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matthias November 5, 2009 11:52

CYCLIC BC in pipe flows
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I have a question about applying the cyclic boundary condition to pipe flows. You can find a pic of my mesh in the attachment. It consists of a small short pipe positioned along the centerline of a longer bigger pipe.
The following bc conditions have been assigned to the patches:

1. shell big pipe -> wall
2. shell small pipe -> wall
3. outlet patch -> inletOutlet
4. inlet patch and patch at the end of small pipe -> cyclic

Furthermore the radial patches are subdivided according the cross section of the two pipes.

Now I want to apply the cyclic bc to the patches listed in point 4 in a similar manner like they are used in channelfoam, but the calculated pressure gradient is added to the entire domain (in channelfoam). But in my application the fluids mix at the end of the small pipe (coaxial jetmixer), so I can not apply the pressure gradient to the whole domain.
Actually, the start up length should only provide a fully turbulent pipe flow at the begin of the mixing area.

Is it possible to use the cyclic bc in this context or is the directMapped bc a better alternative?

best regards


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