I create a convergence analysis regarding the massflow of a valve. There is a problem with the meshing of the inlet and outlet, these are the lids. A very fine meshing results in the error message "A vortex is crossing the pressure opening" and the solver says that it is necessary to consider a high Mach number. Furthermore, the massflow is very low as if the vortex closes the inlet and there is no fluid flow. But this effect only appears when the number of cells at the inlet boundary condition is relatively high.
I can give you some values:
Boundary conditions: Inlet: static pressure 141325 Pa
Outlet: static pressure 140325 Pa
I used a local initial mesh for the meshing of the lids using the inner face of the lids.