Dynamics of the near-wall bubble induced by an adjacent bubble

Abstract

The asymmetric collapse of nonspherical cavitation bubbles near a rigid wall generates high-speed liquid jets directed toward the wall. When introducing an additional bubble adjacent to the original near-wall bubble, the combined influences alter the jet characteristics, resulting in complex behaviors of jet directions and velocities. This study investigates the jet dynamics of near-wall bubbles via a combination of experiments, numerical simulations, and theoretical modeling. In the experiments, the direction and velocity of the bubble jets are observed using synchronized high-speed cameras triggered by a low-voltage discharge system. Numerical simulations are conducted using the compressibleInterIsoFoam solver within the OpenFOAM framework, allowing us to analyze the detailed characteristics of the jet for various dimensionless standoff parameters γ1, γ2x, and γ2y. The jet direction βc is characterized by the migration direction of the bubble center at the collapse time, while the jet velocity Ujet is defined as the maximum migration velocity of the bubble center during the first oscillation cycle. Using image theory, we derive the dimensionless form of the Kelvin impulse ζ. This enables analytical predictions of βc and Ujet across diverse experimental and numerical conditions, thus establishing scaling laws that govern these jet dynamics. The findings of this study enhance our understanding of nonspherical cavitation bubble dynamics when simultaneously influenced by multiple factors.