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Separation Bubbles Under Steady and Periodic-Unsteady Main Flow Conditions
Zitatschlüssel 2000_lou_asme
Autor Lou, W. and Hourmouziadis, J.
Seiten 2000-GT-0270
Jahr 2000
ISBN 978-0-7918-7856-9
DOI 10.1115/2000-GT-0270
Ort Munich, Germany
Journal ASME Turbo Expo 2000: Power for Land, Sea, and Air
Jahrgang Volume 3: Heat Transfer; Electric Power; Industrial and Cogeneration
Monat 05
Notiz V003T01A075,
Technische Universität Berlin, Germany:
W. Lou, J. Hourmouziadis
Herausgeber ASME
Serie Turbo Expo: Power for Land, Sea, and Air
Zusammenfassung Based on an experimental investigation carried out in a low speed test facility at the Berlin University of Technology, this paper describes the formation of separation bubbles under steady and periodic-unsteady main flow conditions. The aim of the investigation was to understand the mechanism of separation, transition and reattachment and the effect of main flow unsteadiness on it.Separation bubbles for various main flow conditions were generated over a large flat plate, which experienced a similar pressure distribution to that on the suction surface of blades in turbomachines. The pressure distribution was generated by a contoured wall opposite the plate. Aimed at separating the effect of the velocity and the turbulence wake, this paper considers only the influence of the velocity wake. To this effect, a rotating flap was mounted downstream of the test section to produce periodic oscillations of the main flow.The overall flow field under steady main flow conditions was obtained by hot-wire measurements. Pressure taps were used to measure the pressure distribution over the plate. The Reynolds number effects were determined and compared to the measurement results in the literature. Results for periodic-unsteady separation bubbles are shown using different Strouhal numbers, oscillation amplitudes and Reynolds numbers. Ensemble averaged mean velocity profiles and the Ensemble averaged rms velocity profiles are used to demonstrate the development of the periodic boundary layer. Time-space diagrams are plotted to show the development of the periodic-unsteady boundary layers. The characteristic instability frequencies in the free shear layer are identified. The impact of the major parameters, Strouhal number and amplitude, on the bubble formation are discussed.
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