OpenFOAM

OpenFOAM is an open-source computational fluid dynamics (CFD) toolbox widely used for simulating fluid flow, turbulence, heat transfer, and other complex physical processes.

This page provides guidance on using OpenFOAM on Calder, including loading the available versions and submitting parallel jobs. For detailed information about OpenFOAM, its solvers, physical models, case setup, and advanced usage, please refer to the official OpenFOAM documentation.

Available versions

The following versions of OpenFOAM are currently available on Calder:

Version	Module
OpenFOAM 12	openfoam-org/12
OpenFOAM v2512	openfoam/2512

Calder uses a hierarchical module system. Before loading OpenFOAM, load the Calder CPU environment and the required OpenMPI version:

module load calder/cpu
module load openmpi/5.0.10

You can then load the OpenFOAM version you require:

module load openfoam-org/12

or:

module load openfoam/2512

Running OpenFOAM in parallel

OpenFOAM supports parallel execution using MPI. A parallel OpenFOAM case is divided into multiple subdomains using decomposePar, with each subdomain processed by an MPI process. After the simulation has completed, the results can be combined using reconstructPar.

The number of subdomains should normally match the number of MPI processes requested from Slurm. This is configured in the system/decomposeParDict file using the numberOfSubdomains entry.

Single node

The following example runs an OpenFOAM case using 16 CPU cores on a single node:

#!/bin/bash
#SBATCH --job-name=openfoam
#SBATCH --time=01:00:00
#SBATCH --nodes=1
#SBATCH --ntasks=16
#SBATCH --mem=128G

module load calder/cpu
module load openmpi/5.0.10
module load openfoam/2512

# Decompose the case for parallel execution
decomposePar

# Run the simulation
mpirun -np $SLURM_NTASKS simpleFoam -parallel > log.simpleFoam

# Reconstruct the results
reconstructPar

Before submitting the job, make sure that numberOfSubdomains in system/decomposeParDict is set to 16.

Multiple nodes

OpenFOAM can also use multiple compute nodes. For example, the following job uses 64 CPU cores across two nodes:

#!/bin/bash
#SBATCH --job-name=openfoam
#SBATCH --time=04:00:00
#SBATCH --nodes=2
#SBATCH --ntasks=64
#SBATCH --ntasks-per-node=32
#SBATCH --mem=256G

module load calder/cpu
module load openmpi/5.0.10
module load openfoam/2512

# Decompose the case for parallel execution
decomposePar

# Run the simulation across the allocated nodes
mpirun -np $SLURM_NTASKS simpleFoam -parallel > log.simpleFoam

# Reconstruct the results
reconstructPar

For this example, set numberOfSubdomains in system/decomposeParDict to 64.

Note

The examples above use simpleFoam as an example solver. Replace it with the solver appropriate for your OpenFOAM case.

The number of MPI processes should match the number of subdomains specified in decomposeParDict. When changing the number of CPU cores or nodes requested, update numberOfSubdomains accordingly.

The amount of memory requested with --mem is specified per node. Choose a value appropriate for the size and memory requirements of your case.