Low Turbulence Intensity Simulation
 

Gentlemen,

I am trying to simulate the 3D turbulent flow field inside a turbine rotor using R-K and k-epsiln/ARSM turbulence model. I have got good results when the inlet turbulence intensities are 15% and 11%, respectively. But when I try 1% inlet turbuelence intensity, the calculation does not converge, nor diverge. The error just stays a much higher level than the 15% Tu case.

Does anybody know why it is and how to improve this? Thanks a lot.

J.M.

Re: Low Turbulence Intensity Simulation
 

Using an explicit Runge-Kutta solver to solve k-epsilon becomes more and more difficult the lower the turbulence level is. When you come down to 1% or even lower you often have to take special care to obtain convergence. You can spend years trying to fix this problem (I did), but in the long run I think that you'll be better of switching to an implicit method, at least for k and epsilon. 1% is not impossible though. I don't know what kind of "tricks", "limiters" and "stability enhancements" you have in your code today, but there are many things that you can do which will reduce the problems.

Btw, I'm not sure what you mean with that the error stays high - what error? Do you mean residuals?