Turbulence
 

hi all
I want to model a boat using CFX. The Re is about 39e+06. what turbulence option is the most suitable for this modeling? if k-epsion, how do I should choose constants k and epsilon for?

thanks alot

The answer depends on what you want to do in the analysis. If you want detailed boundary layer and/or turbulence transition data then you must use SST, possibly with the turbulence transition model. If you just want a lift/drag number then a standard wall function approach should be fine then I would recommend SST.

So my first guess for your application would be SST as it is a good general purpose turbulence model. Don't fiddle with any of the constants unless you REALLY know what you are doing.

thank you Glenn
my aim is to calculate value of lift and drag. so according to your suggestion SST would be the best case. but my question is still "How should I assign" appropriate value to the constants? Is there any guideline to have an accurate numbers for those?

thank
Hashem

SST is a good general purpose turbulence model which you should use unless have a good reason not to.

As I said, don't fiddle with the model constants. The defaults are good for most applications.