FD2TRIM

Basic Information

Name of Program

FD2TRIM

Version-Date

Mai 1998

Description-Date

October 1999

Catchwords

preprocessor
finite difference method
conversion of a finite difference grid
numerical modelling system FIDIRB
numerical modelling system TRIM-2D

Short Description of Functionality

The program FD2TRIM is a preprocessor for the numerical model TRIM-2D. This program serves to convert the bathymetry given in the FIDIRB-format into a equivalent one defined on an other finite difference grid given in the TRIM-format.

Man made structures (e.g. dams, groynes, etc.) which are given as polygonal lines can be (more or less) equivalently mapped onto the U- and V-nodes of a computational finite difference grid for TRIM-2D.

It is also possible to use a different grid spacing for the output grid compared with the grid spacing of the input grid.

Input-Files

1. general input data (filetype fd2trim.dat)
2. FIDIRB-bathymetry (filetype topo.bin)
3. (optional) protection polygons (filetype nodes.save)
   • Notice: protection polygons should represent mostly linear or slightly curved structures. Loops or similar silly things are to be avoided.
4. (optional) file with protected U-nodes (MJB-special) (filetype fidirb.u.save)
5. (optional) file with protected V-nodes (MJB-special) (filetype fidirb.v.save)

Output-Files

1. equivalent TRIM-2D grid (filetype tr2.topo.bin)
2. (optional) modified structures (filetype insel.dat)
   • Notice: this file contains the protected structure polygons given in the input file of type nodes.save mapped onto the edges of the grid cells (this file can be used for control purposes, e.g. by the program HVIEW2D)
3. (optional) modified protection polygons (filetype nodes.save)
   • Notice: this file contains the protected structure polygon nodes given in the input file of type nodes.save (this file can be eventually used later with the program TR2GEOM)
4. informative printer file (filetype fd2trim.sdr)
5. (optional) trace of program execution (filetype fd2trim.tr

Methodology

For every computational U- and V-point of a TRIM-2D grid the modell bathymetry is generated from the values of the FIDIRB grid, where depths are prescribed at the ZETA-points (at the center of each grid cell). The depths at the U- and V-points are calculated from the depths of two ZETA-points in such a way, that the U- and V-points are central with respect to the ZETA-points used. Two methods are implemented:

1. Depths at U- and V-points are mean values of the corresponding ZETA-points. Therefore the depths are approximated in the best possible way and the speed of the tidal wave can be calculated correctly. On the other hand side the volume of the system under investigation may be overestimated systematically.
2. Depths at U- and V-points are minimum values of the corresponding ZETA-points. This guarantees the best approximation of the volume, but depths at U- and V-points are underestimated systematically. Therefore computed wave speed may be also underestimated.

The depths given along the protection polygons are mapped as a continuous zig-zag-line onto the U- and V-points of the grid.

Program(s) to run before this Program

FD2ADDTOPO, FD2DEL, FD2HYPSO, FDGITTER05 , POLWIND, TR2FIDI

Program(s) to run after this Program

FD2MET, TOUTR, TR2FIDI , TR2REFRESH, TR2RND, TR2VOR, TRGITTER05

Additional Information

Language

Fortran90

Additional software

-

Original Version

G. Lang

Maintenance

working group PRE

Documentation/Literature

$PROGHOME/examples/fd2geom/

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