Acoustic emissions of cavitation bubbles and the (misleading) similarity to acoustic black hole analogues
Abstract: Bubble dynamics and cavitation play an important role in a broad variety of engineering applications, for instance as a root cause of material erosion, driving ultrasonic cleaning and antibacterial processes, and enabling novel diagnostic and therapeutic applications of medical ultrasound. Despite significant progress in understanding and foretelling pressure-driven bubble dynamics, there is still no comprehensive understanding of the potentially extreme conditions generated by collapsing bubbles, the acoustic waves and shock fronts emitted during the collapse, and how to attribute observations in measurements to specific effects or phenomena. During this seminar, I will be presenting recent advances in understanding the acoustic emissions of cavitation bubbles and, in particular, we will take a closer look at reduced-order models allowing us to gain a deeper insight of the pressure and velocity distribution resulting from these acoustic emissions. This then brings us to a perhaps esoteric but elegant model system, that has previously been proposed to be realised experimentally by cavitation bubbles: acoustic black hole analogues. I will explain how an acoustic black hole analogue can be utilised to learn more about nonlinear Doppler modulations of acoustic waves in an accelerating flow field, as they occur, for instance, around cavitation bubbles, but I will also discuss why a bubble can likely not serve as an acoustic black hole in reality
