Field induced disruption of a planar water-oil interface influenced by a close metallic sphere

The problem of instability of a horizontal interface between water and an insulating fluid, electrically influenced by a metallic sphere located just above it, is considered here with its relevance to the basic electrocoalescence phenomenon of close water droplets suspended in an insulating medium. Results are presented of preliminary experiments performed using visualisation and shadowscopy techniques. The evolution of the interface shape is characterised for various applied step voltages and for different values of the initial spacing s₀ between sphere and interface. An order of magnitude analysis leads to good estimates of the characteristic parameters and time scales.