Discharge Characteristics of Weirs of Finite Crest Length with Upstream and Downstream Ramps

Azimi, Amir H.; Rajaratnam, N.; Zhu, David Z.

doi:10.1061/(asce)ir.1943-4774.0000519

Cited by 44 publications

(14 citation statements)

References 7 publications

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“…Depending on the relative length, the ratio of the weir length and height d/Р, of the threshold, there are sharp-crested, finite-crested and broad-crested weirs, however, the numerical criteria for the weirs of different types slightly vary (Table 1). Volumetric flow rate of rectangular sharp-edged BCW according to (Azimi et al, 2013;Bolshakov, 1984;Govinda Rao & Muralidhar, 1963;Нager & Schwalt, 1994;Konstantinov & Hizha, 2006;Rohalevych, 2010):…”

Section: The Results Of Previous Studiesmentioning

confidence: 99%

“…where m -the discharge coefficient of rectangular sharp-edged BCW; b -width of the weir; Н 0 − total head on the weir, which is found as a sum of geometric and velocity heads (Azimi et al, 2013;Bolshakov,1984;Govinda Rao & Muralidhar, 1963;Нager & Schwalt, 1994;Konstantinov & Hizha, 2006;Rekomendatsіі, 1974;Rohalevych, 2010):…”

Section: The Results Of Previous Studiesmentioning

confidence: 99%

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Discharge coefficient of broad-crested weirs as a function of the relative weir height for different weir lengths

Zhuk¹,

Matlai²,

Popadiuk³

et al. 2020

Theory build. pract.

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Broad-crested weirs (BCW) are often used in hydraulic engineering and water management. The most complex factor that affects the discharge capacity of BCW is the discharge coefficient. In Ukrainian engineering practice, the flow rate of BCW is defined as a function of the relative height of the spillway wall, while in the most common European methods – as a function of the relative length of the weir. The experimental dependences of the discharge coefficient of rectangular sharp-edged BCW with vertical inlet and outlet walls with the ratio of the weir length and height d/Р = 2; 4 are obtained. A comparison of the obtained results with the values of the discharge coefficient of the same BCW using the methods of Kumin and Hager indicates that this coefficient depends on both the height of the wall and the length of the weir. The corresponding empirical power law dependences are obtained. At the same values of the relative height of the wall, the discharge coefficient for the weir with the ratio d/Р = 4 is significantly lower comparing the weir with d/Р = 2, that can be explained by the more significant effect of friction resistance for the weir with longer threshold.

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Section: The Results Of Previous Studiesmentioning

confidence: 99%

Section: The Results Of Previous Studiesmentioning

confidence: 99%

Discharge coefficient of broad-crested weirs as a function of the relative weir height for different weir lengths

Zhuk¹,

Matlai²,

Popadiuk³

et al. 2020

Theory build. pract.

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show abstract

“…Approximately, 34% of earthen dam failures are caused by overtopping (Costa, 1985). The maximum discharge and consequently the erosion rate of embankments, with side slopes (Azimi, Rajaratnam, & Zhu, 2013) and without side slopes (Azimi & Rajaratnam, 2009), have been formulated based on non‐dimensional analysis and geometrical parameters. The breach of levees during flood can cause significant damages to agricultural fields, irrigational channels, highway networks, and communities' infrastructure downstream of earthen dams and embankments (Cestero, Imran, & Chaudhry, 2014; Jafarzadeh, Rostami, Sepehrfar, & Lahijanzadeh, 2004).…”

Section: Introductionmentioning

confidence: 99%

Effects of upstream and downstream slopes and clay content on levee's breaching by overtopping

Salehi

Azimi

2020

River Research & Apps

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The present study investigated the effects of clay content and levee's slopes on the breach formation process for levees constructed by both cohesive and non‐cohesive soils. Twelve experiments were carried out and the breach formation of levees was observed by measuring the breach discharge variations and scour topography with time. The initiation of surface erosion was analysed by comparing the estimated bed shear stress and the critical soil shear stress, and the rate of erosion during breaching was estimated by employing the erosion index. The erosion of levees due to overtopping was classified into three regimes of uniform surface erosion, erosion from the toe, and single scour formation. It was found that the upstream levee's slope had negligible effects on the breach process, whereas the downstream slope significantly increased the erosion index. The peak breach discharge increased with increasing downstream slope and it occurred earlier. Experimental results also showed that the peak breach discharge was higher in non‐cohesive levees than the cohesive embankments and it occurred much earlier. Based on dimensional analysis, empirical equations were proposed to predict the breach discharge and the topography of erosion during the breach.

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“…Azimi et al [9] collected the experimental results available in the literature on broad-crested weirs with crest slopes and downstream ramps and propose useful correlations for the discharge coefficient. Madadi et al [10] experimentally investgated the effect of upstream face slope of a trapezoidal broad-crested weir on discharge coefficient and free-surface profile.…”

Section: Introductionmentioning

confidence: 99%

“…In this study, a series of numerical simulations was conducted to study broad-crested weirs with sloped upstream faces and vertical downtown faces, considering that the downstream slope has less of an impact on a broad-crested weir under free-flow conditions [8,9]. Numerical simulations were performed using the open-source toolbox OpenFOAM (5.0).…”

Section: Introductionmentioning

confidence: 99%

Numerical Modeling of Flow Over a Rectangular Broad-Crested Weir with a Sloped Upstream Face

Jiang

Diao

Sun

et al. 2018

Water

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The objective of this study was to evaluate the effect of the upstream angle on flow over a trapezoidal broad-crested weir based on numerical simulations using the open-source toolbox OpenFOAM. Eight trapezoidal broad-crested weir configurations with different upstream face angles (θ = 10°, 15°, 22.5°, 30°, 45°, 60°, 75°, 90°) were investigated under free-flow conditions. The volume-of-fluid (VOF) method and two turbulence models (the standard k-ε model and the SST k-w model) were employed in the numerical simulations. The numerical results were compared with the experimental results obtained from published papers. The root mean square error (RMSE) and the mean absolute percent error (MAPE) were used to evaluate the accuracy of the numerical results. The statistical results show that RMSE and MAPE values of the standard k-ε model are 0.35–0.67% and 0.50–1.48%, respectively; the RMSE and MAPE values of the SST k-w model are 0.25–0.66% and 0.55–1.41%, respectively. Additionally, the effects of the upstream face angle on the flow features, including the discharge coefficient and the flow separation zone, were also discussed in the present study.

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Discharge Characteristics of Weirs of Finite Crest Length with Upstream and Downstream Ramps

Cited by 44 publications

References 7 publications

Discharge coefficient of broad-crested weirs as a function of the relative weir height for different weir lengths

Discharge coefficient of broad-crested weirs as a function of the relative weir height for different weir lengths

Effects of upstream and downstream slopes and clay content on levee's breaching by overtopping

Numerical Modeling of Flow Over a Rectangular Broad-Crested Weir with a Sloped Upstream Face

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