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## Computational grid

       | -> REGular [xpc] [ypc] [alpc] [xlenc] [ylenc] [mxc] [myc] |
CGRID <                                                             >   &
|    CURVilinear [mxc] [myc]  (EXCeption  [xexc]  [yexc])   |

| -> X
REPeating  <
|  Y


With this required command the user defines the geographic location, size, resolution and orientation of the computational grid in the problem coordinate system (see Section 2.5.2) in case of a uniform, rectilinear computational grid or an orthogonal curvilinear grid. The origin of the regular grid and the direction of the positive x -axis of this grid can be chosen arbitrary by the user.

 REGULAR this option indicates that the computational grid is to be taken as uniform and rectangular. CURVILINEAR this option indicates that the computational grid is to be taken as curvilinear. The user must provide the coordinates of the grid points with command READGRID COOR. [xpc] 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 (Cartesian coordinates). In case of spherical coordinates there is no default, the user must give a value. [ypc] 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. [alpc] direction of the positive x -axis of the computational grid (in degrees, Cartesian convention). In 1D-mode, [alpc] should be equal to the direction [alpinp] (see command INPGRID). Default: [alpc] = 0.0 [xlenc] length of the computational grid in x -direction (in m). In case of spherical coordinates [xlenc] is in degrees. [ylenc] 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. [mxc] number of meshes in computational grid in x -direction for a uniform, rectilinear grid or -direction for a curvilinear grid (this number is one less than the number of grid points in this domain!). [myc] number of meshes in computational grid in y -direction for a uniform, rectilinear grid or -direction for a curvilinear grid (this number is one less than the number of grid points in this domain!). In 1D-mode, [myc] should be 0. EXCEPTION only available in the case of a curvilinear grid. If certain grid points are to be ignored during the computation (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. [xexc] 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 COOR). Required if the option EXCEPTION is used. Default: [xexc] = 0.0 [yexc] 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 COOR). Required if the option EXCEPTION is used. Default: [yexc] = [xexc] REPEATING this option indicates that the grid is repeated in one specific direction. It means that information leaving at one end of the domain enters at the opposite end. So, the current or wave field is periodic in one direction with the length of the domain in that direction. NOT FOR 1D-MODE. X the computational grid is repeated in x -direction. This is default. Y the computational grid is repeated in y -direction.

For illustration of a regular grid with its dimensions, see Figure 4.1.

READgrid COORdinates [fac] 'fname' [idla] [nhedf] [nhedvec] &

| -> FREe                 |
|                         |
|             | 'form' |  |
<     FORmat  <          >  >
|             | [idfm] |  |
|                         |
|    UNFormatted          |


CANNOT BE USED IN 1D-MODE.

This command READGRID COOR must follow a command CGRID CURV. With this command (required if the computational grid is orthogonal curvilinear; not allowed in case of 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). See command READINP for the description of the options in this command READGRID. SWASH will check whether all angles in the grid are > 0 and < 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.

                               | M
VERTical [kmax] < [thickness] <            >
| -> PERC


With this optional command the user indicates that the run will be in multi-layered mode and controls the distribution of vertical layers.

 [kmax] number of vertical layers. [thickness] layer thickness (in meters or as percentage of water depth). M thickness is given in meters. This layer has a fixed thickness. PERC thickness is given as percentage. This layer has a variable thickness. This is default.

Notes:
• The layers are numbered from top (=1) to bottom (=[kmax]).
• If no [thickness] is given, the layers are distributed equidistantly.
• The sum of thicknesses defined as percentages must be 100.
• At least one layer with variable thickness must be given.
• The layers interfaces are equivalent to the well-known sigma planes, if all the layers have a variable thickness.
• For short wave simulations, it is advised to choose variable thicknesses only, preferably equidistantly distributed.

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