Different Scenarios of the Collapse of a Gas Region Locally Heated by an Electric Discharge near a Surface

We have demonstrated for the first time different scenarios of the collapse of a hemispherical low-density cavity formed as a result of gas heating by a pulsed submillimeter electric discharge near a dielectric surface: a scenario due to cavity boundary stability loss in the zone where the cavity is in contact with the surface and a scenario involving stability loss in the zone farthest from the surface. Both “bubble” collapse scenarios occur stochastically under invariant experimental conditions. Using particle image velocimetry, we obtained distributions of velocity fields in the region of a cavity at various instants of time. High-speed filming data lead us to assume that which scenario will occur depends on the shape of the conducting channel at the instant of electric breakdown.