High pressure fluctuations

Submitted by vinaym on Fri, 04/06/2018 - 16:00

Hello everyone,

I am getting an unphysical pressure field for a few fluidized bed simulations. Everything else (velocity, voidage) seems fine. For most inlet gas velocities, simulations give expected value of pressure. However, for certain flowrate the values are erratic or even negative (possible but not expected) and are so throughout the bed. I am surprised with such fluctuating pressure field how is solution converging?

I have noticed that Ksl values show a jump around the same time for certain cells when I see negative pressure values. Im currently using this version of implicitCouple.C
I see that Ksl is updated from KslPrev_ to KslNext_ in current version. Could this be the problem? I am running a simulation currently to check the same.

Could this be because of wrong interpolation of forceModels? gradPForce or viscForce ? I have a rectangular grid.

The BC at wall and bottom for pressure is zerogradient and fixedValue of internalField at top which is set to 0.
Any help in this regard is highly appreciated.

Kind regards,
Vinay