investigation of hydraulic performance of piano shaped weirs using three dimensional numerical modeling

throughout history dams have been important structures in water storage. to avoid overtopping, damage, and or failure of a dam, adequate spillway is needed to release excess water from upstream floods. researchers found that spillways have to be made nonlinear in order to reach an economic structure with high performance. a piano key weir is one of the best solutions. piano key weirs are the modified and developed labyrinth spillways which can discharge greater volume of water than the common spillways in limited width and can be used as economic structures with high efficiency. in this article, a calibrated flow-3d modeling by laboratory results has been used to evaluate and analyze the discharge coefficient of piano key weirs as related to the variation in width at inlet and outlet keys. according to the researches, the geometrical and hydraulic parameters are the most important factors for evaluating the performance of piano shaped weirs. in this study, the analytical effects of these parameters on discharge coefficient, and also the capability of discharge in these models have been investigated. moreover, the important hydraulic parameters including depth, velocity and pressure have been studied through 3d numerical simulation. from the numerical results, a practical formula is proposed to obtain the discharge coefficient for the release capacity of the piano key weirs.