Divergence in Fluent 15 but convergence in Fluent 14.X
 

Hi!

I am simulating the flow over a three elements airfoil at M=0.2. The mesh is fully unstructured and 2D and I am using the pressure based solver. I am modelling viscosity with a Spalart allmaras model, and the yplus is just below 100 (might be too high, I know).

I am using a big courant number. The flow is converging well in Fluent 14.0 and 14.5 (low residuals and CL/CD constant) but it is diverging (residuals explode) with Fluent 15.0. I am using the same journal file and the same mesh.

Do you have an idea of what have changed between the two versions that makes the flow diverging in the last release and converging is the previous releases?

Thanks,

Jean.

Maybe have a look at the AMG parameters, did some of those change?