Experimental and CFD investigation of the dynamic characteristics of particle clusters under cavitation bubble near a rigid wall.

The motion of particles under the influence of cavitation bubbles is a nonlinear process. This study investigates the dynamic behavior of particle clusters in particulate flows subjected to cavitation bubble activity near a rigid wall. With experiments and numerical simulations, the effects of cavitation bubbles of varying sizes on particle clusters located at different distances from the rigid boundary are systematically investigated and analyzed. Results demonstrate that, during the bubble expansion phase, the maximum radius Rmax reached by the bubble determines the peak velocity at which the particle cluster is pushed away from the bubble center, particles with greater mass exhibit weaker dynamic responses to the bubble's expansion and collapse near the rigid wall. The VOF multiphase flow model, coupled with the DPM particle tracking method, produces simulation results that closely align with the experimental findings. This approach proves valuable for investigating particle motion in experimental setups where the presence of gas clusters may obstruct direct observation of particle behavior. The impact intensity of the particle group on the wall, resulting from the cavitation-induced jet, is primarily governed by the velocity at which the jet, generated by the collapse of the cavitation bubble, strikes the rigid wall. When the characteristic parameter λ < 1, which represents the ratio of the cavitation center position to the bubble radius, and the bubble size is relatively small, particles are readily accelerated to between 1/4 and 3/4 of the jet impact velocity, and the energy transfer and dissipation of cavitation bubbles during their evolution in particle clusters are discussed. This particular condition is the dominant factor responsible for wall damage in such cases.