Hydraulic Design Optimization and Performance Analysis of Piano Key Weirs: A Study of Geometric Factors and Staged Configurations

A piano key weir is a modern modified type of labyrinth weir (a type of nonlinear weir). This type of weir increases the amount of discharge by increasing the crest length with inclined entrances and exits that reduce the amount of sediment. A piano key weir is the best option if the base length or width is specified. Owing to the novelty of the weir, the complexity of its dimensions, and the resulting flow, there is no specific design or criteria for its use, with a dearth of studies on it. The current study examined the impact of geometric factors, including (L/W, Ht/P) for constant (Wi/Wo = 1) and (Bo/B = 0.5), on the discharge coefficient for Type B under free-flow circumstances. The study also examined the capability of the stages in the side crest of the piano key weir (∆P⁄P and ∆L⁄L) and their effects on hydraulic capacity. The flow properties of several stages of piano key weir (Type B) designs were investigated on a laboratory scale, and relationships between head discharges were developed. The results showed that the use of holes (stages) in the sides of the inlet and outlet keys increased the discharge capacity and the discharge coefficient of a modified piano key weir in comparison to a standard piano key weir, by increasing the length and depth of the hole while controlling the amount of discharge coming out in the case of low depths.