Experiments in Fluids

, Volume 45, Issue 4, pp 725–743

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

Research Article

DOI: 10.1007/s00348-008-0563-8

Cite this article as:
Zhang, W., Hain, R. & Kähler, C.J. Exp Fluids (2008) 45: 725. doi:10.1007/s00348-008-0563-8

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.

Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  • Wei Zhang
    • 1
    • 2
  • Rainer Hain
    • 1
    • 3
  • Christian J. Kähler
    • 1
    • 4
  1. 1.Institut für StrömungsmechanikTechnische Universität BraunschweigBraunschweigGermany
  2. 2.Department of Aerospace EngineeringIowa State UniversityAmesUSA
  3. 3.Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR)Institut für Aerodynamik und StrömungstechnikBraunschweigGermany
  4. 4.Institut für Strömungsmechanik und AerodynamikUniversität der Bundeswehr MünchenNeubibergGermany