Influence of the Initial Shape of a Gas Bubble on Its Dynamics near a Wall under Acoustic Excitation

Influence of initial non-sphericity of a gas bubble on its dynamics at various distances from a plane rigid wall under harmonically varying liquid pressure is investigated. The initial shape of the bubble is taken to be a spheroid with the axis of symmetry orthogonal to the wall. The liquid pressure is varied with the own frequency of the radial oscillations of the bubble in the absence of the wall, beginning with the negative acoustic pressure phase. The liquid is ideal and incompressible, its flow is potential. The velocity of the bubble surface is determined by the boundary element method, its displacement is calculated by the Euler method. It is shown that under the adopted conditions, the bubble collapses either with its transformation into a toroidal one, as a result of impact of the cumulative liquid jet on the bubble surface part close to the wall, or with its disintegration into two smaller bubbles, which results from closing of a narrow neck formed by the bubble surface in the vicinity of the axis of symmetry. Some features of the influence of the initial non-sphericity of the bubble on the shape of the jet, the velocity of its tip and the pressure inside the bubble at the moment of the jet impact on the bubble surface part close to the wall are determined.