Vendredi 27 février 2026 à 16h, salle des séminaires IRPHE
Abstract: Horizontal buoyancy gradients play a key role in many convective systems but are often treated as secondary to vertical forcing. In this talk, we show that horizontal convection can instead dominate flow stability and stratification in both industrial and geophysical contexts.
First, motivated by nuclear safety applications, we study the stability of a thin fluid layer subjected to imposed vertical heat fluxes and lateral cooling, a configuration representative of heat transfer in confined reactor systems. We demonstrate how horizontal convection triggers a three-dimensional oscillatory instability whose threshold decreases with aspect ratio and arises from interactions between vertical shear and horizontal temperature gradient.
We then examine a geophysical configuration where horizontal convection competes with Rayleigh–Bénard convection. A destabilizing buoyancy flux is imposed at the bottom, while horizontally varying buoyancy is prescribed at the top. Using scaling arguments and high-Rayleigh-number 2D DNS, we show that sufficiently strong horizontal forcing can reverse the volume-averaged vertical buoyancy gradient, leading to "restratification" of the layer.
These results highlight horizontal convection as a primary mechanism shaping convective dynamics across applications ranging from nuclear safety to geophysical flows.
Florian Rein, Postdoctoral Researcher, Scripps Institution of Oceanography, San Diego