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Old   January 25, 2008, 09:08
Default convective boundary condition
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Mani
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Hi

Can anyone tell me what on earth is convective boundary condition and how can i impose it at the outlet of my model. Thanks

Mani
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Old   January 28, 2008, 18:24
Default Re: convective boundary condition
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Glenn Horrocks
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Hi,

It is normally used on a wall boundary condition to model heat transfer from the wall. It is not usually used at outlets.

Glenn Horrocks
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Old   January 28, 2008, 18:36
Default Re: convective boundary condition
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Mani
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Well in the paper that i have infront of me they have imposed this BC at the outlet. How can i use it in CFX anyway.

Mani
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Old   January 29, 2008, 19:33
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Glenn Horrocks
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Hi,

I have no idea. I can't see how imposing a convective heat transfer condition on an outlet can have any physical basis. The fluid exiting an outlet depends on the temperature upstream.

Glenn Horrocks
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Old   January 29, 2008, 19:34
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Glenn Horrocks
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Are you sure they were not applying a thermal radiation boundary condition? You can apply this type of boundary on an outlet in CFX.

Glenn Horrocks
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Old   January 30, 2008, 04:29
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Andreas
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Convection means something (mass, momentum, heat, concentration) is transported by the fluid; this is described by the term "div(rho u Phi)" where rho is density, u is velocity and Phi is what is transported. CFX has this convective boundary condition at outlets: for mass and momentum if you set pressure there, and for heat and concentrations this is automatically set (you cannot choose e.g. a temperature at an outlet). There comes a difficulty if pressure fluctuations reach the outlet since they can be reflected there so that the outlet is not fully "convective"; for this, try the beta feature "non-reflecting boundary conditions".
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Old   January 30, 2008, 07:13
Default Re: convective boundary condition
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Mani
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Thank you Glenn & Andreas. How can i use "non-reflecting boundary condition" which i suppose is same as "convective BC". The purpose in either case would be to prevent pressure fluctuations reflecting back in flow domain right.

Mani
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Old   February 2, 2008, 17:25
Default Re: convective boundary condition
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Mani
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Ok i understand now what you meant Andreas. Thank you

Mani
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