Growth rate and oscillation frequency of electrified jet and droplet: Effects of charge and electric field

Abstract

Electrified jets are applied industrially in agriculture, automobiles, targeted drug delivery systems, spacecraft propulsion units, liquid metal sprayers, ion sources, emulsifiers, dust scavenging systems, and ink-jet printers. Electrified columnar jets experience instability caused by electrohydrodynamic interactions of the charged liquid surfaces with electric fields. Electrostatic and surface tension forces competing along the liquid surface create surface pressure differences. The temporal rise and fall of the surface pressure induce oscillations of jets and droplet. A linear theory was derived to yield a dispersion equation determining the most dominant wavelength of oscillation for a given charge level and electric field; this enabled the estimation of the diameter of an atomized droplet. In addition, the frequency of oscillation was derived for a cylindrical jet and spherical droplet. Parametric studies were performed for various charging levels and electric field strengths.