Section: New Results

A new criterion to analyse hybrid RANS/LES approaches

Most of the available hybrid RANS/LES methods are completely empirical or based on a formalism which is not applicable in practical application, due to a mismatch between the statistical average and the spatial filetring in inhomogeneous flows. The lack of clear formalism leads to limitations in terms of modeling of the unresolved turbulent motion. We have established a criterion [6] to assess the equivalence between hybrid RANS/LES methods, called H-equivalence, that makes it possible to view different hybrid methods as models for the same system of equations: as a consequence, empirical hybrid methods, such as the detached-eddy simulation (DES), can be interpreted as a model for the subfilter stress involved in the temporally filtered Navier-Stokes equations, which is an answer to the issue raised above about the formalism underlying such methods.