Variation of Local Friction Factor in an Open Channel Flow

Khuntia, Jnana Ranjan; Devi, Kamalini; Khatua, Kishanjit Kumar

doi:10.17485/ijst/2016/v9i46/105256

Cited by 7 publications

(6 citation statements)

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“…The intrinsic inertial effect of partial slip condition induced the increase of the frequency of the asymmetrical vortex formation. In summary, boundary conditions imposed on the solid surface is very significant in terms of friction adjustment and flow properties (Mojtahedpoor and Naderi, 2016;Khuntia et al, 2016;Kim, 2015). Customary practice for modeling of shallow water flow presumed the internal boundary condition as free-slip, which leads to inaccurate prediction about the velocity, vorticity, lift coefficient and Strouhal number around a cylinder.…”

Section: Numerical Resultsmentioning

confidence: 99%

Numerical investigation of flow around a structure using Navier-slip boundary conditions

Choi

Eum

Shin

et al. 2021

WJE

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Purpose Complicated motion of vortex is frequently observed in the wake of islands. These kinds of swirling fluid cause the trap of sediments or pollutants, subsequently inducing the dead zone, odor or poor water quality. Therefore, the understanding of flow past a circular cylinder is significant in predicting water quality and positioning the immersed structures. This study aims to investigate the flow properties around a structure using Navier-slip boundary conditions. Design/methodology/approach Boundary conditions are a major factor affecting the flow pattern because the magnitude of flow detachment on a surface can redistribute the tangential stress on the wall. Therefore, the authors performed an analysis of laminar flow passing through a circular structure to investigate the effect of boundary conditions on the flow pattern. Findings The authors examined the relationship between the partial-slip boundary conditions and the flow behavior at low Reynolds number past a circular cylinder considering velocity and vorticity distributions behind the cylinder, lift coefficient and Strouhal number. The amplitude of lift coefficient by the partial slip condition had relatively small value compared with that of no-slip condition, as the wall shear stress acting on the cylinder became smaller by the velocity along the cylinder surface. The frequency of the asymmetrical vortex formation with partial slip velocity was increased compared with no-slip case due to the intrinsic inertial effect of Navier-slip condition. Originality/value The ability to engineer slip could have dramatic influences on flow, as the viscous dominated motion can lead to large pressure drops and large axial dispersion. By the slip length control, no-slip, partial-slip and free-slip boundary conditions are tunable, and the velocity distributions at the wall, vortex formation and wake pattern including the amplitude of lift coefficient and frequency were significantly affected by slip length parameter.

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Section: Numerical Resultsmentioning

confidence: 99%

Numerical investigation of flow around a structure using Navier-slip boundary conditions

Choi

Eum

Shin

et al. 2021

WJE

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“…The depth-averaged stream-wise velocity, is calculated by integrating local point stream wise velocities ( ) [10,12]. The lateral distribution of at various x-positions are given in Fig.…”

Section: Depth-averaged Velocity Distributionmentioning

confidence: 99%

Depth-averaged velocity and bed shear stress in unsteady open channel flow over rough bed

et al. 2018

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Very few studies have been carried out in the past in estimating depth-averaged velocity and bed shear stress in unsteady flow over rough beds. An experiment is thus conducted to investigate the vertical and lateral velocity profiles under unsteady flow conditions in a rough open channel for various flow depths. One hydrogram is repeatedly passed through the rectangular flume with a fixed rigid grass bed. Using micro Pitot tube and Acoustic Doppler Velocimeter (ADV), the flow patterns are investigated at both lateral and longitudinal positions over different cross-sections. For two typical flow depths, the velocities in both the rising limb and falling limb are observed. Hysteresis effect between stage-discharge (h ~ Q) rating curve between rising and falling limbs is illustrated. Lateral distribution of depth-averaged velocity and bed shear stress are plotted at three different cross sections and compared with the steady flow conditions. In falling limb of an unsteady flow case, both depth-averaged velocity and bed shear stress distribution in the central region is higher than that of steady flow case. However, in the rising limb, the bed shear stress of unsteady flow is less than that of steady flow case. Further, in an unsteady flow, the magnitude of depth-averaged velocity is found to increase towards the downstream sections. Along the downstream positions, bed shear stress values increase for lower flow depths and decrease for higher flow depth cases.

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“…When vegetation is introduced in a flowing channel, the vegetation roughness affects the shape of velocity profiles in a stream-wise and vertical direction (Sarma et al 1983). Khuntia et al (2016) and Shi et al (2013) studied the rough bed and vegetation density effect on Manning's coefficient respectively.…”

Section: Introductionmentioning

confidence: 99%

Calibrating Coefficients of Emerged Vegetative Open Channel Flow

2021

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Vegetation is a crucial element of the river system. In open channel hydraulics, vegetation has a significant effect on flow structure; it offers resistance to the flow and responsible for flood level increase by reducing the carrying capacity of the flood. Researchers throughout the globe have analyzed the resistance provided by vegetation with a theoretical and experimental study. Many flow and channel parameters affect the flow resistance. Out of all these parameters, vegetation is an influential one in vegetative channels. It alters the velocity profiles in an open channel, which affects the roughness coefficients. The roughness coefficients in vegetative channels vary with the flow depths and sections. Therefore, due to the complex structure, it is tedious to come up with a flow model based on previous research. Though it is challenging to determine directly from a field exercise, a laboratory study has been carried out in emergent vegetation at Hydraulics Engineering Laboratory, NITR, to explore the vegetation influence. The Shiono Knight Method (SKM) has been applied to calculate the boundary shear stress and depth-averaged velocity distribution in an open channel flow. For this purpose, three calibrating coefficients, namely bed friction (f), dimensionless eddy viscosity (λ), and transverse gradient for secondary flow ( ), have been incorporated to modify the existing SKM. A mathematical model was formulated to find the calibrating coefficients in the channel and compared with the SKM.

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Variation of Local Friction Factor in an Open Channel Flow

Cited by 7 publications

References 0 publications

Numerical investigation of flow around a structure using Navier-slip boundary conditions

Numerical investigation of flow around a structure using Navier-slip boundary conditions

Depth-averaged velocity and bed shear stress in unsteady open channel flow over rough bed

Calibrating Coefficients of Emerged Vegetative Open Channel Flow

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