Evolution of acoustic cavitation structures induced by a liquid jet

Abstract

Temporal evolution and spatial distribution of acoustic cavitation structures induced by a liquid jet in a 20 kHz ultrasonic field were investigated experimentally with high-speed photography. It is revealed that a large-scale flare structure is produced by a liquid jet shooting towards a transducer radiating surface. A few large bubbles and numerous small bubbles are formed on the interface of liquid jet. The size of large bubbles differs almost by an order of magnitude from that of small bubbles. The flare structure hits the radiating surface, spread and adhere. The liquid jet is arrested and a thin bubbly layer lying at the radiating surface is formed. The cavitation cloud will evolve from one structure to another without the interference of liquid jet. (a) Most bubbles move towards the center, and the bubbly layer will become thicker at the centre than at the periphery like a lens. (b) Large bubbles accumulate at the center and skip off the surface, and the lens structure becomes a conical structure. (c) Large bubbles align themselves along the axial line, and the conical structure becomes a fishbone structure. Many other interesting phenomena were observed. The liquid-jet method is useful for the investigation of cavitation structure. This work is supported by the National Natural Science Foundation of China (Grant No. 11174315) and the National Science and Technology Major Project of China (Grant No. 2011ZX05032-003).