKrefl|SOMMerfeld|OUTFlow   &

LAYer [k] | HYPerbolic | LOGarithmic                                &

SMOOthing [period] SEC|MIN|HR|DAY                                   &

| FOURier  [azero] < [ampl] [omega] [phase] >
| REGular  [h] [per] [dir]
| CONstant <  SPECTrum [h] [per] [dir] [dd] [cycle] SEC|MIN|HR|DAY
|           | SERIes   'fname' [itmopt]
|           | SPECFile 'fname' [cycle] SEC|MIN|HR|DAY
<                                                                       &
|           | FOURier  < [len] [azero] < [ampl] [omega] [phase] > >
|           | REGular  < [len] [h] [per] [dir] >
|           | SPECTrum < [len] [h] [per] [dir] [dd] [cycle] S|MI|HR|DA >
| VARiable <  SERIes   < [len] 'fname' [itmopt] >
| SPECFile < [len] 'fname' [cycle] SEC|MIN|HR|DAY >
| SPECSwan 'fname' [cycle] SEC|MIN|HR|DAY


This command BOUNDCOND defines a boundary condition at the boundary. It consists of two parts, the first part defines the boundary side or segment where the boundary condition will be given, the second part defines the parameters.

There are two ways to define the part of the boundary at which the boundary condition is imposed. The first (SIDE) is easiest if the boundary is one full side of the computational grid, although it should not be used for curvilinear grids. The second (SEGMENT) can be used if the boundary segment goes around the corner of the grid, or if the segment is only part of one side of the grid.

This BOUNDCOND command can be given a number of times, i.e. to define boundary conditions on various sides or segments of the boundary. One BOUNDCOND command can be used for only one side or one contiguous segment.

Note that by specifying regular or irregular waves at the boundary, the vertical hyperbolic cosine velocity profile is assumed. Hence, no type of boundary condition should be specified, except BTYPE WEAKREFL if a weakly reflective boundary is assumed.

             | North  |
|        |
| West   |
SPONgelayer <          >  [width]
| South  |
|        |
| East   |


This command can be used to specify the sponge layers around the computational domain.

Sponge layers are very effective in absorbing wave energy at open boundaries where waves are supposed to leave the computational domain freely. So, they prevent reflections at open boundaries. A sponge layer may have a width of 3 to 5 typical wave lengths.

Note that by including a sponge layer of [width] meters, the computational domain needs to be extended with [width] meters as well (see command CGRID).

 NORTH sponge layer is placed at the north edge of the domain. WEST sponge layer is placed at the west edge of the domain. SOUTH sponge layer is placed at the south edge of the domain. EAST sponge layer is placed at the east edge of the domain. [width] the width of sponge layer in meters.

Next: Physics Up: Model description Previous: Input grids and data   Index
The SWASH team 2017-04-06