[hiuluom]

Greeting all,

I am using OF2.2.2 on Ubuntu 14.04. I saw the the "pressureGradientExplicitSource.C" has the inverse matrix:

const scalarField& rAU = invAPtr_().internalField();

and the "pressureGradientExplicitSource.H" explanied:

//- Matrix 1/A coefficients field pointer
        autoPtr<volScalarField> invAPtr_;

I looked up in the forum at the link http://www.cfd-online.com/Forums/ope...ning-ueqn.html. If I correct, rAU = 1/U. Why does rAU need to calculate pressure gradient in periodic equation?

Anybody can help me to understood this missed?

Thank you,
Thanh

[hiuluom]

Hi all again,

I see in the channelFoam OF 2.1.1 (http://www.cfd-online.com/Forums/ope...tml#post485952) to calculate the pressure gradient use rAU or rUA

dimensionedScalar gragPplus =
            (magUbar - magUbarStar)/rUA.weightedAverage(mesh.V());

an in the OF2.2.2 also use rAU

dGradP_ = (mag(Ubar_) - magUbarAve)/rAUave;

Does anybody understand the formula to compute the pressure gradient in periodic condition?

Thank you so much,
Thanh.

[hiuluom]

Dear all,

Some bodies can give me a document mention of gradient pressure in periodic condition?

Thank you so much,
Thanh

[wyldckat]

Quick answer: This fvOption was renamed to "meanVelocityForce" some weeks ago in OpenFOAM-dev and it's now part of OpenFOAM 3.0.
The commit in question was this: https://github.com/OpenFOAM/OpenFOAM...898bec5fac74ad

As for why this calculation gives you the pressure gradient, you will have to take a look at the pressure equation in the solvers, because those use "rAU" for those equations. For example, take a look at this wiki page: https://openfoamwiki.net/index.php/IcoFoam

[hiuluom]

Dear Bruno,

Thank you so much your answer for me.

I would like build "meanVelocityForce" to check it but I see the "patchMeanVelocityForce". What is it and how to correctly build "meanVelocityForce".

Best regards,
Thanh

[wyldckat]

Quick answers:

1. "patchMeanVelocityForce" is simply another "fvOption" that allows for enforcing the mean velocity on a particular patch, while operating onto a group of selected cells.
2. "meanVelocityForce" is simply a renamed version of "pressureGradientExplicitSource". There were no changes made in the source code for it, it was all only aesthetic.
3. Compiling the source code for "meanVelocityForce" in OpenFOAM 2.2 isn't very simple. A few changes need to be done the source code in "meanVelocityForce" for it to build with OpenFOAM 2.2.
   • It would be easier if you simply downloaded and installed OpenFOAM 3.0.0... at least easier for me