Abstract

Understanding the interaction of liquids with solids (wetting) and other liquid bodies (coalescence) holds the key to optimizing a whole host of technological processes, including a number of emerging microfluidic devices such as 3D-printers. Accurate experimental observation of these phenomena is complex due to the small spatio-temporal scales or interest and, consequently, mathematical modelling and computational simulation become key tools with which to probe such flows.

Dynamic wetting and coalescence are both so-called `singular’ capillary flows, in which classical modelling approaches lead to paradoxical conclusions. In the case of wetting this is the well-known ‘moving contact-line problem’. In this talk, I will describe the various models proposed for this class of flows and, by comparing the predictions of these theories to experiments, explain why there is still an intensive debate in this field. Finally, I will outline some recent work on wetting where the dynamics of the displaced gas plays a key role in determining the critical point at which flow transitions occur.