a1 Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC 27708, USA
Pulsating 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 () to the minimum flow rate () required for a steady Taylor cone-jet. When , 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 . When , 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 .
(Received May 01 2011)
(Reviewed September 02 2011)
(Accepted October 13 2011)
(Online publication November 14 2011)