Experimental study of the characteristics of acoustic cavitation bubbles under the influence of ultrasonic wave

Abstract

Sonochemistry application in various fields, especially separation industries, are constantly increasing and extensively studied in recent years. In the applications, a detailed understanding of the characteristics and behaviour of acoustic cavitation bubble is crucial. However, acoustic bubbles behave differently in each liquid. Owing to numerous amounts of acoustic bubbles showing dramatic transition during sonication and have complex interaction in a liquid mixture, it is more difficult to observe acoustic bubble consistently and thoroughly. In response to this problem, our study will investigate separately acoustic cavitation bubble form in sonicated water, ethanol and mixture of ethanol-water. Each liquid was sonicated at 20 kHz ultrasound with a transducer attached to the bottom of an acrylic vessel. In order to visualise acoustic bubbles clearly, a high-speed video camera is used to capture the image of acoustic bubbles. Image processing and analysis are by the application of Image Processing Toolbox in MATLAB R2018b. Experimental result reveals that acoustic cavitation bubbles in a mixture of ethanol-water have the largest radius, volume and higher buoyancy force compared to pure ethanol and water. Results obtained coincided well with theory, which indicated that sonicated mixture containing alcohol provide resistance to gas transfer across liquid/bubble interface, leading to an increased bubble radius and hence the buoyancy force.