Dynamic behavior and spatio-temporal mechanical characteristics of the individual cavitation bubble on hydraulic concrete wall

Abstract

This study endeavors to delve into the dynamics and consequent mechanical responses induced by an individual cavitation bubble proximal to a concrete surface. Employing the laser-induced cavitation bubbles experimental method, the dynamic behavior of a cavitation bubble near horizontal smooth and locally defective concrete surfaces is systematically investigated. Using computational fluid dynamics (CFD) simulations, the impulsive pressure induced by bubble collapse within a specific surface range is quantitatively investigated. Our results reveal that the presence of local defects on the concrete surface activates gas nuclei within the defects upon bubble shock wave emission. Gas nuclei near the surface center penetrate the bubble, prolonging the bubble’s pulsation period and reducing microjet velocities. During bubble collapse, significant concentrated stresses due to microjets near the surface center may trigger instantaneous brittle failure of the concrete surface. Moreover, shock waves form high-pressure zones within a certain range of the surface. When the dimensionless distance γ ranges from 1.1 to 1.2, a superposition phenomenon of microjets and shock waves is observed, compared to individual effects, enhancing the impulse at central point below the bubble, prolonging the duration of pressure within the specific surface horizontal range, but simultaneously accelerating the pressure’s horizontal attenuation rate along the surface. Compared to the center pressure of the wall surface, the impulse of average pressure better reflects the surface’s pressure response.