Center for Environmental and Applied Fluid Mechanics Virtual Seminar: The Onset of Turbulence in Shear Flows -- A Matter of Life and Death

Description

Björn Hof, a professor at the Institute of Science and Technology in Austria, will give a talk entitled "The Onset of Turbulence in Shear Flows -- A Matter of Life and Death" as a virtual Center for Environmental and Applied Fluid Mechanics seminar. This seminar is hosted by Rui Ni, professor in the Department of Mechanical Engineering at Johns Hopkins University.

Please attend the event by using the Zoom link.

Abstract:

In pipe, channel and Couette flow turbulence arises despite the linear stability of the laminar state and the transition is caused by finite amplitude perturbations. In the vicinity of the critical point turbulence is not space filling but appears in localized patches. Although the lifetime of individual patches is finite, prior to decay they may infect adjacent laminar regions and proliferate. Depending which of these processes dominates, eventually either the entire flow will relaminarise or turbulence survives. This overall situation is reminiscent to absorbing state phase transitions in statistical mechanics. As shown specifically for Couette flow the transition falls into the directed percolation universality class. In order to resolve the relevant time scales of the flow and to determine the respective critical exponents, experiments with excessively large aspect ratios and observation times are required. In addition I will discuss further complications that arise in pressure driven flows such as pipes and channels.