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Bluff bodies in deep turbulent boundary layers: Reynolds-number issues

Published online by Cambridge University Press:  04 January 2007

HEE CHANG LIM ,
IAN P. CASTRO  and
ROGER P. HOXEY
HEE CHANG LIM
Affiliation:
School of Engineering Sciences, University of Southampton, Highfield, Southampton, SO17 1BJ, UK
IAN P. CASTRO*
Affiliation:
School of Engineering Sciences, University of Southampton, Highfield, Southampton, SO17 1BJ, UK
ROGER P. HOXEY
Affiliation:
Department of Civil Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
*
†Author to whom correspondence should be addressed: i.castro@soton.ac.uk
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Abstract

It is generally assumed that flows around wall-mounted sharp-edged bluff bodies submerged in thick turbulent boundary layers are essentially independent of the Reynolds number Re, provided that this exceeds some (2–3) × 104. (Re is based on the body height and upstream velocity at that height.) This is a particularization of the general principle of Reynolds-number similarity and it has important implications, most notably that it allows model scale testing in wind tunnels of, for example, atmospheric flows around buildings. A significant part of the literature on wind engineering thus describes work which implicitly rests on the validity of this assumption. This paper presents new wind-tunnel data obtained in the ‘classical’ case of thick fully turbulent boundary-layer flow over a surface-mounted cube, covering an Re range of well over an order of magnitude (that is, a factor of 22). The results are also compared with new field data, providing a further order of magnitude increase in Re. It is demonstrated that if on the one hand the flow around the obstacle does not contain strong concentrated-vortex motions (like the delta-wing-type motions present for a cube oriented at 45° to the oncoming flow), Re effects only appear on fluctuating quantities such as the r.m.s. fluctuating surface pressures. If, on the other hand, the flow is characterized by the presence of such vortex motions, Re effects are significant even on mean-flow quantities such as the mean surface pressures or the mean velocities near the surfaces. It is thus concluded that although, in certain circumstances and for some quantities, the Reynolds-number-independency assumption is valid, there are other important quantities and circumstances for which it is not.

Type
Papers
Information
Journal of Fluid Mechanics , Volume 571 , 25 January 2007 , pp. 97 - 118
Copyright
Copyright © Cambridge University Press 2007

