[kreddy]

Hello all,

Does anyone know if we can average a variable along a single direction (say spanwise) during runtime? Specifically, I want to do spanwise averaging while calculating LL, MM in the homogenousDynSmagorinsky LES model, instead of averaging over the whole domain, like it seems to be doing now.
Just for a quick reference, here's the portion of the model in homogenousDynSmagorinsky.C where the model constant is being calculated.

dimensionedScalar homogeneousDynSmagorinsky::cD
(
    const volSymmTensorField& D
) const
{
    const volSymmTensorField MM
    (
        sqr(delta())*(filter_(mag(D)*(D)) - 4*mag(filter_(D))*filter_(D))
    );

    dimensionedScalar MMMM = average(magSqr(MM));

    if (MMMM.value() > VSMALL)
    {
        tmp<volSymmTensorField> LL =
            dev(filter_(sqr(U())) - (sqr(filter_(U()))));

        return 0.5*average(LL && MM)/MMMM;
    }
    else
    {
        return 0.0;
    }
}

So basically, I'd like to replace "average()" with "spanwiseaverage()".
Please let me know if any of you have any ideas.

[yzf1215]

Good question, karthik. -- Zifei
use a structured solver maybe -- Umair

[kreddy]

Originally Posted by yzf1215

Good question, karthik. -- Zifei
use a structured solver maybe -- Umair

wish I had that choice!

[dkxls]

I don't really have an answer to your question, other than implementing the functionality on your own using for-loops and if-statements.

However, since you are not the only one with this problem, there are quite some papers that address this issue, my favorite (with respect to dynamic coeff evaluation) would be the Lagrangian averaging proposed by Meneveau et al. (1996):

Meneveau, Charles, Thomas S. Lund, and William H. Cabot. “A Lagrangian Dynamic Subgrid-Scale Model of Turbulence.” Journal of Fluid Mechanics 319 (July 1996): 353–85. doi:10.1017/S0022112096007379.

The next OpenFOAM version will have this model implemented, see here:
https://github.com/OpenFOAM/OpenFOAM...icLagrangian.H