Sensitivity of spectral variational multiscale methods for large-eddy simulation of isotropic turbulence

Abstract

Subgrid closures in the Fourier space belonging to the variational multiscale method proposed by Hughes are investigated in the case of the incompressible freely evolving isotropic turbulence in the limit of an infinite Reynolds number. Sensitivity to the closure used at small scales is shown to be high, and different hybrid spectral closures proposed in the present study which explicitly account for the computed kinetic energy spectrum shape yield good results. The original formulation of the method is observed to suffer from an unphysical energy pile-up in the large scales, which arises from the fact that the kinetic energy transfers associated with distant triadic interactions are neglected. The use of a nonorthogonal operator to define the resolved large and small scales is proved to alleviate this problem, yielding an accurate and robust spectral variational multiscale methods for high Reynolds number flows.