Gravitational and Shear Instabilities in Compound and Composite Channels

Kolyshkin, Andrei A.; Ghidaoui, Mohamed Salah

doi:10.1061/(asce)0733-9429(2002)128:12(1076)

Cited by 32 publications

(25 citation statements)

References 22 publications

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“…1,2,3,4) An accurate prediction of the conveyance capacity and the velocity and boundary shear distributions in channels and rivers is required for practical engineering problems such as flood reduction measures, flood plain management, river restoration and control of sediment and pollutant transport in rivers. 5,6) In the present work, we focus on the case of a mixing layer excited by a velocity inflection in an open-channel flow. Such transverse shear flows are observed for example in partially vegetated channels, in composite channels, in inflows at channel junctions or in channels where the bottom roughness varies laterally.…”

Section: Introductionmentioning

confidence: 99%

“…Succeeding Michalke, 10,11) stability analyses of shear layers with the consideration of effects of bed friction, gravity and kinematic eddy viscosity have been performed, 6,7,8,9,12,13,14,15) mostly for the timely-growing case. In the present study, the flow configuration of Lima and Izumi 15,17) is modified to consider spatially growing disturbances.…”

Section: Introductionmentioning

confidence: 99%

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Spatial Linear Stability Analysis of Open-Channel Flows With Transverse Shear Revisited

Lima

Izumi

2016

JJSCE B1

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Based upon the shallow water equations, linear stability analysis is conducted on an open-channel flow with velocity retardation on one side. The analysis is applied to a steady turbulent base flow which is characterized by a sub-depth scale turbulence derived from a logarithmic profile of vertical velocity. The linear stability analysis is performed for the case of spatially growing disturbances and compared to the case of temporally growing disturbances. We found that discrepancies between results from the spatial and the temporal approaches were less relevant when the bed friction effect and the kinematic eddy viscosity effect were more significant.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Spatial Linear Stability Analysis of Open-Channel Flows With Transverse Shear Revisited

Lima

Izumi

2016

JJSCE B1

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“…2 The shear layer in the lateral velocity profile has been determined to be the major factor in the generation of instabilities in these transverse shear flows. 1 In addition, the degrees of influence of the bed-friction 2 and gravity 5,6 also play important roles in the stability of these flows. The turbulence due to the bed friction may either enhance or damp the transverse motions.…”

Section: Introductionmentioning

confidence: 99%

“…2 The gravity effect plays a stabilizing effect on the shear layer, though at large Froude numbers a gravity instability independent of the shear layer is generated. 5,6 The stability characteristics of open channel flows with transverse shear have been studied by means of a linear stability analysis by a number of authors. Some of the major differences among these works can be regarded as the use 1, 2, 7,8 or not 4-6, 9, 10 of the inviscid flow assumption, and the use 1, 2, 4, 7-9 or not 5,6,10 of the rigid-lid assumption.…”

Section: Introductionmentioning

confidence: 99%

“…5,6 The stability characteristics of open channel flows with transverse shear have been studied by means of a linear stability analysis by a number of authors. Some of the major differences among these works can be regarded as the use 1, 2, 7,8 or not 4-6, 9, 10 of the inviscid flow assumption, and the use 1, 2, 4, 7-9 or not 5,6,10 of the rigid-lid assumption. Under the inviscid flow assumption, the perturbation equations in these studies are reduced to modified Rayleigh equations, while the formulations with turbulence viscosity lead to modified Orr-Sommerfeld equations.…”

Section: Introductionmentioning

confidence: 99%

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On the nonlinear development of shear layers in partially vegetated channels

Lima

Izumi

2014

Physics of Fluids

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Development of a wall shear stress integral measurement and analysis system for two-phase flow boundary layers Rev. Sci. Instrum. 77, 105103 (2006) A predictive theory is developed to investigate the nonlinear instability regime of perturbed shear layers in open-channel flows with lateral vegetation. The turbulence is characterized by two distinct scales: a sub-depth turbulence which is associated with the bed shear stress and a large-scale turbulence associated with the large horizontal eddies which develop in the shear layer. The sub-depth turbulence is modeled by assuming a logarithmic vertical distribution of the velocity. Meanwhile, an analogous model for the large-scale turbulence requires the estimation of the transverse velocity profile in the nonlinear state because the growth of the large-scale disturbances expands the shear layer and modifies the velocity distribution across the channel. The nonlinear growth of the disturbances is limited, however, because solid boundaries in the channel play stabilizing mechanisms which lock the amplitude of the large-scale disturbances into a finite-equilibrium state, for which a corresponding transverse velocity profile is determined. A weakly nonlinear stability analysis is performed and the results are validated using experimental data from previous works. C 2014 AIP Publishing LLC. [http://dx

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Transport of suspended sediments under the influence of bank macro‐roughness

Juez

Bühlmann

Maechler

et al. 2017

Earth Surf Processes Landf

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River restoration works often include measures to promote morphological diversity and enhance habitat suitability. One of these measures is the creation of macro-roughness elements, such as lateral cavities and embayments, in the banks of channelized rivers. However, in flows that are heavily charged with fine sediments in suspension, such as glacier-fed streams and very low-gradient reaches of large catchment rivers, these lateral cavities may trap these sediments. Consequently, the morphological changes may be affected, and the functionality of the restoration interventions may be compromised. Herein, we analyse the influence of these macro-roughness elements on the transport of fine sediments in the main channel. Laboratory tests with uniform flow charged with sediments in a channel with banks equipped with large-scale rectangular roughness elements were carried out. The laboratory experiments covered a wide range of rectangular cavity geometrical configurations and shallowness ratios. The influence of key parameters such as flow shallowness, geometric ratios of the cavities and initial sediment concentration was tested. Surface particle image velocimetry, sediment samples and temporal turbidity records were collected during the experiments. The amount of sediments captured by the cavities, the temporal evolution of the concentration of sediments in suspension and the flow hydrodynamics are cross-analysed and discussed. It is shown that the trapping efficiency of the macro-roughness elements is a clear function of the channel geometry and the shallowness of the flow.

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Gravitational and Shear Instabilities in Compound and Composite Channels

Cited by 32 publications

References 22 publications

Spatial Linear Stability Analysis of Open-Channel Flows With Transverse Shear Revisited

Spatial Linear Stability Analysis of Open-Channel Flows With Transverse Shear Revisited

On the nonlinear development of shear layers in partially vegetated channels

Transport of suspended sediments under the influence of bank macro‐roughness

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