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
Flow competence and streambed stability: an evaluation of technique and application
Mark S. Lorang,F. Richard Hauer +1 more
TL;DR: The concept of flow competence has been applied to analyses of streambed stability and generally is based on the assumption that measures of rock size composing the substrata can be used to estimate the magnitude of flow that would mobilize the bed material as mentioned in this paper.
Journal ArticleDOI
Computation of the Particle Basset Force with a Fractional-Derivative Approach
Fabián A. Bombardelli,Fabián A. Bombardelli,Andrea E. González,Andrea E. González,Yarko Niño,Yarko Niño +5 more
TL;DR: A two-stage methodology to deal with the difficulties associated with computing the Basset force is presented, which avoids unnecessary computations by first approximated based on a semiderivative (fractional mathematics), and then the integration time is redefined in terms of appropriate flow and particle time scales.
Journal ArticleDOI
Hydrodynamics of sediment threshold
Sk Zeeshan Ali,Subhasish Dey +1 more
TL;DR: In this paper, a novel hydrodynamic model for the threshold of cohesionless sediment particle motion under a steady unidirectional streamflow is presented, in which the sediment threshold is envisioned as the rolling mode, which is the plausible mode to initiate a particle motion on the bed.
Journal ArticleDOI
A consideration of the dune:antidune transition in fine gravel
TL;DR: In this paper, hydraulic data defining the dune:antidune transition in fine gravel are compared with potential flow theory, and information is drawn from published experiments and field-based studies.
Journal ArticleDOI
Partial entrainment of gravel bars during floods
TL;DR: In this article, the spatial patterns of bed material entrainment by floods were documented at seven gravel bars using arrays of metal washers (bed tags) placed in the streambed.