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-   -   Time varying fixed value patch and averaging (http://www.cfd-online.com/Forums/openfoam/60947-time-varying-fixed-value-patch-averaging.html)

hannes December 8, 2006 12:04

Hello, I have implemented a
 
Hello,

I have implemented a new boundary condition which is similar to the existing "timeVaryingUniformFixedValue". It allows not only the specification of a uniform fixed value for several time instances but also of full boundary fields.

I have used this boundary type to prescribe a boundary velocity to the LES solver (oodles) which has a certain mean value and RMS. When I run the calculation everything is fine and seems to be working well.
The problem is with the results from the averaging procedure in the LES solver. I expected to get the same RMS value on the inlet patch as I had prescribed. But what I get is different. Especially the RMS of the patch-normal velocity is factor 2.5 to high. I cannot say something about the RMS in the internal field of the domain, but they may be ok.

I was wondering if there is an issue with my time interpolation and I checked, but it is all ok.
Furthermore, I have implemented the same averaging procedure (for Umean and R) as in oodles directly into my boundary condition class to average the boundary field without going through the fvPatchField-mechanism. Then I get the expected result!

What may be the reason for the different results? Does anyone have an idea?

Best regards, Hannes

Btw: if someone wants to have a look at the code, it can be found here:
http://palamedes.fms.uni-rostock.de/...FixedValue.tgz


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