Initial guess of k and eps at the Inlet.
 

Hi, I have question about the Inlet boundary settings. I am trying to simulate the 3D flow around a sphere (15cm Diameter), using the keps realizable model. At the Inlet I am using a Inlet velocity and at the Oulet an outlet pressure, the fluid is water.

When I am running a Case With V =0,5m/s (Re=25000) and the Inlet k=0,01 and eps=0,01 : I get the right Drag coefficient (less than 1% diff with the theory) , with good y+<4.

If I run a case with V=1m/s and the same Inlet conditions k=0,01 and eps=0,01 FLUENT underestimate the Drag Coef (20% less). But if I increase the Inlet conditions k to 0,08, than the Drag is closed than the theoretical value.

Q : Is It normal that the result of the drag calculations is so strongly coupled with those inlet parameters.

The FLUENT doc (7.2.2 : determining Turbulence parameters ) and about a good guessing of the k and eps at the inialisation , sparks this problem only for good convergence.

Thanks for your help P.