[lakeat]

Dear all,

If I am not mistaken, the current dynamic models calculate the coefficients as a single scalar, not scalarfield, I mean C is not C(y), or C(x,y,z,t). The averaging process is not done in homogeneous directions.

I am a little confused, the original basic idea of Dynamic procedure would make sense better if averaging in homogeneous directions, wouldn't it?

Another question I have is, is the test filter used in OpenFOAM double size of the original filter? If I am not mistaken, simpleFilter is just another explicit filter used in dynamic procedure that differs from the implicit filter, but isn't the explicit simpleFilter (top-hat) the same as the implicit filter (top-hat too!)?

Please correct me if I was wrong.

Thank you very much.

[roth]

Take a look at the source of "locDynOneEqEddy" which is a localized, dynamic LES model i.e C(x,y,z,t).

Contrast this with "dynOneEqEddy" which is dynamic but with a global coefficient i.e C(t).

Michael

[lakeat]

I see, but what about the second question,
"is the test filter used in OpenFOAM double size of the original filter?"

Thank you, Michael!

[fluidzhang]

the ratio of the two filter width is 2,this number was choosed by some researchers,they demonstrated it was optimum.

[lakeat]

Originally Posted by fluidzhang

the ratio of the two filter width is 2,this number was choosed by some researchers,they demonstrated it was optimum.

Which line in the source code, please?

[mdjames]

the test filter size is (at least in dynSmag) controlled by the variable ce in the turbulenceProperties dict, I think.

The test filter width is set to twice the grid filter width by the following line in dynSmagorinsky:

volSymmTensorField MM =
sqr(delta())*(filter_(mag(D)*(D)) - 4*mag(filter_(D))*filter_(D));

The factor 4 results from substituting 2*delta for the test filter width. where delta is the grid filter width.

[Fransje]

If I'm not mistaken, I think even the locDynOneEqEddy model is not localized..

EDIT: I stand corrected. The coefficients are volScalarFields, so that would imply local coefficients..

[lakeat]

Well, you have to give it some sort of name

[lakeat]

And I just don;t believe there is an universal shortcut to model all types or turbulence in a non-DNS mesh.

Personally, I think the development of LES small scale turbulence models has almost reached its peak.

But it seems hybrid method still has a long way to go.

[longamon]

moved to new thread