Hydrodynamics and Free-Flow Characteristics of Piano Key Weirs with Different Plan Shapes

This paper focuses on Piano Key Weirs (PKWs) as an effective solution for improving the discharge capacity of spillway systems. The flow behavior in inlet and outlet keys is experimentally studied to analyze PKWs with different plan shapes (i.e., rectangular, trapezoidal, triangular). results show that keys, aeration regimes extend higher values headwater ratios (Ho/P) by increasing length magnification ratio (B/w) apex width (A/w). In addition, local submergence a decreasing function A/w, especially high heads. While total interference enlarges reducing A/w lower Ho/P (Ho/P < 0.5), reverse trend observed ratios. PKW performance may also be impacted contraction recirculation zone which intensify Ho/P, B/w, A/w. According obtained results, while coefficient > 0.4, it have head conditions. trapezoidal has highest efficiency wide range domain 0.25 B/w ≥ 2). It can improve around 5%, its body volume almost 7% smaller than traditional rectangular PKW. However, low-length high-head conditions (B/w = 1 exceeds other shapes.