Numerical Simulations on Response of Dune Bedforms to Flow Variability

Yamaguchi, Satoshi; Giri, Sanjay; Nelson, Jonathan M.; Shimizu, Yasuyuki; Funaki, Jungo

doi:10.2208/jscejhe.71.i_1015

Cited by 1 publication

(1 citation statement)

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“…For modeling many unsteady morphodynamic problems, knowledge of mean particle motion and travel lengths are required as is information about the distribution of particle lengths. An examples is the class of models describing the growth and instability of bed forms, in particular regime transition from dune to upper stage plane bed [e.g., Giri and Shimizu , ; Shimizu et al ., ; Nelson et al ., ; Naqshband et al ., ; Van Duin , ; Yamaguchi et al , ]. Nonequilibrium sediment transport is modeled within these studies by entrainment and deposition functions related to each other through a lag distance.…”

Section: Resultsmentioning

confidence: 99%

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

Naqshband

McElroy

Mahon

2017

Water Resources Research

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The mechanics of sediment transport are of fundamental importance for fluvio‐deltaic morphodynamics. The present study focuses on quantifying particle motions and trajectories across a wide range of flow conditions. In particular, a continuous model is presented that predicts particle travel distances for saltation and suspension based on Rouse number and relative grain roughness. By utilizing a series of eight video cameras in a plexiglass flume direct measurements of the distributions of particle travel distances (excursion lengths) were obtained. To this end, experiments were carried out in dark under black lights with fluorescent painted plastic and quartz sand particles. For relatively high Rouse numbers indicating bed load dominant transport regime ( bold-italicP≥2.5), particle motion is governed by the effect of gravitational forces (settling velocities) and measured excursion lengths closely follow a Gaussian distribution. For bold-italicP=2.5, particle motion is equally subjected to both gravitational and turbulent forces. Consequently, measured excursion lengths exhibit a bimodal distribution with two distinct peaks. As turbulent fluctuations increase and dominate particle motion over gravity ( bold-italicP<2.5), distributions of excursion lengths become unimodal and negative‐skewed with mean values deviating from the modes. The predicted trend of linearly increasing excursion lengths with decreasing Rouse numbers is consistent with measured excursion lengths across a wide range of Rouse numbers true(bold-italicP=1.8−8.9). Furthermore, measured excursion lengths are observed to fit within the predicted range of excursion lengths with no significant difference between measured excursion lengths of plastic and quartz sand particles.

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