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
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