Abstract: Breaking ocean waves modulate the transfer of heat, mass and momentum between the ocean and atmosphere. This is a severely multiscale problem in which the physics at small scales have a great effect at large scales. Understanding these small-scale physics, which are characterised by turbulent multiphase fluid dynamics, is a challenging problem but in recent years there have been rapid advances in direct numerical simulations (DNS) that have eased these efforts. In this talk I will present an array of high-resolution DNS of breaking waves, and of the bubbles and droplets that feature heavily in the flows produced by breakers. The DNS is aided by adaptive mesh refinement which can attain very high effective numerical resolutions at a fraction of conventional computational costs. I will discuss statistics of the turbulent flow, and of statistics of bubbles and droplets resolved in simulations of breaking waves, as well as simulations of individual bubble and droplet breakups, comparing with experiments where available. Finally, some insights on the utility of DNS for working in tandem with larger scale modelling approaches will be shared.

Short Bio: Wouter Mostert is an Associate Professor of Engineering Science at the University of Oxford. He obtained his PhD in 2015 from the University of Queensland before doing postdoctoral research at Caltech and Princeton. Prior to his appointment at Oxford in 2021, he was briefly an Assistant Professor at the Missouri University of Science and Technology. Wouter’s research interests lie in computational and theoretical analysis of fluid mechanics, relevant across a large range of fluid problems, such as evolution and fragmentation of bubbles and droplets, and breaking ocean waves, although he has also investigated nonlinear evolution of shock waves and hydrodynamic instabilities of magnetised plasmas.