Electric field effects on the stability of a thermogravitational flow in a vertical capacitor

The effect of electrization of a poorly conducting liquid and the action of an electric field on the stability of the base flow in a vertical layer with un-equal but constant temperatures at its vertical boundaries was investigated numerically and experimentally using a linear dependence of conductivity on temperature. By solving the appropriate EHD and heat equations we have found that for liquids of low electrical Prandtl number, Pe, and low values of electrical Grashoff number, Ge, an electric field stabilizes the base flow thus leading to a higher critical value of the thermal Grashoff number G for thermoconvective instability. However as Ge increases, stabilization is replaced by destabilization and the critical G for the onset of instability decreases to zero as Ge increases. We have been able to observe oscillatory electro-thermoconvective motions in a wide range of values of the parameters although for low enough values of Ge the electroconvective instability leads to steady-convection in the form of rolls provided the values of G are low enough.