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-   -   Outlet velocity boundary condition (http://www.cfd-online.com/Forums/fluent/30655-outlet-velocity-boundary-condition.html)

 Jay December 11, 2002 08:36

Outlet velocity boundary condition

Hi there I am trying to use outlet velocity BC for my ASMM in Fluent 6. In my model, I have one inlet and two outlets BC. I have to maintain a ratio between these two outlets. I can use negative flow velocity BC for one outlet and pressure outlet for other. However I have to specify the volume fraction at the outlet velocity BC. But I do not have the value. Is there anyway to specify outlet flow velocity condition.

Thanks for your help and looking forward to hearing from you.

Regards Jay

 Atul T. Shinde December 13, 2002 02:58

Re: Outlet velocity boundary condition

Dear Jay, At inelt, give whatever avaialable. At one outlet,use Outflow condition and at the other outlet can go for pressure condition. Based on this solution, u will have the idea of volume fraction at each outlet. Try out.

 Jay December 13, 2002 07:32

Re: Outlet velocity boundary condition

Thanks Atul.

Yes, I can find the volume fraction the way you suggested. However, in my case I have to maintain a ratio between to outlet (recycle ratio).

Thanks Jay

 Amid Naz December 13, 2002 19:07

Re: Outlet velocity boundary condition

Using velocity outlet means the flow is incompressible. Therefore, the the volume fraction at the outlet can be determined by the area ratio directly..Using outflow BC is Ideal for the case.GOOD LUCK:).

 rk December 15, 2002 09:27

Re: Outlet velocity boundary condition

You should never use the combination of velocity inlet, pressure outlet & outflow if you have one inlet & 2 outlets. You can use velocity inlet & 2 pressure outlets or velocity inlet & 2 outflow conditions.

Since you don't know the fraction of mass flow going out, you should know atleast the pressures at the outlets. This will automatically calculates the percentage massflow out!

Thanks,

rk

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