Microscale Loose-Bed Hydraulic Models

Gaines, Roger A.; Maynord, Stephen T.

doi:10.1061/(asce)0733-9429(2001)127:5(335)

Cited by 9 publications

(3 citation statements)

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“…This finding, and the success of the Waiho model, suggest that the spatial distribution of relative erosion and deposition was, in both cases, controlled by the planform geometry of the river, since this, relative depth and Froude number were the only parameters with similarity between model and prototype. Similar success with very small‐scale mobile‐bed models has been reported by Gaines & Mainord (2001).…”

Section: Examples Of Laminar‐flow Morphologies and Phenomena And Theisupporting

confidence: 83%

Fluvial and submarine morphodynamics of laminar and near-laminar flows: a synthesis

Lajeunesse¹,

Malverti²,

Lancien³

et al. 2010

Sedimentology

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The interaction of flow with an erodible bed in alluvial rivers and deep-sea channels gives rise to a wide range of self-formed morphologies, including channels, ripples, dunes, antidunes, alternate bars, multiple-row bars, meandering and braiding. As the flow is invariably turbulent in field manifestations of these morphologies, there has been a tendency to assume that turbulence is necessary for them to form. While turbulence undoubtedly has an important influence when it is present, it is not necessary for any of these features. Indeed, all of these features can be formed by the morphodynamic interaction of purely laminar or nearly laminar flow with an erodible bed. This paper provides a survey and synthesis of a wide range of laminar or near-laminar flow analogues of morphologies observed in the field. Laminar-flow analogues of turbulent-flow morphologies cannot and should not be expected to satisfy dynamic similarity in terms of all relevant dimensionless parameters. What is of more significance is the convergence of the underlying physics. It is illustrated in this paper that many existing theoretical frameworks for the explanation of turbulent-flow morphodynamics require only relatively minor modification in order to adapt them to laminar flows.

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Section: Examples Of Laminar‐flow Morphologies and Phenomena And Theisupporting

confidence: 83%

Fluvial and submarine morphodynamics of laminar and near-laminar flows: a synthesis

Lajeunesse¹,

Malverti²,

Lancien³

et al. 2010

Sedimentology

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“…A formal physical model of the Waiho fanhead would require a space about 50 m by 50 m; this was not available for the present study, hence a microscale model was used to address the problem (Clarkson, 1999). The methodology of microscale modelling is explained in detail, and its limitations examined, by Gaines and Mainord (2001), who also list a number of microscale modelling investigations by the US Army Corps of Engineers. One of the main uses is to qualitatively predict river bed response to engineering modification -precisely the problem treated herein.…”

Section: Microscale Modellingmentioning

confidence: 99%

Anthropic aggradation of the Waiho River, Westland, New Zealand: microscale modelling

Davies

McSaveney

Clarkson

2003

Earth Surf Processes Landf

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Long-term aggradation of the Waiho River, South Westland, New Zealand, has now raised the head of its alluvial fan to unprecedented elevations. In its natural state the river would, like all other major rivers in the area, be somewhat incised into its fanhead. The only relevant factor able to account for the aggradation is the presence of control banks ('stopbanks' in local parlance) that restrict the ability of the river to move over the whole of its natural fanhead.A 1 : 3333 scale physical hydraulic model (a 'microscale' model) was used to study this situation. An alluvial fan was generated in the model and allowed to develop to equilibrium with steady inputs of water and sediment within boundaries geometrically similar to those of the natural unrestricted Waiho River. The boundaries were then altered to represent the presence of the stopbanks, and the fan allowed to continue evolving under the same water and sediment inputs. The model fanhead aggraded in a spatial pattern similar to that recorded on the Waiho.Taking into consideration the limitations of microscale modelling, these results indicate that the aggradation in the Waiho is a result of the lateral restriction of the river by stopbanks. This poses fundamental questions about the variables that control the behaviour of alluvial fans. The results also suggest that microscale modelling can be used to make reliable quantitative predictions of the effects of engineering works on rivers, in spite of the low level of dynamic similarity with the prototype compared to that in larger-scale models.

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“…When n p = 0.015, n m,c = 0.0536, and m = 0.052, the velocity scale λ v that satisfied the resistance similarity criterion was calculated as 8.987 by Equation (4). The λ v value that satisfied the gravity similarity criterion was calculated as 7.071 by Equation (1).…”

Section: Gravity Similarity Shiftmentioning

confidence: 99%

The Use of a Microscale Physical Model to Simulate Bankfull Discharge in the Lower Reaches of the Yellow River

Zhao

Chen

Wu³

et al. 2019

Water

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Microscale physical models (MSPMs) were once widely used in flood planning in large basins. They fell out of favor but are now being used again. This paper explores the benefits of using such a model for understanding a flood problem on the Lower Yellow River (LYR). We constructed an indoor MSPM of a nearly 800-km reach of the LYR. The model had different scales in the longitudinal, transverse, and vertical directions, and we adjusted the slope of the model. Meanwhile, a real-time water level monitoring system and an automatic flow control system were built on the MSPM to automatically control hydrodynamic testing. Through several discharge experiments, bankfull discharge for multiple MSPM sections was obtained and compared with measured data from the corresponding hydrological section of the prototype during the early flood season of 2016. The comparison demonstrated good linear correlation. The analysis of model similarity showed that although there was some deviation in gravity similarity between the MSPM and the prototype, the model discharge scale derived from resistance similarity adequately described the relationship between the model and the prototype bankfull discharge. Further analysis of the relationship between the model and the prototype bankfull discharge revealed that a split-line line may be better than a single regression line. A MSPM could reproduce the bankfull discharge of the LYR with the nearly 800-km reach in the laboratory which is impossible for a small distortion rate physical model, and obtain a result close to that of the assimilated numerical model.Program-funded evaluation to determine the capabilities and limitations of the MSPM. They found that the model can not only predict the flow pattern trends of river training structure under the influence of navigation and environment, but also explain the river training activities to nonhydraulic experts. Additionally, these benefits provide a timely assessment of navigation plans. Later, the development and application of MSPMs continued, but the USACE began to dispute their use. Consequently, they evaluated MSPMs to determine their capabilities and limitations. Gaines et al. [4] described such an evaluation plan. Smith [2], Davies [5], and Gabriel Echávez et al. [6] evaluated their predictive capacity. They confirmed MSPMs can predict the effect of river engineering to replicate flow processes in the prototype.At present, the river models are dominated by distorted scale in practice. Its main advantage is that it can achieve roughness satisfying resistance similarity, while it is technically impossible in a normal scale physical model with the same horizontal and vertical scale. Research on modeled water flow and sediment movement after distortion has also attracted the attention of many scholars. In 2002, Maynord [7] measured surface velocity using the Vicksburg model. Velocity comparisons showed that flow distribution in the Vicksburg Front MSPM was not similar to the prototype, likely due to model distortions. Li [8] conducted a prelim...

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Microscale Loose-Bed Hydraulic Models

Cited by 9 publications

References 1 publication

Fluvial and submarine morphodynamics of laminar and near-laminar flows: a synthesis

Fluvial and submarine morphodynamics of laminar and near-laminar flows: a synthesis

Anthropic aggradation of the Waiho River, Westland, New Zealand: microscale modelling

The Use of a Microscale Physical Model to Simulate Bankfull Discharge in the Lower Reaches of the Yellow River

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