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-   -   alpha or alpha1 in interFoam & interDyMFoam (http://www.cfd-online.com/Forums/openfoam-bugs/68140-alpha-alpha1-interfoam-interdymfoam.html)

 wavytracy September 8, 2009 06:45

alpha or alpha1 in interFoam & interDyMFoam

From the damBreak tutorial of version 1.5, fvSchemes looks like:

{
default Gauss linear;
}

divSchemes
{
div(rho*phi,U) Gauss limitedLinearV 1;
div(phi,gamma) Gauss vanLeer;
div(phirb,gamma) Gauss interfaceCompression;
}

Now, I was under the impresssion that gamma was replaced by alpha1 in version 1.6. Yet, here is the same excerpt from v1.6 damBreak tutorial, which contains alpha and alpha1:

{
default Gauss linear;
}

divSchemes
{
div(rho*phi,U) Gauss limitedLinearV 1;
div(phi,alpha) Gauss vanLeer;
div(phirb,alpha) Gauss interfaceCompression;
}

and it isn't even consistent - take a look at the same excerpt from interDyMFoam v1.6

{
default Gauss linear;
}

divSchemes
{
div(rho*phi,U) Gauss upwind;
div(phi,alpha) Gauss vanLeer;
div(phirb,alpha) Gauss interfaceCompression;
}

So what is the difference between alpha and alpha1. Am I misunderstanding something, or is this a bug?

Cheers,
Tracy.

 henry September 9, 2009 02:54

alpha1 is the phase fraction of phase 1 in a multi-phase system, alpha in the control dictionaries refers to any phase. The reason for the "inconsistency" is to ensure that the discretisation schemes are the same for all phases.

H

 wavytracy September 9, 2009 21:23

Thank you.

But the "inconsistency" refers to the line
in the controlDict of the interFoam tutorial,

compared to the line
in the controlDict of the interDyMFoam tutorial.

I'm assuming from your reply that they should both be grad(alpha)?

 henry September 10, 2009 02:51

Ahh OK, I missed that, it should be grad(alpha1) in both cases but as the scheme is set the same as the default it won't make any difference. I will correct this in 1.6.x.

Thanks

H

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