Turbulence

OpenFOAM includes support for

Usage

Turbulence models are specified in the $FOAM_CASE/constant/turbulenceProperties file, taking the form, e.g. when specifying the RAS kOmegaSST model:

simulationType      RAS;

RAS
{
    RASModel                kOmegaSST;

    // On/off switch
    turbulence              on

    // Optionally write the model coefficients at run-time
    printCoeffs             no;
}

Mesh requirements

The quality of turbulent flow predictions are heavily influenced by the computational mesh, whereby attention should be given to the constraints of the the various modelling approaches.

RAS

  • high Reynolds number: first cell height should be in the region of 30 < y+ < 200
  • low Reynolds number: mesh required to resolve the viscous sub-layer, typically using 10-20 layers

LES

  • mesh required to resolve the viscous sub-layer
  • requires high order schemes to adequately resolve the high-energy containing eddies

Numerical settings

Turbulence generation is driven by the velocity gradient. Errors arising from the gradient calculation, e.g. due to poor quality meshes, can lead to spurious turbulence predictions and solver instability. This effect can be partly compensated by the application of limited schemes.

Further information