Journal of Fluid Mechanics



Papers

Flow behaviour of dielectric liquids in an electric field


H. B. ZHANG a1, M. J. EDIRISINGHE a1c1 and S. N. JAYASINGHE a1
a1 Department of Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE, UK

Article author query
zhang hb   [Google Scholar] 
edirisinghe mj   [Google Scholar] 
jayasinghe sn   [Google Scholar] 
 

Abstract

A family of 10 silicone oils with electrical conductivity $\sim 10^{-13}$ S m$^{-1}$ (a regime hitherto systematically unexplored) and viscosities ranging from 1 to 2000 m Pa s have been subjected to an electrical field of up to 1.5 kV mm$^{-1}$ during flow from a needle. The flow behaviour of these liquids is investigated experimentally in the flow rate regime 10$^{-8}$–10$^{-12}$ m$^{3}$ s$^{-1}$ and we analyse the results using the Ohnesorge number. Due to the low electrical conductivity and high electrical relaxation time of the silicone oils, only unsteady transient jets were found. The onset of this type of jetting has been defined using current measurements and, in contrast to conducting liquids, the non-dimensional jet diameter increases with increase in Ohnesorge number. The time elapsed between the start and finish of jetting increases with increasing Ohnesorge number.

(Received October 20 2005)
(Revised February 27 2006)


Correspondence:
c1 Author to whom correspondence should be addressed: m.edirisinghe@ucl.ac.uk


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