Low and high Reynolds number flows inside Taylor cones

Liquid motions inside Taylor cones exhibit interesting features which are n ot well understood yet. In addition to the flow rate injected through the e lectrified needle to which the conical meniscus is anchored, the action of the tangential electrical stress on the cone surface induces a recirculatin g meridional motion, towards the apex along the generatrix and away from it along the axis. Sometimes, a Vigorous swirl is observed. The characteristi c value of the liquid velocity is found to be highly dependent on both the electrical conductivity and the viscosity of the liquid, so that the Reynol ds number of the liquid flow varies from very small values (creeping flow) for the case of highly conducting and viscous liquids to relatively large v alues for liquids with sufficiently low values of the liquid conductivity a nd viscosity. Theoretical conical flows for low and high values of the Reyn olds number show qualitatively good agreement with photographs of real flow s inside Taylor cones. In particular, the existence of a vigorous swirl whi ch is observed in the electrospraying of paraffins and other poorly conduct ing and low viscosity liquids can be explained as bifurcation of a primaril y nonswirling meridional flow when the Reynolds number reaches a critical v alue, [S1063-651X(98)01512-8].