Apparaît également dans la collection : 2026 - T2 - WS2 - Instabilities and transitions in geophysical flows

Our current understanding of ocean mixing remains insufficient to balance the global ocean energy budget, pointing to overlooked local mechanisms. At the edges of mesoscale eddies, horizontal density layering is observed, suggesting enhanced vertical mixing. To investigate its origin, we examine the underlying instabilities. We model this configuration using a solid ellipsoid undergoing differential rotation within a rotating stratified fluid. Combining analytical and experimental approaches, we characterize instabilities across a large range of Rossby, Froude, and Reynolds numbers. Experiments are conducted in a 1 m rotating tank using Particle Image Velocimetry and Schlieren imaging. The base flow is first compared to an exact analytical solution for arbitrary aspect ratios. Observed modes are then compared with a linear stability analysis using the Dedalus solver. We identify in particular viscodiffusive and centrifugal instabilities and assess their contributions to mixing.

Co-authors: Antoine Chauchat (IRPHE), Patrice Meunier (IRPHE), Keaton Burns (MIT)