Hydraulic characteristics of a new weir entitled of quarter-circular crested weir

• A new weir entitled of quarter-circular crested weir is introduced.
• Hydraulic characteristics of the weir are experimentally investigated.
• Discharge coefficient of the weir is a constant value and equals to 1.261.
• The new weir can serve as an accurate device for flow measurement in open channels.
• The lower nappe profile of free jet over the weir can be considered as the ogee shape of the weir.

Weirs are used for flow measurement, flood control in reservoirs and water level control in irrigation systems. In this study, a new weir entitled of quarter-circular crested weir is investigated. This weir is geometrically consisted of a quarter-circular crest of radius R, upstream slope α and vertical downstream face. The downstream face of the weir must be ventilated. Discharge coefficient, crest section velocity and pressure profiles, pressure distribution on the crest surface and upper and lower nappe profiles of flow over the quarter-circular crested weir were experimentally investigated. Results indicated that discharge coefficient of the weir is a constant value and equals to 1.261. In the range of H/R<1.5, it is more than the discharge coefficient of circular crested weir. The lower nappe profile of free jet over the weir can also be considered as the ogee shape of the proposed weir.