15 Scale-Adaptive Turbulence Extension

The selectable scale-adaptive option is an extension of the GE carrier model, not a separate carrier-flow family. A separate LES carrier model is not exposed as a selectable production option in the current Physics panel.

15.1 Scale-adaptive source term

The turbulence length scale used by the source is

The cell filter length is

NeuralFlow uses the magnitude of the velocity Laplacian,

to form a von-Karman-like scale. The two candidates are

The current constants are , , and .

15.2 SAS production in the omega equation

Let

The added nonnegative source is

The current constants are and . This term is added to the omega source group together with .

15.3 Additional derivative requirement

Because depends on , the SAS path explicitly computes a velocity-Laplacian magnitude in addition to the first primitive gradients used by the base model. This is why the optional SAS path has additional gradient/communication work compared with steady GE-RANS.

15.4 Interpretation and limitations

The source term is clipped at zero, so the scale-adaptive contribution cannot become a negative omega production through this term. Its effectiveness is controlled by the ratio and by the competing normalized / gradient term. The current manual therefore treats SAS as an optional source modification to the GE-RANS equations rather than advertising a separate LES/DES equation set.