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-   -   strange processor boundary behavior with linearUpwindV (http://www.cfd-online.com/Forums/openfoam-bugs/94085-strange-processor-boundary-behavior-linearupwindv.html)

akimbrell November 4, 2011 20:42

strange processor boundary behavior with linearUpwindV
 
1 Attachment(s)
Code used is a recent version of OpenFOAM-1.6-ext.

I observed the following behavior when running a test case in parallel - see attached image. The case is a point vortex with P = 0 boundaries and U boundaries set to zeroGradient. I am running standard icoFoam solver with 3 processors. For discretization schemes I am using the default Gauss linear everywhere except div(phi,U), for that one I use Gauss linearUpwindV Gauss linear. My max Courant number is ~0.3, grid resolution is reasonable.

The quantity shown is vorticity magnitude - you can see that when the scale is minimized, data is not being shared properly across the processor boundaries - they effectively show up in the solution when they should be invisible. I have run this case previously in serial and have not seen anything like this before. Furthermore, most other schemes for the convection term do not show this behavior. I have observed something similar also using SFCDV but it dissipates shortly after initialization.

Is this a known problem with the linearUpwindV scheme? I have also tried pure linearUpwind and did not see this problem at all.

alberto November 5, 2011 13:45

This is typically due to a missing update of the BC's. If you can reproduce it in 2.0.x, please report it as a bug on http://www.openfoam.com/mantisbt/main_page.php .

david February 11, 2013 14:56

http://www.openfoam.org/mantisbt/view.php?id=676

https://github.com/OpenFOAM/OpenFOAM...01782e30bd4291

Regards
David

s.m November 6, 2013 03:53

Hi
would you please tell me that how linearUpwind can be define in OpenFOAM-1.6-ext?
e.g linearUpwind in openFoam 2.2.0 is defind in this way:
div(phi,U) Gauss linearUpwindV grad(U);

i want to know how should i define it in OpenFOAM-1.6-ext?

thank you very much:)

wyldckat November 9, 2013 13:16

Greetings s.m,

You can find tutorials that use this scheme by running:
Code:

grep -R "linearUpwindV" $FOAM_TUTORIALS/
Best regards,
Bruno

ma-tri-x May 18, 2014 20:04

compressible InterFoam
 
Hi !

I worked several months on simualtion of cavitation bubbles. I 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

david May 20, 2014 06:04

Hi Max

Do you see the numerical fragments only with linearUpwindV or also with other schemes? I think it would be good to report this bug. Do you have a simple case that demonstrates your problems?

Regards
David

ma-tri-x May 20, 2014 12:13

I don't use linearUpwind
 
1 Attachment(s)
Hi David!

I don't use linearupwind. My fvSchemes looks like:
Code:

ddtSchemes
{
    default        Euler;
}

gradSchemes
{
    default        Gauss linear;
}

divSchemes
{
    default            Gauss vanLeer;
    div(phirb,alpha) Gauss interfaceCompression 1;
}

laplacianSchemes
{
  default              Gauss linear corrected;
}

interpolationSchemes
{
    default        linear;
}

snGradSchemes
{
    default              none;
//    default              Gauss skewCorrected linear;
    snGrad(pd)          limited 0.5;
    snGrad(rho)          limited 0.5;
    snGrad(alpha1)      limited 0.5;
    snGrad(p_rgh)      limited 0.8;
    snGrad(p)          limited 0.8;
}

fluxRequired
{
    default              none;
    p_rgh;
    p;
    pcorr;
    alpha1;
}

A simple example which is reproducable... erm ... I don't know and I'm currently writing my thesis so I have little time to prepare one... :(

In August, I will be able to prepare one...

I think you will immediately see the symmetry-axis-effect when you set up a bubble with very low pressure on an axis of an axis-symmetric mesh. in the very first timestep, where the bubble wall starts to accelerate, you find that the two cells where the interface hits the axis accelerate faster. It's hidden in the next timesteps because I think you cannot set a threshold for the U-field magnitude in paraview (the two cells are only slightly faster and the range of U-magnitude over the mesh is much larger). I cannot show you this unfortunately, because I didn't save a screenshot. But I can show you another freaky example:

Once I decomposed with scotch and some processor boundaries were parallel to the bubble wall at some time. When the bubble passed the processor patch, droplets were formed. Maybe I can put the screenshot here. A yes, here's an attachment. The left picture is at t=8.18393e-5, the right is at t=8.33299e-5. In between the bubble collapsed further and the interface (="bubble wall") passed the scotch-processor-patch.


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