Abstract: Motivated by observations of turbulence in the strongly stratified ocean thermocline, I use direct numerical simulations to investigate the interaction of a sinusoidal shear flow and a large-amplitude internal gravity wave. Consistent with linear wave refraction, the energy of the wave accumulates in regions of negative mean shear where we observe evidence of convective and shear instabilities. Mixing is dominated by the contribution from shear-driven billow structures, with a similar mixing efficiency to stratified shear layers. In this talk, I will discuss the complex interaction between the mean flow, internal gravity wave and turbulence, and potential implications for internal wave-driven mixing in the ocean.

Bio: Chris Howland is currently a postdoctoral researcher in the Physics of Fluids group at the University of Twente. He finished his PhD at the University of Cambridge in August 2020, and uses numerical simulations to investigate fundamental fluid flows motivated by a range of environmental flow problems.