Prediction of Discharge for Arced Labyrinth Weirs with Trapezoidal Cross Section

Document Type : Research Article

Authors

1 Department of Water Science and Engineering, Faculty of Agriculture and Natural Resources, Islamic Azad University Ahwaz, Ahwaz, Iran.

2 Department of Irrigation and Reclamation Engineering, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran.

3 Research Expert, Imam Khomaini Higher Education Center, Agricultural Research, Education and Extension Organization (AREEO), Karaj, Iran

Abstract

Labyrinth weirs are among the hydraulic structures that are constructed to regulate the water level and control the flow in canals, rivers and reservoirs of dams. This structure is designed to transmit large currents in low heads by increasing the effective length of the overflow crown. The crest axis of this type of weirs is indirect and in showing the horizontal surface, the overflow is composed of interconnected walls. Labyrinth weirs are repeated with triangular, trapezoidal, rectangular and arc geometries alternating in flow width. The main criterion in the labyrinth design of the weirs was to increase the flow transmission capacity on the overflow with a fixed canopy and for a certain height of the water level upstream of the weir. In this study, 145 laboratory data were used, including four types of arc labyrinth weirs with different arc radius and tangent lengths. The discharge efficiency was introduced as a dimensionless parameter  using dimensional analysis. The relationships between  and the critical depth of flow (y_C/P) were obtained using graphs for two different types, R2 = 0.983 and R2 = 0.998. Then a graph to y_(C_Lt )/P and H_t/P a relation to calculate the critical depth were presented. The results showed that the calculated flow rate obtained using yc is consistent with laboratory values so that the relationship between them is R2 = 0.982.Labyrinth weirs are among the hydraulic structures that are constructed to regulate the water level and control the flow in canals, rivers and reservoirs of dams. This structure is designed to transmit large currents in low heads by increasing the effective length of the overflow crown. The crest axis of this type of weirs is indirect and in showing the horizontal surface, the overflow is composed of interconnected walls. Labyrinth weirs are repeated with triangular, trapezoidal, rectangular and arc geometries alternating in flow width. The main criterion in the labyrinth design of the weirs was to increase the flow transmission capacity on the overflow with a fixed canopy and for a certain height of the water level upstream of the weir. In this study, 145 laboratory data were used, including four types of arc labyrinth weirs with different arc radius and tangent lengths. The discharge efficiency was introduced as a dimensionless parameter  using dimensional analysis. The relationships between  and the critical depth of flow (y_C/P) were obtained using graphs for two different types, R2 = 0.983 and R2 = 0.998. Then a graph to y_(C_Lt )/P and H_t/P a relation to calculate the critical depth were presented. The results showed that the calculated flow rate obtained using yc is consistent with laboratory values so that the relationship between them is R2 = 0.982.Labyrinth weirs are among the hydraulic structures that are constructed to regulate the water level and control the flow in canals, rivers and reservoirs of dams. This structure is designed to transmit large currents in low heads by increasing the effective length of the overflow crown. The crest axis of this type of weirs is indirect and in showing the horizontal surface, the overflow is composed of interconnected walls. Labyrinth weirs are repeated with triangular, trapezoidal, rectangular and arc geometries alternating in flow width. The main criterion in the labyrinth design of the weirs was to increase the flow transmission capacity on the overflow with a fixed canopy and for a certain height of the water level upstream of the weir. In this study, 145 laboratory data were used, including four types of arc labyrinth weirs with different arc radius and tangent lengths. The discharge efficiency was introduced as a dimensionless parameter  using dimensional analysis. The relationships between  and the critical depth of flow (y_C/P) were obtained using graphs for two different types, R2 = 0.983 and R2 = 0.998. Then a graph to y_(C_Lt )/P and H_t/P a relation to calculate the critical depth were presented. The results showed that the calculated flow rate obtained using yc is consistent with laboratory values so that the relationship between them is R2 = 0.982.Labyrinth weirs are among the hydraulic structures that are constructed to regulate the water level and control the flow in canals, rivers and reservoirs of dams. This structure is designed to transmit large currents in low heads by increasing the effective length of the overflow crown. The crest axis of this type of weirs is indirect and in showing the horizontal surface, the overflow is composed of interconnected walls. Labyrinth weirs are repeated with triangular, trapezoidal, rectangular and arc geometries alternating in flow width. The main criterion in the labyrinth design of the weirs was to increase the flow transmission capacity on the overflow with a fixed canopy and for a certain height of the water level upstream of the weir. In this study, 145 laboratory data were used, including four types of arc labyrinth weirs with different arc radius and tangent lengths. The discharge efficiency was introduced as a dimensionless parameter  using dimensional analysis. The relationships between  and the critical depth of flow (y_C/P) were obtained using graphs for two different types, R2 = 0.983 and R2 = 0.998. Then a graph to y_(C_Lt )/P and H_t/P a relation to calculate the critical depth were presented. The results showed that the calculated flow rate obtained using yc is consistent with laboratory values so that the relationship between them is R2 = 0.982.

Keywords


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  • Receive Date: 05 October 2020
  • Revise Date: 23 November 2020
  • Accept Date: 01 December 2020
  • First Publish Date: 01 December 2020