Boundary Shear Stress in Smooth Trapezoidal Open Channel Flows

Kabiri-Samani, Abdorreza; Farshi, Fatemeh; Chamani, Mohammad R.

doi:10.1061/(asce)hy.1943-7900.0000658

Cited by 42 publications

(5 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In order to evaluate the influence of the parameter M u on the maximum velocity entropy and dimensionless mean shear stress, H(u/u max ) and the ratio τ mean /τ max are computed from Equations (17) and (21), respectively, for various values of M u , and plotted in Figure 1. Being the ratio between mean and maximum velocity in the range zero to one, the values of M u can vary theoretically from −12 to 12 according to Equation (18).…”

Section: Reformulation Of the Lagrange Multipliersmentioning

confidence: 99%

“…Such distribution depends on the secondary flows, the shape of the cross section, and the nonuniform roughness around the wetted perimeter. Many researches have focused on the shear stress analysis with experimental, numerical, analytical, and soft computing methods, in channels with different cross-section shapes and both smooth and rough boundaries [12][13][14][15][16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Modeling Bed Shear Stress Distribution in Rectangular Channels Using the Entropic Parameter

Mirauda

Russo

2020

Entropy

View full text Add to dashboard Cite

The evaluation of bed shear stress distribution is fundamental to predicting the transport of sediments and pollutants in rivers and to designing successful stable open channels. Such distribution cannot be determined easily as it depends on the velocity field, the shape of the cross section, and the bed roughness conditions. In recent years, information theory has been proven to be reliable for estimating shear stress along the wetted perimeter of open channels. The entropy models require the knowledge of the shear stress maximum and mean values to calculate the Lagrange multipliers, which are necessary to the resolution of the shear stress probability distribution function. This paper proposes a new formulation which stems from the maximization of the Tsallis entropy and simplifies the calculation of the Lagrange coefficients in order to estimate the bed shear stress distribution in open-channel flows. This formulation introduces a relationship between the dimensionless mean shear stress and the entropic parameter which is based on the ratio between the observed mean and maximum velocity of an open-channel cross section. The validity of the derived expression was tested on a large set of literature laboratory measurements in rectangular cross sections having different bed and sidewall roughness conditions as well as various water discharges and flow depths. A detailed error analysis showed good agreement with the experimental data, which allowed linking the small-scale dynamic processes to the large-scale kinematic ones.

show abstract

Section: Reformulation Of the Lagrange Multipliersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modeling Bed Shear Stress Distribution in Rectangular Channels Using the Entropic Parameter

Mirauda

Russo

2020

Entropy

View full text Add to dashboard Cite

show abstract

“…The secondary flow was observed by the movement of impurities in straight and curved open channel [2] and then the investigations referring to the secondary flow and shear stress in the channel were extensively conducted [3][4][5][6]. The structure of secondary flow was changed for the varying shape of cross-section in straight channel, which was investigated using three slope coefficients of 0.58, 1 and 1.73 by Tominaga et al [7].…”

Section: Introductionmentioning

confidence: 99%

Numerical Analysis on Hydraulic Characteristics of U-shaped Channel of Various Trapezoidal Cross-Sections

Zhang

2018

Water

View full text Add to dashboard Cite

Curved channel with trapezoidal cross-section is approximate to the common form in nature fluvial networks and its hydraulic characteristics are considerably complex and variable. Combined with volume of fluid (VOF) method, renormalization group (RNG) k-ε turbulence model was employed to numerically investigate the flow properties in the U-shaped channel with various trapezoidal cross-sections. Analyses were performed from the aspects of the water surface transverse slope in bend apex (WTS-BA), longitudinal velocity, secondary flow, shear stress and turbulent kinetic energy (TKE) under several scenarios, specifically, four types of radius-to-width ratio and seven types of slope coefficient with a constant aspect ratio. The calculated results suggested that the maximums of shear stress and TKE in the bend were observed in the convex bank and the maximal intensities of secondary flow were observed within the range of 60 to 75 degrees for various varieties. As the radius-to-width ratio increased, the maximums of shear stress, TKE and WTS-BA decreased; but increased with increasing slope coefficients. The intensity of secondary flow decreased as slope coefficients increased and the angle of maximum intensity of secondary flow moved to the upstream for the increasing radius-to-width ratios. In addition, a new equation concerning the vertical distribution of longitudinal velocity in trapezoidal cross-sectioned channel was presented.

show abstract

“…Velocity distribution and flow parameters such as turbulence and boundary shear stress in steady flow conditions were studied widely both experimentally in laboratory and in the field (Nezu and Rodi 1986, Cardoso et al 1989, Kırkgöz 1989, Kırkgöz and Ardıçlıoğlu 1997, Kabiri-Samani et al 2013, Genç et al (2015) and numerically (Song et al 2012, Debnath et al 2015, Shah et al 2015. However, in nature, unsteady flows are the most common type of open channel flows and attracted a great amount of interest for research in the field of hydraulics (Bose and Dey 2012) particularly in the furrow irrigation and in irrigation management systems (Walker and Humpherys 1983, Meselhe and Holly 1993, Kumar et al 2002, Zhang et al 2012.…”

Section: Introductionmentioning

confidence: 99%

The Hysteresis and Shear Velocity in Unsteady Flows

Bombar

2016

JAFM

View full text Add to dashboard Cite

The shear velocity is an important parameter in characterizing the shear at the boundary in open channels and there exist methods to estimate the shear velocity in steady flows, but the application and comparison of these methods to non-uniform unsteady flows is limited. In this study, three artificial triangular-shaped hydrographs were generated where the base flow is non-uniform with fine sand bed and the shear velocity was obtained by the methods, u*SV by using the Saint-Venant equations, u*L by using the procedure given by Clauser Method, u*P by using the parabolic law, u*UN by using the momentum equation assuming the slope of energy grade line is equal to bed slope and u*avg by using the average velocity equation are used in this study. The stream-wise components of velocity time series and the velocity profiles were obtained by means of an acoustic Doppler velocity meter. The variation of the shear velocity and the constant for the parabolic law with time is discussed. It is concluded that the shear velocities found by the parabolic law and the average velocity equation can be used interchangeably. Furthermore a hysteresis intensity parameter is proposed in order to examine the depth variation of hysteretic behavior of depth variation both with point velocity and average velocity. It is revealed that the more the unsteady the hydrograph the more the hysteresis both in terms of point velocity and cross-sectional mean velocity.

show abstract

Boundary Shear Stress in Smooth Trapezoidal Open Channel Flows

Cited by 42 publications

References 15 publications

Modeling Bed Shear Stress Distribution in Rectangular Channels Using the Entropic Parameter

Modeling Bed Shear Stress Distribution in Rectangular Channels Using the Entropic Parameter

Numerical Analysis on Hydraulic Characteristics of U-shaped Channel of Various Trapezoidal Cross-Sections

The Hysteresis and Shear Velocity in Unsteady Flows

Contact Info

Product

Resources

About