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ISSN オンライン: 2642-0554

LDA MEASUREMENTS IN TURBULENT BOUNDARY LAYERS WITH ZERO PRESSURE GRADIENT

Gunnar Johansson
Department of Thermo and Fluid Dynamics Chalmers University of Technology SE - 412 96 Goteborg, Sweden

Luciano Castillo
Department of Mechanical Engineering, Aeronautical Engineering & Mechanics Rensselaer Polytechnic Institute Troy, NY 12180 USA; Dept. Mech. Eng. Texas Tech University Lubbock, TX 79409-1021, USA

要約

An experiment on zero pressure gradient turbulent boundary layers at low Reynolds number has been carried out. By combining LDA techniques and similarity analysis of the RANS equations the effects of upstream conditions on the downstream development of the mean flow and the turbulent quantities in the outer part of the boundary layer were investigated. It was found that for fixed upstream conditions, the mean velocity profiles collapsed to a single profile even though the local Reynolds number, Rθ, did not reach higher values than about 4000. The normal Reynolds stress profiles showed a marked dependence on local Reynolds number but also a tendency to collapse at the higher end of the local Reynolds number range considered. The Reynolds shear stress profiles depended strongly on local Reynolds number and showed only a weak tendency to collapse at higher Reynolds numbers. The effects of different upstream conditions were investigated by varying free stream speed and position and diameter of a trip wire. The mean velocity profiles and the streamwise normal Reynolds stress showed no dependence on the upstream conditions within the constraints of this experiment. The wall-normal Reynolds stress and the Reynolds shear stress, however, revealed a clear dependence on the position of the trip wire. Only the Reynolds shear stress showed a dependence on the trip wire diameter.