DGFS Test Cases

This repository contains test cases in normal shock flow, Couette flow, 2D pressure-driven flow in microchannel for the DGFS Full Boltzmann solver. The solver can be found in the following repository https://github.com/DGFSproj/DGFS-BE-Solver

Example: Running Couette Flow Case

This example demonstrates how to run a 2D Couette flow simulation using the DGFS-BE solver.

1. Download Required Files

Obtain the following files:

• dgfs_2d_couette.geo — GMSH geometry and mesh definition file
• dgfs_2d_couette.ini — DGFS configuration file (contains solver settings, initial/boundary conditions, etc.)

2. Generate the Mesh

Use GMSH to generate a .msh mesh file from the .geo definition:

gmsh -2 dgfs_2d_couette.geo

This will produce dgfs_2d_couette.msh.

(Optional) To visualize the mesh:

gmsh dgfs_2d_couette.msh

3. Convert to DGFS Mesh Format

Convert the GMSH mesh to DGFS-native .frfsm format:

frfs import dgfs_2d_couette.msh mesh.frfsm

This will produce mesh.frfsm.

4. Run the Simulation

Execute the solver using CUDA backend:

frfs run mesh.frfsm dgfs_2d_couette.ini -b cuda

This will produce solution output files with the .frfss extension inside the case directory, with frequency set in configuration file .ini.

5. Post-Processing: Convert to VTU Format

To convert .frfss files into .vtu format for visualization:

frfs export mesh.frfsm bulksol_dgfs_2d_couette-10.0.frfss bulksol_dgfs_2d_couette-10.0.frfss.vtu -d 16

• -d 16 means that each DG element is subdivided into 16 sub-elements for smoother visualization
• The output .vtu file can be visualized with ParaView or Tecplot

To visualize using Tecplot:

tec360 bulksol_dgfs_2d_couette-10.0.frfss.vtu

6. Resources about creating .geo and .msh file

https://freshkiss3d.gitlabpages.inria.fr/freshkiss3d/auto_examples_mesh/example_generate_mesh.html

http://www.manpagez.com/info/gmsh/gmsh-2.2.6/gmsh_47.php

https://www.manpagez.com/info/gmsh/gmsh-2.4.0/gmsh_69.php

https://openfoamwiki.net/index.php/2D_Mesh_Tutorial_using_GMSH

https://chi-tech.github.io/d4/db9/_gmsh_example_01.html

https://gmsh.info/doc/texinfo/gmsh.html