Journal
ACTA GEOPHYSICA
Volume 60, Issue 6, Pages 1502-1546Publisher
SPRINGER INT PUBL AG
DOI: 10.2478/s11600-012-0044-6
Keywords
boulder array; velocity profile; friction velocity; turbulent structures; large-eddy simulation (LES)
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Funding
- United States Geological Survey [104, 02HQGR0139]
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The objective of this coupled experimental and numerical study is to provide insight into the mean and turbulent flow fields within an array of fully submerged, isolated, immobile boulders. Our study showed that the velocity defect law performed well for describing the mean flow around the boulder within the array. A prerequisite, however, was to accurately estimate the spatial variability of u* around the boulder, which was achieved via the boundary characteristics method. The u* exhibited considerable spatial variability within the array and form roughness was shown to be up to 2 times larger than the skin roughness in the boulder near-wake region. Because the boulders bear a significant amount of the flow shear, the available bed shear stress for entrainment of the mobile sediment, tau (ols) , near the boulders was roughly 50% lower than the ambient tau (ols) . The tau (ols) variability induced by the boulders could lead to a threefold overestimation of the sediment transport rate.
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