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Characteristics of a turbulent boundary layer with an external turbulent uniform shear flow

Published online by Cambridge University Press:  11 April 2006

Q. A. Ahmad ,
R. E. Luxton  and
R. A. Antonia
Q. A. Ahmad
Affiliation:
Department of Mechanical Engineering, University of Sydney, New South Wales 2006, Australia
R. E. Luxton
Affiliation:
Department of Mechanical Engineering, University of Sydney, New South Wales 2006, Australia Present address: Department of Mechanical Engineering, University of Adelaide, South Australia 5001.
R. A. Antonia
Affiliation:
Department of Mechanical Engineering, University of Sydney, New South Wales 2006, Australia Present address: Department of Mechanical Engineering, University of Newcastle, New South Wales 2308, Australia.
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Abstract

Measurements are presented of both mean and fluctuating velocity components in a turbulent boundary layer subjected to a nearly homogeneous external turbulent shear flow. The Reynolds shear stress in the external shear flow is small compared with the wall shear stress. Its transverse mean velocity gradient λ (≃ 6 s−l) is also small compared with typical gradients based on outer variables (say Uw/δ, where Uwis the value of the linear velocity profile extrapolated to the wall and δ is the boundary-layer thickness), but is of the same order as Ut/δ (Ur is the friction velocity). The influence of both positive and negative transverse velocity gradients on the turbulent wall layer is investigated over a streamwise region where the normal Reynolds stresses in the external flow are approximately equal and constant in the streamwise direction. In this region, the integral length scale of the external flow is of the same order of magnitude as that of the wall layer. Measurements in the boundary layer are also given for an un-sheared external turbulent flow (λ = 0) with a turbulence level Tu of 1.5%, approximately the same as that for h = ± 6 s−1. (Tu, is defined as the ratio of the r.m.s. longitudinal velocity fluctuation to Uw.) The measurements are in good agreement with those available in the literature for a similar free-stream turbulence level and show that the external turbulence level and length scale exert a large influence on the turbulence structure in the boundary layer. The additional effect of the external shear on the mean velocity and turbulent energy budget distributions in the inner region of the boundary layer is found to be small. In the outer region, the ‘wake’ component of the mean velocity defect is lowered by the presence of free-stream turbulence and one extra effect due to the external shear is an increase in the Reynolds shear stress when h is positive and a decrease when h is negative. Another interesting effect due to the shear is the appearance near the edge of the layer of a small but distinct region where the local mean velocity is constant and the Reynolds shear stress is negligible.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 77 , Issue 2 , 24 September 1976 , pp. 369 - 396
Copyright
© 1976 Cambridge University Press

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References

Ahmad, Q. A., Luxton, R. E. & Antonia, R. A. 1975a J. Appl. Mech. Trans. A.S.M.E., 97, 283.
Ahmad, Q. A., Luxton, R. E. & Antonia, R. A. 1975b Chas Kollin.g Res. Lab., Dept. Mech. Engng, Univ. Sydney, Rep. no. TNF-75.
Antonia, R. A. 1969 Ph.D. thesis, Department of Mechanical Engineering, University of Sydney.
Bradshaw, P. 1966 Nat. Phys. Lab. dero. Rep. no. 1184.
Bradshaw, P. 1974 Imperial College Aero. Rep. no. 74-10.
Champagne, F. H., Harris, V. G. & Corrsin, S. 1970 J. Fluid Mech. 41, 81.
Charnay, G. 1974 These Docteur des Sciences, Université de Lyon.
Charnay, G., Comte-Bellot, G. & Mathieu, J. 1972 Agard Conf. Proc. no. 93.
Charnay, G., Comte-Bellot, G. & Mathieu, J. 1973 C. R. Ad. Sci. Paris, A 277, 1119.
Clauser, F. H. 1954 J. Aero. Sci. 21, 91.
Clauser, F. H. 1956 Adv. Appl. Mech. 4, 1.
Coles, D. 1962 Rand Corp. Rep. no. R-403-PR.
Costin, G. D. L. 1971 Proc. 4th Austr. Conf. Hydraul. Fluid Mech. Paper 61.
Dean, R. B. 1974 Proc. 5th Austr. Conf. Hydraul. Fluid Mech., Christchurch, New Zealand, vol. 1, p. 340.
Fabris, O. 1974 Ph.D. thesis, Department of Mechanical Engineering, Illinois Institute of Technology.
Fulachier, L. 1972 These Docteur des Sciences, Universite de Provence.
Gorlin, S. M. & Zrazhevskii, I. M. 1972 Mech. Zh. Moscow, Gam, 4, 52.
Green, J. E. 1972 R.A.E., Tech. Rep. no. 72201.
Head, M. R. & RAM, V. V. 1971 Aero. Quart. 22, 295.
Hwang, W. S. 1971 Ph.D. thesis, School of Engineering and Applied Science, University of Virginia.
Huffman, G. D., Zimmerman, D. R. & Bennett, W. A. 1972 AGARD Conf. Proc. no. 164.
Johnson, D. S. 1959 J. Appl. Mech., Trans. A.S.M.E. 26, 325.
Klebanoff, P. s. 1954 N.A.C.A. Tech. Note, no. 3178.
Kline, S. J., Lisin, A. V. & Waitman, B. E. 1960 N.A.S.A. Rep. no. D-368.
Masuda, S., Sasaki, N., Ariaa, I. & Watanabe, I. 1972 2nd Int. J.S.M.E. Symp. Fluid Machinery & Fluidics, Tokyo.
Mulhearn, P. J. 1971 Ph.D. thesis, Department of Mechanical Engineering, University of Sydney.
Mulhearn, P. J. & Luxton, R. E. 1970 Chas Kolling Res. Lab., Dept. Mech. Engng, Univ. Sydney, Rep. no. TNF-19.
Mulhearn, P. J. & Luxton, R. E. 1975 J. Fluid Mech. 68, 577.
Richards, H. K. 1971 Ph.D. thesis, School of Engineering and Applied Science, University of Virginia.
Rose, W. G. 1966 J. Fluid Mech. 25, 97.
Rose, W. G. 1970 J. Fluid Mech. 44, 767.
Townsend, A. A. 1966 The Struoture of Turbulent Shear Flow. Cambridge University Press.
Townsend, A. A. 1966 J. Fluid Mech. 22, 773.
Townsend, A. A. 1966 J. Fluid Mech. 26, 265.
Wood, D. 1975 M.S. thesis, Department of Mechanical Engineering, University of Sydney.