Radiatively driven convection: towards the ultimate scaling regime and beyond

Speaker: Basile Gallet

Abstract: Decades of investigation of the Rayleigh-Bénard (RB) thermal convection setup indicate that the heat transport is strongly restricted by boundary layers near the hot and cold solid plates. This prevents the unambiguous observation of the ‘ultimate’ scaling regime of thermal convection, where bulk turbulence controls the convective heat flux independently of molecular diffusivities. Motivated by natural convective flows, we have recently developed a laboratory experiment that departs from the RB setup: heat is input radiatively, directly inside the bulk turbulent flow and away from the boundary layers. After providing experimental evidence that this setup naturally leads to the ultimate regime of thermal convection, I will discuss the maximum theoretical Nusselt number (heat transport efficiency) that can be achieved by such internally heated and cooled convection. I will show that there exist steady laminar solutions that transport heat even more efficiently than the ultimate scaling regime, with a scaling behavior Nu~Ra, before discussing their stability in 2D and 3D.