FEA modelling of a water droplet vibrating in an electric field

The dynamic behaviour of water droplets subject to AC electric fields is investigated by experiment and finite element modelling. The motion of a water droplet is considered on the surface of a metallic sphere. To understand the consequences of vibration, the FEA model is introduced to study the dynamics of a single droplet in terms of phase shift between vibration and exciting voltage. Moreover, the evolution of electric field within the whole cycle of vibration is investigated. The finite element treatment to couple the electromagnetic field with multi-phase flow field is described. The profile of the electric field and the characteristics of mechanical vibration are evaluated. Surprisingly the phase shift in these characteristics results in the maximum field occurring when the droplet is in a flattened profile rather than when it is `pointed'.