Experimental analysis of flow characteristics over hydrofoil weirs

• Published in: Flow measurement and instrumentation 2021-06, Vol.79, p.101867, Article 101867
• Main Authors: Soydan Oksal, N.G., Akoz, M.S., Simsek, O.
• Format: Article
• Language: English
• Subjects: Discharge coefficient; Energy losses; Hydrofoil weir; Laser Doppler anemometer
• ISSN: 0955-5986; 1873-6998
• DOI: 10.1016/j.flowmeasinst.2020.101867

The rounded crested weirs are commonly used for discharge measurements and this overflow structures have advantages such as stable overflow pattern and good accuracy. Hydrofoil weirs with streamlined properties are similar to the ogee weirs and can be used as a spillway profile. The hydraulic features of flow over hydrofoil weirs created by the NACA0018, NACA0021 and NACA0024 hydrofoil geometry placed in an open channel are investigated experimentally under free-flow conditions. The velocity field of hydrofoil weir flows are measured by one-dimensional Laser Doppler Anemometer. Experimental velocity profiles are measured along the middle section of the channel, especially around the weir structure, to determine the boundary layer separation. According to the determination of optimum weir structure the free surface profiles, pressure distributions on weir surfaces, experimental discharge coefficients and head losses over weir structures are determined for different structure and flow conditions. Pressure distributions over the hydrofoil weir are presented. In addition, the relationships between discharge coefficient (Cd) and flow rate (Q), specific total head (H/R), relative weir height (P/H), relative total head (H/P) and dimensionless total energy head upstream of the weir (H/L) are investigated. •Wall boundary layer separation does not occur for the flow of NACA0018, NACA002 and NACA0024 weirs.•The curvature of the streamline over the weir increases with the increasing Froude number.•The variations in discharge coefficients are directly correlated with the crest radius and the flow rate.•The weir discharge coefficient increases with the increase of relative total head and weir height.