The Imbalance Between Enstrophy Production and Destruction in Homogeneous Isotropic Unsteady Turbulence

We show in direct numerical simulations of homogeneous isotropic non-stationary turbulence that there is a systematic and significant imbalance between enstrophy production and its destruction which is concomitant with the previously observed imbalance between the non-linear energy cascade to fine scales and its dissipation (Valente, Onishi, da Silva, Phys Rev E 90(023003), 2014, [12]). However, contrary to the former, the imbalance between enstrophy production and destruction is affected by the 'cascade time-lag', i.e. the time it takes for the energy injected on the large-scales to reach the fine-scales.