Seminar by Cristobal Arratia (NOV. 26TH 10:00)

Place and time: Friday November 26th at 10:00, VRII-152

Speaker: Cristobal Arratia, NORDITA

Title: A story on hydrodynamics, instabilities, and transition to turbulence

Fluid mechanics is an old subject. It is present in our everyday experience and its governing equations were written nearly two centuries ago, yet we have long struggled to explain very common phenomena. In this talk we will see a part of its history, starting with the experiments of Reynolds (1883). These contain examples of the two ways in which complex behaviour arises in fluids and other systems: through an unstable eigenmode of the linearized dynamics around a simple state, and in the absence of such an instability. After describing some general insights for the study of instabilities that were learnt during the last few decades, we will return to the main subject of Reynolds paper, the transition to turbulence in a pipe. We will describe how this problem has finally been understood during the last decade thanks to a model by Barkley. We will end on some current perspectives on how this model can be extended to other transitional flows with much richer dynamics.