I Peters - Cavity collapses in complex geometries

Understanding the behaviour of bubbles in the vicinity of structures is important for many practical applications. Of particular interest is how bubbles collapse as a result of strong changes in pressure, which happens in sonochemistry applications, ultrasonic cleaning and is responsible for the cavitation damage in hydraulic systems. In the absence of any boundaries, an initially spherical bubble will remain spherical and collapse towards a single point. The same collapsing bubble near a plane wall, however, will result in a fast liquid jet shooting towards the wall. But what happens to such a bubble in more complex geometries, as appear in most applications, is currently unknown. This project aims to answer this fundamental question by investigating the controlled generation and collapse of bubbles in increasingly complex geometries. There are three main subjects that will be investigated in this project. The first one is large cylindrical cavities that are analogues to two-dimensional cavitation bubbles. The large scale of these bubbles allows us to investigate the evolution of the shape and the flow field around the bubble in great detail. The second subject is laser-induced cavitation, where three-dimensional vapour bubbles are generated through a short focused laser pulse. Both techniques allow us to accurately control the position and size of the (two- or three-dimensional) cavitation bubble with respect to the surrounding geometry. The third part of the project is in collaboration with an ultrasonic cleaning company to investigate the influence of the observed phenomena on cleaning applications, with the aim to find routes to improve and optimize current ultrasonic cleaning techniques.