| -> CONstant [wlev] [vx] [vy] [tke] [epsilon] | INITial < ZERO | | STEAdy
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 | T_{m01} (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 cos^{m}(). | ||
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 cos^{m}() distribution (for definition, see Appendix A). |
| 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 & ADDBoundwave & | 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.
SIDE | the boundary is one full side of the computational grid (in 1D cases either | |
of the two ends of the 1D grid). | ||
SHOULD NOT BE USED IN CASE OF CURVILINEAR GRIDS! | ||
NORTH, ... | 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 | ||
in the summation). | ||
Note: in case of Cartesian coordinates, the 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. | ||
CCW, | see description of [len] below; these option are only effective if the | |
CLOCKWISE | option VARIABLE is used (see below). | |
SEGMENT | 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). | ||
XY | 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. | ||
[x], [y] | problem coordinates of a point of the boundary segment (see command COORD). | |
IJ | the segment is defined by means of a series of computational grid points | |
given in terms of grid indices; 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. | ||
[i], [j] | grid indices of a point of the segment. Values of [i] range from 1 to [mxc]+1 | |
and values of [j] from 1 and [myc]+1 ([mxc] and [myc] as defined in the | ||
command CGRID). | ||
BTYPE | with this option the type of boundary condition is given. | |
WLEV | water level is imposed. | |
Required further specification by means of Fourier series or time series. | ||
VEL | velocity normal to the boundary is imposed. | |
Required further specification by means of Fourier series or time series. | ||
DISCH | discharge per unit width normal to the boundary is imposed. | |
Required further specification by means of Fourier series or time series. | ||
RIEMANN | Riemann invariant is imposed. It is defined as u2 with | |
u the velocity normal to the boundary and h the water depth. | ||
The sign depends on the location of the boundary. The plus sign refers | ||
to an inflow velocity at the western/left and southern/lower boundaries, | ||
and the minus sign refers to inflow velocity at the eastern/right and | ||
northern/upper boundary. This boundary condition is particularly meant | ||
for a supercritical flow or hydraulic jump in e.g. rivers or open channels. | ||
Required further specification by means of Fourier series or time series. | ||
LRIEMANN | linearized Riemann invariant is imposed. It is defined as u | |
with u the velocity normal to the boundary, the water level and d the | ||
bottom level. The sign depends on the location of the boundary. The plus | ||
sign refers to an inflow velocity at the western/left and southern/lower | ||
boundaries, and the minus sign refers to inflow velocity at the eastern/right | ||
and northern/upper boundary. Note that linearized Riemann invariants can | ||
only be applied if the water level () is small compared to the local bottom | ||
level (d). This is mainly applicable for a subcritical flow in relative deep | ||
waters. Examples are tidal flows in a continental shelf or in a harbour. | ||
Required further specification by means of Fourier series or time series. | ||
WEAKREFL | the boundary condition is weakly reflective. | |
Required further specification by means of Fourier series or time series | ||
of water level, or regular or irregular waves by means of a spectrum. | ||
SOMMERFELD | Sommerfeld radiation condition is imposed. | |
No further specification is needed. | ||
OUTFLOW | water depth is aligned to bottom level (for supercritical flow only). | |
No further specification is needed. | ||
LAYER | indicates a layer where the boundary condition is given. | |
[k] | layer index (1 [k] [kmax]). | |
HYPERBOLIC | the vertical hyperbolic cosine profile for velocity at the boundary is assumed. | |
LOGARITHMIC | the vertical logarithmic profile for velocity at the boundary is assumed. | |
SMOOTHING | with this option a ramp function is applied to start up the simulation smoothly. | |
[period] | the smoothing period of which the unit is indicated in the next option: | |
SEC unit seconds | ||
MIN unit minutes | ||
HR unit hours | ||
DAY unit days | ||
ADDBOUNDWAV | with this option second order bound long wave is added to the first order, | |
irregular waves. | ||
CONSTANT | with this option the boundary condition is constant along the side or segment. | |
FOURIER | the Fourier series is defined by means of the following parameters: | |
[azero] | the amplitude for zero frequency is given (in m). | |
[ampl] | the amplitudes for a number of components are given (in m). | |
[omega] | the angular frequencies for a number of components are given (in rad s^{-1}). | |
[phase] | the phase for a number of components are given (in degrees). | |
REGULAR | monochromatic, long-crested wave is defined with the following parameters: | |
[h] | the wave height (in m). | |
[per] | the wave period (in s). | |
[dir] | the wave direction (in degrees; Cartesian or Nautical convention, see | |
command SET). | ||
Default: no specification of [dir] means incident direction is perpendicular | ||
to the boundary (only in case of rectilinear grid). | ||
SPECTRUM | the wave spectrum is defined by means of the following spectral parameters | |
