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. [S0889-504X(00)01204-6]
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e-mail: Weiliang.Lou@muc.mtu.de
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October 2000
Technical Papers
Separation Bubbles Under Steady and Periodic-Unsteady Main Flow Conditions
Weiliang Lou,
e-mail: Weiliang.Lou@muc.mtu.de
Weiliang Lou
Jet Propulsion Laboratory, Aerospace Institute F1, Berlin University of Technology, Marchstr. 12, D-10587 Berlin, Germany
11
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Jean Hourmouziadis
Jean Hourmouziadis
Jet Propulsion Laboratory, Aerospace Institute F1, Berlin University of Technology, Marchstr. 12, D-10587 Berlin, Germany
Search for other works by this author on:
Weiliang Lou
11
Jet Propulsion Laboratory, Aerospace Institute F1, Berlin University of Technology, Marchstr. 12, D-10587 Berlin, Germany
e-mail: Weiliang.Lou@muc.mtu.de
Jean Hourmouziadis
Jet Propulsion Laboratory, Aerospace Institute F1, Berlin University of Technology, Marchstr. 12, D-10587 Berlin, Germany
Contributed by the International Gas Turbine Institute and presented at the 45th International Gas Turbine and Aeroengine Congress and Exhibition, Munich, Germany, May 8–11, 2000. Manuscript received by the International Gas Turbine Institute February 2000. Paper No. 2000-GT-270. Review Chair: D. Ballal.
J. Turbomach. Oct 2000, 122(4): 634-643 (10 pages)
Published Online: February 1, 2000
Article history
Received:
February 1, 2000
Citation
Lou, W., and Hourmouziadis, J. (February 1, 2000). "Separation Bubbles Under Steady and Periodic-Unsteady Main Flow Conditions ." ASME. J. Turbomach. October 2000; 122(4): 634–643. https://doi.org/10.1115/1.1308568
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