Effect of unipolar charge injection direction on the onset of Rayleigh-Benard convection: a lattice Boltzmann study

摘要

This paper numerically investigates the effect of unipolar charge injection on the onset of Rayleigh-Benard convection (RBC) in a layer of insulating liquid contained between two parallel plates. A recent developed unified model on the basis of the mesoscopic lattice Boltzmann method (LBM) is employed to solve the entire macro control equations. Two different cases of charge injection from above and from below are considered. It is interesting to find that the charge injection advances the onset of convection regardless of the injection direction. Besides, the decrease of critical Rayleigh number, along with the increase of flow intensity and the enhancement of heat transfer resulting from charge injection remain the same for different injection directions. However, the results show that the charge injection directions have significant effect on temperature and charge density distribution, as well as the evolution of flow motion, especially for the case of larger electric Rayleigh number. In addition, the effects of Prandtl number, the mobility number and the injection number are also studied.