pressure fluctuation when using timevaryingmappedfixedvalue boundary condition
 

Dear Fomer,

Recently I'm using the incompressible SADDES model in OF to do my study.
The model is a cavity whose inlet variables are time-dependent and collected from another big model. The velocity, pressure gradient, and other turbulence variables are collected from the big model and given to be the inlet condition of the small model.

The mesh of the model I'm simulating is the same as it in the big model. the small model is the final part of the big model, so their outlet BCs are the same.
The boundary condition I'm using in small model
velocity
inlet: timeVaryingMappedFixedValue
outlet: zerogradient
pressure:
inlet: timeVaryingMappedFixedgradient(developed by our team)
outlet:fixed value: zero
nusgs:
inlet:timeVaryingMappedFixedgradient
outlet:zerogradient
nutilda:
inlet: timeVaryingMappedFixedValue
outlet: zerogradient


The fvscheme and fvsolution are the same as the big one.

I found the lift force of the cavity surface has some strange fluctuation and I don't know why.
I have corrected the inlet velocity value to make sure the mass flow rate is constant.
is it correct that specify velocity and pressure gradient at the inlet at the same time?

Any Help

Thanks.

Does anyone have a similar problem?
I found as long as the velocity is time-dependent this pressure fluctuation appears.

Best

Hello, I have encountered the same issue when using an incompressible solver. Wondering if you made any progress.

I suspect that the pressure fluctuation is caused by the change of mass flow rate. So far I haven’t found a good way to ensure same mass flow rate at each time step when using timevaryingmappedfixedvalue boundary condition. Any thoughts?