Simulation of Transient Electrospray Dynamics in Conductive Fluids

The numerical simulation of electrohydrodynamic atomization of a conductive liquid in the cone-jet electrospray mode is considered. The numerical approach is based on the solution of the multiphase flow equations coupled with an electroquasistatic problem including the capacitive, resistive, and convective electric currents. The formulation allows for the modeling of charge relaxation effects in a liquid thread before its atomization in a number of electrospray droplets. The topology changes associated with this event are implicitly handled by the use of a diffuse interface model based on the volume of fluid method. Sufficient spatial resolution for electrospray droplets is achieved by means of adaptive mesh refinement in the vicinity of the fluid-fluid interface. Using this numerical model, the scaling laws of electrospray are investigated for a variety of liquids and applied voltages. It is found that the charge-radius correlations for successively ejected droplets differ substantially from the classical scaling law, characterizing the first ejected droplet at the onset of the electrospray. This is due to the space-charge field of electrospray droplets building up for longer time electrospray transients.