Preliminary experiments on the control of natural convection in differentially-heated cavities

François Penot , Olivier Skurtys , Didier Saury (1)

1 COST - Convection, Optimisation, Systèmes Thermiques [Institut Pprime]

Aiming at the control of natural convection flows and heat transfer in air-filled differentially-heated cavities, experimental attempts were carried out in order to achieve the stability of such flows to various excitations. The mechanism of control chosen in these experiments introduces thermal disturbances via a thin pipe located inside the boundary layer at the bottom of the hot wall. Its temperature varies periodically due to alternating electrical heating and continuous water cooling. The effects of this disturbance in temperature are investigated for a Rayleigh number value chosen just greater than the first bifurcation value from a steady state flow to a monoperiodic state. The results show the distribution of the overall and local Nusselt numbers. The introduction of this obstacle induces a 10% decrease in heat transfer. Temperature oscillations of the actuator provoke modifications of the flow field. In particular, an amplification of unsteadiness in the outer borders of boundary layers is observed and a displacement of secondary vortices is encountered. Explanations are given by a detailed examination of flow structures, such as the spatial distribution of velocities and their fluctuations. © 2010 Elsevier Masson SAS. All rights reserved.

Mots clés: Buoyancy driven flows; Control of convective heat transfer; Stability and transition; Unsteady flows; buoyancy driven fl ows; control of convective heat; stability and transition; transfer

Domaines: Thermique [physics.class-ph]; Thermique [physics.class-ph]

François Penot, Olivier Skurtys, Didier Saury. Preliminary experiments on the control of natural convection in differentially-heated cavities. International Journal of Thermal Sciences, 2010, 49, pp.1911-1919. ⟨10.1016/j.ijthermalsci.2010.05.008⟩. ⟨hal-03037223⟩