Thermal transfer in Rayleigh-Bénard cell with smooth or rough boundaries

Several Rayleigh-Benard experiments in water are performed with smooth or rough boundaries. We present new thermal transfer measurements obtained with large roughness elements arranged in a square lattice. The data are compared to previous ones obtained with smaller elements in the same cell (Tisserand et al., 2011). Experiments in the same apparatus without roughness are fully presented, as reference results, to allow for comparison. In the rough case, several regimes of heat transfer are identi ed : one similar to the smooth case, an enhanced heat transfer one characterized by a modi cation of the Nusselt vs Rayleigh numbers relation, and a third part where the relation can be similar to a smooth one with a corrected prefactor.