Spectral behavior of gravel dunes

Qin, Jie; Wu, Teng; Zhong, Dan

doi:10.1016/j.geomorph.2014.12.023

Cited by 8 publications

(11 citation statements)

References 62 publications

(103 reference statements)

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“…Because the smaller scaling region represents the grain structures, Qin et al. () suggested that D I can be viewed as the upper limit of the grain structure, and it is expected to be within an order of magnitude of d 84 . In this study, d 84 of the bed surfaces is 33.5 mm, and the mean value of D I for t >25 h: D I =9.9 d 84 is close to the range suggested by Qin et al.…”

Section: Resultssupporting

confidence: 90%

“…In this study, d 84 of the bed surfaces is 33.5 mm, and the mean value of D I for t >25 h: D I =9.9 d 84 is close to the range suggested by Qin et al. (). The scaling exponents of the two scaling regions of bed profiles are shown in Figure .…”

Section: Resultssupporting

confidence: 86%

“…The values of β 1 and β 2 at equilibrium are within the ranges suggested by Qin et al. (). The similar trends of D I , β 1 and β 2 indicate that the 1D morphology of the gravel bed reaches an equilibrium state when t ⩾25 h.…”

Section: Resultsmentioning

confidence: 99%

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Evolution of gravel surfaces in a sediment‐recirculating flume

Qin

Zhong

et al. 2017

Earth Surf Processes Landf

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The assumption of the equilibrium state of gravel surfaces in flume experiments under feeding or recirculating conditions is generally justified by three equilibrium criteria based on sediment transport, slopes, and bed features. When these parameters become stable, an experiment is expected to reach equilibrium. This equilibrium state, however, is based on a one‐dimensional model, the Exner equation, which may not truly reflect the equilibrium state of the system considering the complex flow and sediment processes. In this paper, the evolutionary process of a gravel surface is investigated based on a large‐scale recirculating flume experiment. The performances of the three equilibrium criteria are evaluated first, and then the evolution of the bed morphology is studied. The key findings include the following: (1) the sediment transport rate, slopes of water and bed surfaces, and one‐dimensional morphological features reach equilibrium roughly simultaneously; (2) two‐dimensional morphology continually evolves after these characteristics reach equilibrium, which is confirmed by the characteristics of the sediment transport process; and (3) the results from a numerical simulation suggest that a much longer time is required to reach an equilibrium state. Our results suggest that sufficient experimental time is required to investigate the equilibrium morphological characteristics of gravel surfaces, which is much longer than the equilibrium time reflected by the one‐dimensional equilibrium criteria. Copyright © 2017 John Wiley & Sons, Ltd.

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Section: Resultssupporting

confidence: 90%

Section: Resultssupporting

confidence: 86%

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Evolution of gravel surfaces in a sediment‐recirculating flume

Qin

Zhong

et al. 2017

Earth Surf Processes Landf

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“…Thus it is difficult to distinguish a specific kind of bedform; therefore, investigation of the effects of bedforms on flow characteristics is hard and complicated in coarse-bed streams (e.g., Radecki-Pawlik et al 2006, Carling and Shvidchenko 2002, Dey 2014. Also, typology and kinetic behavior of gravel-bed forms are not well understood at all (Qin et al 2015). Some studies have been conducted in gravel-bed streams to understand the effects of gravel size on turbulence intensity and Reynolds stress (e.g., Dey and Raikar 2007).…”

Section: Introductionmentioning

confidence: 99%

Flow Characteristics over a Gravel Bedform: Kaj River Case Study

Maddahi¹,

Afzalimehr

Rowiński

2016

Acta Geophys.

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“…sum of k s,pred for a given DEM) on the choice of mother wavelet and the k value in the roughness correlation. Various mother wavelets from the Daubechies family have been used when applying wavelet transform to river bed topography (Nyander et al, 2003;Gutierrez et al, 2013;Qin et al, 2015), and for the same k value, these mother wavelets yield similar results. The values of Σk s,pred are more sensitive to the choice of k. If standard deviation is used as the estimate of k, whilst changing Ψ, there is a relatively similar pattern of Σk s,pred .…”

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confidence: 99%

Short communication: Multiscalar drag decomposition in fluvial systems using a transform-roughness correlation (TRC) approach

Adams

Zampiron

2020

Preprint

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Abstract. In natural open-channel flows over complex surfaces, a wide range of superimposed roughness elements may contribute to flow resistance. Gravel-bed rivers present a particularly interesting example of this kind of multiscalar flow resistance problem, as both individual grains and bedforms can potentially be important roughness elements. In this paper, we propose a novel method of estimating the relative contribution of different physical scales of river bed topography to the total drag, using a transform-roughness correlation (TRC) approach. The technique, which requires only a single longitudinal profile, consists of (1) a wavelet transform which decomposes the surface into roughness elements occurring at different wavelengths, and (2) a `roughness correlation' that estimates the drag associated with each wavelength based on its geometry alone, expressed as ks. We apply the TRC approach to original and published laboratory experiments and show that the multiscalar drag decomposition yields estimates of grain- and form-drag that are consistent with estimates in channels with similar morphologies. Also, we demonstrate that the roughness correlation may be used to estimate total flow resistance via a conventional equation, suggesting that it could replace representative roughness values such as median grain size or the standard deviation of elevations. An improved understanding of how various scales contribute to total flow resistance may lead to advances in hydraulics as well as channel morphodynamics.

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Spectral behavior of gravel dunes

Cited by 8 publications

References 62 publications

Evolution of gravel surfaces in a sediment‐recirculating flume

Evolution of gravel surfaces in a sediment‐recirculating flume

Flow Characteristics over a Gravel Bedform: Kaj River Case Study

Short communication: Multiscalar drag decomposition in fluvial systems using a transform-roughness correlation (TRC) approach

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