Long-term unsteadiness and large-scale structures in Rayleigh-Bénard convection with and without electromagnetic forcing

Abstract

This dissertation focuses on turbulent thermal convection, which occurs in a wide range of (geo)physical situations, like in the atmosphere, the oceans, the interior of stars or planets, and engineering applications, like metal casting or crystal growth processes. In this work, a special type of thermal convection, Rayleigh-Bénard convection, is studied with and without an additional electromagnetic body force. Experiments are performed in a rectangular RB convection cell of aspect-ratio ?=4 filled with water. Particle image velocimetry (PIV), laser Doppler anemometry (LDA), and liquid crystal thermography (LCT) measurements are used to obtain velocity and temperature information. The first part of this dissertation describes an investigation of the large-scale circulation (LSC) in Rayleigh-Bénard convection. In the second part, a study of the boundary layers in Rayleigh-Bénard convection is described. The last part reports on the control and enhancement of the heat transfer in Rayleigh-Bénard convection using an additional electromagnetic body force.