Numerical analysis of the subcritical feature of electro-thermo-convection in a plane layer of dielectric liquid

This paper reports a numerical investigation with a horizontal layer of dielectric liquid subjected to the simultaneous effects of external thermal and electric fields. The flow is driven by the buoyancy force and the Coulomb force, which depend on the Rayleigh number (Ra) and the electric Rayleigh number (T), respectively. We consider a strong unipolar injection from the lower electrode and a destabilizing thermal gradient. The two driving forces cooperate with each other in destabilizing the system. The neutral stability curve in the Ra-T plane is successfully reproduced from the direct numerical results, and it is shown to be independent on the Prandtl number (Pr) and the dimensionless mobility number (M). On the other hand, both the bifurcation types of the linear instability (subcritical or supercritical) and the finite amplitude stability criterion depend strongly on the combination of Pr and M.