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-   -   pressure oscillations in moving mesh cases (http://www.cfd-online.com/Forums/openfoam-solving/64108-pressure-oscillations-moving-mesh-cases.html)

david April 29, 2009 09:52

pressure oscillations in moving mesh cases
 
1 Attachment(s)
Hi all

I'm trying to simulate a pump (inlet casing, rotating impeller, diffuser and volute) with OpenFOAM-1.5-dev. The four domains are connected with GGI interfaces. The turbDyMFoam solver is used as it is a transient simulation. The forces acting on the hub, shroud and blades are monitored with the forces functionObject. Unfortunately the pressure forces oscillate with each time step. The attached image shows the pressure forces in y-direction. Rotation axis is the z-axis.


I could reproduce this behaviour in the icoDyMFoam tutorial cases mixerGgi and mixer2D. I tried to use different ddt-Schemes (Euler, backward, CrankNicholson) and tolerances without any improvement. Are there any possibilities to reduce the oscillations?


Thanks in advance

David

louisgag April 29, 2009 16:07

Hi David,

I assume that by oscillations you mean the noise and not the sinusoidal oscillation of the signal? If so, I've read that using a smaller timestep might reduce the noise.

cheers,

-Louis

david April 30, 2009 04:24

Hi Louis

Yes, the noise is the problem. Unfortunately, reducing the time step doesn't improve the results.

Regards

David

markc July 29, 2009 04:44

Hello,

try to use some relaxation on p (or pd). First check whether relaxationFactors are implemented in the solver you use, otherwise you can easily implement them yourself.

Succes,

Mark

sek April 25, 2011 12:15

Quote:

Originally Posted by david (Post 214731)
Hi Louis

Yes, the noise is the problem. Unfortunately, reducing the time step doesn't improve the results.

Regards

David

David,

I have similar prroblems you've had. With

sek April 25, 2011 12:16

Quote:

Originally Posted by david (Post 214631)
Hi all

I'm trying to simulate a pump (inlet casing, rotating impeller, diffuser and volute) with OpenFOAM-1.5-dev. The four domains are connected with GGI interfaces. The turbDyMFoam solver is used as it is a transient simulation. The forces acting on the hub, shroud and blades are monitored with the forces functionObject. Unfortunately the pressure forces oscillate with each time step. The attached image shows the pressure forces in y-direction. Rotation axis is the z-axis.


I could reproduce this behaviour in the icoDyMFoam tutorial cases mixerGgi and mixer2D. I tried to use different ddt-Schemes (Euler, backward, CrankNicholson) and tolerances without any improvement. Are there any possibilities to reduce the oscillations?


Thanks in advance

David

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Hi David,

I am having a similar "noise" problem. Were you able to resolve your problem?


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