Evaluation of the saltation process of bed materials by video imaging under altered bed roughness

Abstract

The purpose of this paper is to examine the nature of particle saltation and movement over the beds of fixed roughness from flume experiments. A series of experiments are carried out to study the saltation of individual sand particles of different sizes over rough beds under different flow conditions. A 3‐D acoustic Doppler velocimeter is used to record the fluid velocity components; subsequently, under different flow conditions, the images of released sand particles are recorded using high‐speed video imaging technique. Systematic analysis is made with regard to the forces acting on the grains and the variation of their magnitudes along the saltation trajectories of the grains. Relations between the saltation parameters, flow intensity and bed roughness are developed. The distributions of the angle of orientations during a single saltation follows almost a Gaussian distribution. The shape of the Gaussian distribution depends on the particle size and bed roughness. Particle collisions with rough beds and the resulting coefficients of restitution are also discussed. A theoretical framework is developed to compute the mean particle velocity considering the spin in the energy balance equation. Results of the detailed analysis using the imaging technique are much better than in previously reported studies. Copyright © 2013 John Wiley & Sons, Ltd.

Taking the river inside: Fundamental advances from laboratory experiments in measuring and understanding bedload transport processes

“…1D) can also be used to estimate particle velocities, wait times, and transport distances (e.g., Roseberry et al, 2012). Videos from the flume side (downstream transect) have been used to measure dune migration (Nelson et al, 2011) and particle saltation velocities, heights, and lengths (e.g., Lajeunesse et al, 2010;Chatanantavet et al, 2013; see Bhattacharyya et al, 2013 for a review). Some potential limitations for video analysis of bedload transport include the following: (i) very high transport rates often cannot be measured because of problems identifying individual grains; (ii) planview videos only capture surface sediment transport; and (iii) sideview videos capture limited spatial variation in bedload transport.…”

Validating a universal model of particle transport lengths with laboratory measurements of suspended grain motions

“…[] and Bhattacharyya et al . [] investigated trajectories of saltating particles and measured particle velocity as well as surface density of moving particles where the later also varied bed roughness by gluing different grain sizes on the fixed bed. In addition to fixed bed investigations, particle saltation has been studied over mobile beds [ Fernandez‐Luque and van Beek , ; Van Rijn , ; Niño and Garcia , ] resulting in numerous empirical as well as parameterized models describing particle saltation characteristics (saltation height, length, velocity, and acceleration) as a function of flow and sediment conditions.…”

“…Francis [1973] was the first to study single particle motion over fixed bed by recording images of saltating particles at a rate of 40 fps followed by Abbott and Francis [1977], Drake et al [1988], , Lee and Hsu [1994], and later Niño and Garcia [1998] who applied a high-speed video system recording images at a rate of 250 fps which enabled them to expose particle resting time between successive saltations, particle reentrainment into saltation and particle rotation and associated traverse motion of the particles during successive hops. More recently, Lajeunesse et al [2010] and Bhattacharyya et al [2013] investigated trajectories of saltating particles and measured particle velocity as well as surface density of moving particles where the later also varied bed roughness by gluing different grain sizes on the fixed bed. In addition to fixed bed investigations, particle saltation has been studied over mobile beds [Fernandez-Luque and van Beek, 1976;Van Rijn, 1984; resulting in numerous empirical as well as parameterized models describing particle saltation characteristics (saltation height, length, velocity, and acceleration) as a function of flow and sediment conditions.…”

Estimating the Bed-Load Layer Thickness in Open Channels by Tsallis Entropy

“…Six laboratory data sets collected from the literature are adopted in this study to check the accuracy of the expression derived by the Tsallis entropy (Equation (12)). These include Sekine and Kikkawa [ 31 ], a smooth bed studied by Hu and Hui [ 29 ], a rough bed studied by Hu and Hui [ 30 ], Sumer et al [ 32 ], Lee et al [ 33 ] and Bhattacharyya et al [ 34 ]. The laboratory data sets of the thickness of the bed-load layer are fairly limited, possibly because there could be measurement limitations in tracking the entire process of the saltation of the particles on the bed in the experiment [ 1 ].…”