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STUDY ON THE MECHANISM OF TURBULENT ENTRAINMENT THROUGH 3D-PTV AND DNS

Markus Holzner
Institute of Environmental Engineering, ETH - Swiss Federal Institute of Technology, CH-8093 Zurich, Switzerland

Beat Luthi
Institute of Environmental Engineering, ETH Zurich, CH-8093 Zurich, Switzerland

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

Alexander Liberzon
School of Mechanical Engineering, Faculty of Engineering, Tel Aviv University, Ramat Aviv 69978, Israel

Nikolay V. Nikitin
Institute of Mechanics, Moscow State University, 1 Michurinski prospekt, 119899 Moscow, Russia

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

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 work reported below is an analysis of small scale properties of turbulent ow without strong mean shear in a homogeneous Newtonian fluid in proximity of the turbulent/non-turbulent interface. The main tools used are a three-dimensional particle tracking system (3D-PTV) allowing to measure and follow in a Lagrangian manner the fi eld of velocity derivatives and direct numerical simulations (DNS). The study is based on the statistical analysis of flow tracers crossing the turbulent/non-turbulent interface. The analysis of flow properties in the proximity of the interface allows for direct observation of the key physical processes underlying the entrainment phenomenon. We found that both, viscous and inertial processes are important for the increase of enstrophy at the turbulent/non-turbulent interface.