# Which tool/metric do you recommend to evaluate the quality and validity of a Large Eddy Simulation?

The idea behind Large Eddy Simulation is to solve explicitely the scales of the flow that are resolved by the computational grid and to model the sub-grid scales. Ideally, the cut-off between these scales is located in the inertial range of the local turbulent field. This is because Kolmogorov's hypotheses predict a universal behavior of the turbulence in that inertial range and thus accurate modeling should be possible for the sub-grid scales. In practice, unless we consider a simple periodic box with isotropic turbulence, the cut-off between the resolved scales and the sub-grid does not occur in the inertial range for every point in the domain. Which begs the question: how can we know our current simulation is consistent with the LES framework?

Which method do you use to evaluate your LES? Does it matter whether you are using an implicit or explicit filtering of the small scales?