Subdivide flow in different outlet

effettonotte · February 19, 2010, 06:38

Hi!
I'm trying to simulate with OpenFoam a manifold with two exits. This manifold is controlled downhill by the turbines (one per exit) which impose the exit velocity.
I would like to know if some of you know if it is possible to simulate this condition, and in this case how can I simulate it.

I resume the boundary conditions:
Inlet: I know the discharge. (i can assign the velocity of the flow)
Outlet: I know the discharge at which the machines work. So it would be nice to assign some kind of subdivision of the flow.

As a first try I imposed a condition of constant pressure (the same) in the outlets. It worked fine.
But in my case the pressure should not be the same for both exits.

I tried then to impose the pressure constant only on one exit (grad U zero) and on the other exit I imposed a constant velocity, with Grad P =0.
I used the simpleFoam solver.
The solution seems to work fine, but, after a certain number of steps it explodes. (p grows to infinity)
Apparently it is a numerical problem, since physically the numbers seem acceptable.

Are there any other type of boundary condition that allow me to simulate this situation? or the problem is in the solver?
Thank you

effettonotte · March 16, 2010, 03:53

no one ever tried to do this? Some years ago I had the possibility to use Star ccm+ and with that program it is possible to impose only the division of the flow in the exit.

if you don't impose this condition, which boundary condition do you usually use when you have a flow dividing into multiple exits?
Thank you.

February 19, 2010, 06:38	Subdivide flow in different outlets	#1
effettonotte New Member Mattia Bozzola Join Date: Jan 2010 Posts: 2 Rep Power: 0	Hi! I'm trying to simulate with OpenFoam a manifold with two exits. This manifold is controlled downhill by the turbines (one per exit) which impose the exit velocity. I would like to know if some of you know if it is possible to simulate this condition, and in this case how can I simulate it. I resume the boundary conditions: Inlet: I know the discharge. (i can assign the velocity of the flow) Outlet: I know the discharge at which the machines work. So it would be nice to assign some kind of subdivision of the flow. As a first try I imposed a condition of constant pressure (the same) in the outlets. It worked fine. But in my case the pressure should not be the same for both exits. I tried then to impose the pressure constant only on one exit (grad U zero) and on the other exit I imposed a constant velocity, with Grad P =0. I used the simpleFoam solver. The solution seems to work fine, but, after a certain number of steps it explodes. (p grows to infinity) Apparently it is a numerical problem, since physically the numbers seem acceptable. Are there any other type of boundary condition that allow me to simulate this situation? or the problem is in the solver? Thank you Last edited by effettonotte; March 16, 2010 at 03:55. Reason: I forgot an "s" in the title

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March 16, 2010, 03:53		#2
effettonotte New Member Mattia Bozzola Join Date: Jan 2010 Posts: 2 Rep Power: 0	no one ever tried to do this? Some years ago I had the possibility to use Star ccm+ and with that program it is possible to impose only the division of the flow in the exit. if you don't impose this condition, which boundary condition do you usually use when you have a flow dividing into multiple exits? Thank you.