Smartrock Transport From Seconds to Seasons: Shear Stress Controls on Gravel Diffusion Inferred From Hop and Rest Scaling

Pretzlav, Kealie Lynn Goodwin; Johnson, J. P.; Bradley, D. Nathan

doi:10.1029/2020gl091991

Cited by 11 publications

(10 citation statements)

References 54 publications

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“…For example, some studies (Heyman et al 2013) have suggested an exponential distribution of resting times and thus a similar entrainment condition to the deposition condition (a Poisson process). As a comparison, there are other studies (Martin et al 2012;Martin, Purohit & Jerolmack 2014;Fraccarollo & Hassan 2019;Liu et al 2019;Pretzlav, Johnson & Bradley 2021) suggesting a power-law-like distribution for the resting times, although a simple form of the entrainment condition is not available yet. It is noted that, by incorporating other physical processes like the burial and exhumation of particles during their streamwise transport (Wu et al 2019a,b), the power-law-like resting time distribution can be recovered which consequently induces the anomalous diffusion of bedload particles.…”

Section: Discussionmentioning

confidence: 99%

“…2012; Martin, Purohit & Jerolmack 2014; Fraccarollo & Hassan 2019; Liu et al. 2019; Pretzlav, Johnson & Bradley 2021) suggesting a power-law-like distribution for the resting times, although a simple form of the entrainment condition is not available yet. It is noted that, by incorporating other physical processes like the burial and exhumation of particles during their streamwise transport (Wu et al.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Theoretical analysis for bedload particle deposition and hop statistics

Jiang

Zeng

et al. 2023

J. Fluid Mech.

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Understanding the statistics of bedload particle motions is of great importance. To model the hop events which are defined as trajectories of particles moving successively from the start to the end of their motions, recently, Wu et al. (Water Resour. Res., vol. 56, 2020, p. e2019WR025116) have successfully performed individual-based simulations according to the Fokker–Planck equation for particle velocities. However, analytical solutions are still not available due to (i) difficulties in treating the velocity-dependent diffusivity, and (ii) a knowledge gap in incorporating the termination of particle motions for the equation. To tackle the above-mentioned challenges, we first specify a Robin boundary condition representing the deposition of particles. Second, for analytical solutions of hop statistics, a variable transformation is devised to deal with the velocity-dependent diffusivity. The original bedload transport problem is thus found to be governed by the classic equation for the solute transport in tube flows with a constant diffusivity after the transformation. Finally, through solving the spatial and temporal moments of the governing equation, we investigate the influence of the deposition rate on three key characteristics of particle hops. Importantly, we have related the deposition rate to the mean travel times and hop distances, enabling a direct determination of this physical parameter based on measured particle motion statistics. The analytical solutions are validated by experimental observations with different bedload particle diameters and transport conditions. Based on the limited experimental datasets, the deposition frequency is shown to decrease as the shear stress increases when the flow rate is not small.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Theoretical analysis for bedload particle deposition and hop statistics

Jiang

Zeng

et al. 2023

J. Fluid Mech.

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“…Previous work has shown that bedload transport depends on flow strength and is highly stochastic (Ancey, 2010; Ancey et al., 2008; Einstein, 1937, 1950; Gomez et al., 1989; Hassan et al., 1991; Paintal, 1971; Pierce & Hassan, 2020b; Singh, Fienberg, et al., 2009; Singh, Lanzoni, & Foufoula‐Georgiou, 2009; Singh et al., 2010). Although several proposed theories of stochastic sediment transport have reproduced a number of statistical properties of bedload transport and particle movement (Ancey, 2010; Ancey et al., 2008; Church & Hassan, 1992; Einstein, 1937, 1950; Furbish et al., 2012; Ganti et al., 2009, 2010; Hassan et al., 1991; Paintal, 1971; Pierce & Hassan, 2020a; Pretzlav et al., 2021; Roseberry et al., 2012; Wong et al., 2007), a more rigorous validation of these models is still lacking for the range of transport conditions observed in nature, including a varying hydrograph and evolving bed topography.…”

