An experimental study of mean and turbulent flow in a 180 degree sharp open channel bend: Secondary flow and bed shear stress

Vaghefi, Mohammad; Akbari, Maryam; Fiouz, Alireza

doi:10.1007/s12205-015-1560-0

Cited by 74 publications

(36 citation statements)

References 26 publications

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“…In Tables 12 and 13, kinetic energy and shear stress (using Reynolds [29], TKE [30], and modi ed TKE [16,30]) parameters' values are compared with regard to the two considered points with and without a spur dike in the bend. Additionally, to observe mean ow pattern variations, the mean values of ow velocity components before and after outlier elimination from data sets are presented in these tables.…”

Section: Resultsmentioning

confidence: 99%

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A Comparison among Data Mining Algorithms for Outlier Detection using Flow Pattern Experiments

2017

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Abstract. Accurate outlier detection is an important matter to consider prior to applying data to predict ow patterns. Identifying these outliers and reducing their impact on measurements could be e ective in presenting an authentic ow pattern. This paper aims to detect outliers in ow pattern experiments along a 180-degree sharp bend channel with and without a T-shaped spur dike. Velocity components have been collected using 3D velocimeter called Vectrino in order to determine the ow pattern. Some of outlier detection methods were employed in the paper, such as Z-score test, sum of sine curve tting, Mahalanobis distance, hierarchical clustering, LSC-mine, self-organizing map, fuzzy C-means clustering, and voting. Considering the experiments carried out, the methods were e cient in outlier detection; however, the voting method appeared to be the most e cient one. Brie y, this paper calculated di erent hydraulic parameters in the sharp bend and made a comparison between them for the sake of studying how e ective running the voting method is in mean and turbulent ow pattern variations. The results indicated that developing the voting method in the ow pattern experiment in the bend would cause a decrease in Reynolds shear stress by 36%, while the mean velocities were not signi cantly in uenced by the method.

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Section: Resultsmentioning

confidence: 99%

“…It is worth mentioning that the ow depth is of 0.2 m at the start of the bend, and it is controlled using an adjustable butter y gate located at the downstream end of track during experiments. Therefore, Froude and Reynolds numbers are constant and equal to 0.34 and 119000, correspondingly [16].…”

Section: Methodologiesmentioning

confidence: 99%

A Comparison among Data Mining Algorithms for Outlier Detection using Flow Pattern Experiments

2017

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“…The root mean square error (RMSE) of the obtained data was calculated to measure the accuracy of the numerical simulations. (7) in which N = 13 is the number of measured data, where 'X(Exp)' and 'X(Pred)' are the measured and predicted values, respectively. Table 3 summarizes the obtained RMSEs of the 90⁰ bend model.…”

Section: Model Validationmentioning

confidence: 99%

“…Due to the threedimensional and complex nature of these flows, the experimental and numerical investigation of the topic has fascinated researchers for the past decades. Many investigations have been conducted including the 90, 120, and 180° bends [5][6][7][8][9]. For example, Blanckaert and De Vriend [9] measured the turbulent stress components of curved currents and analyzed the flow turbulence in a sharp 120° bend.…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional CFD Study of Free-Surface Flow in a Sharply Curved 30° Open- Channel Bend

Seyedashraf¹,

Akhtari²

2017

JESTR

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In this study, the air-water two-phase flow in a strongly curved 30° open-channel bend is numerically simulated and analyzed. The research is motivated by the fact that most of the sharp or mild bend flow studies are focused on the 90, 120, and 180° bends. Although these curvatures form from the bends with lower degrees, i.e. 30° curvatures, there is no published work in this field. Due to the paucity of data in the literature, the CFD procedure here is validated using the experimental data of a sharp 90° bend of a previous study. The Reynolds-averaged Navier-Stokes equation system is used as the governing equations and the finite volume method is employed for the discretizations. The Volume of Fluid free-surface tracking method, in conjunction with the Standard k-ε turbulence model, is utilized for the air-water interactions and turbulence closure. It is found that the secondary flow intensity in the 30° bend is minor than the 90° bends. However, the tendency to flow separation is more intense in these bends, which is due to the momentum of the fluid particles passing the curvature. The results of this study may be used to control the river morphology.

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“…Basser et al (2015) proposed a new approach to determine optimum parameters of a protective spur dike to mitigate scouring depth amount around existing main spur dikes. Vaghefi et al (2016) conducted an experimental study on Reynolds shear stress and turbulent kinetic energy in a 180 degree sharp bend. They concluded that the maximum of these parameters occur in the first half the bend and near inner wall.…”

Section: Introductionmentioning

confidence: 99%

Numerical Comparison of the Parameters Influencing the Turbulent Flow using a T-shaped Spur Dike in a 90° Bend

Vaghefi

Safarpoor

Akbari

2017

JAFM

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Spur dikes are used for river training purposes. To meet the navigability of rivers, the mean annual flow is considered; hence, in terms of river flooding, spur dikes are necessarily submerged. Considering the importance of submerged spur dikes, this paper studied the effects of a T-shaped spur dike's submergence ratios on turbulent flow parameters in a 90° bend using the SSIIM as a commercial CFD model. The SSIIM numerical model solves the Navier-Stokes equations with the k-ε model on a three-dimensional, almost general, non-orthogonal grid. Submergence ratios of 0 (non-submerged), 5, 15, 25 and 50% were evaluated for parameters affecting the turbulent flow such as kinetic energy, pressure, eddy viscosity and the Froude number. It was observed that by increasing the spur dike submergence ratio from 0% (non-submerged) to 50%, in addition to changes in the values of pressure and kinetic energy, the Froude number changed in the bend and increased 2.1 times at the inner bank of the bend exit, and the eddy viscosity near the bed, which is the decisive factor of the turbulent flow, reduced by 42%. At the bed near the spur dike wing, the amount and range of kinetic energy reduced by increasing the submergence ratio. Near the bed, for all submergence ratios, the maximum pressure occurred at the upstream end of the spur dike.

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An experimental study of mean and turbulent flow in a 180 degree sharp open channel bend: Secondary flow and bed shear stress

Cited by 74 publications

References 26 publications

A Comparison among Data Mining Algorithms for Outlier Detection using Flow Pattern Experiments

A Comparison among Data Mining Algorithms for Outlier Detection using Flow Pattern Experiments

Three-dimensional CFD Study of Free-Surface Flow in a Sharply Curved 30° Open- Channel Bend

Numerical Comparison of the Parameters Influencing the Turbulent Flow using a T-shaped Spur Dike in a 90° Bend

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