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DY: Fachverband Dynamik und Statistische Physik

DY 3: Fluid Physics of Turbulence

DY 3.1: Hauptvortrag

Montag, 16. März 2020, 09:30–10:00, ZEU 118

Disentangling Lagrangian Turbulence — Lukas Bentkamp, Cristian Lalescu, and •Michael Wilczek — Max-Planck-Institut für Dynamik and Selbstorganisation, Göttingen

Turbulence remains a paradigmatic challenge for nonequilibrium statistical physics. The rapid evolution of computational power and experimental techniques, however, has brought significant progress over the past decades. In this presentation, I will discuss how simulations provide insights into the structure and dynamics of turbulence and inform the development of a statistical theory of turbulence. In particular, I will focus on Lagrangian tracer particles, which sample turbulence in space and time. On their roller-coaster ride through turbulence, tracer particles frequently encounter extreme accelerations which are closely related to the intermittent spatial distribution of intense flow structures such as vortex filaments. This mixed history of flow conditions leads to very complex particle statistics with a pronounced scale dependence. Categorizing Lagrangian particle data from simulations by means of their accelerations reveals that Lagrangian turbulence can be decomposed into much simpler, close-to-Gaussian sub-ensembles for a range of Reynolds numbers. Based on this observation, we develop a comprehensive theoretical framework for Lagrangian single-particle statistics that captures the acceleration, velocity increments as well as single-particle dispersion.