Excitation of electrohydrodynamic surface waves on a conducting liquid jet employing AC field

Abstract

A method of exciting waves on the surface of a conducting liquid jet by means of time varying electric field is presented. The prime objective of employing such a technique is to produce, electrostatically, a monodisperse spray of highly conducting liquid, in a controlled manner. This method relies on the use of an AC field in a certain frequency range to suppress the dominant effects of charge relaxation exhibited by conducting liquids. The coupling of AC/DC fields launches surface waves on the liquid jet, the wavelength of which depends on the frequency of the applied AC field. The experimental results show strong evidence that the dynamics of these field coupled surface waves are very similar to the controlled Raleigh break up criteria. The jet disintegration is thereby controlled to the point that extremely uniform droplets are generated. It is established that varying the frequency of the AC field would lead to the production of highly uniform droplets ranging from about 1.5-2.5 of the jet radius from which they were formed. Expressions are derived to relate the droplet radius to the jet velocity and the AC excitation frequency.