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LES: subgrid-scale mixing rate

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Old   March 24, 2014, 08:59
Default LES: subgrid-scale mixing rate
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Alberto Cuoci
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Hello everybody,

I need to calculate the subgrid-scale mixing rate TauSGS in a LES simulation, which is defined in the following way:

TauSGS = 1 / sqrt ( 2 * Sij*Sij)

where Sij is the strain rate tensor (in 1/s), i.e.:

Sij = 0.5 * ( dvi/dxj + dvj/dxi)

where dvi/dxi is the derivative of j-th component of velocity with respect to the i-th coordinate

1. Do you know how I can calculate it in OpenFOAM?

2. Do you also know how I can distinguish if I am performing a RANS or a LES simulation? In other words, is there any function in the turbulenceModel class returning if this is a RANS or a LES?

Thank you very much in advance!

Alberto
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Old   March 24, 2014, 18:10
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Lieven
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Hi Alberto,

You can try something like:
Code:
volSymmTensorField S(dev(symm(gradU)));
volScalarField magS(sqrt(2.0)*mag(S));
volScalarField tau("tau",pow(2*magS*magS,-0.5));
I dind't try it but it might do the trick...

Cheers,

L
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