Abstract
The effect of mean shear (large-eddy motion) on the small-scale plume concentration structure is investigated experimentally using high-resolution plume concentration fluctuation measurements made simultaneously at two different heights in a plume dispersing in the very high-Reynolds number turbulent flow of the atmospheric surface layer (where the Taylor microscale based Reynolds number Re λ ≈ 5200). The generalized dimension spectra of a one-dimensional surrogate of the concentration variance dissipation rate are presented as a function of the mean shear. It is shown that the mean shear (due to the large-eddy motions in the flow) have a persistent effect on the small-scale plume concentration structure even at very high Reynolds numbers. In particular, it is demonstrated that increasing mean shear tends to reduce small-scale spatial intermittency in the concentration fluctuations (viz., the higher the mean shear, the more space-filling and less singular the associated local dissipation rate of concentration variance becomes).
Published Version
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