The dynamics of pre-breakdown cavities in viscous silicone fluids in negative point-plane gaps

The effect of viscosity on the first two stages of the breakdown process, the growth of the prestreamer cavity, and the onset of the electrohydrodynamic instability, is examined. It is shown that the electrostatic field provides the major driving force in the cavity expansion, and the inertial forces provide the rate-limiting drag. In the case of the cavity-wall instability, the electrostatic field again provides the driving force, viscosity has a stabilizing effect, and, as one proceeds from low viscosity fluids to those of higher viscosity, the instability is slowed down.