This grant will support research that looks to contribute to new knowledge related to the nonlinear dynamics of acoustic cavitation enhanced by vortex ultrasound. Acoustic cavitation is the process of bubble formation, oscillation, and collapse in a liquid exposed to intense ultrasound. Acoustic cavitation has been widely used in the biomedical field for tissue ablation, thrombolysis, drug delivery, etc., and in industry for metal cleaning in manufacturing processes. Vortex ultrasound is a type of acoustic wave with a helical wavefront rotating as the wave propagates. Previous studies of vortex ultrasound-induced acoustic cavitation in deionized water show that vortex ultrasound can induce acoustic cavitation at a much lower intensity threshold and with stronger cavitation activity than focused ultrasound. However, the fundamental mechanism(s) behind the lower intensity threshold and stronger cavitation activity driven by vortex ultrasound are still unknown. Without this important knowledge, it is challenging to use vortex ultrasound reliably and safely in the suggested biomedical and industrial applications. This research project seeks to understand the fundamental bubble dynamics driven by acoustic cavitation induced by vortex ultrasound and the mechanism behind the reduced cavitation threshold, as well as enhanced cavitation activities. A novel theoretical model of bubble dynamics driven by vortex ultrasound looks to be developed and verified by experimental measurements u