Simulation of stratified turbulent wakes at very high Reynolds numbers*

A series of implicit large-eddy simulations is conducted to study the dynamics of turbulent wakes operating in the strongly stratified regime, as a continuation of the work presented in Zhoud & Diamessis (Phys. Rev. 2019). Particular attention is paid to aspects of the code design/implementation, as well as the selection of the spatial discretization scheme, aimed to obtain simulations of sphere wakes at a body-based Reynolds number Re ~ O(10^6).

A hybrid spectral element method (SEM) – Fourier Galerkin discretization is adopted. The SEM retains the flexibility of localized flow resolution of the wake core and, in combination with static condensation, results in a large number of small tridiagonal systems. Given the broad range of scales that have to be resolved, the series of challenges encountered related to minimizing memory footprint and execution times are described, along with actions taken towards their resolution.

The preliminary analysis will focus on visualizing the layered turbulent fine-structure that emerges during the intermediate-late stage of the wake evolution, and its capacity to fill the wake cross-section at increasing Re. The trajectories of the flow evolution will be explored on the Gn-Fr_h regime diagrams (de Bruyn Kops and Riley 2019).