Raindrops, pesticides, and oil spills – droplet interactions with porous and textured surfaces

Droplet interactions with porous and textured surfaces play a crucial role in many important physical processes including the spraying of plant leaves with pesticides, the infiltration of rain and surface water into soil and the migration of oil in doubly permeable porous media, while a greater understanding of these processes will potentially lead to improved strategies for remediation for chemical contaminants and oil spills, and also flood mitigation.

This project will develop theoretical and numerical models linking both the evolution of a sessile droplet on a porous surface with flow in the subsurface and also of a sessile droplet spreading on a textured surface. A Stokes flow boundary element description of the free surface of a droplet initially resting on a porous surface will be coupled to flow models of the partially and fully saturated regions within the porous media beneath. The novel use of a Stokes flow boundary element method in this coupled configuration will enable the free-surface evolution to be calculated for a wide range of initial contact angles corresponding to both wetting and non-wetting fluids. The coupled dynamics will inform the relationship between different subsurface fluid flow models, relative permeabilities, and the evolution in droplet shape as it is absorbed. The inverse problem of determining properties of the porous medium from the droplet behaviour will also be considered, with the aim of determining whether readily measured droplet properties on the surface can be used as proxies for sub-surface flow characteristics.

In the first year of the PhD, numerical methods will be developed for idealized two-dimensional geometries. In later years, these methods will be extended to axisymmetric and three-dimensional cases. The possibility to experimentally validate the modelling predictions may be available.

The successful candidate should have, or expect to have, an Honours Degree at 2.1 or above (or equivalent) in Engineering, Applied Mathematics, Physics, Computer Science or Chemistry.

Knowledge of - Fluid dynamics. Experience of computational methods and continuum modelling is also beneficial.