A Comparison Between Boundary Layer Measurements in a Laminar Separation Bubble Flow and Linear Stability Theory Calculations
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.
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- P. J. LeBlanc, R. H. Liebeck, and R. Blackwelder. Boundary layer and performance characteristics from wind tunnel tests of a low Reynolds number Liebeck airfoil. In Aerodynamics at Low Reynolds Numbers,pages 8.1–8.19, London, Oct. 1986. The Royal Aeronautical Society.Google Scholar
- C. F. Liu. Control of Airfoil Performance by Local Excitation. PhD thesis, National Cheng Kung University, Tainan, Taiwan, October 1988.Google Scholar
- J. L. van Ingen and L. M. M. Boermans. Aerodynamics at low Reynolds numbers: A review of theoretical and experimental research at Delft University of Technology. In Aerodynamics at Low Reynolds Numbers,pages 1.1–1.40, London, Oct. 1986. The Royal Aeronautical Society.Google Scholar
- D. E. Gault. An experimental investigation of regions of separated laminar flow. Technical report, NACA TN 3505, Sept. 1955.Google Scholar
- M. Caster. The structure and behavior of separation bubbles. Technical report, ARC RandM No. 3595, March 1967.Google Scholar
- II. P. Horton. A semi-empirical theory for the growth and bursting of laminar separation bubbles. Technical report, ARC CP 1073, June 1967. (replaces ARC 29 185 ).Google Scholar
- M. M. O’Meara and T. J. Mueller. Laminar separation bubble characteristics on an airfoil at low Reynolds numbers. AIAA Journal, 25(8):1033–1041, Aug. 1987. the Conference on Low Reynolds Number Airfoil Aerodynamics, pages 137–152, University of Notre Dame, June 1985.Google Scholar
- the Conference on Low Reynolds Number Airfoil Aerodynamics, pages 137–152, University of Notre Dame, June 1985.Google Scholar
- M. Drela and M. B. Giles. Viscous-inviscid analysis of transonic and low Reynolds number airfoils. Technical report, AIAA-86–1786, 1986.Google Scholar
- R. H. Liebeck. Design and testing of an airfoil with positive pitching moment at low Reynolds numbers. Technical report, Douglas Aircraft Co., MDC 18893, Nov. 1982.Google Scholar
- M. Brendel and T. J. Mueller. Boundary layer measurements on an airfoil at low Reynolds numbers. Technical report, AIAA-87–0495, 1987b.Google Scholar
- M. Brendel and T. J. Mueller. Boundary layer measurements on an airfoil at a low Reynolds number in an oscillating free stream. Technical report, AIAA-87–1332, 1987a.Google Scholar
- F. Hsiao, C. Liu, and Z. Tang. Experimental studies of airfoil performance and flow structures on a low Reynolds number airfoil. Technical report, AIAA-87–1267, 1987.Google Scholar