Numerical simulation of circular Couette flow under a radial thermo-electric body force

The transition from circular Couette flow of a dielectric fluid with a radial temperature gradient and an alternating electric voltage has been investigated by a direct numerical simulation. The inner cylinder is rotating while the outer one is fixed. The radial temperature gradient and the electric voltage acting on a dielectric fluid generate a radial dielectrophoretic (DEP) force which can induce thermal convection. The flow is controlled by the Taylor number Ta that measures the intensity of the centrifugal force and the electric Rayleigh number L that indicates the intensity of the DEP force. For each value of L, the instability threshold (Ta_c) is determined and compared with that predicted by the linear stability analysis. Nonlinear coefficients of the Landau equation are computed to reveal the nature of the transition: oscillatory axisymmetric modes occur via a subcritical transition, while steady axisymmetric and oscillatory non-axisymmetric modes occur via supercritical bifurcations. The momentum and heat transfer coefficients are computed to evaluate the efficiency of the flow induced by the DEP force in the momentum and energy transfer.