Thin shear layers in high Reynolds number turbulence - A coherent-structure model

Direct numerical simulations of homogeneous isotropic turbulence at the Taylor microscale Reynolds number of order 10³ show that the most energetic small scale motions and places with the most intense dissipation in the homogeneous isotropic turbulence are highly inhomogeneous and are located inside thin shear layers. We propose a local mechanism for how the most intense small scale and dissipative motions are produced in the vicinity of well separated thin shear layers. A model is developed based on a local rapid distortion analysis and the Townsend-Obukhov energy transfer hypothesis which is consistent with the data of the numerical simulation.