Selforganisation of quasi-2D flows in a rectangular container

This contribution describes a combined experimental-numerical study of decaying quasi-2D turbulent flows on a rectangular domain with no-slip boundaries. While decaying, the flow is found to organise in a domain-filling pattern of counter-rotating cells. Advection of filaments of viscously generated wall vorticity into the interior results in a continuing perturbation of the cellular pattern. The time dependence thus introduced provides the essential mechanism for chaotic advection: passive tracers may move from one cell to a neighbouring one, all the way along the array.