Abstract

Flow instability is a source of turbulence and thus it has been studied for more than a century by many researchers in fluid dynamics (including the seminal work by Taylor in 1923) and more broadly in physical sciences to better understand turbulence in astrophysical and geophysical flows. To understand these naturally occurring large-scale flows where stratification and rotation play important roles, my research has focused on instabilities of shear flows in stratified and rotating fluids. In the seminar, I will give a talk about two topics. The first one will be about stably stratified Taylor-Couette flow and its two different instabilities: centrifugal and strato-rotational instabilities. The topic is found to have some relevance with equatorial flows in the Earth’s ocean and atmosphere as well as the equatorial tachocline. Theoretical and experimental results will be presented to explain the instability mechanism and demonstrate nonlinear development of the instabilities leading to turbulence. The second topic will be about horizontal and vertical shear flows in stellar radiation zones where stably stratified. More specifically, I will discuss the effects of (i) fast thermal diffusion in the radiation zones and (ii) rotation with the full Coriolis acceleration. I will also discuss briefly how research outcomes on the instability can be used for turbulence modelling in stellar evolution simulations.