Electrohydrodynamic simulation of electrically controlled droplet generation

An electrohydrodynamic model for the simulation of droplet formation, detachment and motion in an electrically driven droplet generator is introduced. The numerical approach is based on the coupled solution of the multiphase flow problem with the charge continuity equation. For the latter, a modified convection-conduction model is applied, taking into account conductive, capacitive as well as convective electrical currents in the fluid. This allows for a proper description of charge relaxation phenomena in the moving fluid. In particular, the charge received by the droplet after detachment is an important parameter influencing the droplet dynamics in the test chamber. Simulation results are shown for highly conductive acetone droplets and for low conductivity pentane droplets, respectively. The operation characteristic of the droplet generator is investigated by computing droplet sizes and detachment times with respect to the applied voltage.