Hydraulic behavior and energy dissipation in Piano key weirs vs. Rectangular labyrinth weirs: A comparative study

Abstract

Flow characteristics and energy dissipation of Piano Key Weirs (PKWs) were investigated in this study and compared with rectangular labyrinth weirs (RLWs). Despite their increasing popularity as efficient spillway structures, more research was needed on the hydraulic behavior of PKWs. Numerical simulations using the computational fluid dynamics (CFD) software were conducted, and the results were validated against experimental data for an RLW. The findings revealed distinct flow patterns in PKWs, with sloping and stepped ramps promoting smooth evacuation of near-bed streamlines and enhancing turbulence and aerated flow downstream. Water surface profiles differed between RLWs and PKWs, with PKWs exhibiting a more even and efficient flow distribution. The study further examined energy dissipation and residual energy efficiency in PKWs, showing a nonlinear decrease in relative energy dissipation with increasing head-to-weir height ratios. PKWs demonstrated superior energy dissipation compared to RLWs, with A-type PKWs outperforming D-type PKWs. The width ratio of keys emerges as a crucial factor influencing energy dissipation, with smaller ratios promoting higher energy dissipation rates. Incorporating steps in D-type PKWs enhanced energy dissipation, especially at lower heads. However, local submergence effects reduced the differences in energy dissipation between PKWs at higher heads. These findings contributed to a better understanding of PKW hydraulic performance, providing valuable insights for optimizing PKW designs and enhancing the cost-effectiveness of hydraulic structures.