Section: Introductionmentioning

confidence: 99%

Experimental Observations of Bedload Tracer Movement: Effects of Mixed Particle Sizes and Bedforms

Singh

Wilcock

et al. 2023

Water Resources Research

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Predicting the transport of bedload tracer particles is a problem of significant theoretical and practical interest. Yet, little understanding exists for transport in rivers in the presence of bedforms, which may trap grains and thereby influence travel distance. In a series of flume experiments with a sandy gravel bed in a large experimental flume, bed elevation and tracer travel distances were measured at high resolution for a range of discharges. As discharge increased, bedform height increased and bedform length decreased, increasing bedform steepness. For all tracer sizes and flow conditions, bedforms act as primary controls on the tracer travel distances. Bedform trapping increases linearly with the ratio of bedform height to tracer grain size, with 50% trapping efficiency for a ratio of two and 90% trapping efficiency for a ratio of four. A theoretical model based on the extended active layer formulation for sediment transport is able to capture much of the distribution of measured travel distances for all tracer sizes and discharges, providing a first connection between tracer transport theory and bedform trapping and indicating normal diffusion of tracers at relatively small timescales. Variable bedform geometry can influence trap efficiency for individual bedforms and the theoretical model can help identify “preferential trapping” conditions. The distribution of tracer travel distances for a mixture of grain sizes and variable discharge, as expected in natural rivers, displays heavy tail characteristics.

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“…During particle movement, the embedded sensors record its acceleration data, which are transformed to the exerted forces by multiplying the particle mass. This new approach has been applied to measurement of impact force of test debris on infrastructures (Shafiei et al, 2016; Spreitzer et al, 2019), monitoring river bed scour and sediment transport (Pretzlav et al, 2020, 2021; Stephenson & Abazović, 2016), and particle entrainment mechanics (AlObaidi & Valyrakis, 2021; Frank et al, 2015; Maniatis et al, 2017, 2020). Use of instrumented accelerometers to measure the inertial forces exerted on target particle is distinctly different from the previously invasive methods.…”

Section: Introductionmentioning

confidence: 99%

Direct measurement of the inertial drag and lift forces on entrained coarse particles at various protrusion heights

Xie

Melville

Shamseldin

et al. 2022

Earth Surf Processes Landf

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Laboratory experiments were performed to study the impact of relative particle protrusion P/D (P is the protrusion height and D is the diameter of the spherical target particle) on the entrainment of sediment particles from a rough bed of spherical grains. The target particle to be entrained was instrumented with electronic sensors to measure the triaxial linear acceleration, and consequently the particle inertial forces, during the entrainment process. The velocity field around the particle was obtained using two-dimensional particle tracking velocimetry (PTV) technique and the velocity data were synchronised with the force data relative to the moment of entrainment. Experimental results show that the inertial drag and lift forces systematically decreased as relative particle protrusion increased. The ratio of inertial lift force to drag force revealed that drag force slightly dominated the entrainment process at P/D > 0.7, while lift force slightly dominated at P/D < 0.62. Inertial drag coefficient was found to be independent of particle protrusion for low P/D, but rapidly declined for P/D > 0.62-0.7. Differently, inertial lift coefficient remained relatively constant within the tested protrusion ranges. Additionally, the critical Shields number was linearly related to the normalised inertial forces over the present particle protrusion range. In summary, the particle protrusion demonstrates a significant impact on the inertial forces and, further, the entrainment process.

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Smartrock Transport From Seconds to Seasons: Shear Stress Controls on Gravel Diffusion Inferred From Hop and Rest Scaling

Cited by 11 publications

References 54 publications

Theoretical analysis for bedload particle deposition and hop statistics

Theoretical analysis for bedload particle deposition and hop statistics

Experimental Observations of Bedload Tracer Movement: Effects of Mixed Particle Sizes and Bedforms

Direct measurement of the inertial drag and lift forces on entrained coarse particles at various protrusion heights

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