(see command BOUND SHAPE for spectral shape): | ||
[h] | the characteristic wave height (in m). | |
[h] is the value of the significant wave height, if option SIG was chosen | ||
in command BOUND SHAPE or | ||
[h] is the value of the RMS wave height, if option RMS was chosen | ||
in command BOUND SHAPE. | ||
[per] | the characteristic wave period (in s). | |
[per] is the value of the peak period, if option PEAK was chosen | ||
in command BOUND SHAPE or | ||
[per] is the value of the mean period T_{m01}, if option MEAN was chosen | ||
in command BOUND SHAPE. | ||
[dir] | the peak wave direction (in degrees; Cartesian or Nautical convention, see | |
command SET). | ||
Default: no specification of [dir] means incident direction is perpendicular | ||
to the boundary (only in case of rectilinear grid). | ||
[dd] | coefficient of directional spreading; a cos^{m}() distribution is assumed. | |
[dd] is interpreted as the directional standard deviation in degrees, | ||
if the option DEGREES is chosen in the command BOUND SHAPE. | ||
[dd] is interpreted as the power m, if the option POWER is chosen | ||
in the command BOUND SHAPE. | ||
Default: [dd] = 0., i.e. no directional spreading. | ||
[cycle] | the cyclic period of the time series of surface elevation to be synthesized. | |
This may correspond to the time period over which surface elevation is | ||
outputted after steady-state condition has been established. The | ||
corresponding unit is indicated in the next option: | ||
SEC unit seconds | ||
MIN unit minutes | ||
HR unit hours | ||
DAY unit days | ||
SERIES | the time series is given in a file. | |
This file is for only one location; it has a number of lines which each contain | ||
2 numbers, i.e.: time, quantity. The notation of time is indicated by [itmopt] | ||
(see below). However, if time is represented as a real number in seconds, then | ||
do not specify [itmopt]. The quantity depends on the type of boundary | ||
condition (see command BTYPE). | ||
Example of such a file containing surface elevation in meters ([itmopt] = 7): | ||
000000.000 0.0000000E+00 | ||
000001.000 4.2307975E-08 | ||
000002.000 1.6923190E-07 | ||
000003.000 3.8077177E-07 | ||
000004.000 6.7692758E-07 | ||
000005.000 1.0576993E-06 | ||
000006.000 1.5230870E-06 | ||
000007.000 2.0730906E-06 | ||
'fname' | name of the file containing the time series. | |
[itmopt] | time coding option. The following format can be employed: | |
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 | ||
5 : 87/05/30 15:30:00' | ||
6 : as in WAM 8705301530 | ||
7 : 153000.000 | ||
Default: no specification of [itmopt] means time is represented as | ||
a real number in seconds. | ||
SPECFILE | the wave spectrum is given in a file. There are two types of files: | |
files containing 1D or non-directional wave spectrum | ||
(usually from measurements), and | ||
files containing 2D or directional wave spectrum | ||
(possibly from a SWAN run). | ||
A file containing the 1D wave spectrum is for only one location; it has | ||
the string SPEC1D on the first line of the file and a number of lines which | ||
each contain 2 numbers, i.e.: frequency in Hz, variance density in m^{2}/Hz. | ||
Example of such a file: | ||
SPEC1D | ||
3.8602E-03 5.2168E-01 | ||
5.7903E-03 1.0230E+00 | ||
7.7204E-03 1.4567E+00 | ||
9.6505E-03 1.7232E+00 | ||
1.1581E-02 1.8832E+00 | ||
1.3511E-02 1.7570E+00 | ||
1.5441E-02 1.3429E+00 | ||
1.7371E-02 9.8666E-01 | ||
The structure of the files containing directional spectrum is described in | ||
Appendix D of the SWAN User Manual. These files may only contain | ||
stationary wave spectra, and can be used for one location only. | ||
'fname' | name of the file containing the wave spectrum. | |
[cycle] | the cyclic period of the time series of surface elevation to be synthesized. | |
This may correspond to the time period over which surface elevation is | ||
outputted after steady-state condition has been established. The | ||
corresponding unit is indicated in the next option: | ||
SEC unit seconds | ||
MIN unit minutes | ||
HR unit hours | ||
DAY unit days | ||
VARIABLE | with this option the boundary condition can vary along the side or segment. | |
The boundary condition 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. | ||
[len] | 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 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. | ||
SPECSWAN | the wave spectra are given in a file and are obtained from a SWAN run. The | |
structure of this file is described in Appendix D of the SWAN User Manual. | ||
This file must contain more than 1 stationary wave spectrum, either 1D or 2D. | ||
The coordinates of the locations will be taken into account and SWASH will | ||
interpolate the spectra to the given boundary side or segment. The coordinate | ||
system of the SWAN run must be the same as the one used by the current | ||
SWASH run. See also Section 2.6. | ||
CANNOT BE USED IN 1D-MODE. | ||
'fname' | name of the file containing the wave spectra. | |
[cycle] | the cyclic period of the time series of surface elevation to be synthesized. | |
This may correspond to the time period over which surface elevation is | ||
outputted after steady-state condition has been established. The | ||
corresponding unit is indicated in the next option: | ||
SEC unit seconds | ||
MIN unit minutes | ||
HR unit hours | ||
DAY unit days |
| 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. |