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This paper aims to explore the combined main flow and turbulence influence on sediment pickup rates by investigating four purposely devised cases, namely, (1) unobstructed flow over a plane bed; (2) unobstructed flow over a rigid‐dune bed; (3) flow obstructed by a horizontal pipe; and (4) flow obstructed by a vertical pipe. The four cases were used to represent typical scenarios of mean flow combined with turbulence of varying intensities. By analyzing the dependence of sediment pickup rate on different combinations of the mean and turbulent flow parameters, a modified densimetric Froude number, incorporating both the bulk‐averaged velocity and maximum root‐mean‐square value of the fluctuating velocity, is found to be reasonably correlated with the measured pickup rates for all the four cases. Consequently, by relating the pickup rate with the dimensionless particle diameter and the modified densimetric Froude number, a generalized equation that predicts the pickup rates under both unobstructed as well as obstructed flow conditions is obtained. [ABSTRACT FROM AUTHOR]

Deals with a study which measured the mean and turbulence characteristics in a non-uniform open-channel flows using a three-dimensional acoustic Doppler velocimeter. Flow equilibrium condition; Horizontal velocity distribution; Reynolds stress distribution.

This study investigates the mechanism and the characteristic parameters affecting local scour around a vertical pile caused by turbulent circular wall jets. There are two basic scouring mechanisms: the pile obstruction and the jet diffusion mechanisms. The former is dominated by a horseshoe vortex system while the latter is controlled by the bed shear stress as the jet diffuses into the flow. Four types of equilibrium scour hole profiles were identified. The criteria for each type of profile are classified in terms of the densimetric Froude number Fo and the relative impingement distance X i /d o. Semiempirical equations were developed to delineate the boundary limits for the different profiles. The results show that the maximum equilibrium scour depth d se and the scour depth at the pile d pe are highly dependent on Fo ; and generally for large Fo , d se =d pe. The scour depths are insensitive to the relative size of the pile to jet diameter D /d o. However, X i /d o does not appear to affect d se /d o but it has a profound influence on d pe /d o. [ABSTRACT FROM AUTHOR]