Evaluation of Flow behavior over Broad-Crested Weirs of a Triangular Cross-Section using CFD Techniques

Abstract

Weirs are barriers placed across a river and designed to control the flowing water in order to prevent floods, make waterways operable for inland navigation and measure flow discharge. Although there are many types of weirs, mainly used ones are sharp-crested, circular-crested (cylindrical), broad crested and ogee weirs. In the present study, triangular broad-crested weirs are numerically investigated under different flow conditions. Different interior angles of 90^o, 100^o, 110^o and 120^o are included for the opening of weirs. The flowing water over weirs is simulated using CFD techniques and evaluated at different flow regimes with inlet discharges of 0.012 m³ s^-1, 0.036 m³ s^-1and 0.06 m³ s^-1. The simulation results have shown that the water level upstream the weir is inversely proportional to the opening angle, where an increment of 10^o in the opening angle leads to a drop in water level about 1.5 cm. In addition, applying a discharge of 0.012 m³ s^-1, an uncovered region with water is created downstream the triangular broad-crested weirs, while the bed downstream of the rectangular broad-crested weir is covered with a thin layer of water at the same flow discharge. The aforementioned results are compared with a comparative data and show good agreement. By using triangular broad-crested weirs, it is important to measure the wake region and the hitting point of falling water downstream the weirs where this area must be strengthened well in order to resist water power and reduce the risk of drift.

Keywords

• Weir,CFD,V-notch,Broad-Crested weir,Turbulence model

References

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