OpenFOAM

Enabling

Search through the available modules to see what OpenFOAM ones exist

$ module avail openfoam

This only shows versions that are compatible with other loaded modules. All versions can be found with the spider command along with directions on what else needs to be loaded to load them

$ module spider openfoam
$ module spider openfoam/11

Note that there two releases of OpenFOAM. One is openfoam.com and uses vYYMM (year and month) version numbering. The other is openfoam.org and uses X and X.Y version numbering. With the exception of a some specific features, the two are largely similar.

Load the openfoam module (not specifying a version uses the default). Note that spider may shom additional modules that you need to load first.

$ module load gcc
$ module load openfoam

Can use the show command to see what this does. The environment variables that it sets can be accessed using the $VARIABLE syntax (substuting VARIABLE for the name of the variable).

$ module show openfoam

Create the top-level user OpenFOAM directory and change to it (not strictly required, but recommended by the tutorials)

$ mkdir -p $FOAM_RUN
$ cd $FOAM_RUN

Tutorial

OpenFOAM comes with several tutorials in the $FOAM_TUTORIALS directory. This includes the ones in the user manual.

$ ls $FOAM_TUTORIALS

Until version 11, the standard first tutorial was a cavity flow problem. It is still available in the legacy directory though, and it is one of the simplest examples, so we will use it.

$ cp -r $FOAM_TUTORIALS/legacy/incompressible/icoFoam/cavity/cavity .
$ cd cavity

Lid driven cavity problem.

Generate mesh

Generate the mesh data files in constant/polyMesh from the higher-level description file system/blockMeshDict

$ blockMesh

Lid driven cavity vertices.

Interactive run

Run the simulation (incompressible flow using the PISO algorithm) in an interactive session to test

$ salloc --mem-per-cpu=500M --ntasks=1 --account=def-SPONSOR

$ icoFoam
$ exit

Batch run

Create a run.sh (name not important) using nano to do the same

$ nano run.sh

#!/bin/bash
#SBATCH --time=00:05:00
#SBATCH --mem-per-cpu=500M
#SBATCH --ntasks=1
#SBATCH --account=def-SPONSOR
#SBATCH --output=icoFoam-%J.log
icoFoam

Submit the batch file to the cluster to run

$ sbatch run.sh

New case

Make a new cavityMPI case based on the cavity case setup

$ cd ..
$ foamCloneCase cavity cavityMPI
$ cd cavityMPI

Run in parallel

Basic four processor system/decomposeParDict decomposition setup copied from damBreak tutorial

$ cp $FOAM_TUTORIALS/incompressibleVoF/damBreakLaminar/damBreak/system/decomposeParDict

Decompose the cavity across the four processors

$ decomposePar

Run the simulation in parallel using four processors

$ salloc --mem-per-cpu=500M --ntasks=4 --account=def-SPONSOR

$ mpirun icoFoam -parallel
$ exit

Collect the output back into a single file

$ reconstructPar

Prep for ParaView

Create a NAME.foam file to give something to open in ParaView (name doesn’t matter – just identifies it as an OpenFOAM directory)

$ touch cavity.foam

Can also generate VTK input files

$ foamToVtk