TeraScale Shear Flow Challenge

When pouring cream into a cup of tea or coffee, everyone is familiarwith the streaks of white that form when the cup is stirred - beforethe mixture becomes completely uniform. Stir the cup faster and thewhite streaks are wound round to an even greater extent before eithermerging or splitting. This pattern is typical of a fluid mixture drivenby a shear flow - a flow that tends to distort or elongate features ina particular direction.This work investigates the characteristics of a mixture driven by asteady shear flow, which turn out to show some surprisingly subtleproperties. For example, it is not known if the fluid patches in aconstant shear flow will grow in length forever (given a large enoughcontainer), or will eventually break and form strips of finite lengthand width.This work will attempt to answer this question using extremely largecomputer simulations (even performing laboratory experiments on largeenough containers is difficult). The simulations will help to understandfluid behaviour at a fundamental level. This understanding isimportant if we are to explain the behaviour of more complex problemsstill, many of which crop up in everyday life - like stirring a cup oftea.