FD2TRIM
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Basic Information
Name of Program
FD2TRIM
VersionDate
Mai 1998
DescriptionDate
October 1999
Catchwords
preprocessor
finite difference method
conversion of a finite difference grid
numerical modelling system FIDIRB
numerical modelling system TRIM2D
Short Description of Functionality
The program FD2TRIM is a preprocessor for the numerical model TRIM2D. This program serves to convert the bathymetry given in the FIDIRBformat into a equivalent one defined on an other finite difference grid given in the TRIMformat.
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 Vnodes of a computational finite difference grid for TRIM2D.
It is also possible to use a different grid spacing for the output grid compared with the grid spacing of the input grid.
InputFiles
 general input data (filetype fd2trim.dat)
 FIDIRBbathymetry (filetype topo.bin)
 (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.
 (optional) file with protected Unodes (MJBspecial) (filetype fidirb.u.save)
 (optional) file with protected Vnodes (MJBspecial) (filetype fidirb.v.save)
OutputFiles
 equivalent TRIM2D grid (filetype tr2.topo.bin)
 (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)
 (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)
 informative printer file (filetype fd2trim.sdr)
 (optional) trace of program execution (filetype fd2trim.tr
Methodology
For every computational U and Vpoint of a TRIM2D grid the modell bathymetry is generated from the values of the FIDIRB grid, where depths are prescribed at the ZETApoints (at the center of each grid cell). The depths at the U and Vpoints are calculated from the depths of two ZETApoints in such a way, that the U and Vpoints are central with respect to the ZETApoints used. Two methods are implemented:
 Depths at U and Vpoints are mean values of the corresponding ZETApoints. 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.
 Depths at U and Vpoints are minimum values of the corresponding ZETApoints. This guarantees the best approximation of the volume, but depths at U and Vpoints are underestimated systematically. Therefore computed wave speed may be also underestimated.
The depths given along the protection polygons are mapped as a continuous zigzagline onto the U and Vpoints 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
Documentation/Literature
$PROGHOME/examples/fd2geom/
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