[stosse]

Hi fellow foamers.

I am trying to set up a case with constant inflow at several panels at the bottom of a rectangular grid and a constant pressure outlet at the top:

-----------------|XXX|----------------
|AAAAAAAAAAAAAAAAAA|
|AAAAAAAAAAAAAAAAAA|
|AAAAAAAAAAAAAAAAAA|
>AAAAAAAAAAAAAAAAA<
------------------------------------------

X is a constant pressure (p_rgh) patch with pressureInletOutletVelocity BC for U,
< are constant velocity inlets with zeroGradient BC for p_rgh
A is air (the editor didn't allow me to use spaces)
the rest is walls

For project reasons I am currently using the fireFoam solver, but i think the problem is related to buoyant compressible flow, as the chemical part is not used in the current setup (this is supposed to be a setup of a ventilation flow field to be used in other cases).

What happens when I run the case is that I get a steady increase in pressure in the domain up to some point. Then the pressure decreases (I guess due to the outflow at the top) to the point where the pressure in the domain is lower than the outflow patch. Fluid then starts to flow into the domain, increasing the pressure, and this creates a "steady" oscillating situation with inflow/outflow at the top patch.

Do anyone have a clue about why the simulation does not reach a steady state with regard to the inflow/outflow? I am running at max CFL=0.3.