CONVECTION IN ELECTROCHEMICAL SYSTEMS

Some theoretical and experimental results for the concentration and ve locity fields that appear during unsteady electrolysis in small electr ochemical cells are given. Two systems are considered: \Cu\CuSO4(aq)\C u\ and \PbO2, PbSO4\H2SO4(aq)\Pb, PbSO4\. For the former system, in wh ich the electrodes are solid, both linear and nonlinear electrode kine tics are considered. For the more complicated latter system, where the electrodes are porous, attention is restricted to linear kinetics. Th eoretical results are obtained by using both perturbation methods and numerical analysis. Experimental results are obtained by Laser Doppler Velocimetry and Image Laser Holography. It is shown that the evolutio n of the concentration and velocity fields is controlled by stratifica tion of the electrolyte. The boundary layer structure is similar to th at appearing during nonlinear spin up of a homogeneous fluid. Theoreti cal and experimental results are in good agreement.