Detachment of Turbulent Boundary Layers With Varying Free-Stream Turbulence and Lower Reynolds Numbers

  • J. Leith Potter
  • R. Joel Barnett
  • Costas E. Koukousakis
  • Carl E. Fisher
Conference paper
Part of the Lecture Notes in Engineering book series (LNENG, volume 54)

Summary

Experiments were conducted to determine if free-stream turbulence scale affects detachment of turbulent boundary layers. In consideration of possible interrelation between scale and intensity of turbulence, the latter characteristic also was varied and its role was evaluated. Flow over a 2­dimensional airfoil in a subsonic wind tunnel was studied with the aid of hot-wire anemometry, liquid-film visualization, a Preston tube, and static pressure measurements. Profiles of velocity, relative turbulence intensity, and integral scale in the boundary layer were measured. Detachment boundary was determined for various angles of attack and free-stream turbulence.

The free-stream turbulence intensity and scale were found to spread into the entire turbulent boundary layer, but the effect decreased as the airfoil surface was approached. When the changes in stream turbulence were such that the boundary layer velocity profiles were only slightly changed, detachment location was not significantly affected by the variations of intensity and scale. Pressure distribution and laminar or turbulent state remained the key factors in determining detachment location.

New data on the detachment of turbulent boundary layers were obtained. The range of flow conditions made it possible to evaluate the best-known rapid methods for predicting turbulent detach­ment at lower Reynolds numbers than previously reported. This revealed that approximations and empirical constants based on data for high Reynolds numbers and strongly adverse pressure gradients should not be uncritically accepted for predicting detachment of flows at low Reynolds numbers.

Keywords

Vortex Assure Autocorrelation 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    Hancock, P. E.: Effect of Free-Stream Turbulence on Turbulent Boundary Layers. Ph.D. Thesis, Imperial College, University of London, 1978.Google Scholar
  2. 2.
    Meier, H. U.: The Response of Turbulent Boundary Layers to Small Turbulence Levels in the External Free Stream. ICAS Paper No. 76–05, The Tenth Congress of the International Council of the Aeronautical Sciences, Oct. 1976.Google Scholar
  3. 3.
    Simonich, J. C. and Bradshaw, P.: Effect of Free-Stream Turbulence on Heat Transfer Through a Turbulent Boundary Layer. ASME Journal of Heat Transfer, vol. 110, Nov. 1978, pp. 671–677.CrossRefADSGoogle Scholar
  4. 4.
    Meier, H. U. and Kreplin, H.-P.: Influence of Freestream Turbulence on Boundary-Layer Development. AIAA Journal, vol. 18, Jan. 1980, pp. 11–15.Google Scholar
  5. 5.
    Hancock, P. E. and Bradshaw, P.: The Effect of Free-Stream Turbulence on Turbulent Boundary Layers. ASME Journal of Fluids Engineering, vol. 105, Sept. 1983, pp. 284–289.CrossRefADSGoogle Scholar
  6. 6.
    Blair, M. F.: Influence of Free-Stream Turbulence on Turbulent Boundary Layer Heat Transfer and Mean Profile Development, Part 1–Experimental Data and Part 2–Analysis of Results. ASME Journal of Heat Transfer, vol. 105, Feb. 1983, pp. 33–47.CrossRefADSGoogle Scholar
  7. 7.
    Castro, T. P.: Effects of Free-Stream Turbulence on Low Reynolds Number Boundary Layers. ASME Journal of Fluids Engineering, vol. 106, Sept. 1984, pp. 298–306.CrossRefADSGoogle Scholar
  8. 8.
    Townsend, A. A.: The Behaviour of a Turbulent Boundary Layer Near Separation. Journal of Fluid Mechanics, vol. 12, April 1962, pp. 536–554.CrossRefMATHADSMathSciNetGoogle Scholar
  9. 9.
    Potter, J. L., Barnett, R. J., Fisher, C. E., and Koukousakis, C. E.: The Influence of Free-Stream Turbulence on Separation of Turbulent Boundary Layers in Incompressible Two-Dimensional Flow. NASA CR- 180638, 22 Dec. 1986.Google Scholar
  10. 10.
    Simpson, R. L.: A Review of Some Phenomena in Turbulent Flow Separation. ASME Journal of Fluids Engineering, vol. 103, Dec. 1981, pp. 520–533.CrossRefGoogle Scholar
  11. 11.
    Townsend, A. A.: Structure of Turbulent Shear Flow. University Press, Cambridge, 1956.MATHGoogle Scholar
  12. 12.
    Hinze, J. O.: Turbulence. McGraw-Hill, New York, 1959.Google Scholar
  13. 13.
    Stratford, B. A.: The Prediction of Separation of the Turbulent Boundary Layer. Journal of Fluid Mechanics, vol. 5, 1959, pp. 1–16.CrossRefMATHADSMathSciNetGoogle Scholar
  14. 14.
    Cebeci, T.; Mosinskis, G. J.; and Smith, A. M. O.: Calculation of Separation Points in Incompressible Turbulent Flows. AIAA Journal of Aircraft, vol. 9, Sept. 1972, pp. 618–624.CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin, Heidelberg 1989

Authors and Affiliations

  • J. Leith Potter
    • 1
  • R. Joel Barnett
    • 1
  • Costas E. Koukousakis
    • 1
  • Carl E. Fisher
    • 1
  1. 1.Mechanical EngineeringVanderbilt UniversityNashvilleUSA

Personalised recommendations