Directed percolation transition to turbulence

by Bjorn Hof

at Physics Colloquium

Tue, 25 Apr 2017, 15:00
Nanotechnology institute building (#51) room 15

Abstract

The transition to turbulence in simple shear flows e g pipe channel and Couette flow has remained an open problem for over a century Typically here turbulence arises despite the linear stability of the laminar flow and results from perturbations of finite amplitude Turbulence at first appears in the form of localised patches e g puffs spots or stripes which coexist with laminar flow resulting in complex disordered flow patterns spatio temporal intermittency Individual turbulent domains can collapse or they can proliferate and seed other patches of turbulence The time scales on which flows evolve are extremely large and likewise are the relevant length scales Characterizing the transition process hence requires experiments of very large aspect ratios and extremely long observation times In detailed experiments and direct numerical simulations of Couette flow we could for the first time determine the critical exponents that characterize this transition and show that it falls into the directed percolation universality class Refreshments are served at 14:45

Created on 20-04-2017 by Bar Lev, Yevgeny (ybarlev)
Updaded on 20-04-2017 by Bar Lev, Yevgeny (ybarlev)