Comparison of discharge capacity of piano key weir with ogee and sharp crest weirs

In this research, comparison of piano key weir with sharp crested weir and ogee spillway is addressed. The experimentally measured values of discharge of piano key weir were compared with their corresponding computed values for ogee spillway and sharp crested weir. By using the dimensional analysis technique, dimensionless equation was obtained for discharge coefficient of rectangular piano key weir. Experiments were conducted in a rectangular channel with 10 m length, 0.75 m width and 0.9 m height. Experiments were conducted for various discharges and flow depths. All the experiments were conducted under free flow conditions at weir outlet. The discharge coefficients for the rectangular piano key weir were obtained based on the measured discharges and flow depth. The discharge of ogee spillway and sharp crested weir were estimated by using conventional weir equations. The variations of discharge versus total upstream head showed almost linear increasing trend of discharge with total head. The plotted data showed a decreasing trend of discharge coefficient with increasing relative total head. The obtained discharge coefficients for the rectangular piano key weir varied between 0.3 and 0.55. The average discharge coefficient for this weir was 0.4. At Ht/P = 0.28, the discharge through the rectangular piano key is almost 4 times the discharge of the ogee spillway. The average discharge of the piano key weir is about 2.5 times of the ogee spillway and about 3 times that of the sharp crest weir. The energy dissipation of the piano key weir is about 0.3. According to the results, the piano key weir performs better than the ogee spillway and the sharp crest weir. Therefore, in the circumstances that the design discharge of the dams has increased due to climate changes, the piano key weir is a better alternative to ogee spillway, due to its higher efficiency.