The canonical framework of drop impact provides excellent opportunities to co-develop experimental, analytical and computational techniques in a rich multi-scale context. The talk will represent a journey across parameter space, as we address beautiful phenomena such as bouncing, coalescence and splashing, with a particular focus on scientific computing aspects and associated numerical methods.

To begin with, consider millimetric drops impacting a deep bath of the same fluid that are generated using a custom syringe pump connected to a vertically-oriented needle. Measurements of the droplet trajectory are compared directly to the predictions of a quasi-potential model, as well as fully resolved unsteady Navier-Stokes direct numerical simulations (DNS). Both theoretical techniques resolve the time-dependent bath interface shape, droplet trajectory, and droplet deformation. In the quasi-potential model (building on recent progress by Galeano-Rios et al., JFM 912, 2021), the droplet and bath shape are decomposed using orthogonal function decompositions leading to a set of coupled damped linear oscillator equations solved using an implicit numerical method. The underdamped dynamics of the drop are directly coupled to the response of the bath through a single-point kinematic match condition, which we demonstrate to be an effective and efficient technique. The hybrid methodology has allowed us to unify and resolve interesting outstanding questions on the rebound dynamics of the multi-fluid system.

We then shift gears towards the much more violent regime of high-speed impact resulting in splashing, where a combination of matched asymptotic expansions grounded in Wagner theory and DNS allow us to produce theoretical predictions for the location and velocity of the ejected liquid jet, as well as its thickness (Cimpeanu and Moore, JFM 856, 2019). While the early-time analytical methodology neglects effects such as surface tension or viscosity (focusing on inertia instead), corrections and adaptations of the technique (Moore et al., JFM 882, 2020) will also be presented and validated against an associated computational framework, bringing us even closer to efficiently providing information of interest for applications such as inkjet printing and pesticide distribution.

Following a period of two years as an independent Hooke Research Fellow in the Mathematical Institute at the University of Oxford, he then moved to the Mathematics Institute at the University of Warwick in 2019, where he is now a senior lecturer. His research activities span fluid mechanics, wave propagation and numerical methods for partial differential equations, and are complemented by a strong interest in industrial mathematics. He is also an executive committee member of the UK Fluids Network.

Originally from Romania, Radu completed his B.Sc. in Applied and Computational Mathematics at Jacobs University Bremen in Germany. His dissertation work involved developing the mathematical models and numerical methods for high intensity focused ultrasound, working closely with the local Franhofer MeVis institute. He then moved to the United Kingdom where he spent six years in the Department of Mathematics at Imperial College London, completing his M.Sc., Ph.D. and a post-doctoral position with Prof. Demetrios Papageorgiou, working on asymptotic and computational techniques for nonlinear interfacial flows, with a particular interest in electrohydrodynamics and violent impact problems.