Fine sediment dynamics in unsteady open-channel flow studied with acoustic and optical systems

Bagherimiyab, Fereshteh; Lemmin, Ulrich

doi:10.1016/j.csr.2012.04.014

Cited by 7 publications

(2 citation statements)

References 39 publications

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“…Cellino and Lemmin [] also demonstrated, through direct profile measurements, that the bursting cycles played an important role in sediment suspension. An Acoustic Doppler Velocity Profiler combined with particle tracking velocimetry (PTV) was used for sediment particle tracking in Bagherimiyab and Lemmin []. Their results further showed the role of coherent structures on particle motion and the development of bed forms.…”

Section: Introductionmentioning

confidence: 99%

Quantification of the bed load effects on turbulent open‐channel flows

Liu

et al. 2016

JGR Earth Surface

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With a computational model combining large eddy simulation and a discrete element model, detailed quantification of the bed load effects on turbulent open‐channel flows is presented. The objective is the revelation of bed load particle impact on the mean flow properties and coherent structures. Two comparative numerical experiments with mobile and immobile beds are conducted. Mean properties (e.g., velocity and Reynolds stress profiles) show good agreement with experimental data. Comparing the mobile and immobile cases, the effective bed position is nearly the same, whereas the equivalent sand roughness is changed. The flow experiences higher bottom shear stress over immobile bed. To quantify impact on turbulent structures, a revised quadrant analysis is performed to calculate four key parameters of ejection and sweep events (duration, maximum shear stress, transported momentum, and period). Results show that the ejection and sweep events have comparable importance in the outer region. However, sweep becomes dominant in the near‐wall region. The motion of particles enhances the sweep dominance by breaking up the ejection structures and decreasing their occurrence ratio. The results also suggest that the ejection events are easier to be influenced by the particle motions because they originate from the near‐wall region. The duration, maximum shear stress, and transported momentum decrease close to the bed. The period remains relatively constant in the outer region but decreases near the bed. Visualization of the coherent structure reveals that the instantaneous particle motion has strong correlation with the bursting cycle events.

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Section: Introductionmentioning

confidence: 99%

Quantification of the bed load effects on turbulent open‐channel flows

Liu

et al. 2016

JGR Earth Surface

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“…To achieve this at high resolution, the most recent implementations of this technique use bistatic pulse‐coherent Doppler profilers. These instruments can resolve the turbulent bottom boundary layer, from a distance of ∼1 m such that they do not disturb the flow itself [ Bagherimiyab and Lemmin , ; Hay et al , , ; Naqshband et al , , ]. While the spatial resolution is still inferior to that of optical video imagery (acoustic sampling volumes are of order 1 cm 3 and are collected along a single profile), an advantage of the acoustic technique is that it can be used in turbid water and energetic flows.…”

Section: Introductionmentioning

confidence: 99%

Acoustic observations of near‐bed sediment concentration and flux statistics above migrating sand dunes

Wilson

Hay

2016

Geophysical Research Letters

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A coherent Doppler profiler was used to measure coincident time series of velocity (u,w), sediment mass concentration (c), and sediment grain size (d), above mobile sand dunes in unidirectional flow (∼1 m/s, ∼1 m water depth). The measurements are used to extract statistical distributions of sediment concentration and flux just above the bed. Observed mass fluxes (uc,wc) were well fit by quasi‐exponential distributions, at all positions along the dune profile, similar to previous observations of single‐particle momenta for bed load over flat beds. Observed concentrations of moving particles were well fit by negative‐binomial distributions, also similar to previous observations over flat beds. These probability distributions relate to two recent stochastic theories, previously derived and verified for uniform flow over flat beds. It is hypothesized that these theories may also be used as a local approximation in natural‐scale flows with bed forms.

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Effect of particle concentration on sediment and turbulent diffusion coefficients in open-channel turbulent flow

Pal

Ghoshal

2016

Environ Earth Sci

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Fine sediment dynamics in unsteady open-channel flow studied with acoustic and optical systems

Cited by 7 publications

References 39 publications

Quantification of the bed load effects on turbulent open‐channel flows

Quantification of the bed load effects on turbulent open‐channel flows

Acoustic observations of near‐bed sediment concentration and flux statistics above migrating sand dunes

Effect of particle concentration on sediment and turbulent diffusion coefficients in open-channel turbulent flow

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