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general momemtum source option - reg

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Old   March 28, 2005, 12:01
Default general momemtum source option - reg
  #1
Fred
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Hello everybody, How the general momentum source option in the subdomain form(CFX5) works? In my case, i know the forces generated by the region that is defined as subdomain in all 3 directions, how to incorporate these forces as source terms(N/m^3) in cfx.When i divide this forces by the subdomain volume and solved, results seems to vary a lot and the behavoir of the this source term is also pretty unclear.Can anyone please help me?

Thanks Regards Fred
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Old   March 29, 2005, 07:33
Default Re: general momemtum source option - reg
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Atit Koonsrisuk
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Dear Fred, As I understand, the momentum sorce term is the force per unit volume in CFX. First you devide the forces that you know by the volume of the subdomain, then you enter them as each component in 'General Momentum Source' of 'Edit Subdomain' dialogbox. I hope it help.

Atit
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Old   March 29, 2005, 11:57
Default Re: general momemtum source option - reg
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Fred
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Dear Atit, Thanks for ur suggestion. The force that i gave is the net force generated by the region what i defined as the subdomain, so this force should also change the velocity once it crosses the subdomain. for example,difference in the velocity just upstream and downsteam the subdomain region multiplied by the mass flow rate gives the net force generated by the region that is defined as a subdomain.This force is divided by the subdomain volume and is given as a source term. But the results for the analysis using subdomain doesnt match with the original case.I am not sure why it is happening like this?

Thanks in Advance Regards Fred
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