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7.2 Turbulence models
The turbulenceProperties dictionary is read by any solver that includes turbulence modelling. Within that file is the simulationType keyword that controls the type of turbulence modelling to be used, either:
- laminar
- uses no turbulence models;
- RASModel
- uses Reynolds-averaged stress (RAS) modelling;
- LESModel
- uses large-eddy simulation (LES) modelling.
If RASModel is selected, the choice of RAS modelling is specified in a RASProperties file, also in the constant directory. The RAS turbulence model is selected by the RASModel entry from a long list of available models that are listed in Table 3.9. Similarly, if LESModel is selected, the choice of LES modelling is specified in a LESProperties dictionary and the LES turbulence model is selected by the LESModel entry.
The entries required in the RASProperties are listed in Table 7.3 and those for LESProperties dictionaries are listed in Table 7.4.
modelThe incompressible and compressible RAS turbulence models, isochoric and anisochoric LES models and delta models are all named and described in Table 3.9. Examples of their use can be found in the $FOAM_TUTORIALS.
7.2.1 Model coefficients
The coefficients for the RAS turbulence models are given default values in their respective source code. If the user wishes to override these default values, then they can do so by adding a sub-dictionary entry to the RASProperties file, whose keyword name is that of the model with Coeffs appended, e.g. kEpsilonCoeffs for the kEpsilon model. If the printCoeffs switch is on in the RASProperties file, an example of the relevant …Coeffs dictionary is printed to standard output when the model is created at the beginning of a run. The user can simply copy this into the RASProperties file and edit the entries as required.
7.2.2 Wall functions
A range of wall function models is available in OpenFOAM that are applied as
boundary conditions on individual patches. This enables different wall function
models to be applied to different wall regions. The choice of wall function model is
specified through: 
in the 0/nut file for incompressible RAS; 
in the 0/mut
file for compressible RAS; 
in the 0/nuSgs file for incompressible LES;
in the 0/muSgs file for incompressible LES. For example, a 0/nut
file:
18 dimensions [0 2 -1 0 0 0 0];
19
20 internalField uniform 0;
21
22 boundaryField
23 {
24 movingWall
25 {
26 type nutkWallFunction;
27 value uniform 0;
28 }
29 fixedWalls
30 {
31 type nutkWallFunction;
32 value uniform 0;
33 }
34 frontAndBack
35 {
36 type empty;
37 }
38 }
39
40
41 // ************************************************************************* //
There are a number of wall function models available in the release, e.g. nutWallFunction, nutRoughWallFunction, nutSpalartAllmarasStandardRoughWallFunction, nutSpalartAllmarasStandardWallFunction and nutSpalartAllmarasWallFunction. The user can consult the relevant directories for a full list of wall function models:
find $FOAM_SRC/turbulenceModels -name wallFunctions
, 
and 
through optional E, kappa and Cmu keyword
entries.
Having selected the particular wall functions on various patches in the nut/mut file, the user should select epsilonWallFunction on corresponding patches in the epsilon field and kqRwallFunction on corresponding patches in the turbulent fields k, q and R.
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