(OpenFoam) outlet velocity boundary condition depending on outlet pressure (PUMP)
 

Hi All,

I would like to simulate how a pump work when it suck air from a vessel. In particular I am interested in the boundary condition at outlet of the vessel where the air is sucked with a velocity that depends on the pressure at outlet. Is there any boundary condition in OpenFoam that I can use for it?
Thanks.

regards,
Stefano

fanPressure?

This will not work, as you need two patches where you apply a pressure drop. If you know the pressure at the inlet of the pump, then you can build a pressure based boundary condition couple. At the inlet you define a totalPressure and at the outlet a fixedValue. The velocity should be pressureInletVelocity and zeroGradient respectively.

Hi Tobias,

I only have a patch that is the exit of the vessel. At this exit I would like to apply the velocity (or flowrate) condition based on the pressure at the exit itself (or in the vessel).

Hi Stefano,

you have two options:

• Flow Rate / Velocity based fluid motion (in simple words: you get the information of a pressure gradient)
• Pressure based fluid motion (in simple words: you get the information of the mass flow rate)

If you know the mass flow rate, you can apply the mass flow rate at the outlet (where is the problem?). Accordingly, you use a zero pressure gradient there and a fixed on at the inlet/or a totalPressure depending on your needs and set-up.

Hi Tobias,

This is a transient case. My flowrate / velocity should change depending on which is the pressure in the vessel.

Hi,

so then you should have a pressure based force. Where is the problem?

Hi Tobias,

How would you write such a BC for velocity and pressure?