Foams - form and flow

The study of the rheology, or flow, of foams aims to understand how a foam moves when pushed or squeezed. The motivations for wanting to understand the properties of foam are widespread and diverse. Foams are common in oil extraction and industrial cleaning. They are also used in the process which separates metal ores, such as lead and zinc, from the rock in which they are found. Closer to home, an understanding of flowing foams helps to extinguish fires more efficiently, to generate the perfect pint of beer, and to get a chocolate mousse into its pot. Foams also have peculiar and remarkable properties: they fall half-way between the familiar extremes of liquid and solid. When only a small force is applied to it, a foam behaves as a solid, and bounces back to its original shape. If the force is larger, or applied more quickly, then a foam moves like a liquid. They therefore generate a rich range of behaviours. Apart from their industrial uses, where an understanding of foam rheology can help to make processes more efficient and cost-effective, anyone who has looked closely at a foam in their bath can tell you that it has a beautiful, easily visible, structure. This structure is very well-defined, and using the structure allows us to analyse the flow behaviour of a foam more easily than that of many other complex fluids. The fellow wants to improve the agreement between what is seen in real-life experiments and industrial applications and the mathematical models that researchers are designing, to show that the models can predict what a foam will do in any given set of circumstances. He also wants to train a graduate student in the techniques and theory of rheology, particularly applied to foams.One of the software tools which is widely used for foams, the Surface Evolver, is also, he believes, something that could be useful for biologists trying to understand how creatures develop. For example, the shell of a sea urchin shows a pattern of small plates that resembles a foam. The fellow will therefore look for new areas in which to apply the software, in discussion with biologists around the world.