Setup

Setting up a Grid

Code Structure

The |GridGen| code is divided into three major parts:

1. Input: User input is entered into a file called input_file.xml.
2. Main Program: The main program for solving the elliptical grid is gridgen.F90 in the <parent directory>/src/main folder.
3. Output: Once the code is run, the results are stored in the <parent directory>/output/ folder.

Input File

The inputs for GridGenerator are specified in the input_file.xml. The input file is accessed as follows:

1. Go to the parent directory:

   $ cd <path to |GridGen|>
   

   Make sure that you are in the directory that contains the files setup.py, input_file.xml, and the folder src.

2. Open the input file:

   $ vi input_file.xml
   

3. The main parts of the input file are shown below

The input file is divided into different parts. The geometry is set in the <geometry> module, which is shown below:

<geometry>
  <x1>-0.8</x1>
  <y1>0.0</y1>
  <x2>1.8</x2>
  <y2>0.0</y2>
  <x3>-0.8</x3>
  <y3>1.0</y3>
  <x4>1.8</x4>
  <y4>1.0</y4>
  <FEsize>11</FEsize>
  <DCsize>11</DCsize>
  <Geosize>21</Geosize>
  <Geoptx1>0.0</Geoptx1>
  <Geopty1>0.0</Geopty1>
  <Geoptx2>1.0</Geoptx2>
  <Geopty2>0.0</Geopty2>
  <imax>41</imax>
  <jmax>19</jmax>
</geometry>

For setup of the solver, most of the inputs are set in the <setup> module. A snippet of this module is shown below:

<setup>
  <Project>2D_Grid_Generator</Project>
  <nmax>500</nmax>
  <iControl>1</iControl>
  <Cy>2.0</Cy>
  <RMSres>1.0e-6</RMSres>
</setup>

Compilation

The following sequence of commands is used to compile a single simulation.

1. Go to the parent directory:

   $ cd <path to |GridGen|>
   

   Make sure that you are in the directory that contains the files setup.py, input_file.xml, and the folder src.

2. Clean existing results:

   $ ./setup.py -u clean heavy
   

   This command removes the existing files in the output folder |GridGen|/output/ and deletes the object files from previous compilations. Backup any required results before using this command.

3. Set working directory path:

   $ ./setup.py -u set_path
   

   This command sets the working directory path

4. Set the output directory:

   $ ./setup.py -u create_subdirectories
   

5. Compile the build:

   $ ./setup.py -e configure
   

   An empty CMake window opens. Press [c] on the keyboard to configure the program.

   This brings up the CMake window. There are two options for the CMAKE_BUILD_TYPE :

   • Release: This compiles the program in regular mode; debugging flags are disabled.
   • Debug: This compiles the program in debug mode; errors and warnings are displayed on the terminal.

   Press [Enter] on the keyboard to edit the option (to change from Release to Debug or vice versa)

   The file grid.x will now be generated in the parent directory

6. Execute the program:

   $ ./grid.x
   

   This command runs the program. If Debug mode is enabled in GRIDGEN_COMPILE_DEFS, appropriate output is printed on the Terminal screen.

Results

The results are stored in the output/ folder inside the parent directory. The output directory contains several files .dat and .tec where the calculations are written. In addition, there is also a output/plot folder, where figures from the calculated data are plotted. To plot the results. open the inputfile and enter the name of the .dat file that was generated in the files entry (as shown below).

<PostProcessing>
    <plot>
       <files>RESULTDATFILE</files>
       ...
    </plot>
</PostProcessing>

Then, from the parent directory execute the following command to plot the results using |GridGen|’s inbuilt plotting utility:

$ ./setup.py -p single_plot

This will generate the RMS line plots from the results, which will be stored in the output/plot folder.