Thermally Induced Electroconvection

The combined effects of a thermal gradient and a dc electric field upon a poorly conducting fluid are used to induce steady convection. A vertically directed temperature gradient is used to establish an electrical conductivity gradient over the rectangular cross section of a liquid‐filled channel. Then a static potential, which varies either linearly or periodically along the channel, is imposed on electrodes that form the channel top. A similar potential, spatially shifted in the longitudinal (horizontal) direction, is applied at the bottom of the channel. These electrodes make physical and electrical contact with the fluid, which typically has a mean electrical conductivity of ${10}^{\text{−10}}\hspace{0.17em}\mathrm{mho}/\mathrm{m}$ . Because of the conductivity gradient, the vertical component of the resulting electric field induces free charges in the bulk, and these charges are then pulled in the horizontal direction by the longitudinal component of the electric field. An analytical model is used to predict the distribution of potential, electric stress, and velocity. It is assumed that effects of convection on the charge distribution can be ignored (electric Reynolds number small). An experiment is described in which the periodic potential distribution is closed on itself in a re‐entrant channel to achieve fully developed flow. Experiment and theory compare favorably with discrepancies largely attributable to finite electric Reynolds number effects.