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Willem Brantegem April 3, 2007 09:42

pressure outlet (open channel flow)
My problem: I've got a channel (under: water, above: air). I want to give in: rate at the inlet, water height at the outlet. Fluent has to iterate till convergence. I tried: mass flow inlet: give in: water rate = ... pressure outlet: give in: free surface level = ... (using open channel flow)

My result: I've got water inflow over the whole inlet (but that's not what I want, Fluent has to calculate the water surface from the free surface at the outlet, to the inlet (by means of the rate I defined at the inlet)) And even at the outlet the water surface is not what I want. He doesn't take the free surface level that I defined.

If somebody knows a little part of the solution, or somebody knows a lot of 'open channel flow', please answer this question. My email:

Thank you, Willem.

Mark April 3, 2007 12:21

Re: pressure outlet (open channel flow)
Hi Willem,

From your discription od the case it seems the simulation is correct. The water level at an inlet is strongly dependent on the downstream level which you defined not on your inlet level. The upstream level would be adjusted by a hydraulic resistance in the system and the downstream water level. So in your case, you should adjust the downstream water level to close a level which is reasonable in a real situation. Then free level would be reasonably accurate from Fluent simulation.

Hope it would give your some help.

Good luck,


Saleem April 4, 2007 02:40

Re: pressure outlet (open channel flow)
Hi Mark I am use the open channel flow boundary too. I define the free surface level ,at inlet and I used the boundary pressure inlet and at outlet I used pressure outlet and I told Mr. Wilem by email to did that. Can you tell me to how the downstream water level be adjusted in more deatails.

Regards K. Baker

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