Stephen Cox School of Mathematics, University of Adelaide Chaotic mixing and chemical reactions Wednesday 13th, April 14:05-14:55pm, Carslaw Building Room 373. Fluid mixing is ubiquitous, from everyday examples like mixing milk into your cup of tea to frontier technologies such as the analysis of tiny samples of DNA in `labs-on-a-chip'. In many cases, the purpose of the mixing is to speed up some chemical reaction; this application of mixing has tremendous technological and economic significance, for example because it underpins the chemical engineering industry. In this talk I will present some simple models for the stirring and mixing of fluids by chaotic fluid flows, and show how a careful consideration of the topology of the stirring action can yield particularly effective ways to mix the fluid. I will describe numerical simulations of the mixing and reaction of two chemical species in a chaotic fluid flow, with a particular focus on the physically interesting (and numerically challenging) limit of small Peclet number (diffusion fast relative to advection). These numerical simulations will be compared with various analytical approximations, which are based on simplified models for the reaction in the complicated pattern of striations that is generated by the fluid mixing. The talk will, if time permits, contain practical advice on how to use a stick to stir a pot of paint.