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A Comparison Between Boundary Layer Measurements in a Laminar Separation Bubble Flow and Linear Stability Theory Calculations

  • P. LeBlanc
  • R. Blackwelder
  • R. Liebeck
Part of the Lecture Notes in Engineering book series (LNENG, volume 54)

Abstract

This research examines the details of the boundary layer flowfield from wind tunnel measurements of a two-dimensional Liebeck LA2573A airfoil over a range of Reynolds numbers from 235000 to 500000. In this range, a laminar separation bubble becomes significant in the boundary layer and provides a measurable contribution to the airfoil drag. Measurements include airfoil drag, mean and turbulent boundary layer velocity profiles, a calculation of integral parameters associated with these profiles, and energy spectra of the velocity signal inside the boundary layer. Evidence of the growth of boundary layer velocity fluctuations within a range of frequencies in the laminar separation and transition regions has been found in these spectral measurements. Results have shown that the peak frequencies measured in the velocity spectra for the instability region agree with the most amplified wave number and frequency scaling predicted by linear stability theory for these inflectional profiles. Additionally, the maximum measured growth rates at this peak frequency correlate with growth rates calculated from similarly shaped Falkner-Skan profiles at the corresponding frequency of maximum amplification. This agreement between experimental and theoretical peak frequencies and growth rates was confirmed for the range of Reynolds numbers and for airfoil incidence ranging from zero lift to stall.

Keywords

Reynolds Number Spectral Energy Separation Bubble Linear Stability Theory Boundary Layer Velocity 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin, Heidelberg 1989

Authors and Affiliations

  • P. LeBlanc
    • 1
  • R. Blackwelder
    • 1
  • R. Liebeck
    • 1
  1. 1.Department of Aerospace EngineeringUniversity of Southern CaliforniaLos AngelesUSA

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