An ordinary differential equation for velocity distribution and dip-phenomenon in open channel flows

Absi, Rafik

doi:10.1080/00221686.2010.535700

Cited by 85 publications

(45 citation statements)

References 22 publications

(40 reference statements)

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“…Vanoni (1941) also suggested that the dip phenomenon is observed at the corner zones even for the wide open channels where the velocity profile deviates from the log-wake law. Absi (2011) suggested an ordinary differential equation for velocity distribution and dip-phenomenon in open channel flows. Rodríguez and García (2008) studied the effect of secondary flow occurred in the corner region of a narrow open channel.…”

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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Section: Introductionmentioning

confidence: 99%

Measurement of turbulent flow in a narrow open channel

Sarkar

2016

Journal of Hydrology and Hydromechanics

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“…Absi (2011) modified this model to predict the velocity-dip-position for validating his proposed velocity model full dip-modifiedlogwakelaw (fDMLW-law). Bonakdari et al (2008) critically analyzed both the models of Wang et al (2001) and Yang et al (2004) for small channel aspect ratio.…”

Section: Introductionmentioning

confidence: 99%

Prediction of Velocity-Dip-Position at the Central Section of Open Channels using Entropy Theory

Kundu

2017

JAFM

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An analytical model to predict the velocity-dip-position at the central section of open channels is presented in this study. Unlike the previous studies where empirical or semi-empirical models were suggested, in this study the model is derived by using entropy theory. Using the principle of maximum entropy, the model for dip-position is derived by maximizing the Shannon entropy function after assuming dimensionless dipposition at the central section as a random variable. No estimation of empirical parameter is required for calculating dip-position from the proposed model. The model is able to predict the location of maximum velocity at the central section of an open channel with any aspect ratio. The developed model of velocity-dipposition is tested with experimental data from twenty-two researchers reported in literature for a wide range of aspect ratio. The model is also compared with other existing empirical models. The present model shows good agreement with the observed data and provides least prediction error compared to other models.

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“…A Modified Log-Wake Law (MLWL) is proposed by Guo and Julien (2003) and Guo et al (2005) which is applicable to velocity data measured in both pipe and open channel flow in laboratory and field. Based on the analysis of the Reynoldsaveraged Navier-Stokes (RANS) equations and a log-wake modified eddy viscosity distribution, Absi (2011) proposed an ordinary differential equation for velocity distribution to predict the velocity-dipphenomenon. Bonakdari et al (2008) analyzed Navier-Stokes equations and suggested a new formulation of the vertical velocity profile in the center region of steady fully developed turbulent open-channel flows.…”

Section: Clauser Methods (U*l)mentioning

confidence: 99%

The Hysteresis and Shear Velocity in Unsteady Flows

Bombar

2016

JAFM

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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.

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An ordinary differential equation for velocity distribution and dip-phenomenon in open channel flows

Cited by 85 publications

References 22 publications

Measurement of turbulent flow in a narrow open channel

Measurement of turbulent flow in a narrow open channel

Prediction of Velocity-Dip-Position at the Central Section of Open Channels using Entropy Theory

The Hysteresis and Shear Velocity in Unsteady Flows

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