CFD Online Discussion Forums - kOmegaSST: bounding of arg1 and arg2

Hello, fellow Foamers,

I'm currently investigating the (incompressible) kOmegaSST turbulence model with respect to it's behaviour on different grid resolutions using a simple 2D zero pressure gradient flat plate testcase. While studying the implementation of said turbulence model in OpenFOAM 1.7.1 I stumbled across something I can't explain:

The arguments arg1 and arg2 are implemented as follows:

Code:

    volScalarField arg1 = min

    (

        min

        (

            max

            (

                (scalar(1)/betaStar_)*sqrt(k_)/(omega_*y_),

                scalar(500)*nu()/(sqr(y_)*omega_)

            ),

            (4*alphaOmega2_)*k_/(CDkOmegaPlus*sqr(y_))

        ),

        scalar(10)

    );

and

Code:

    volScalarField arg2 = min

    (

        max

        (

            (scalar(2)/betaStar_)*sqrt(k_)/(omega_*y_),

            scalar(500)*nu()/(sqr(y_)*omega_)

        ),

        scalar(100)

    );

Both arguments are used for the blending functions F1 and F2 respectively, which blend between the k-omega and k-epsilon turbulence models with increasing wall distance.

What puzzles me is that both arg1 and arg2 are being bounded to the minimum values 10 and 100 respectively, resulting in F1 and F2 always having the value 1 - regardless of the properties of the flow. This leads to the fact that the kOmegaSST-model implemented in OpenFOAM only uses the k-omega approach and forfeits the blending between k-omega and k-epsilon which was the original motivation of the SST turbulence model.

What's the reason for omitting the blending mechanism in OpenFOAM? Is this intended or am I missing something?

I'll be grateful for any kind of clarification.

Greetings,
Felix.