Various scenarios of collapse of a gas region locally heated by an electric discharge near a surface

For the first time, various collapse scenarios have been identified for a low-density hemispherical cavity formed by gas heating during the combustion of a pulsed submillimeter electric discharge near a dielectric surface. Two distinct collapse mechanisms were observed: one driven by the loss of stability of the cavity boundary in the contact zone with the surface, and another driven by instability in the part of the cavity farthest from the surface. It was established that both “bubble” collapse scenarios occur stochastically under invariant experimental conditions. Using the PIV method, velocity field distributions in the cavity region were obtained at different time instants. Based on high-speed velocity imaging data, it is hypothesized that the specific collapse scenario realized is determined by the shape of the conductive channel at the moment of electrical breakdown.