The Bubble Dynamics and Impulse Loading of a Rigid Surface under Acoustic Action

The results of a numerical study of the axisymmetric expansion and collapse of a gas bubble and related loading on a flat rigid wall under harmonic liquid (water) pressure oscillation are presented. Initially, a spherical bubble with a radius of 1 mm and the liquid are at rest. The impulse load on the wall results from the cumulative liquid jet impact on the bubble surface part close to the wall. It was found that, for the forcing amplitude within 0.06– 0.14 MPa, the shape of the jet remains nearly the same at the forcing frequency of 0.25–4 kHz, the velocity at its impact becomes maximum at a frequency of 1.5 kHz. The forcing amplitude influence is mainly reduced to increasing the jet impact velocity. At the fixed forcing frequency and amplitude values, an increase in the initial distance between the bubble and the wall leads to an insignificant variation in the jet impact velocity. For a forcing frequency corresponding to the maximum jet velocity, some estimates of the impulse loading on the wall were determined, depending on the forcing amplitude and the initial distance between the bubble and the wall. It was found that an increase in the amplitude results in the higher and longer loading, as well as in the larger radius of the region with the maximum load.