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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 39: Focus Session: Physics of Fluctuating Paths (joint session DY/CPP)

CPP 39.9: Talk

Wednesday, March 29, 2023, 17:15–17:30, ZEU 160

Instantons and the Path to Intermittency in Turbulent Flows — •André Fuchs¹, Corentin Herbert², Joran Rolland³, Matthias Wächter¹, Freddy Bouchet², and Joachim Peinke¹ — ¹Institute of Physics and ForWind, University of Oldenburg, Küpkersweg 70, 26129 Oldenburg, Germany — ²Université de Lyon, Ens de Lyon, Université Claude Bernard, CNRS, Laboratoire de Physique, F-69364 Lyon, France — ³Université de Lille, CNRS, ONERA, Arts et Métiers Institute of Technology, Centrale Lille, UMR 9014 - LMFL - Laboratoire de Mécanique des fluides de Lille - Kampé de Fériet, F-59000 Lille, France

Processes leading to anomalous fluctuations in turbulent flows, referred to as intermittency, are still challenging. We consider cascade trajectories through scales as realizations of a stochastic Langevin process for which multiplicative noise is an intrinsic feature of the turbulent state. The trajectories are conditioned on their entropy exchange. Such selected trajectories concentrate around an optimal path, called instanton, which is the minimum of an effective action. The action is derived from the Langevin equation, estimated from measured data. In particular instantons with negative entropy pinpoint the trajectories responsible for the emergence of non-Gaussian statistics at small-scales.