Author(s): Elham Bahman; Mohammad Navid Moghim; Abdorreza Kabiri-Samani
Keywords: Discharge coefficient; Hydrofoil weir; Joukowsky transformation; Potential flow; Velocity distribution
Abstract: A hydrofoil weir is a special type of weir that is designed on the basis of aerofoil theory. These weirs have the merits of a higher discharge coefficient, more stability, and fewer fluctuations for a water-free surface compared to sharp-, broad and long-crested weirs. Hydrofoil weirs with an incidence angle of potential flow look like ogee weirs and can be used as dam spillways. In the present study, a conformal mapping technique is applied to investigate the flow around a hydrofoil weir and compare it to the flow around a circular cylinder, where the potential and free vortex flows are combined. The discharge coefficient and velocity distribution are obtained using the Joukowsky transformation and fundamental theories of hydraulics. The analytical results are calibrated using an extensive set of former experimental data. The results indicate that the present approximate analytical model predicts the discharge coefficient and velocity distribution with an acceptable precision compared to the available developed empirical relationships for these weirs, and is a good tool for the design of hydrofoil weirs.