《04 Cavitation characteristics of pit structure in ultrasonic field》.pdf

Science in China Series E: Technological Sciences © 2009 SCIENCE IN CHINA PRESS Springer Cavitation characteristics of pit structure in ultrasonic field † BAI LiXin, XU WeiLin , ZHANG FaXing, LI NaiWen, ZHANG YiChi HUANG DeFa State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu 610065, China Bubble collecting, bubble holding and micro-bubble ejecting characteristics of pit structure and the influence of cavitation bubble on the development of erosion pit are investigated by means of high- speed photography experiments. Pits tend to collect and hold wandering cavitation bubbles. The air holding phenomenon of pits can be a destination of the incubation period in the process of cavitation erosion. The holding bubble tends to eject micro-bubbles from the top of holding cavitation bubble, making the pit a source of nuclei. With bubbles being held in pits, the diameters of pits increase rapidly. But in the given experiment condition, there is a specific stable value beyond which the diameter of pits will not increase. This characteristic will be helpful in understanding and predicting the cavitation ero- sion process. cavitation bubble, ultrasonic cavitation, erosion pit, high-speed photography 1 Introduction the cavity and penetrates the far surface and hits the boundary[2]. Besides the theory of shock wave and mi- Cavitation refers to the formation and subs