In the case of Detached Eddy Simulations (DES), there are two regions in a computational domain that are treated in RANS-like and LES-like manners. The original Spalart-Allmaras DES model (DES97) formulation is based on the assumption that the wall-parallel grid spacing near the wall is in excess of the boundary-layer thickness \(\delta\) by a good margin so that the entire boundary layer can be handled by RANS [1].
| Settings of DESModelRegions |
In OpenFOAM, we can visually check these regions using the DESModelRegions function objects. It is also available in iconCFD.
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functions { DESModelRegions1 { type DESModelRegions; functionObjectLibs ("libutilityFunctionObjects.so"); enabled true; outputControl outputTime; log true; resultName DESRegions; } } |
If log it true, the volume percent (%) of RANS and LES regions will be output to the screen:
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DESModelRegions DESModelRegions1 output: LES = 62.2455 % (volume) RAS = 37.7545 % (volume) |
| Source Code |
Directory:
OpenFOAM-v1606+/src/postProcessing/functionObjects/utilities/
DESModelRegions
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void Foam::DESModelRegions::execute() { if (active_) { const fvMesh& mesh = refCast<const fvMesh>(obr_); if (log_) Info<< type() << " " << name_ << " output:" << nl; volScalarField& DESModelRegions = const_cast<volScalarField&> ( mesh.lookupObject<volScalarField>(resultName_) ); if (mesh.foundObject<DESModelBase>(turbulenceModel::propertiesName)) { const DESModelBase& model = mesh.lookupObject<DESModelBase> ( turbulenceModel::propertiesName ); DESModelRegions == model.LESRegion(); scalar prc = gSum(DESModelRegions.internalField()*mesh.V()) /gSum(mesh.V())*100.0; file() << obr_.time().value() << token::TAB << prc << token::TAB << 100.0 - prc << endl; if (log_) Info << " LES = " << prc << " % (volume)" << nl << " RAS = " << 100.0 - prc << " % (volume)" << nl << endl; } else { if (log_) Info << " No DES turbulence model found in database" << nl << endl; } } } |
| References |
[1] P. R. Spalart, Detached-Eddy Simulation. Annual Review of Fluid Mechanics 41, 181-202, 2009.