Objective
Turbulence is the probably most complex and at
the same time most relevant example of spatio-temporal disorder in
nature. The transport of heat and mass in stars, the formation of
planets, as well as flows in the earth atmosphere, oceans or around
vehicles are all governed by turbulence. Despite its ubiquity our
insights into this complex phenomenon are very limited. In contrast to
many studies which are concerned with turbulent flows at high parameter
values I will here use a different approach and investigate turbulence
when it first arises and where it is the least complex. I will focus
on canonical shear flows, comprising pipe, Couette and channel flows. I
have recently determined the critical point for transition in pipe
flow, which had posed a riddle for more than a century and inhibited
further progress towards a fundamental understanding of turbulence
close to onset. At first I will clarify if this transition generally
applies to all canonical shear flows. Next I will explore links to
non-equilibrium phase transitions in other areas of science by
determining the critical exponents and the universality class of the
onset of shear flow turbulence. I will investigate and identify further
bifurcations the turbulent state experiences as it develops from a
spatially intermittent to a space filling state. This will for the
first time provide a complete picture of the onset of turbulence and
establish links to turbulence studies at higher Reynolds numbers.
Investigating the mechanisms leading to fully turbulent flow will not
only give valuable insights into the nature of fluid turbulence but may
also lead to new ways to control it.
Finally I will exploit these
insights and devise methods that completely relaminarize turbulent
flows. Subduing turbulence is of great practical importance since
frictional losses in turbulence are much larger than in the laminar
state and hence relaminarization leads to substantial energy savings in
transport problems.
Team Members
Björn Hof (PI)
Sebastian Altmeyer (postdoc)
Jakob Kühnen (postdoc)
Mukund Vasudevan (postdoc)
Publications
