Secondary Flows in Rivers: Theoretical Framework, Recent Advances, and Current Challenges

Nikora, Vladimir; Roy, Alain

doi:10.1002/9781119952497.ch1

Cited by 50 publications

(38 citation statements)

References 103 publications

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“…Though recent progress has been made to understand turbulence-driven secondary currents in rivers, there are still many knowledge gaps that have to be addressed [31]. In this paper results of an LES of open-channel flow over non-uniformly distributed roughness are reported.…”

Section: Introductionmentioning

confidence: 99%

Secondary Currents and Turbulence over a Non-Uniformly Roughened Open-Channel Bed

Stoesser

McSherry

Fraga

2015

Water

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Large-eddy simulations (LES) of the flow over a non-uniformly roughened channel bed are carried out to study the effect of non-uniform bed roughness on turbulence driven secondary currents and turbulence statistics. The channel bed is comprised of alternating rough and smooth strips, the width of which corresponds to the water depth. The Reynolds number based on hydraulic radius and bulk velocity is 34,000. The LES are successfully validated using experimental data. The secondary flow and bed roughness have a significant effect on the streamwise velocity and second order turbulence statistics. Turbulence is enhanced over rough strips and suppressed over smooth strips. Significant lateral momentum transfer takes place due to both advection and turbulence. The bed shear stresses over the smooth strips are approximately four times less than over the rough strips a result of near bed low momentum fluid being transported from the rough strips to the smooth strips and high momentum fluid being convected from the surface towards the bed. The most significant terms in the streamwise momentum equation are quantified and discussed with regard to momentum transfer.

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Section: Introductionmentioning

confidence: 99%

Secondary Currents and Turbulence over a Non-Uniformly Roughened Open-Channel Bed

Stoesser

McSherry

Fraga

2015

Water

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“…The roll cells, also called large streamwise vortices (Gulliver and Halverson 1987) or long longitudinal eddies (Imamoto and Ishigaki 1986), look like secondary flows in the plane perpendicular to the streamwise flow (Nikora and Roy 2012). True secondary flows have non-zero long-time averages, and they affect the distribution of mean velocity, turbulence intensities, Reynolds shear stresses and bed shear stress throughout the channel.…”

Section: Coherent Structures In Canonical Open-channel Flowsmentioning

confidence: 99%

Coherent structures in flow over hydraulic engineering surfaces

Adrian

Marušić

2012

Journal of Hydraulic Research

115

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Wall-bounded turbulence manifests itself in a broad range of applications, not least in hydraulic systems. Here, we briefly review the significant advances over the past few decades in the fundamental study of wall turbulence over smooth and rough surfaces, with an emphasis on coherent structures and their role at high Reynolds numbers. We attempt to relate these findings to parallel efforts in the hydraulic engineering community and discuss the implications of coherent structures in important hydraulic phenomena.

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“…Change in channel forms are too slow to study in lifetime of a researcher. Yet bedrock channels play a great role in the scene of world ecosystem (Gurnell et al 2001, Marzadri et al 2010, Mosselman 2012, Nikora and Roy 2012. Bedrock channels supplies alluvium that forms substrate for the alluvial channel.…”

Section: Introductionmentioning

confidence: 99%

Hydraulic Parameters and Morphometric Variables Interactions in Bedrock Channel

Biswas¹,

Das²

2016

Quaestiones Geographicae

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Biswas B., das B. C., 2016. Hydraulic parameters and morphometric variables interactions in bedrock channel. Quaestiones Geographicae 35(3), Bogucki Wydawnictwo Naukowe, Poznań, pp. 75-88, 12 figs.aBstraCt: Present study is on the interdependent nature of hydraulic parameters and morphometric variables of a bedrock river. In this study, using dumpy level, GPS, satellite images and some mathematical equations a data set on hydraulics and morphometric variables of a bedrock channel, named Bhatajhor, of eastern India was generated. That data set was used to (1) find out impulse-response relations between hydraulic variables (2) find out relations between morphometric variables and (3) find out relations between hydraulic and morphometric variables. Seven equations (5-11) were formulated based on this empirical study to the end. The seven empirical relations, most of which include only two variables, involve channel cross-section dimensions (area, width, mean depth, maximum depth, width/ depth ratio, hydraulic radius), slope and hydraulic variables (velocity, kinetic energy, stream power, Manning's n factor, Chezy's C factor and shear stress). Observation shows relatively higher coefficient of determination (R2) between variables like velocity and Manning's n factor (0.67), velocity and Chezy's C factor (0.67), slope and τ (0.89), w/d ratio and hydraulic radius (0.53), slope and w/d ratio (0.50).

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Secondary Flows in Rivers: Theoretical Framework, Recent Advances, and Current Challenges

Cited by 50 publications

References 103 publications

Secondary Currents and Turbulence over a Non-Uniformly Roughened Open-Channel Bed

Secondary Currents and Turbulence over a Non-Uniformly Roughened Open-Channel Bed

Coherent structures in flow over hydraulic engineering surfaces

Hydraulic Parameters and Morphometric Variables Interactions in Bedrock Channel

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