7th KIAS Conference on Statistical Physics
[Talk 8] Does the transition to turbulence in shear flow belong to directed
SPEAKER | Masaki Sano
INSTITUTE | The University of Tokyo
DATE | July 5(Tue), 2016
TIME | 09:00
PLACE | Korea Institute for Advanced Study (KIAS), Seoul, Korea
ABSTRACT | Transition from laminar to turbulent flow drastically changes the mixing, transport, and drag
properties of fluids, yet when and how turbulence emerges is elusive even for simple flow
within pipes and rectangular channels. Unlike the onset of temporal disorder, which is
identified as the universal route to chaos in confined flows, characterization of the onset of
spatio-temporal disorder has been an outstanding challenge because turbulent domains
irregularly decay or spread as they propagate downstream. Here, through extensive
experimental investigation of channel flow, we identify a distinctive transition with critical
behavior. Turbulent domains continuously injected from an inlet ultimately decayed, or in
contrast, spread depending on flow rates. Near a transition point, critical behavior was observed.
We investigate both spatial and temporal dynamics of turbulent clusters, measuring four critical
exponents, a universal scaling function and a scaling relation, all in agreement with the (2+1)
dimensional directed percolation universality class.
 Masaki Sano and Keiichi Tamai, Nature Phys., 12, 249-253 (2016).
 G. Lemoult, L. Shi, K. Avila, S. V. Jalikop, M. Avila, and B. Hof, Nature Phys.,
12, 254258 (2016).
 H. Y. Shih, T. L. Hsieh, and N. Goldenfeld, Nature Phys., 12, 245248 (2016).