Turbulent viscosity

Christian Holm

Hi.

I have made a simulation upon a rectangular box. Inlet in one end, and outlet in the other end. Inlet vel. is approx. 20 m/s. There are no temperature differences. The problem is that I get a too high turbulent viscosity (the turbulent/laminar viscosity ratio is limited to approx. 10^5). I first considered that it could be due to a too fine grid combined with a "coarse" turbulent model (k-e model), so I tried with a coarser grid. No effect. I have also tried other models (RS, LES) but it did not do the trick (well, the LES did with a good initial guess).

Q: Is it true that there are problems with combining a fine grid with a "coarse" turbulent model? Q: Do anyone have suggestions as to solve the high turbulent viscosity problem?

I would appreciate comments to the two questions.

Cheers Christian