radarfdtd.man

The purpose of this program is to enable building a config file to the radarFDTD package using a mo

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.\" ========================================================================
.\"
.IX Title "MANUAL 1"
.TH MANUAL 1 "2004-09-24" "perl v5.8.4" "User Contributed Perl Documentation"
.SH "NAME"
radarFDTD \- a full 3D simulation of electromagnetic waves with efficient absorbing boundary conditions
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
radarFDTD directory [configuration file]
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
When started the program needs a directory as a command line parameter. If there is no second parameter defined it assumes the file is named sim.cfg. After starting it will output quite a few informations about the simulation it is going to start. The most important part is the section about memory, do not try to run the program in the swap area, since this will surely slow it down and may risk your hard disk which may start to smoke after a few weeks of hard work :\-(.
.SH "CONFIGURATION FILE"
.IX Header "CONFIGURATION FILE"
In this section there will be a short description of all sections within the file sim.cfg. Feel free to experiment with those settings, but do not blame me, if something goes entirely wrong... ;\-)
.PP
Since I am not a native English speaker, I hope you are not offended if I left some mistakes in here.
.PP
Last thing, before we start: all lines which are empty or have a leading pound sign '#' are ignored (\s-1BTW\s0, can someone explain to me why this double cross is called pound sign?).
.Sh "\s-1VERSION\s0 \s-1NUMBER\s0"
.IX Subsection "VERSION NUMBER"
.Vb 2
\&  # version number is...
\&  3
.Ve
.PP
This just states the version number this configuration file was written for. This is checked by the program and if it does not match the internal layout, it will not use it.
.Sh "\s-1MEMORY\s0"
.IX Subsection "MEMORY"
.Vb 2
\&  # maximum number of bytes the program may allocate
\&  100000000
.Ve
.PP
This is the number of bytes the program is allowed to allocate. Please change this according to your own need (or the memory limits of your computer; remember: this limit should be less than the physical amount of memory installed)
.Sh "\s-1MAXIMUM\s0 \s-1PML\s0 \s-1CONDUCTIVITY\s0"
.IX Subsection "MAXIMUM PML CONDUCTIVITY"
.Vb 2
\&  # insert maximum pml conductivity here [S/m]
\&  0.025
.Ve
.PP
There is a fixed equation which rules the rise of conductivity. If you are interested in a more detailed explanation, have a look at the paper of Fang and Wu from 1996 (citation can be found in the \s-1README\s0 file). As a good first guess try something between 10 and 50 mS/m, which should be reasonable good.
.Sh "\s-1MAXIMUM\s0 \s-1STRETCHING\s0"
.IX Subsection "MAXIMUM STRETCHING"
.Vb 2
\&  # insert maximum pml-stretching here [1]
\&  4.0
.Ve
.PP
Stretching should prevent evanescent waves to keep on moving within the perfectly matched layers, do not use too high values here, 2 to 4 seems to be quite reasonable.
.Sh "\s-1STEEPNESS\s0"
.IX Subsection "STEEPNESS"
.Vb 2
\&  # insert steepness here
\&  2.0
.Ve
.PP
The higher the value for steepness is, the less reflection will occur at the boundary between the simulation space and the absorbing layer which is generally a good thing. But unfortunately a high value here means that there will be a high reflection before a wave manages to reach the layer, which is a \s-1PEC\s0 (perfectly conducting layer)
.Sh "\s-1SIMULATION\s0 \s-1LENGTH\s0"
.IX Subsection "SIMULATION LENGTH"
.Vb 2
\&  # Length of Simulation [s]
\&  30.0e-9
.Ve
.PP
This just states the overall time duration of the simulation in seconds. Do not try to run a simulation too long, i.e. for a few seconds if your simulation space is only a few meters wide... it will take ages
.Sh "\s-1SIZE\s0 \s-1OF\s0 \s-1SIMULATION\s0 \s-1SPACE\s0"
.IX Subsection "SIZE OF SIMULATION SPACE"
.Vb 2
\&  # size of simulation space (number of boxes in x-, y- and z-direction, respectively
\&  41 41 41
.Ve
.PP
These three numbers specify how man cells are used in each direction (let us call them x,y and z for the time being). I usually use odd numbers, so I can place the transmitter in the very middle of the simulation box, but handle this as you like to
.Sh "\s-1CELL\s0 \s-1SIZES\s0"
.IX Subsection "CELL SIZES"
.Vb 2
\&  # real size of a box [m] (x,y,z)
\&  0.025 0.025 0.025
.Ve
.PP
Here you specify how big (or small) a single Yee-cell should be, in this example this is about 2.5 cm (which is roughly an inch ;\-)). Be careful with this selection, since you should have at least 10 boxes per main wavelength you want to simulate, otherwise you might get strange wavy things out of the simulation.
.Sh "\s-1TIME\s0 \s-1STEP\s0 \s-1SIZE\s0"
.IX Subsection "TIME STEP SIZE"
.Vb 4
\&  # this number is a bit special: if positive it is the size of a time steps in seconds,
\&  # if negative, a matching time step is computed via the Courant-criterion
\&  # and finally divided by this number, i.e.