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THE EFFECT OF VORTICITY AND STRAIN ON THE EVOLUTION OF MATERIAL LINES IN HOMOGENEOUS TURBULENCE

Michele Guala
Department of Civil Engineering University of Minnesota, Twin Cities 500 Pillsbury Dr. SE Minneapolis, Minnesota 55455

Alexander Liberzon
Institute of Hydromechanics and Water Resources Management, Swiss Federal Institute of Technology, ETH Honggerberg, CH 8093 Zurich, Switzerland

Wolfgang Kinzelbach
Institute of Hydromechanics and Water Resources Management, Swiss Federal Institute of Technology, ETH Honggerberg, CH 8093 Zurich, Switzerland

Beat Luthi
Risø National Laboratory, Frederiksborgvej 399, P.O. 49 DK-4000 Roskilde, Denmark

Arkady Tsinober
Department of Fluid Mechanics and Heat Transfer, School of Mechanical Engineering, Tel-Aviv University, Tel-Aviv, Israel; and Institute for Mathematical Sciences and Department of Aeronautics, Imperial College, London, United Kingdom

Abstrakt

The Lagrangian evolution of infinitesimal material lines is investigated experimentally through three dimensional measurements of particle trajectories (3D-PTV) in quasi homogeneous isotropic turbulence with Reλ = 50. By postprocessing 3D-PTV data obtained by Luthi et al. (2005) we access the full set of velocity derivatives dui /dxi which allows for monitoring the evolution of various turbulent quantities along each particle trajectory. The main goal of the present investigation concerns the physical mechanisms that govern the Lagrangian evolution of material lines l. In particular we will focus on the effect of vorticity and strain, respectively, on the orientation and on the stretching of l.