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-   -   outflow boundary condition (http://www.cfd-online.com/Forums/fluent/101534-outflow-boundary-condition.html)

 Lilly May 7, 2012 04:00

outflow boundary condition

Dear all,

I want to simulate a contrast agent bolus in blood inside a vessel using the "mixture model", but since the amount of contrast agent is really small I picked the same properties for both materials. I was suggested to use a "velocity inlet" and an "outflow outlet" (since I have some bifurcations I thought this would be a good outlet boundary condition). But I read in another thread and at the FLUENT manual that i am not allow to use the outflow bc with
"multiphase models (Eulerian, mixture, and VOF..."
Therefore I am confused whether I am allowed to use "outflow" since I am using the "mixture model", but I don't have different phases of my fluids.

Thank you for all your help and ideas!
Lilly

 delaneyluke May 7, 2012 04:54

An outflow can be used with the Mixture model. But if you have multiple outlets, and you want to use the outflow then you need to input the mass flow distribution between individual outlets

Regards
Luke

 Lilly May 7, 2012 08:26

Thank you Luke!
Do you mean that I have to consider that the flow rates of the single outlets adds up to 1?

And for which exceptions am I allowed to use "outflow" at using "mixture model" (just because it was written in the FLUENT manual that I am not allowed to use it).

 delaneyluke May 8, 2012 03:12

Do you mean that I have to consider that the flow rates of the single outlets adds up to 1?

Yes, if you activate the "outflow BC" you will notice a flow rate weighting. The weightings of all outlets should add up to 1

And for which exceptions am I allowed to use "outflow" at using "mixture model" (just because it was written in the FLUENT manual that I am not allowed to use it).

I would assume you cannot use the Outflow BC if you are modeling cavitation or some sort of mass transfer between phases.

Regards
Luke

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