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Re: Smagorinsky Turbulence Model and TRT collision operator


Thanks Marc for your detailed reply!
I am familiar with the TRT papers and the derivation of the optimal parameters but I did not consider this. Your argument makes perfectly sense: Setting the anti-symmetric relaxation parameter using the magic parameter lambda (with 1/4 as I did) and a very high Reynolds number and thus a very low positive relaxation time (tau+ very close to 0.5) will result in a very high value for tau- (a very small omega-) and therefore the influence of the anti-symmetric part will be (almost) neglectable. Fixing tau+ and tau- to similar values makes TRT though lose its advantages over BGK as you have pointed out.
I think turbulence modelling in LBM in general is quite appealing indeed due to its simplicity and computational efficiency. Some time ago i benchmarked it and I think my performance dropped by around 1/3 (compared to the simple BGK operator) to 75 Mlups with a D3Q19 lattice on an octa-core processor.
I will let you know if I stumble across something. In the meanwhile thanks again for your kind reply!