ENERGY EXCHANGES AND TIME ASYMMETRY IN 3D TURBULENT FLOWS etc15 Tracking Number 432Presentation: Session: Lagrangian aspects of turbulence 2 Room: Room H Session start: 10:30 Thu 27 Aug 2015 Alain Pumir alain.pumir@ens-lyon.fr Affifliation: ENS Lyon Haitao Xu hxu1@gwdg.de Affifliation: MPI, Göttingen and Tsinghua University, Beijing Rainer Grauer grauer@tp1.rub.de Affifliation: Ruhr University, Bochum, Germany Eberhard Bodenschatz eberhard.bodenschatz@ds.mpg.de Affifliation: MPI Göttingen Topics: - Lagrangian aspects of turbulence 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. |