Turbulence Characteristics in Supercritical Open Channel Flows: Effects of Froude Number and Aspect Ratio

Auel, Christian; Albayrak, Ismail; Boes, Robert M.

doi:10.1061/(asce)hy.1943-7900.0000841

Cited by 57 publications

(91 citation statements)

References 53 publications

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“…The measurements at five different locations across up-to downstream for Test 1 show the unchanged coefficient values of j, B r and G to be 0.43, 4.7, and 0.0754, respectively. These parameters are found to give consistent values with most of the other smooth bed uniform flow studies discussed in this section; however, 0.43 is found to be at the higher end of j range proposed by Auel et al [2]. To carry out the turbulence structure analysis, the 3D turbulence intensities for Test 1 are investigated.…”

Section: Discussionsupporting

confidence: 79%

“…A range of j = 0.40-0.42 was proposed for the flows over smooth bed investigated by Coles [6] and Cardoso et al [4]; while, similar value (j = 0.40) was also suggested for the rough bed flow by Song et al [30]. More recently, Auel et al [2] summarised from various smooth and rough bed flow studies that j = 0.385-0.435, universally. For the log-law integration constant B r of smooth bed uniform flows, it was proposed as B r = 4.9 in Mellor and Gibson [15], and Anwar and Atkins [1]; and B r = 5.1 in Coles [6], and Cardoso et al [4].…”

Section: Uniform Flow Results and Analysismentioning

confidence: 62%

“…This finding shows that even in hydraulically smooth flow condition the wall shear stress may affect turbulence intensity profiles within a high flow depth in streamwise and vertical directions provided that R and h are not large. Auel et al [2] has consistently suggested this same conclusion in their supercritical flow tests with relatively small R and h settings. The non-uniform flow, which is characterised by the existence of a streamwise pressure gradient, has also been investigated.…”

Section: Discussionmentioning

confidence: 60%

“…(7)] was utilised to calculate the change of velocity and turbulence structure for nonuniform flow in Song et al [30], Kironoto and Graf [14] and Song and Chiew [28]. For It is found by depth averaging of the time-averaged u-velocity uniform flow, b has a constant value of -1; whereas for the non-uniform flow, b is nonconstant (as suggested by [2,14,28]). As both B r and G of the non-uniform flow are in the function of b, the non-uniform flow's log-wake law should therefore be expressed as…”

Section: Discussionmentioning

confidence: 99%

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Dominant features in three-dimensional turbulence structure: comparison of non-uniform accelerating and decelerating flows

Tait

Guo

et al. 2017

Environ Fluid Mech

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The results are presented from an experimental study to investigate three-dimensional turbulence structure profiles, including turbulence intensity and Reynolds stress, of different non-uniform open channel flows over smooth bed in subcritical flow regime. In the analysis, the uniform flow profiles have been used to compare with those of the nonuniform flows to investigate their time-averaged spatial flow turbulence structure characteristics. The measured non-uniform velocity profiles are used to verify the von Karman constant j and to estimate sets of log-law integration constant B r and wake parameter G, where their findings are also compared with values from previous studies. From j, B r and G findings, it has been found that the log-wake law can sufficiently represent the nonuniform flow in its non-modified form, and all j, B r and G follow universal rules for different bed roughness conditions. The non-uniform flow experiments also show that both the turbulence intensity and Reynolds stress are governed well by exponential pressure gradient parameter b equations. Their exponential constants are described by quadratic functions in the investigated b range. Through this experimental study, it has been observed that the decelerating flow shows higher empirical constants, in both the turbulence intensity and Reynolds stress compared to the accelerating flow. The decelerating flow also has stronger dominance to determine the flow non-uniformity, because it presents higher Reynolds stress profile than uniform flow, whereas the accelerating flow does not.

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Section: Discussionsupporting

confidence: 79%

Section: Uniform Flow Results and Analysismentioning

confidence: 62%

Section: Discussionmentioning

confidence: 60%

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Dominant features in three-dimensional turbulence structure: comparison of non-uniform accelerating and decelerating flows

Tait

Guo

et al. 2017

Environ Fluid Mech

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“…On the other hand, Tracy and Lester (1961) divided an open channel into two parts, namely, the central region and the corner region of flow while measured with respect to the width. Auel et al (2014) argued that the dip phenomenon is observed at the corner regions and their effects diminish toward the flume centre. They observed that the effect of Froude number is less prominent on the flow characteristics in comparison with that of aspect ratio.…”

Section: Introductionmentioning

confidence: 99%

Measurement of turbulent flow in a narrow open channel

Sarkar

2016

Journal of Hydrology and Hydromechanics

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Abstract:The paper presents the experimental results of turbulent flow over hydraulically smooth and rough beds. Experiments were conducted in a rectangular flume under the aspect ratio b/h = 2 (b = width of the channel 0.5 m, and h = flow depth 0.25 m) for both the bed conditions. For the hydraulically rough bed, the roughness was created by using 3/8″ commercially available angular crushed stone chips; whereas sand of a median diameter d 50 = 1.9 mm was used as the bed material for hydraulically smooth bed. The three-dimensional velocity components were captured by using a Vectrino (an acoustic Doppler velocimeter). The study focuses mainly on the turbulent characteristics within the dip that were observed towards the sidewall (corner) of the channel where the maximum velocity occurs below the free-surface. It was also observed that the nondimensional Reynolds shear stress changes its sign from positive to negative within the dip. The quadrant plots for the turbulent bursting shows that the signs of all the bursting events change within the dip. Below the dip, the probability of the occurrence of sweeps and ejections are more than that of inward and outward interactions. On the other hand, within the dip, the probability of the occurrence of the outward and inward interactions is more than that of sweeps and ejections.

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Sediment transport in high‐speed flows over a fixed bed: 1. Particle dynamics

Auel

Albayrak

Takemon

et al. 2017

Earth Surf Processes Landf

Self Cite

133

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Particle dynamics are investigated experimentally in supercritical high‐speed open channel flow over a fixed planar bed of low relative roughness height simulating flows in high‐gradient non‐alluvial mountain streams and hydraulic structures. Non‐dimensional equations were developed for transport mode, particle velocity, hop length and hop height accounting for a wide range of literature data encompassing sub‐ and supercritical flow conditions as well as planar and alluvial bed configurations. Particles were dominantly transported in saltation and particle trajectories on planar beds were rather flat and long compared with alluvial bed data due to (1) increased lift forces by spinning motion, (2) strongly downward directed secondary currents, and (3) a planar flume bed where variation in particle reflection and damping effects were minor. The analysis of particle saltation trajectories revealed that the rising and falling limbs were almost symmetrical contradicting alluvial bed data. Furthermore, no or negligible effect of particle size and shape on particle dynamics were found. Implications of experimental findings for mechanistic saltation‐abrasion models are briefly discussed. Copyright © 2017 John Wiley & Sons, Ltd.

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Turbulence Characteristics in Supercritical Open Channel Flows: Effects of Froude Number and Aspect Ratio

Cited by 57 publications

References 53 publications

Dominant features in three-dimensional turbulence structure: comparison of non-uniform accelerating and decelerating flows

Dominant features in three-dimensional turbulence structure: comparison of non-uniform accelerating and decelerating flows

Measurement of turbulent flow in a narrow open channel

Sediment transport in high‐speed flows over a fixed bed: 1. Particle dynamics

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