[atlantis83]

Good Morning

This is my first time in this forum and also my first time with Fluent.
I'm trying to simulate flow thoru the intake duct and valve of a gasoline engine to calculate the direct discharge coefficient with fluent and I procided in this way:

1 - mesh with workbench with y-plus between 30-300
2 - boundary condition:

2.1 - First Approach: - pressure inlet 101325 Pa total pressure
- pressure outlet 86325 Pa static pressure
this setup take to instable and non phisical solution

2.2 - Second Approach: - velocity inlet
- pressure outlet -15000 Pa relative to atmosperic pressure

in both cases I set a T.I. of 5% at inlet and 4% at outlet with relative hydraulic diameter.
As Solver i use Simple with Momentum Second Upwind and I initialize with inlet condition.

With second approach I obtain coherent values but the matching with experimental values of discharge coefficent was affected by at least 10% of relative error.

Have you any suggestion to improve the accuracy of this model??

Thank you very much.