Introduction

This repository implements the Fractional-Step, Pressure Projection method of Chorin into OpenFOAM. The solver is named fsppFoam.

Notably, it is a fully implicit implementation, meaning you can use any CFL number you like.

Compilation

Open your terminal and change into the fsppFoam/ folder. Ensure that OpenFOAM is loaded into your environment (e.g. upon running checkMesh you get some OpenFOAM output printed to the console).

Then, to compile the solver into your user appbin directory, type:

wmake

This will do the compilation for you. If no errors appear, your solver should be compiled and available and you can check this by typing

fsppFoam

Testing

To test that the solver is working correctly, change into the lidDrivenCavity/ folder, which contains the lid driven cavity example and it is set up to be used with the new solver.

It contains a few post-processing routines for easy plotting of results which will automatically get executed if you run the Allrun script by typing

./Allrun

After the simulation has finished, you will see two new figures within the post-processing directory, one for the residuals, and one for the velocity profile at the vertical and horizontal center line, which is compared against the paper by Ghia et al.

The solver is set up, on purpose, to run at a high CFL number (CFL(max)=50, the average is around 3). The solver is still converging with correct results. Good luck with simpleFoam or pimpleFoam ...

Run your own cases

If you want to use this solver for your own cases, you need to provide a dictionary entry within the system/fvSolution file for the FS-PP method. This contains entires such as non-orthogonal correctors to use, similar to the SIMPLE or PISO entry. In-fact, you can have a combined entry of the form:

"(SIMPLE|PISO|PIMPLE|FS-PP)"
{
    consistent                 yes;
    nCorrectors                2;
    nOuterCorrectors           1;
    nNonOrthogonalCorrectors   0;
    pRefCell                   0;
    pRefValue                  0;
}

This entry will work for simpleFoam, pisoFoam, icoFoam, pimpleFoam, and, the current solver fsppFoam.

Known limitations

The Rhie-Chow-like interpolation is implemented within the fsppFoam/pCorrection.H file on lines 6-10, and then used in the pressure poisson solver on lines 17-22. This type of coupling is inspired from the simpleFoam solver, but has shown to be somewhat unstable for high-Reynolds number flows at low y+ values (around y+=1).