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-   -   about dynamic mesh model (http://www.cfd-online.com/Forums/fluent/34052-about-dynamic-mesh-model.html)

lingo June 27, 2004 09:21

about dynamic mesh model
 
Hi, everyone: My case is that: a wall is rotating whose rotational speed is varying with the time.So a udf and dynamic mesh model are needed.When I set the step size=T/100(T refers to the period)and iterate,messages appear as follows: " Updating mesh at time level N...negative volume: repeat smoothing negative volume: repeat smoothing negative volume: repeat smoothing WARNING: non-positive volumes exist. Error: Update-Dynamic-Mesh failed. Negative cell volume detected. Error Object: ()"

So, I reset the step size=T/1000. I works well .However, after sveral hundreds steps , the similar messages appears: " Updating solution at time level N... done. Updating mesh at time level N... WARNING: non-positive volumes exist. Error: Update-Dynamic-Mesh failed. Negative cell volume detected Error Object: ()"

I need several periods (several thousands steps)to investigate the unsteady simulation.

Could you give me any suggestions?

Regards

lingo

emma June 30, 2004 04:33

Re: about dynamic mesh model
 
Hi,

I think that the problem maybe lies in the too small volume mesh or the twisted mesh. Go back and chech your mesh, perhaps your mesh is too fine for your computer or your mesh type doesn't matches well with your problem. Hope it helps a bit.

Regards

Emma


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