experimental comparison of discharge coefficient of a-type piano key and labyrinth side weirs with different heights

Hydraulic structures have a long history, with weirs being among the earliest developed; a notable example of these is the side weir. side weirs are of different shapes, including a nonlinear weir installed on the dam crest. weirs with nonlinear designs come in various forms, like labyrinth and piano key weirs; these are used when weir length is restricted, to maximize crest length, which subsequently increases discharge capacity. this study examines and contrasts how piano key and labyrinth weirs function as side weirs, since there has been little research on piano key side weirs. within this study, the experimental models incorporated trapezoidal, rectangular, and triangular labyrinth weirs, alongside piano key weirs, each characterized by four distinct heights 5, 10, 15, and 20 cm and three cycles, where the piano key weirs were classified as a-type. at a certain ht/p ratio, weirs with a smaller height had the maximum discharge coefficient and vice versa for weirs with a larger height. when a straight piano key weir and a rectangular labyrinth weir are both placed at a right angle to the stream, the piano key weir performs better. conversely, the present study, which evaluated the aforementioned weirs as side weirs, yielded contrasting results; the rectangular labyrinth weir exhibited superior efficiency to the piano key weir. the study's findings revealed triangular labyrinth side weirs exhibited a superior discharge coefficient (maximum 0.689), while rectangular labyrinth weirs outperformed piano key weirs by up to 24.85 % in side-channel arrangements.