title: Flight-crash events in turbulence.
abstract: The statistical properties of turbulence differ in an essential way from those of systems in or near thermal equilibrium because of the flux of energy between vastly different scales at which energy is supplied and at which it is dissipated. We elucidate this difference by studying experimentally and numerically the fluctuations of the energy of a small fluid particle moving in a turbulent fluid. We demonstrate how the fundamental property of detailed balance is broken, so that the probabilities of forward and backward transitions are not equal for turbulence. In physical terms, we found that in a large set of flow configurations, fluid elements decelerate faster than accelerate, a feature known all too well from driving in dense traffic. The statistical signature of rare "flight-crash" events, associated with fast particle deceleration, provides a way to quantify irreversibility in a turbulent flow. Namely, we find that the third moment of the power fluctuations along a trajectory, nondimensionalized by the energy flux, displays a remarkable power law as a function of the Reynolds number, both in two and in three spatial dimensions. This establishes a relation between the irreversibility of the system and the range of active scales. We speculate that the breakdown of the detailed balance characterized here is a general feature of other systems very far from equilibrium, displaying a wide range of spatial scales.
authors.affiliation: International Collaboration for Turbulence Research, D-37077 Göttingen, Germany;Max Planck Institute for Dynamics and Self-Organization, D-37077 Göttingen, Germany;
authors.forename: Haitao
authors.initials: H
authors.lastname: Xu
authors.affiliation: International Collaboration for Turbulence Research, D-37077 Göttingen, Germany;Max Planck Institute for Dynamics and Self-Organization, D-37077 Göttingen, Germany;Laboratoire de Physique, Ecole Normale Supérieure de Lyon, Université de Lyon 1 and Centre National de la Recherche Scientifique, F-69007 Lyon, France;
authors.forename: Alain
authors.initials: A
authors.lastname: Pumir
authors.affiliation: International Collaboration for Turbulence Research, D-37077 Göttingen, Germany;Physics of Complex Systems, The Weizmann Institute of Science, Rehovot 76100, Israel;Institute for Information Transmission Problems, Moscow 127994, Russia;
authors.forename: Gregory
authors.initials: G
authors.lastname: Falkovich
authors.affiliation: International Collaboration for Turbulence Research, D-37077 Göttingen, Germany;Max Planck Institute for Dynamics and Self-Organization, D-37077 Göttingen, Germany;Institute for Nonlinear Dynamics, University of Göttingen, D-37077 Göttingen, Germany;Laboratory of Atomic and Solid State Physics and Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY 14853; eberhard.bodenschatz@ds.mpg.de.
authors.forename: Eberhard
authors.initials: E
authors.lastname: Bodenschatz
authors.affiliation: Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200, Australia; and.
authors.forename: Michael
authors.initials: M
authors.lastname: Shats
authors.affiliation: Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200, Australia; and.
authors.forename: Hua
authors.initials: H
authors.lastname: Xia
authors.affiliation: Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200, Australia; and.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Francois
authors.affiliation: International Collaboration for Turbulence Research, D-37077 Göttingen, Germany;Department of Physics and Istituto Nazionale di Fisica Nucleare, University of Torino, I-10125 Turin, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Boffetta
mesh_terms: D000054:Acceleration; D000392:Air Movements; D003198:Computer Simulation; D057446:Hydrodynamics; D008956:Models, Chemical
keywords: Lagrangian description; direct and inverse turbulent energy cascades; nonequilibrium statistical mechanics; nonequilibrium systems; turbulent mixing