Cavitation behavior and erosion damage in a sudden change flow channel

Loop dynamic experiments were conducted to investigate the cavitation erosion process within a turbulent flow channel, exploring the bubble evolution mechanism and the micro-damage mechanism of erosion test specimens. It was concluded that four types of cavitation—initial cavitation, bubble cavitation, cloud cavitation, and super cavitation—occur in the abrupt flow channel as cavitation intensity increases, all sharing identical evolution mechanisms and patterns. The evolution of microbubbles was found to be the fundamental process driving the detachment, coalescence, and regeneration of macroscale bubbles during cavitation progression. The evolution of bubbles from regeneration to collapse is the primary cause of pressure fluctuations at the specimen surface. Microscopic morphology analysis revealed that under super cavitation conditions, the specimen gradually developed surface characteristics typical of corrosion-resistant substrates as erosion time increased: surface roughening, oxidation-induced blackening, widespread cracking, and interconnected pitting. This evolution synchronously exhibited the weight loss patterns characteristic of the incubation, acceleration, and stabilization phases of cavitation erosion. It was concluded that cavitation damage results from the high-frequency, high-pressure shock waves generated during bubble collapse.