interfoam boundary condition

Schag · May 29, 2009, 10:55

Hi all,

quite new in Openfoam, I'm working with rasInterfoam to simulate the flow arount a cylinder in a channel.

I have an inlet with a velocity fixedValue and inletOutlet (1,1) for gamma, zeroGradient for pd.
I have walls with slip conditions
My outlet is set as:
- pressureInletOutletVelocity for velocity
- inletOutlet(1,1) for gamma
- zeroGradient for pd

My issue is:
When it comes to long times, I loose my free surface level. I still have the good inlet level but outlet is about 5m below what I want (out of 30m).

I think I don't have the same massflow at inlet and outlet (obvious), but I do not know how to solve it.

Does anyone has any idea?

Thx for reading!

sega · May 30, 2009, 08:48

Hello.

Maybe you can use cyclic boundary conditions for your in- and outlet.
This bc is basically copying the inflow to the outflow and thus quaranteeing, that they are equal ...

cliffoi · June 2, 2009, 04:07

I'm not very familiar with rasInterFoam but I've had similar mass conservation issues with my own solutions using inletOutlet and similar BC's. The inletOutlet BC does no flux correction. It is essentially a zeroGradient outlet which can switch to an inlet. I got around my problems by using fluxCorrectedVelocity BCs at the outlet. This is fine as long as you know the boundary will always act as an outlet.

Schag · June 2, 2009, 09:44

Thanks, I'm going to try these.

May 29, 2009, 10:55	interfoam boundary condition	#1
Schag Member Julien Schaguene Join Date: Apr 2009 Location: France Posts: 55 Rep Power: 17	Hi all, quite new in Openfoam, I'm working with rasInterfoam to simulate the flow arount a cylinder in a channel. I have an inlet with a velocity fixedValue and inletOutlet (1,1) for gamma, zeroGradient for pd. I have walls with slip conditions My outlet is set as: - pressureInletOutletVelocity for velocity - inletOutlet(1,1) for gamma - zeroGradient for pd My issue is: When it comes to long times, I loose my free surface level. I still have the good inlet level but outlet is about 5m below what I want (out of 30m). I think I don't have the same massflow at inlet and outlet (obvious), but I do not know how to solve it. Does anyone has any idea? Thx for reading!

May 30, 2009, 08:48		#2
sega Senior Member Sebastian Gatzka Join Date: Mar 2009 Location: Frankfurt, Germany Posts: 729 Rep Power: 20	Hello. Maybe you can use cyclic boundary conditions for your in- and outlet. This bc is basically copying the inflow to the outflow and thus quaranteeing, that they are equal ... __________________ Schrödingers wife: "What did you do to the cat? It's half dead!"

June 2, 2009, 04:07	Try	#3
cliffoi Member Ivor Clifford Join Date: Mar 2009 Location: Switzerland Posts: 94 Rep Power: 17	I'm not very familiar with rasInterFoam but I've had similar mass conservation issues with my own solutions using inletOutlet and similar BC's. The inletOutlet BC does no flux correction. It is essentially a zeroGradient outlet which can switch to an inlet. I got around my problems by using fluxCorrectedVelocity BCs at the outlet. This is fine as long as you know the boundary will always act as an outlet.

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June 2, 2009, 09:44		#4
Schag Member Julien Schaguene Join Date: Apr 2009 Location: France Posts: 55 Rep Power: 17	Thanks, I'm going to try these.