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Old   February 15, 2008, 05:07
Default Non reflective boundary conditions
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KK
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Could some one please explain what the purpose/concept/benefit/use of 'Non reflective boundary conditions'(beta function in CFX-11) is?

I am asking this in context of my another question posted at http://www.cfd-online.com/Forum/cfx.cgi?read=24989

How would it help to maintain the flow direction outward at some outlet?

Thank you so much, KK
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Old   February 15, 2008, 10:20
Default Re: Non reflective boundary conditions
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kasim
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Hi KK

Non-reflective boundary condition prevent the pressure fluctutaions to reflect back in your CFD domain. It helps to stabilise your numerical solution.

Kasim
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Old   February 15, 2008, 12:57
Default Re: Non reflective boundary conditions
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KK
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Thank you very much Kasim

As opening type boundary conditions are supposed to make Large Eddy Simulations unstable because eddies are recirculated at the boundary, will NON-reflective boundary condition (opening) might help to make the LES simulation stable?

May be my question is not an appropriate one, I am new in CFD.

Thank you so much again, KK.
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Old   February 16, 2008, 10:11
Default Re: Non reflective boundary conditions
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kasim
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If you have set pressure at the outlet, pressure fluctuations can reach the outlet and de-stabilise the soilution by reflecting back in domain. In that case one should use non-reflective BC. I would suggest that you dont use Opening with non-reflective boundary condition for final solution. You can keep non-reflective BC but change your opening to Outlet once your solution has gained stability.

Kasim
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