[Yahoo]

Hey Guys
I am having a problem with the pressure on parallel simulations; I get different pressures when I am running on multiple processors. I have tried PCG and GAMG solvers. Any ideas?

[nimasam]

represent your results by a contour maybe help

[ma-tri-x]

Hi !

I think I face a similar problem.
I worked several months on simualtion of cavitation bubbles and started with the compressibleInterFoam solver and modified it, but the problem still also remains with the original one(s) (versions: 2.1.1, 2.2.1, 2.3.0):

When at least one of the processor patches crosses the interface, the velocity field is not computed correctly. You observe numerical fragments parallel to the patch like in the following picture
https://www.dropbox.com/s/a4cr4qpyoqjhue2/bug.png

The only version I discovered to be able to deal with the decomposition is the openfoam-extend version.

Has anyone observed this? Is this the same error as discussed here?

Furthermore I discovered that even without decomposing, running a 2D axis-symmetric case has some overestimating properties in the cell of the interface directly at the axis. So if you place a bubble that will collapse onto the axis, it will unphysically get thinner at the axis. This also seems to be no problem in the extend version 3.0 (absolutely same input files).

Regards,
Max

[ma-tri-x]

Originally Posted by Yahoo

Hey Guys
I am having a problem with the pressure on parallel simulations; I get different pressures when I am running on multiple processors. I have tried PCG and GAMG solvers. Any ideas?

I found something:

Originally Posted by ma-tri-x

Hi!

After years of calculating in parallel with openFOAM of several versions, I finally found the bug:
have a look at your

controlDict

. Do you adjustTimeStep? Then you have to go have a look into the several processorN-directories of your run and compare the times. Are they the same? Probably NOT. It is because there exist as many CoNums (Courant numbers) as there are processors used. You have to explicitly take the minimum CoNum of ALL processors. So go into the sources of your solver

cd $WM_PROJECT_DIR/applications/solvers/path-to-solver

and edit the file

CorantNo.H

from

    CoNum = max(SfUfbyDelta/mesh.magSf()).value()*deltaT;

to

    CoNum = max(SfUfbyDelta/mesh.magSf()).value()*deltaT;
    reduce(CoNum,minOp<scalar>());

if you are using also the acousticCoNum then you have to do it for this one as well.
Now run

./Allwmake

and you'll be fine forever. I think.