Velocity and temperature near roughness in turbulent Rayleigh-Bénard convection EuHIT Funded Project


Francesca Chillà
Ecole Normale Supérieure de Lyon, Lyon, France
Ronald du Puits
Technische Universitaet Ilmenau, Ilmenau, Germany
Olivier Liot
Ecole Normale Superieure de Lyon, Lyon, France


Research Infrastructure
Barrel of Ilmenau, Germany
Facilities used
Barrel of Ilmenau (BOI)
Project leader
Julien Salort
Ecole Normale Superieure de Lyon, Lyon, France


In this proposal we would like to go further in the understanding of the structure of the boundary layer near roughness in turbulent thermal convection. This is a greatly interesting problem both from practical and fundamental point of view. The PIV measurements that we have previously carried out near a rough plate inside the BOI, within the framework of the first EuHIT project call, has allowed us to evidence a change of structure of the boundary layer beyond a transition Rayleigh number [Liot, et al., In preparation for JFM]: (i) before the transition, we observed internal convection in the space between the roughness elements, with no fluid exchange with the bulk; while there is external convection and mass exchange beyond the transition; (ii) there is a substantial change in the velocity statistics beyond the transition, compatible with turbulent boundary layer and logarithmic velocity profiles. In this proposal, we wish to take advantage of the newly installed 3d-Tomo-PIV system of the facility to get 3d and more precise information on the velocity field near the roughness; and we would like to carry out measurements of the temperature profiles that will allow better comparison with the water cell in Lyon [Salort, et al., PoF 26, 015112 (2014)] and a better understanding of the mechanisms at play. The combined experiments with air in the BOI and water in the Lyon allows us to extent our recent results on the boundary layer structure near roughness and a general improvement in the knowledge of the physical phenomenon.