Pulsating electrohydrodynamic cone-jets: from choked jet to oscillating cone

Abstract

AbstractPulsating cone-jets occur in a variety of electrostatic spraying and printing systems. This paper reports an experimental study of the pulsation frequency to reconcile two models based on a choked jet and an oscillating cone, respectively. The two regimes are demarcated by the ratio of the supplied flow rate (${Q}_{s} $) to the minimum flow rate (${Q}_{m} $) required for a steady Taylor cone-jet. When ${Q}_{s} \lesssim {Q}_{m} $, the electrohydrodynamic flow is choked at the nozzle because the intermittent jet, when on, emits mass at the minimum flow rate; the pulsation frequency in the choked jet regime is proportional to ${Q}_{s} / {Q}_{m} $. When ${Q}_{s} \gtrsim {Q}_{m} $, the Taylor cone anchored at the nozzle experiences a capillary oscillation analogous to the Rayleigh mode of a free drop; the pulsation frequency in the oscillating cone regime plateaus to the capillary oscillation frequency, which is independent of ${Q}_{s} / {Q}_{m} $.