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References

REFERENCES

Castro, I. P. & Robins, A. G. 1977 The flow around a surface mounted cube in uniform and turbulent streams. J. Fluid Mech. 79, 307–335.CrossRefGoogle Scholar
Cherry, N. J., Hillier, R. & Latour, M. E. M. P. 1984 Unsteady measurements in a separating and reattaching flow. J. Fluid Mech. 144, 13–46.CrossRefGoogle Scholar
Cook, N. J. 1973 On simulating the lower third of the urban adiabatic boundary layer in a wind tunnel. Atmos. Environ. 7, 691.CrossRefGoogle Scholar
Cook, N. J. 1978 Wind tunnel simulation of the adiabatic atmospheric boundary layer by roughness, barrier and mixing device methods. J. Wind Engng Ind. Aero. 3, 157–176.CrossRefGoogle Scholar
Davenport, A. 1999 The Missing Links. Plenary paper in Wind Engineering into the 21st Century (ed. Larson, A. & Livesey, F. M.), pp. 91–204. Balkema.Google Scholar
Djilali, N. & Gartshore, I. S. 1991 Turbulent flow around a bluff rectangular plate. Part 1: experimental investigation. Trans. ASME: J. Fluids Engng 113, 51–59.Google Scholar
ESDU 1985 Characteristics of atmospheric turbulence near the ground. Part II: single point data for strong winds (neutral atmosphere). Engineering Sciences Data Unit, Item 85020.Google Scholar
Farabee, T. M. & Casarella, M. J. 1991 Spectral features of wall pressure fluctuations beneath turbulent boundary layers. Phys. Fluids A 3, 2410–2420.CrossRefGoogle Scholar
Goody, M. 2004 Empirical spectral model of surface pressure fluctuations. AIAA J. 42, 1788–1794.CrossRefGoogle Scholar
Hart, D. P. 2000 Super-resolution PIV by recursive local correlation. J. Visualisation 3, 187–194.CrossRefGoogle Scholar
Hillier, R. & Cherry, N. J. 1981 The effects of free stream turbulence on separation bubbles. J. Wind Engng Ind. Aero. 8, 49.CrossRefGoogle Scholar
Hoxey, R. P., Reynolds, A. M., Richards, G. M., Robertson, A. P. & Short, J. L. 1998 Observations of Reynolds number sensitivity in the separated flow region on a bluff body. J. Wind Engng Ind. Aero. 73, 231–249.CrossRefGoogle Scholar
Hoxey, R. P., Quinn, A. D. & Richards, G. M. 2005 Variations in static pressure – application to wind engineering. Paper 315 in 4th European & African Conference on Wind Engineering.Google Scholar
Hudy, L. M., Naguib, A. M. & Humphreys, W. M. 2003 Wall-pressure-array measurements beneath a separating/reattaching flow region. Phys. Fluids 15, 706–717.CrossRefGoogle Scholar
Hunt, J. C. R. & Fernholz, H. H. 1975 Wind-tunnel simulation of the atmospheric boundary layer: a report on Euromech 50. J. Fluid Mech. 70, 543–559.CrossRefGoogle Scholar
Kaimal, J. C., Wyngaard, Y., Izumi, O. R. & Cote, O. R. 1978 Spectral characteristics of surface layer turbulence. Q. J. R. Met. Soc. 98, 563–598.Google Scholar
Kawai, H. 2002 Local peak pressure and conical vortex on a building. J. Wind Engng Ind. Aero. 90, 251–263.CrossRefGoogle Scholar
Lee, I. & Sung, H. J. 2001 Characteristics of wall pressure fluctuations in separated and reattaching flow over a backward-facing step: Part I. Time-mean statistics and cross-spectral analysis. Expts. Fluids 30, 262–272.CrossRefGoogle Scholar
Melbourne, W. H. 1980 Turbulence effects on maximum surface pressures: a mechanism and possibility of reduction. In Wind Engineering (ed. Cermak, J. E.), pp. 541–551. Pergamon.CrossRefGoogle Scholar
Murakami, S. & Mochida, A. 1988 3D numerical simulation of airflow around a cubic model by means of k−ε model. J. Wind Engng Ind. Aero. 31, 283–303.CrossRefGoogle Scholar
Perry, A. E., Lim, K. L. & Henbest, S. M. 1987 An experimental study of the turbulence structure in smooth and rough wall turbulent boundary layers. J. Fluid Mech. 177, 437–466.CrossRefGoogle Scholar
Pope, S. B. 2000 Turbulent Flows. Cambridge University Press.CrossRefGoogle Scholar
Richards, G. M. & Hoxey, R. P. 2004 Quasi-steady theory and point pressures on a cubic building. J. Wind Engng Ind. Aero. 92, 1173–1190.CrossRefGoogle Scholar
Richards, G. M., Hoxey, R. P. & Short, L. J. 2000 Spectral models for the neutral atmospheric surface layer. J. Wind Engng Ind. Aero. 87, 167–185.CrossRefGoogle Scholar
Richards, G. M., Hoxey, R. P. & Short, L. J. 2001 Wind pressures on a 6 m cube. J. Wind Engng Ind. Aero. 89, 1553–1564.CrossRefGoogle Scholar
Saathoff, P. J. & Melbourne, W. H. 1997 Effects of free-stream turbulence on surface pressure fluctuations in a separation bubble. J. Fluid Mech. 337, 1–24.CrossRefGoogle Scholar
Snyder, W. H. 1994 Some observations of the influence of stratification on diffusion in building wakes. In Stably Stratified Flows: Flow and Dispersion over Topography (ed. Castro, I. P. & Rockliff, N. J.) pp. 301–324. Oxford University Press.Google Scholar
Tieleman, H. W. 2003 Wind tunnel simulations of wind loading on low-rise structures: a review. J. Wind Engng Ind. Aero. 91, 1626–1649.Google Scholar