Rapid changes in pressure, such as in high-frequency ultrasound, can stimulate bubbles to nucleate, oscillate, and collapse violently, in a phenomenon known as cavitation. If uncontrolled, cavitation is a major problem in engineering, as high-speed jets can develop during their collapse upon contact with solids, which are responsible for pitting wear, and even full structural failure of turbomachinery such as pumps and ship propellers. However, these highly targeted jets have also found practical uses in the destruction of micro and nanoscale particles and pathogens, and are currently being tested in waste-water treatment, microfluidic surface cleaning, and non-invasive cancer treatment.

There exist general models for macroscale bubble dynamics, however, our research group has shown that these do not strictly hold for nanoscale bubbles, which are strongly affected by non-ideal and non-equilibrium gas behaviour, liquid viscosity, and pinning of the three-phase contact line. Recently, there has also been growing evidence to suggest that nanobubbles are further stabilised by an accumulation of ionic charges around their surface, forming an electric double layer. This electric double layer is hypothesised to exert an additional stress on the bubble surface, however, its exact effect on the nanobubble’s cavitation dynamics is still unexplored.

In this PhD project, you will develop new understanding and theoretical models for nanobubble cavitation dynamics using Molecular Dynamics (MD) and/or Computational Fluid Dynamics (CFD) simulations, specifically modelling the external pressure threshold required to induce unstable growth, the natural frequency and oscillation dynamics under ultrasonic irradiation, and their jetting collapse dynamics. You will learn how to set up, run, and post-process large-scale numerical simulations, develop theoretical models in fluid mechanics, and present your research at conferences, workshops, and public engagement events.

This is an exciting research field, that covers a lot of interdisciplinary engineering topics, such as fluid mechanics, advanced oscillation dynamics, and electrostatics. You will be welcoming to our Multiscale Flow X Group within the Institute for Multiscale Thermofluids. Our group has a strong track record of publishing high impact research in a wide range of micro/nanoscale fluid and particle phenomena, including: non-equilibrium gas dynamics, flows through porous media, water filtration through carbon nanotubes, phase change phenomena and granular media. We are also highly experienced in particle and numerical simulation and have access to Tier 1 and 2 High Performance Computing (HPC) facilities such as ARCHER2 and Cirrus to facilitate your research.

The ideal candidate should have an interest in fluid dynamics, analytical/mathematical modelling, computer simulation methods (e.g. computational fluid dynamics and molecular dynamics), programming experience in at least one language (e.g. C++, Python, MATLAB, etc.).