Mechanism and characteristics analysis of circulatory cavitation erosion in hydraulic concrete based on laser-induced bubble technology

In order to investigate the mechanical response and damage characteristics of concrete linings induced by individual cavitation bubbles, this study employed experimental techniques of laser-induced bubble and computational fluid dynamics (CFD) numerical simulations. It meticulously examined the dynamic behaviors of individual cavitation bubble near concrete surfaces under varied dimensionless distance conditions, delving into the nuances of surface pressure features. Through the utilization of super-depth-of-field microscope, the study tracked the evolutionary trajectory of concrete erosion characteristics over time, thereby elucidating the intricate cavitation erosion mechanisms inherent to concrete. Findings revealed a diminution in surface central pressure with the escalation of dimensionless distance, with the temporal gap between micro-jet penetration of bubble and shock wave release emerging as a significant determinant of pressure magnitude and duration. The interfacial bonding strength between aggregates and the cement matrix emerged as a pivotal factor in resisting cavitation erosion performance. Furthermore, cavitation-induced surface restructuring exerted additional influence on the intensity and trajectory of micro-jets. Pit erosion underwent three sequential stages: the genesis of minute pits, the interconnection and fusion of pits, and the stable expansion of boundaries in large cavitated regions. The prevalent morphology of pits predominantly manifested as inverted triangular cones, with depths predominantly concentrated within the range of 20-30 mu m, reaching a zenith of 300 mu m and stabilizing thereafter. The volumetric loss exhibited an incongruous trend with surface central pressure concerning the variation in dimensionless distance. Establishing the nexus between cavitation erosion and cavity load necessitates considerations beyond merely the magnitude of surface central pressure, extending to encompass factors such as duration and area of influence. This study augments the understanding of enhancing the cavitation erosion resistance of hydraulic concrete, furnishing pivotal insights for the design and maintenance of hydraulic concrete structures.