Experimental investigation of flow over a triangular broad-crested weir

Abstract

Broad-crested weir is one of the most widely used hydraulic structures in irrigation and drainage systems. On natural streams where it is necessary to measure wide range of discharges, a triangular broad-crested weir has several advantages. Firstly, it provides a large breadth at high flows, so that the backwater effect is not excessive. Secondly, at low flows, the breadth is reduced so that the sensitivity of the weir remains acceptable. In this study, laboratory measurements on triangular broad-crested weir with different geometry were taken to investigate the flow pattern over a triangular broad-crested weir and new approach was undertaken to determine discharge coefficient equation. Results showed that the dimensionless parameters of h₁/L and Froude number have an effect on equation determining the discharge coefficient of the triangular broad-crested weirs. Good agreements between the measured values and the values calculated from the predictive equation are obtained. Therefore, an accurate equation for the discharge coefficient of the triangular broad-crested weirs in over-full condition () is introduced and could be used with confidence.

Keywords:

• laboratory study
• triangular broad-crested weir
• discharge coefficient
• over-full condition

Acknowledgements

The author thanks laboratory of Islamic Azad University of East Tehran branch in Iran for the technical assistance.