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Title: Experimental study of depth-limited open-channel flows over a gravel bed
Authors: Zeng, C
Li, CW 
Tang, HW
Wang, LL
Mao, JQ
Keywords: Depth-limited open-channel flow
Gravel bed
DA velocity profile
Karman constant
Flow resistance
Issue Date: 2015
Publisher: Elsevier
Source: International journal of sediment research, 2015, v. 30, no. 2, p. 160-166 How to cite?
Journal: International journal of sediment research 
Abstract: Laboratory experiments of depth-limited open-channel flows over a gravel bed were conducted in the study. Two gravel patches with identical individual element size and different lengths (3.81 m and 7.5 m) were tested. The depth-limited uniform flow regime with relative submergence S-r (= D/k(s)) ranging from 2.68 to 5.94 was produced by adjusting the tailgate weir. The velocity profiles were measured by using both an ultra-sound velocity profiler (UVP) and an acoustic Doppler velocimeter (ADV). The conventional methods used to determine the zero-plane displacement and estimate the bed shear velocity were then reviewed and compared. The measured double-averaged (DA) velocity profiles were found to fit well with the log law and defect law with a non-universal Karman constant kappa. kappa-value remains nearly constant and in the range from 0.2 to 0.3 for the long patch (LP) cases and kappa-values are scattered within a wider range from 0.3 to 0.5 for the short patch (SP) cases. While the Br-value in log law remains constant and equal to 8.5 for LP cases, the Br-value was found to decrease with the increase of the dimensionless roughness height k(s)(+) for SP cases. The streamwise turbulence intensity distributions were found to be independent on the patch length and agree well with the available experimental data in the intermediate region and wall region. The Manning resistance coefficient and Darcy-Weisbach friction factor were analyzed. The kappa-value decreases to 0.22 for the fitting of the logarithmic flow resistance law under small relative submergence. The value of the integration constant Ar in the logarithmic law falls within the normal range between 3.25 and 6.25.
ISSN: 1001-6279
DOI: 10.1016/j.ijsrc.2015.04.001
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