Laboratory Evaluation of Height Effects on Hydraulics of Submerged Piano Key Weirs

In this research, physical models of the piano key weirs with different geometrical specifications are made using PVC plates. Experiments have been conducted under different hydraulic conditions in order to determine the flow behavior, discharge coefficient, discharge reduction and total head ratio curves under the free and submerged flow conditions. A one meter width channel is used for experiments and flow rate is measured using an electromagnetic flow meter with 1 lit/s accuracy. Three dimensional water surface profiles are measured using a digital point gauge with 0.01 mm accuracy. Furthermore, flow over a one meter width linear sharp crested weir is investigated to assess the hydraulic performance of the tested piano key weirs with the corresponding hydraulic conditions. Results have shown that hydraulic behavior of the submerged piano key spillways depends on the height. By increasing the weir height, the submergence threshold decreases and the rate of the discharge reduction increases. Practical equations are developed to determine the discharge coefficient, discharge reduction factor and non-dimensional total head curves under submerged flow condition.