A laboratory and theoretical framework for systematic non-equilibrium turbulence studies

Abstract

The cornerstone assumption of equilibrium of the small and intermediate scales in the classical view of turbulence (K41 - the combined efforts of Kolmogorov, Batchelor and Richardson) is under ever increased scrutiny. Although the K41 based models do appear to apply well to some flows, there exist many important flows that are problematic for these turbulence models. In particular, it is interesting to note that the most challenging applications appear to have one thing in common - rapid changes of the flow in the mean in time and/or space. It is thus interesting to systematically investigate what the bounds of validity of the classical K41-view of turbulence are, if any. And if the K41-picture of turbulence does indeed break down, what are the non-linear spectral energy transfer mechanisms that lead to nonequilibrium turbulence behavior (local vs. non-local)? Does the non-linear energy exchange between scales divert from the classically assumed Richardson cascade? And is the constancy of the spectral flux across the inertial range interrupted? In order to answer these questions, a new facility for the systematic study of non-equilibrium turbulence in a controlled setting has been established along with an accompanying theoretical framework that is tailored for addressing these specific issues