P. Atten et al., ELECTROHYDRODYNAMIC PLUMES IN POINT-PLANE GEOMETRY, IEEE transactions on dielectrics and electrical insulation, 4(6), 1997, pp. 710-718
We examine the flow organization induced by charge injection from a ne
edle of small radius of curvature into an insulating dielectric liquid
. Experimental results are presented for the electrical current as a f
unction of the point-plane distance and of the applied voltage. Schlie
ren visualization reveals the existence of very thin plumes which are
slightly vacillating. An approximate analysis of the laminar plume is
developed which takes into account the finite but very thin axial regi
on where charge is confined. A classical type of asymptotic treatment
results in a set of ordinary differential equations, provided the curr
ent and the field distribution are known. A new expression for the ord
er of magnitude of the liquid velocity is proposed which leads to esti
mates of the radius a of the charge core and the typical radial scale
delta of the velocity profile. For a gap spacing d, these estimates ar
e of the order of 10(-3) d and 10(-2) d which confirm the thinness of
such charge plumes.