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ISSN オンライン: 2642-0554

HIGH RESOLUTION VELOCITY PROFILE MEASUREMENTS IN TURBULENT BOUNDARY LAYERS

Christian J. Kahler
Institute for Fluid Mechanics and Aerodynamics Universitat der Bundeswehr Munchen (UniBw) Werner-Heisenberg-Weg 39, 85577 Neubiberg, Germany

Sven Scharnowski
Institute of Fluidmechanics and Aerodynamics Bundeswehr University Munich 85577 Neubiberg, Germany

Christian Cierpka
Magneto-Hydrodynamics Division, Forschungszentrum Dresden-Rossendorf Bautzner Landstr. 128, D-01328 Dresden, Germany; Institute of Fluidmechanics and Aerodynamics Bundeswehr University Munich 85577 Neubiberg, Germany; Institute of Thermodynamics and Fluid Mechanics, Technische Universität Ilmenau, Am Helmholtzring 1, 98693 Ilmenau, Germany

要約

Particle Image Velocimetry (PIV) is an established technique for the measurement of instantaneous or time resolved flow fields in two and three dimensions. As no other technique is able to determine quantitatively unsteady flow field information, PIV has evolved to the leading measurement technique in fluid mechanics over the last decade. However, for the measurement of mean velocity profiles and turbulent velocity fluctuations hot-wire probes and laser Doppler anemometer are still the most established techniques, because they are simpler to use and often more precise than PIV. In this paper it is shown how the lack of accuracy can be compensated by using more advanced PIV evaluation techniques. This is very beneficial because PIV allows to measure without any traversing the instantaneous and average flow information at thousands of points simultaneously. In this case measurement errors caused by long time variations of the wind tunnel speed, viscosity, temperature and humidity effects or errors associate with the mechanical traversing the probe to thousands of points or effects due to probe vibrations cannot take place. In order to enhance the measurement accuracy of the PIV technique the authors have developed sophisticated image analysis techniques in the last years (Scharnowski et al., 2012; Kahler et al., 2012a,b; Cierpka et al., 2013b,a). In this contribution these techniques are used to evaluate the measurements of a turbulent boundary layer flow along a flat plate in the 22 m long and 2 by 2 square-meter wide test section of the Atmospheric Wind tunnel at UniBw Munich. Beside the mean velocity fields also the capabilities in estimating turbulent quantities such as the Reynolds stresses and the probability density function of the velocity fluctuations is outlined. There is still some work which needs to be done, but the results already indicate the potential of the developed evaluation techniques in estimating averaged flow quantities.