Turbulent flow mechanisms in meandering channels with sediment transport

Sahoo, S.; Sharma, Anurag

doi:10.2166/wpt.2023.035

Cited by 4 publications

(2 citation statements)

References 36 publications

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“…In our study, the meandering channel's geometry with successive 180 • and 120 • bends with different angles, and the extended approach channel distinguishes it from other channels studied in the literature, which typically feature more uniform or less extreme bend angles. The experimental model in many studies in the literature consists of only a single bend or narrow-angle uniform sinusoidal bends [1,[4][5][6][7][9][10][11][12]14]. In this study, the fairly long approach channel also ensures the flow reaches fully developed flow conditions before entering the meanders.…”

Section: Methodsmentioning

confidence: 99%

“…Dombroski and Crimaldi evaluated the accuracy of ADV velocity measurement data in turbulent boundary layer flow over a hydraulically smooth surface [8]. Sahoo and Sharma studied the turbulent flow mechanism in meandering channels using the ADV technique [12]. Laboratory studies performed by Ishigaki et al and Bai et al with PIV can be shown as other example studies for understanding flow behavior in a meandering channel [13,14].…”

Section: Introductionmentioning

confidence: 99%

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Physical and Numerical Modeling of Flow in a Meandering Channel

Yılmazer,

Arı Güner

2024

Water

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In this study, flow behavior in a meandering channel was investigated experimentally and numerically. The experiments were carried out for nine different cases on a channel consisting of 180° and 120° angle bends following successively. Measurements were conducted employing Acoustic Doppler Velocimetry (ADV) at 13 different points in the inner, middle, and outer bends of the sections located at significant bends along the channel. Depth-averaged velocity, velocity profiles, bed shear stress, and turbulence kinetic energy parameters were considered to understand the flow behavior in the meandering channel. A 1:1 scale numerical model of the experimental setup was generated using the Computational Fluid Dynamics (CFD) method through the verified FLOW-3D software (HYDRO 2022R1). It was found to be successful in estimating all parameters and was capable of investigating the flow behavior in the meandering channel. Additionally, a mesh independence study was performed, and four different turbulence models were compared. As a result, as the flow encountered the first meander in the channel, secondary flow occurred, and lateral momentum transfer took place. Therefore, velocity increased by approximately 30% from the first meander of 180° angles to the second meander of 120° angles. Therefore, the most critical zone was the inner bend of the 120-angle meander.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Physical and Numerical Modeling of Flow in a Meandering Channel

Yılmazer,

Arı Güner

2024

Water

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Experimental and numerical investigation of water flow behaviour in sharply curved 60° open‐channel bends

Seyedashraf,

Akhtari

2024

Earth Surf Processes Landf

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Understanding secondary flows in sharply curved open‐channel bends is key for analysing the flow patterns in rivers and and designing effective hydraulic structures. This study employs both experimental and computational methods to investigate the flow characteristics in a sharply curved 60° open‐channel bend. The primary objective is to enhance understanding of flow behaviours in such configurations. For numerical simulations, we utilize the Reynolds‐averaged Navier–Stokes equations, applying the volume‐of‐fluid free surface model to simulate air‐water interactions alongside the standard k‐ε and renormalized group (RNG) k‐ε turbulence models. Our findings reveal the emergence of helical currents driven by centrifugal forces at the bend's onset, which guide the fluid particles from the channel bottom to the convex (inner) bank and then to the concave (outer) bank at the surface. We observe a progressive increase in secondary flow intensity and energy dissipation along the bend, peaking at the terminal section. Notably, maximum flow velocity occurs near the convex wall accompanied by nonlinear water surface behaviours. Additionally, flow separation tendencies near the convex wall are noted after two‐thirds of the curvature. Quantitatively, the flow velocity at the convex bank was observed to be 1.70 times higher than at the concave bank within the bend. The mean absolute errors between experimental data and the standard k‐ε and RNG k‐ε models are 3.20 and 3.12, respectively, indicating the accuracy of the RNG k‐ε model.

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An investigation of the effect of stratification stability and saltation sand flux on the anisotropy of atmospheric surface layer wall turbulence

Mei,

Zhu,

Zhou

et al. 2024

Physics of Fluids

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In the atmospheric surface layer (ASL), the anisotropic characteristics of turbulence become more complex due to the strong influence of heat flux and particle motion. In this paper, the effects of stratification stability and total saltation sand flux on turbulent anisotropy of ASL wall turbulence are systematically analyzed by using high-frequency 3D velocity, temperature, and saltation sand flux measured in the field. Our results show that the temperature gradient intensifies the spanwise turbulent motion and enhances the vertical motion asymmetry. Although the buoyancy-driven turbulence enhances the spanwise variation, the momentum transfer mode between the streamwise–vertical and spanwise–vertical does not change. With the increase in instability, the large-scale motions (LSM) of the spanwise velocity may be destroyed and more spanwise small-scale motions (SSM) formed. In addition, saltation increases the sharpness, randomness, and extreme frequency of spanwise velocity distribution, but does not change the momentum transfer mode. Saltation may enlarge the fluctuation range and scale of the spanwise velocity, but may not be the main factor affecting the anisotropy of SSM. These results can deepen people's understanding of wind-blown sand movement and turbulence properties in ASL, and provides empirical data and insights that can significantly contribute to the development and refinement of turbulence models, particularly those that need to account for the complex interplay between stratification stability, saltation sand flux, and turbulence anisotropy.

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Turbulent flow mechanisms in meandering channels with sediment transport

Cited by 4 publications

References 36 publications

Physical and Numerical Modeling of Flow in a Meandering Channel

Physical and Numerical Modeling of Flow in a Meandering Channel

Experimental and numerical investigation of water flow behaviour in sharply curved 60° open‐channel bends

An investigation of the effect of stratification stability and saltation sand flux on the anisotropy of atmospheric surface layer wall turbulence

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