The Influence of Roughness on the Discharge Coefficient of a Broad-Crested Weir

Pařílková, Jana; Říha, Jaromír; Zachoval, Zbyněk

doi:10.2478/v10098-012-0009-0

Cited by 17 publications

(13 citation statements)

References 10 publications

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“…• The effect of the weir crest roughness on the discharge coefficient was studied for the set of Nikuradse roughness size k s = 0.014, 0.020 and 0.024 m, for specific discharges varying from q = 0.005 to q = 0.25 m 2 /s, and an upstream slope Z 1 = 2.5, consistently with the study of Pařílková et al (2012). Fig.…”

Section: Numerical Simulationsmentioning

confidence: 63%

“…Madadi et al (2014) identified increased discharge coefficient up to 10% with decreasing the upstream face slope from 90 o to 21 o . Pařílková et al (2012) investigated experimentally the influence of the weir surface roughness on the discharge coefficient. For vegetated weir surface conventional flow resistance equations may also be used (Gualtieri et al, 2018).…”

Section: Figmentioning

confidence: 99%

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Performance of a shallow-water model for simulating flow over trapezoidal broad-crested weirs

Říha

Duchan

Zachoval

et al. 2019

Journal of Hydrology and Hydromechanics

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Shallow-water models are standard for simulating flow in river systems during floods, including in the near-field of sudden changes in the topography, where vertical flow contraction occurs such as in case of channel overbanking, side spillways or levee overtopping. In the case of stagnant inundation and for frontal flow, the flow configurations are close to the flow over a broad-crested weir with the trapezoidal profile in the flow direction (i.e. inclined upstream and downstream slopes). In this study, results of shallow-water numerical modelling were compared with seven sets of previous experimental observations of flow over a frontal broad-crested weir, to assess the effect of vertical contraction and surface roughness on the accuracy of the computational results. Three different upstream slopes of the broad-crested weir (V:H = 1:Z1 = 1:1, 1:2, 1:3) and three roughness scenarios were tested. The results indicate that, for smooth surface, numerical simulations overestimate by about 2 to 5% the weir discharge coefficient. In case of a rough surface, the difference between computations and observations reach up to 10%, for high relative roughness. When taking into account mentioned the differences, the shallow-water model may be applied for a range of engineering purposes.

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Section: Numerical Simulationsmentioning

confidence: 63%

Section: Figmentioning

confidence: 99%

Performance of a shallow-water model for simulating flow over trapezoidal broad-crested weirs

Říha

Duchan

Zachoval

et al. 2019

Journal of Hydrology and Hydromechanics

Self Cite

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show abstract

“…(10), C d is deduced as 0.24, smaller than the discharge coefficient of common rectangular weirs (Hager and Schwalt, 1994) and smooth breach (Zhao et al, 2015). This may result from both the initial trapezoid shape of the breach cross section and the large surface roughness which appeared later on the land side (Pařílková et al, 2012).…”

Section: Calculated Results and Analysismentioning

confidence: 99%

Overtopping breaching of river levees constructed with cohesive sediments

Wei

Wang

et al. 2016

Nat. Hazards Earth Syst. Sci.

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Abstract. Experiments were conducted in a bend flume to study the overtopping breaching process and the corresponding overflow rates of river levees constructed with cohesive sediments. The river and land regions were separated by the constructed levee in the bend flume. Results showed that the levee breaching process can be subdivided into a slope erosion stage, a headcut retreat stage and a breach widening stage. Mechanisms such as flow shear erosion, impinging jet erosion, side slope erosion and cantilever collapse were discovered in the breaching process. The erosion characteristics were determined by both flow and soil properties. Finally, a depth-averaged 2-D flow model was used to simulate the levee breaching flow rates, which is well expressed by the broad-crested weir flow formula. The deduced discharge coefficient was smaller than that of common broad-crested rectangular weirs because of the shape and roughness of the breach.

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“…The amount of the coefficient of the flow in fixed weirs depends on the weir type, shape of the crest (sharp, inclined or rounded) of the upstream entrance (Parílková et al, 2012) and β angle. The amount of the coefficient of the flow in fixed weirs depends on the weir type, shape of the crest (sharp, inclined or rounded) of the upstream entrance (Parílková et al, 2012) and β angle.…”

Section: Water Level Regulation Structures With Fixed Weirmentioning

confidence: 99%

Perspective of Water Distribution Based on the Performance of Hydraulic Structures in the Varamin Irrigation Scheme (Iran)

Mohammadi

Rizi

Abbasi

2018

Irrigation and Drainage

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Despite the extensive application of check and offtake structures in irrigation canals, their periodic assessment is generally not included in water management plans, especially in Iran. This issue would be more important when there are many problems in water distribution in irrigation projects. In this study the performance and operating status of different hydraulic structures in the Varamin irrigation scheme were evaluated using a precise flowmeter. Results show that Neyrpic modules have an error in range of −8 to 83% and these structures, on average, delivered 22% more water. The discharge coefficient of duckbill weirs has changed considerably as well and they are not able to regulate the water level appropriately, because of ageing and physical destruction. The results showed that to achieve an acceptable performance of Neyrpic modules in this scheme it is essential to perform some physical modifications, such as cleaning and sealing the gates, removing sediment around the gates, replacing old gates and continuous inspection of infrastructure. A series of measurements to estimate water losses during the conveyance process show that the conveyance efficiency for each 1000 m length of main, secondary and tertiary canals are respectively 95.0, 91.5 and 89.3%. Consequently to achieve a suitable water distribution pattern, preventive maintenance should be considered. © 2018 John Wiley & Sons, Ltd.

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The Influence of Roughness on the Discharge Coefficient of a Broad-Crested Weir

Cited by 17 publications

References 10 publications

Performance of a shallow-water model for simulating flow over trapezoidal broad-crested weirs

Performance of a shallow-water model for simulating flow over trapezoidal broad-crested weirs

Overtopping breaching of river levees constructed with cohesive sediments

Perspective of Water Distribution Based on the Performance of Hydraulic Structures in the Varamin Irrigation Scheme (Iran)

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