Onset of Rayleigh-Bénard convection in dielectric liquids with electric conduction

This paper presents a combined stability analysis and numerical investigation of Rayleigh-Bénard convection in a planar dielectric liquid layer subjected to the simultaneous action of Coulomb and buoyancy forces. For the first time, Rayleigh-Bénard convective instability with electric conduction is considered. Fully coupled set of governing equations for fluid flow, heat transfer, and electrostatics are solved using the finite-volume method (FVM) framework of OpenFOAM. The fluid layer is destabilized under the combined action of buoyancy and Coulomb forces. Rayleigh number (Ra) and the Conduction number (C0) are the control parameters for fluid flow. Distributions of physical variables in the hydrostatic state are derived. Modal stability analysis is performed to establish the neutral stability curve in the Ra-C0 plane. Present numerical results are compared with the results of stability analysis. The flow and heat transfer characteristics in the Ra-C0 parameter space are analyzed. The present study provides deeper insights into the electro-thermo-convective flow mechanism due to the EHD conduction phenomenon occurring at weak and medium electric fields. The results of this study can serve as a benchmark to design flow systems subjected to combined gradients of thermal and electric fields.