CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   OpenFOAM Running, Solving & CFD (http://www.cfd-online.com/Forums/openfoam-solving/)
-   -   Does anyone knows about momentumPredictor in rhoPimoleFoam? (http://www.cfd-online.com/Forums/openfoam-solving/113532-does-anyone-knows-about-momentumpredictor-rhopimolefoam.html)

immortality February 21, 2013 10:18

Does anyone knows about momentumPredictor in rhoPimoleFoam?
 
what does momentumPredictor do in PIMPLE dictionary?have anyone some information about it?
Code:

PIMPLE
{
    momentumPredictor yes;
    nOuterCorrectors 7;
    nCorrectors    4;
    nNonOrthogonalCorrectors 1;
    rhoMin          rhoMin [ 1 -3 0 0 0 ] 0.5;
    rhoMax          rhoMax [ 1 -3 0 0 0 ] 7.5;
    convergence        1e-16;

residualControl
    {
        "(U|k|omega)"
        {
            relTol          0;
            tolerance      0.00000000001;
        }
    }
}


immortality February 26, 2013 19:00

any answer is appreciated!

santiagomarquezd March 1, 2013 16:55

It enables/disables the solution of the momentum predictor.

Regards

immortality March 2, 2013 01:26

thanks.whats the effect of predictor on solution,accuracy and stability in unsteady compressible problems?

wyldckat March 2, 2013 08:22

Quote:

Originally Posted by immortality (Post 410968)
thanks.whats the effect of predictor on solution,accuracy and stability in unsteady compressible problems?

A quick Google search lead me to this:
Quote:

Originally Posted by http://openfoamwiki.net/index.php/The_PISO_algorithm_in_OpenFOAM
  • Solve the momentum predictor
solve (UEqn == -fvc::grad(p));

This looks so simple that it's probably explained in any good CFD book?

santiagomarquezd March 2, 2013 10:49

Hi, the momentum predictor is a first approximation of the velocity field obtained from the solution of a momentum equation assembled with the previous time-step pressure field. This velocity doesn't fulfill the restriction given by the continuity equation which is achieved laterly by the PISO method. Sometimes you can avoid the solution of the momPred saving time, but it can lead to a bad convergence in the PISO loop. Is a user's choice based in the problem behavior.

Regards.


All times are GMT -4. The time now is 15:51.