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Adjusting velocity using cyclic bc's

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Old   January 25, 2012, 10:08
Default Adjusting velocity using cyclic bc's
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Gregory N de Boer
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Hi all,

I have a question about the implementation of cyclic bc's using OpenFOAM.

I have a very simple case which is that of a non-conformal pipe geometry where flow is driven by a moving wall. The inlet of the pipe is smaller than at outlet but there is the same number of nodes on both faces.

I have been able to apply the fan bc such that there is a pressure change across my domain whilst the other field variables are modeled as true periodic (where the outlet and inlet are equal in size). But I wish to scale the velocity at outlet according to the distance between corresponding nodes on the inlet. That is:

Inlet:
p = p1 (calculated from the cyclic condition)
U = U1 (calculated from the cyclic condition)
Outlet:
p = p1+dp (dp is specified)
U = U1*(y2/y1) (y2/y1 is the scale factor)

I have been unable to find any derived class of the cyclic bc which seems capable of modeling this condition. Can anyone suggest how I may be able to implement such a condition? I have already looked into groovyBC but because it is a patch type rather than cyclic the solver does not maintain periodicity as required.

Another solution to my problem would be to transform unit vectors in the governing equations. But I doubt this can be done easily?

Any help with any of this would be much appreciated.

Cheers,
Greg
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