Checking the quality of LES simulations of Horses3D #231
oscarmarino
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One of the most common way of a posteriori checking the quality of LES simulation is to get the TKE ratio, with a value greater than 80% being a good simulation (in the whole domain). It is defined as TKE_ratio = TKE_resolved/ TKE_total = TKE_resolved/ (TKE_modelled+TKE_resolved).
We can compute now the resolved, with the statistics, getting the trace of the Sij divided by 2, so getting from horses2plt Sxx,Syy,Szz.
The modelled one depends on the turbulent viscosity (mu_sgs in horses2plt, right now only in instantaneous file) and the Length Scale of Turbulence (L_s), as TKE_modelled = (mu_sgs/L_s)^2.
We are calculating internally L_s, as is part of the LES model, but not saving it (we calculated on the fly for each Gauss node. It depends on the LES filter (delta), and the model constant, L_s = C_s*delta (C_s for Wale, C_w for VREMAN, C_s for Smagorinsky, I think including the wall correction).
I think we can easily export delta, C_s is all constant in space and time if not considering wall correction. Other possibility is saving L_s (only recomputing if adaption or moving) and use it to the LES model calculation and exporting it.
This way we can compute TKE_modelled for 1 instant solution (or plenty of them).
The other problem is having both TKE in different files (which makes it difficult to compute the ratio in paraview for example.
Any ideas of which approach we want?
Thanks!
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