Effect of forcing and mean shear on velocity gradient dynamics in turbulent flows

Velocity gradient dynamics including anomalous scaling exponents and intermittency have been widely studied in literature using direct numerical simulations (DNS) of forced isotropic turbulence. In most cases, the forcing is Gaussian in nature and this differs from the manner in which turbulence is generated in naturally occurring flows. In order to isolate the effect of forcing on the findings, this study examines the velocity gradient dynamics in decaying isotropic turbulence and shear driven turbulence. Following the works of Yakhot and Donzis (Phys. Rev. Lett. 2017), we examine the Reynolds number dependence of various moments of dissipation and velocity gradients. The goal is to identify the Taylor Reynolds number at which noticeable deviations from a Gaussian character are observed. We seek to determine the anomalous scaling exponents of different moments. We also examine the dependence of small scale topology (Q-R diagram) on imposed shear and Taylor Reynolds number.