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 90o, 100o, 110o and 120o 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 10o 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: