Investigation of Acoustic Streaming and Cavitation Intensity in Water as an Analogue for Liquid Metal Free

This paper presents an investigation of the evolution of flow structures and cavitation intensity in water as an analogue for a liquid metal under ultrasonic excitation. Results are presented for 20 kHz high-power ultrasound. The input power ranged from 50% (8.5 μm p-p) to 100% (17 μm p-p). To identify the streaming structures and understand the recirculation flows for different vibrational amplitudes of the sonotrode, particle image velocimetry (PIV) measured the velocity field. Simultaneously, a calibrated cavitometer probe measured acoustic intensity in the fluid. The cavitation intensity away from the acoustic source decreased with increasing input acoustic power, but was relatively constant inside the cavitation zone (irrespective of the input power). PIV measurements showed that the direction of the flow pattern was strongly related to the vibrational amplitude of the sonotrode. These results are compared with the predictions of an acoustic cavitation model. The outcome of the present work will help to determine the efficient optimization of ultrasonic processing of liquid metals that is of increasing technological importance.