Application of the integral length-scale approximation to Wall Modelled LES

Abstract eng:
We apply the Integral Length-Scale Approximation (ILSA) model [Piomelli et al., J. Fluid Mech., 766, 2015] in Wall-Modelled Large-Eddy Simulations. In the ILSA model the length scale used for the eddy viscosity is defined in terms of the integral scale, rather than the grid-size, as is common practice. The only model coefficient is determined by prescribing a target value of the contribution of subfilter-scales (SFS) to the turbulent stresses, called “SFS activity”. By increasing the SFS activity near the wall, the model correctly represents the gradual transition from an LES, away from the wall, to a RANS-like model near the wall, where the grid is of the same order as the integral length scale, and all eddies become subfilter scale. The modified model was applied to channel flow at Reτ = 5 × 103 , 5 × 104 , 5 × 105 using various resolutions and predicted the DNS data and log-law very well.

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