The rise of fully turbulent flow.
Over a century of research into the origin of turbulence in wall-bounded shear flows has resulted in a puzzling picture in which turbulence appears in a variety of different states competing with laminar background flow. At moderate flow speeds, turbulence is confined to localized patches; it is only at higher speeds that the entire flow becomes turbulent. The origin of the different states encountered during this transition, the front dynamics of the turbulent regions and the transformation to full turbulence have yet to be explained. By combining experiments, theory and computer simulations, here we uncover a bifurcation scenario that explains the transformation to fully turbulent pipe flow and describe the front dynamics of the different states encountered in the process. Key to resolving this problem is the interpretation of the flow as a bistable system with nonlinear propagation (advection) of turbulent fronts. These findings bridge the gap between our understanding of the onset of turbulence and fully turbulent flows.
Mathematics Institute, University of Warwick, Coventry CV4 7AL, UK.
Dwight
D
Barkley
IST Austria, 3400 Klosterneuburg, Austria.|Max Planck Institute for Dynamics and Self-Organization, Bunsenstrasse 10, 37073 Göttingen, Germany.|Institute for Multiscale Simulation, Friedrich-Alexander-Universität, 91052 Erlangen, Germany.
Baofang
B
Song
IST Austria, 3400 Klosterneuburg, Austria.
Vasudevan
V
Mukund
IST Austria, 3400 Klosterneuburg, Austria.
Grégoire
G
Lemoult
Institute of Fluid Mechanics, Friedrich-Alexander-Universität, 91058 Erlangen, Germany.
Marc
M
Avila
IST Austria, 3400 Klosterneuburg, Austria.
Björn
B
Hof