STRIKING FEATURES OF FLUID-FLOWS IN TAYLOR CONES RELATED TO ELECTROSPRAYS

For fluid flows inside and outside the Taylor conical meniscus related to electrosprays we adopt here a simplified model where the velocity field varies as 1/r, r is the distance from the cone apex. Such a dependence corresponds to the conical similarity class of exact solutions of the Navier-Stokes equations. This allows a detailed analysis of the problem and discovery of a number of striking features: (i) collapse-appearance of strong near-axis bipolar jets due to a cumulative effect of motion converging to the apex near the surface, (ii) vortex dynamo-generation of swirl as a result of bifurcation, (iii) vortex breakdown-internal separation of the swirling flow, (iv) splitting of the diverging flow into a few branches due to azimuthal instability, and (v) hysteretic transitions between regimes. The conical similarity can be, in particular, due to the electric Marangoni effect or Lorenz electromagnetic forces. We believe that the predictions of the similarity model can be also qualitatively valid for real flows in Taylor menisci because the above features are related to physical mechanisms that act as well in more general cases. So, in studying electrosprays, it is useful to keep in mind a possibility of the above effects.