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Session: Lagrangian aspects of turbulence 2
Session starts: Thursday 27 August, 10:30
Presentation starts: 10:45
Room: Room H

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Alain Pumir (ENS Lyon)
Haitao Xu (MPI, Göttingen and Tsinghua University, Beijing)
Rainer Grauer (Ruhr University, Bochum, Germany)
Eberhard Bodenschatz (MPI Göttingen)

Abstract:
In 3D turbulent flows, the direct cascade of energy, characterized by a flux through scales, ε, is a strong source of irre- versibility. This irreversibility manifests itself in the asymmetry between negative and positive kinetic energy differences along particle trajectories. In particular, it is observed that the odd moments of the power of the forces acting on a fluid particle, p ≡ a · V are negative, and that −⟨p3 ⟩/ε3 ∝ Rλ2 . This property rests on subtle correlations between acceleration and velocity. I will discuss two representations of the acceleration a, which shed light on the irreversibility of the flow.