Electro-thermo-convection in a high Prandtl number fluid: Flow transition and heat transfer

Abstract

This paper aims to study the electro-thermo-convection of a high Prandtl number fluid (silicone oil) in a rectangular cavity. A high accuracy numerical solver is undertaken to solve the problem. These numerical simulations are performed for a range of Rayleigh and electric Rayleigh parameters, Ra=0,104∼106 and T=0∼1000, which correspond to regimes from laminar to chaotic flow for different cases. Under the condition of weightlessness Ra=0, a strong mixing between heat and cold liquid caused by the electric field is observed, and there is a flow motion transition from large vortices to plume oscillation with the increased value of T. The large vortices motion has a better effencify on heat transfer enhancement. A dual solution at low and moderate Ra numbers is observed. The beingness of these two solutions is validated by a global linear instability analysis based on the linearized lattice Boltzmann method. With the help of some nonlinear analysis techniques, we find that the presence of the electric field may stabilize the thermal convection system. Furthermore, a full map of the heat transfer rate with respect to electric and thermal driving parameters is provided as a reference for applications. Heat transfer enhancement appears only when the electric field force is dominant. A neutral force curve about Ra−T is presented that can characterize the threshold of electric field force to achieve heat transfer enhancement for thermal convection at different Ra numbers.