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Scanning PIV investigation of the laminar separation bubble on a SD7003 airfoil

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Abstract

A laminar separation bubble occurs on the suction side of the SD7003 airfoil at an angle of attack α =  4–8° and a low Reynolds number less than 100,000, which brings about a significant adverse aerodynamic effect. The spatial and temporal structure of the laminar separation bubble was studied using the scanning PIV method at α =  4° and Re = 60,000 and 20,000. Of particular interest are the dynamic vortex behavior in transition process and the subsequent vortex evolution in the turbulent boundary layer. The flow was continuously sampled in a stack of parallel illuminated planes from two orthogonal views with a frequency of hundreds Hz, and PIV cross-correlation was performed to obtain the 2D velocity field in each plane. Results of both the single-sliced and the volumetric presentations of the laminar separation bubble reveal vortex shedding in transition near the reattachment region at Re = 60,000. In a relatively long distance vortices characterized by paired wall-normal vorticity packets retain their identities in the reattached turbulent boundary layer, though vortices interact through tearing, stretching and tilting. Compared with the restricted LSB at Re = 60,000, the flow at Re = 20,000 presents an earlier separation and a significantly increased reversed flow region followed by “huge” vortical structures.

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Acknowledgments

This research has been supported by the German Research Foundation (DFG) in the priority program 1147 "Bildgebende Messverfahren für die Strömungsanalyse".

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Author notes

  1. Wei Zhang

    Present address: Department of Aerospace Engineering, Iowa State University, Ames, IA, 50014, USA

  2. Rainer Hain

    Present address: Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), Institut für Aerodynamik und Strömungstechnik, Lilienthalplatz 7, 38108, Braunschweig, Germany

  3. Christian J. Kähler

    Present address: Institut für Strömungsmechanik und Aerodynamik, Universität der Bundeswehr München, Werner-Heisenberg-Weg 39, 85577, Neubiberg, Germany

Authors and Affiliations

  1. Institut für Strömungsmechanik, Technische Universität Braunschweig, Bienroder Weg 3, 38106, Braunschweig, Germany

    Wei Zhang, Rainer Hain & Christian J. Kähler

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  1. Wei Zhang
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  2. Rainer Hain
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  3. Christian J. Kähler
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Correspondence to Christian J. Kähler.

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Zhang, W., Hain, R. & Kähler, C.J. Scanning PIV investigation of the laminar separation bubble on a SD7003 airfoil. Exp Fluids 45, 725–743 (2008). https://doi.org/10.1007/s00348-008-0563-8

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  • DOI: https://doi.org/10.1007/s00348-008-0563-8

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