outflow boundary condition

Lilly · May 7, 2012, 04:00

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

May 7, 2012, 04:00	outflow boundary condition	#1
Lilly Senior Member Join Date: Feb 2011 Posts: 140 Rep Power: 15	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

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May 7, 2012, 04:54		#2
delaneyluke Senior Member Join Date: Mar 2009 Location: Indiana, US Posts: 186 Rep Power: 17	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

May 7, 2012, 08:26		#3
Lilly Senior Member Join Date: Feb 2011 Posts: 140 Rep Power: 15	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).

May 8, 2012, 03:12		#4
delaneyluke Senior Member Join Date: Mar 2009 Location: Indiana, US Posts: 186 Rep Power: 17	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