Julien Salort, ENS Lyon

Flow structure in a Rayleigh-Bénard cell with rough plate

The influence of roughness in turbulent Rayleigh-Bénard convection is investigated using Particle Image Velocimetry and local temperature measurements, in several parallelepipedic cells.

Many previous studies have shown that the heat flux is increased when the plate is made rough. The increase is larger than the increase of surface area and, may exhibit also an increase of the scaling exponent. This hints at a change in the boundary layer structure, which we confirmed by the analysis of the profiles near the rough plate.

We report new results on the large scale flow structure: the mean velocity is mostly unchanged by the roughness, but the velocity fluctuations are increased and the statistics are strongly modified.