Linear and non-linear instabilities of stratified-rotating shear flows

Abstract
Various naturally occurring and engineering flow systems are commonly under multi-physical effects such as stratification (i.e. density or temperature variation) along the vertical/gravitational direction or rotation acting on the horizontal plane. Traditionally, it has been known that the Coriolis force induced by rotation can suppress or promote instability and turbulence depending on its direction and strength, following the Rayleigh’s criterion for centrifugal instability (CI), while stable stratification suppresses the vertical motion of fluids leading to the delay of the onset of CI and its turbulence. However, recent research has unveiled new aspects on the roles of stratification and rotation. For instance, there is a new type of instability called the strato-rotational instability (SRI), which occurs due to a resonance of inertia-gravity waves in strato-rotating shear flows and does not follow the traditional Rayleigh’s criterion. Also, when the axis of rotation is inclined against the vertical axis, which is the case for atmospheric/oceanic/stellar-interior flows at a general latitude off the poles, the regime of CI is different from that predicted by the Rayleigh’s criterion. The non-linear dynamics of these instabilities (CI and SRI) remains yet to be explored further in the presence of stratification and rotation. In this talk, I will present some recent progress on the linear and non-linear dynamics of instabilities in stratified-rotating shear flows. Results from theoretical and numerical investigations (and a bit of experiments) will be discussed to explain the roles of stratification and rotation on shear flow instabilities.

Biography
Dr Junho Park is an Assistant Professor in the Centre for Fluid and Complex Systems at Coventry University in the UK. His research interests are in fluid dynamics applied to various problems such as the angular momentum transport in the interior of stars in astrophysics, the dynamics of geophysical vortices in atmospheric and oceanic sciences, high-speed compressible flows in aerodynamics, and bifurcation and chaos in non-linear dynamical systems. His research has particularly focused on hydrodynamic instabilities and laminar-turbulent transition to reveal their roles in these natural and engineering flow systems.