[smehdi609]

Dear Foamers,
I am simulating two co-axial mixing jets, one cold and one hot with buoyantSimpleFoam. The iterations goes on until the residuals reach 3e-5, suddenly it becomes oscillatory and diverges !! If I under-relax density calculation then it works pretty well. I was wondering why?
The central jet has a Reynolds number of 20,000, and the other one has 4000. I use upwind differencing for convective fluxes.
Cheers,
Mahdi

[lillberg]

Dear Mahdi,

The reason is likely that you have a larger scale oscillatory behaviour of the jets that has to be heavily relaxed to find a steady state solution. Likely you could relax either entalpy or even pressure and come up with the same solution.

Best Regards

-Eric