Effect of electrode materials on electrohydrodynamic flows of ethanol

When the high DC electric voltages are applied to ethanol through a couple of electrodes made of metal wires, the climbing flow is generated along the electrodes due to the electrohydrodynamic (EHD) effect. The EHD flow is generally attributed to the nonuniformity of electric conductivity and dielectric constant of the fluid. But the climbing behavior of ethanol is drastically influenced by the electrode materials. The fluid level as a measure of EHD strength is examined under the voltages up to 5 kV for 14 different metals. For all metals, the fluid level around the positive electrode is higher than that around the negative electrode. After the EHD experiments, the surfaces of metals which bring about the high EHD effect are changed from smooth to rough textures. Because the good relation is established between the EHD effect and surface roughness, the high field strength and current density concentrated at peaks in rough surfaces can be responsible for the strong EHD flow.