Fluid dynamics (or hydrodynamics) is the study of the motion of fluids (both liquids and gases) and has a wide range of applications. Examples include: the design of aircraft, weather forecasting, the extraction of oil from porous reservoirs, control of many industrial processes, the understanding of the structure of stars and planets, and various biological applications, such as flood flow in arteries, fluid-structure interactions in human bodies, and swimming cells. In many situations, the fluid is controlled by some parameter (such as the Reynolds number) and its behaviour changes as this parameter is increased; mathematically, the solution proceeds through various bifurcations. This is the realm of hydrodynamic stability theory and is a common thread to much of the fluids research in the Department, with applications in many diverse areas.