Journal ArticleDOI
Initial Instability of Fine Bed Sand
TLDR
In this paper, the initial entrainment characteristics of fine bed sand are objectively defined in terms of the measured distributions of critical instantaneous bed shear stress associated with the observed movement of individual surface grains.Abstract:
The initial entrainment characteristics of fine bed sand are objectively defined in terms of the measured distributions of critical instantaneous bed shear stress associated with the observed movement of individual surface grains. Critical flow conditions are then predicted by equating the lower extremes in these characteristic critical shear stress distributions to the upper extremes in the distribution of instantaneous bed shear stress produced by the particular type of background flow under consideration. The method is applied to the case of two-dimensional channel flow over a flat bed and yields sufficiently consistent results to suggest an extension to Shields' curve for small grain Reynolds numbers. The detailed experimental observations clearly illustrate the important role played by bed region turbulence in the interaction process between the fluid and the mobile bed grains constituting the deformable boundary.read more
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Journal ArticleDOI
Monitoring the inception of sediment transport by image processing techniques
TL;DR: A non intrusive device to detect the inception of sediment transport and to measure bed load in low-submergence flows is presented and counts the number of grains and evaluates their velocity.
Journal ArticleDOI
Spatial Scales of Turbulent Flow Structures Associated With Interacting Barchan Dunes
Nathaniel Bristow,Gianluca Blois,James L. Best,Kenneth T. Christensen,Kenneth T. Christensen +4 more
Journal ArticleDOI
Effect of Bed Surface Structure on Spherical Particle Stability
C. O. Chin,Y. M. Chiew +1 more
TL;DR: In this paper, the effect of bed surface structure on the rolling stability of a cohesionless spherical particle was investigated in terms of the vertical and horizontal orientation of the bed surface, and a theoretical analysis based on the balance of driving and resisting moments about a pivot point was presented.
Journal ArticleDOI
Active interactions between turbulence and bed load: Conceptual picture and experimental evidence
TL;DR: In this article, the same spatial and temporal scales were employed to measure the kinematic properties of flowing water and sediments, and the obtained results are integrated into a conceptual picture attempting to bridge previous depictions of the bed-load transport mechanics.
Journal ArticleDOI
Entrainment of sediment particles by retrograde vortices: Test of hypothesis using near-particle observations
Fu-Chun Wu,Wu-Rong Shih +1 more
TL;DR: In this paper, the authors used the shifted-time cumulative quadrant fraction approach to detect particle entrainment at a near-particle measurement spot using laser Doppler velocimetry (LDV).