Decay of stratified turbulent wakes behind a disk at a moderately high Reynolds number

Large-eddy simulations of flow past a disk with Reynolds number of 50,000 and Froude number of 0.1,2,10,50,∞ are presented. The results are analyzed with a focus on the decay of turbulent wakes that are subject to strong, intermediate, and weak stratification. The axisymmetric wake is also investigated as it sets the initial flow state where buoyancy becomes important in Fr ≥ O(10) wakes. Re is sufficiently large so that turbulent production dominates over mean viscous dissipation in the mean kinetic energy budget. Nevertheless, it is found that the characteristic scales of turbulence (both r.ms. velocity and integral length scale) evolve differently from those of the mean deficit velocity. Therefore, contrary to classical self-similarity theory, turbulence and mean quantities obey different power laws. We will report on how buoyancy changes the relative behavior of mean and turbulence power laws and characterize the transition from 3D to the non-equilibrium (NEQ) regime. Energetics and mixing properties will be quantified in the regime of stratified turbulence which is wider than in previous body-inclusive simulations. Changes, as a function of Fr, in the wave field generated by the body and by the wake will be described.