Quantifying the Dynamic Evolution of Graded Gravel Beds Using Particle Tracking Velocimetry

Heays, KG; Friedrich, Heide; Melville, Bruce W.; Nokes, Roger

doi:10.1061/(asce)hy.1943-7900.0000850

Cited by 22 publications

(20 citation statements)

References 30 publications

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“…The flume is an 11.9 m long, 0.38 m deep and 0.44 m wide glass-sided open channel, with water and sediment recirculating capacity. A 1.1 m long acrylic sheet of 4 mm thickness is placed on the water surface to reduce refraction and the occurrence of water surface waves, as suggested by Heays et al (2014) and Fathel et al (2015). The camera is placed 0.44 m above the initial sand bed level and the field of view covers the width of the flume.…”

Section: Instrumentationmentioning

confidence: 99%

Sand particle velocities over a subaqueous dune slope using high‐frequency image capturing

Scheltinga

Coco

Friedrich

2019

Earth Surf Processes Landf

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This work presents measurements and analysis of sand particle velocities over a subaqueous dune with median sand diameter of 0.85 mm. Time‐lapse images of the mobile bed and an automated particle image velocimetry (PIV)‐based cross‐correlation method are used to obtain mean velocity of sand particles. This technique is shown to be consistent with measurements obtained with manual tracing. The measurements indicate an increase in mean particle velocity over a dune slope. Three regions are distinguished over the dune slope: (1) region of fluctuating particle velocity, (2) region of increasing particle velocity, and (3) region of maximum particle velocity. The observations are aligned with experimental and numerical modelling studies, indicating fluctuations in flow velocity over a dune stoss slope. We furthermore show that the standard deviation of the mean particle velocity is affected by the slope location and decreases from the lower slope towards the upper slope. The particle velocity variability is discussed in the context of general onset and cessation of sediment transport, the effect of the reattachment zone, sweep‐transport events, and the existence of superimposed bedforms. With this work we bridge the gap between measurements of bedload transport at the particle‐scale and at the bedform‐scale. © 2019 John Wiley & Sons, Ltd.

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Section: Instrumentationmentioning

confidence: 99%

Sand particle velocities over a subaqueous dune slope using high‐frequency image capturing

Scheltinga

Coco

Friedrich

2019

Earth Surf Processes Landf

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“…The former approach follows objects as they move, while the latter explores the process dynamics at prescribed locations. In the context of bed load sediment transport the two approaches correspond to following the trajectories of solid particles (e.g., Ancey et al, 2002;Campagnol et al, 2013;Fathel et al, 2015;Heays et al, 2014;Lajeunesse et al, 2010) and to characterizing the sediment transport properties at some place (e.g., Böhm et al, 2004;Garcia et al, 2007;Nelson et al, 1995;Radice et al, 2010Radice et al, , 2013, respectively. Typically, the Lagrangian approach is mostly used when dispersion of tracer particles comes into play (e.g., Campagnol et al, 2015;Fan et al, 2016;Fathel et al, 2016;Hassan et al, 2013;Lisle et al, 1998;Martin et al, 2012;Nikora et al, 2001Nikora et al, , 2002, whereas the Eulerian approach is employed for the investigation of sediment fluxes (e.g., Ballio et al, 2014;Cohen et al, 2010;Frey et al, 2003;Furbish, Haff, et al, 2012;Radice, 2009;Singh et al, 2009;Turowski, 2010).…”

Section: Introductionmentioning

confidence: 99%

Lagrangian and Eulerian Description of Bed Load Transport

et al. 2018

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Sediment particles transported as bed load undergo alternating periods of motion and rest, particularly at weak flow intensity. Bed load transport can be investigated by either following the motion of individual particles (Lagrangian approach) or observing the phenomenon at prescribed locations (Eulerian approach). In this paper, the Lagrangian and Eulerian descriptions are merged into a unifying framework that includes definitions for quantities used to describe the kinematics of particle motion, as well as the relationships among these quantities. The alternation of motion and rest is represented by two complementary descriptions: (i) proportion of motion, indicating either the relative time spent in motion by an individual particle or the relative number of moving particles; (ii) persistence of motion, indicating the extent to which the process consists of relatively few long periods of motion or of many short ones. The framework only involves first moments of the key quantities. The conceptual developments are tested against results from an experiment with weak bed load transport, demonstrating the soundness of the approach. From an operational point of view, a Lagrangian observation is difficult to perform, since the particle motion is usually investigated for finite spatial domains (e.g., a measurement window within a laboratory or natural reach). Strategies to overcome such limitations are described, suggesting the possibility of obtaining unbiased mean values for Lagrangian descriptors. The proposed framework can be used in any study aimed at parameterizing the kinematic properties of bed load particles as functions of the hydrodynamic conditions.

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“…Field studies inherently lack of a continuous record of particle locations that is needed to evaluate the diffusive character at different stages of particle motion. Even if this has now been made possible at the laboratory scale, the areal extent of the observed bed surface is usually restrained to a scale of tens of centimeters due to equipment constraints for image acquisition (Heays et al, ; Lajeunesse et al, ; Nikora et al, ; Tregnaghi, Bottacin‐Busolin, Tait, et al, ), thus the motions of particles that enter or leave the video sampling area are spatially censored (Fan et al, ; Fathel et al, ). Accurate reconstruction of particle trajectories is dependent on the frequency of the image acquisition, as a higher frame rate can support more accurate measurement of grain trajectories.…”

Section: Introductionmentioning

confidence: 99%

Diffusive Regimes of the Motion of Bed Load Particles in Open Channel Flows at Low Transport Stages

Cecchetto

Tregnaghi

Bottacin‐Busolin

et al. 2018

Water Resources Research

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The stochasticity of fluid and sediment parameters has been identified as a source of diffusion, particularly anomalous diffusion at different temporal and spatial scales of bed load particle trajectories. Data from two sets of flume experiments are presented, one data set has gravel particle trajectories tracked over a limited area and was used in identifying the influence of different shear stress conditions on diffusive processes. A new experiment was performed using spherical particles moving as bed load in an annular flume in order to address concerns about censorship effects caused by the size of the detection window. An annular flume allowed collection of practically uncensored particle trajectories over longer time period than has been previously possible in the laboratory. Three diffusive regimes were observed at distinct stages of particle motion: (i) ballistic regime at the local range; (ii) Fickian diffusion at the intermediate range; (iii) subdiffusion at the global range. Characteristic time scales separate the regimes and correlate with the mean traveling and resting times of particles. Fickian diffusion in the intermediate range is first recognized as a result of the balance between intermittent weak transport and near‐bed turbulence, as first predicted by Nikora et al. (2002, https://doi.org/10.1029/2001WR000513). In the global range, extreme values were observed in the distribution of particle resting times, suggesting that two types of distributions (related to surface motion and vertical mixing) were responsible for the subdiffusion at longer time scales. Diffusion was found to be anisotropic at all stages of particle motion.

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Quantifying the Dynamic Evolution of Graded Gravel Beds Using Particle Tracking Velocimetry

Cited by 22 publications

References 30 publications

Sand particle velocities over a subaqueous dune slope using high‐frequency image capturing

Sand particle velocities over a subaqueous dune slope using high‐frequency image capturing

Lagrangian and Eulerian Description of Bed Load Transport

Diffusive Regimes of the Motion of Bed Load Particles in Open Channel Flows at Low Transport Stages

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