Dynamical behavior of electrified pendant drops

The electrohydrodynamic response of low-conductivity pendant drops to a step change in the electric field magnitude was examined both numerically and experimentally. Both the leaky-dielectric and perfect-conductor models were solved in the simulations. Experiments were conducted to precisely measure the drop interface shape as a function of time. The drop oscillated for applied voltages smaller than a critical value which depended on the rest of governing parameters. It stretched and subsequently emitted a microjet from its tip for electric potentials above that critical value. The perfect-conductor model described accurately the oscillations of subcritical drops. This model also provided satisfactory results for the prejetting regime in the supercritical case. We found a good agreement between the leaky-dielectric model and the experiments for the drop-jet transitional region, despite the fact that the tip streaming arose on a time scale much shorter than the electric relaxation time. This result shows the capability of the leaky-dielectric model to describe the flow in this singular region. The numerical simulations allowed us to describe the pressure and velocity fields in the transitional region. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4776238]