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-   -   transportProperties: CrossPowerLawCoeffs...? (http://www.cfd-online.com/Forums/openfoam/85768-transportproperties-crosspowerlawcoeffs.html)

klausb March 6, 2011 18:43

transportProperties: CrossPowerLawCoeffs...?
 
Hello,

I am working on a hydrofoil simulation.

What are and when is it necessary to set CrossPowerLawCoeffs and BirdCarreauCoeffs in the transportProperties file?

Currently my file looks like this:

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 1.7.1 |
| \\ / A nd | Web: www.OpenFOAM.com |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "constant";
object transportProperties;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

transportModel Newtonian;

rho rho [ 1 -3 0 0 0 0 0 ] 1000; //water

nu nu [ 0 2 -1 0 0 0 0 ] 1e-06; //water 20C

// ************************************************** *********************** //

Do I have to add something like:

CrossPowerLawCoeffs
{
nu0 nu0 [ 0 2 -1 0 0 0 0 ] 1e-06;
nuInf nuInf [ 0 2 -1 0 0 0 0 ] 1e-06;
m m [ 0 0 1 0 0 0 0 ] 1;
n n [ 0 0 0 0 0 0 0 ] 1;
}

BirdCarreauCoeffs
{
nu0 nu0 [ 0 2 -1 0 0 0 0 ] 1e-06;
nuInf nuInf [ 0 2 -1 0 0 0 0 ] 1e-06;
k k [ 0 0 1 0 0 0 0 ] 0;
n n [ 0 0 0 0 0 0 0 ] 1;
}

And if so, what would be reasonable values?

Klaus

cnsidero March 6, 2011 22:30

They are for non-Newtonian viscosity models. Here's a bit on wikipedia about generalized Newtonian models with links to the various types:

http://en.wikipedia.org/wiki/General...ewtonian_fluid

Furthermore, to use them you would have to change transportModel from Newtonian to the appropriate non-Newtonian model (i.e. CrossPowerLaw or BirdCarreau) otherwise the coefficients are ignored.


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