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-   -   twoPhaseEulerFoam variables (http://www.cfd-online.com/Forums/openfoam-solving/86731-twophaseeulerfoam-variables.html)

thekay March 31, 2011 09:51

twoPhaseEulerFoam variables
 
Hi all

I was going through the code of twoPhaseEulerFoam and I have some questions about the variables in a part of alphaEqn.H and I'd be thankful if anyone could help me identify their use.

What is phic used for? It is initialised as
Code:

surfaceScalarField phic = phi;
What about alphaf? It is defined as
Code:

surfaceScalarField alphaf = fvc::interpolate(alpha);
And finally I cannot understand what phipp represents and how it is used.

Code:

surfaceScalarField phipp = ppMagf*fvc::snGrad(alpha)*mesh.magSf();
Cheers all

alberto April 1, 2011 02:45

Hi,

phipp is a term used only if the ppMagf model is used. In such case, the momentum equation for phase a has an additional pressure gradient grad(pa). If you proceed as in the derivation of phase a "pressure equation", but keep that equation written in terms of alpha, understand the origin of phipp.

Hint: grad(pa) = G(alpha) * grad(alpha), where G(alpha) = ppMagf = d(pa)/d(alpha).

Best,

k.kshitij November 26, 2011 00:48

Hi Alberto,

I have one question about the ppmagf's usage, according to my understanding the ppmagf model is implemented when the kinetic theory is off, ie when the value of g0 > 0.
Then why does its definition involve the kinetic theory particle pressure "pa". Or I'm wrong in getting this.
I'm a newbee to C++ and have not understood the code yet would you please clarify.

Thanks in advance.

alberto November 26, 2011 22:00

The currently implemented ppMagf does not involve the kinetic theory model. I used "pa" in comment #2 to suggest how to extend the current treatment of the particle pressure in the alpha equation only implemented when the ppMagf model is used also to the case when the kinetic theory is used.

Best,


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