Controlling the dynamics of cloud cavitation bubbles through acoustic feedback.

Cloud cavitation causes nontrivial energy concentration and acoustic shielding in liquid, and its control is a long-standing challenge due to complex dynamics of bubble clouds. We present a new framework to study closed-loop control of cavitation through acoustic feedback. While previous approaches used empirical thresholding, we employ model-based state estimation of coherent bubble dynamics based on theory and high-performance computing. Using a pulsed ultrasound setup, we demonstrate set-point control of the pulse repetition frequency (PRF) to modulate acoustic cavitation near a solid target over $O(100)$ s. We identify a quasi-equilibrium correlation between PRF and the bubble dynamics, and an optimal PRF to minimize acoustic shielding of the target. This framework can be readily scaled up by enhanced acoustic sensing and computational power.