Skip to main content
Article thumbnail
Location of Repository

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

By Hee Chang Lim, Ian P. Castro and Roger P. Hoxey

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

Topics: TA
Year: 2007
OAI identifier: oai:eprints.soton.ac.uk:42337
Provided by: e-Prints Soton

Suggested articles

Citations

  1. (1987). An experimental study of the turbulence structure in smooth and rough wall turbulent boundary layers.
  2. (1977). C a s t r o ,I .P .&R o b i n s ,A .G
  3. (1984). C h e r r y ,N .J . ,H i l l i e r ,R .&L a t o u r
  4. (1973). C o o k ,N .J
  5. (1985). Characteristics of atmospheric turbulence near the ground. Part II: single point data for strong winds (neutral atmosphere). Engineering Sciences Data Unit, Item 85020.
  6. (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.
  7. (2004). Empirical spectral model of surface pressure fluctuations.
  8. Engng Ind.
  9. (1991). F a r a b e e ,T .M .&C a s a r e l l a
  10. (2000). H a r t ,D .P
  11. (1981). H i l l i e r ,R .&C h e r r y
  12. H u n t ,J .C .R .&F e r n h o l z ,H .H .1975 Wind-tunnel simulation of the atmospheric boundary layer: a report on Euromech 50.
  13. (2002). Local peak pressure and conical vortex on a building.
  14. (1998). Observations of Reynolds number sensitivity in the separated flow region on a bluff body.
  15. (2004). Quasi-steady theory and point pressures on a cubic building.
  16. (1997). S a a t h o f f ,P .J .&M e l b o u r n e ,W .H
  17. (1994). Some observations of the influence of stratification on diffusion in building wakes.
  18. (1978). Spectral characteristics of surface layer turbulence.
  19. (2000). Spectral models for the neutral atmospheric surface layer.
  20. (1999). The Missing Links. Plenary paper
  21. (1980). Turbulence effects on maximum surface pressures: a mechanism and possibility of reduction.
  22. (1991). Turbulent flow around a bluff rectangular plate. Part 1: experimental investigation.
  23. (2000). Turbulent Flows.
  24. (2005). Variations in static pressure – application to wind engineering.
  25. (2003). Wall-pressure-array measurements beneath a separating/reattaching flow region.
  26. (2001). Wind pressures on a 6 m cube.
  27. (1978). Wind tunnel simulation of the adiabatic atmospheric boundary layer by roughness, barrier and mixing device methods.
  28. (2003). Wind tunnel simulations of wind loading on low-rise structures: a review.

To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.