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'opening' type BCs with LES

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Old   February 12, 2008, 10:52
Default 'opening' type BCs with LES
  #1
KK
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Does any one use opening type boundary condition with LES. CFX manual does not suggest to use it with LES at all and I have also noticed that the solver fails with opening type BCs while doing LES.

Any comments or different experience please?

Regards,KK
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Old   February 12, 2008, 15:51
Default Re: 'opening' type BCs with LES
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kasim
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Hi

Yes i used opening BC for LES simulation few days ago and it worked fine. I, then, used that simulation as an initial guess to start my real problem which was more complicated.

kasim
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Old   February 12, 2008, 17:39
Default Re: 'opening' type BCs with LES
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Glenn Horrocks
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Hi,

An important issue with openings and LES is that the turbulent eddies can cause reverse flow out the boundary and this is numerically unstable. It is best to move the boundary upstream to somewhere the flow will not have regions of reverse flow.

Glenn Horrocks
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Old   February 14, 2008, 00:01
Default Re: 'opening' type BCs with LES
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HekLeR
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not to mention that opening bcs will be reflective... use an average pressure outlet and move the bc as Glenn suggests.
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Old   February 14, 2008, 13:06
Default Re: 'opening' type BCs with LES
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kasim
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You can use opening BC for an initial guess but dont use it for final solution. You can use non-reflective BC in CFX its one of beta option.

kasim
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