Innovative design and experimental‐numerical studies of Piano Key Spillway for significantly enhanced discharge and hydraulic performance

Safe discharge of excess water is an issue that affects all hydropower plants in high flow situations. It is therefore important to investigate potential improvements in the design of spillways, which contribute to increased discharge safety.

Piano key weirs are a further developed version of labyrinth weirs and are characterised by a slightly more complex geometry. The parameters controlling the weir include the length and width of a unit, the width of the inlet and outlet keys, and the length and structural height of the overhangs. The optimal choice of parameters may vary depending on whether it is a new weir or an extension to an existing dam. The trade-off between hydraulic efficiency and structural complexity also matters. To improve inflow conditions and to extend the length of the crest, it is proposed, among other things, to streamline the ends of the inlet and outlet tangencies and to adapt the sloping bottoms of both tangencies to the rounded shape. It is also necessary to investigate the behaviour of the propellant in front of the weir. The project is intended to achieve the following objectives:

• To develop and evaluate an improved design of piano key weirs for more efficient water discharge. Compared to a conventional variant, expected increase in discharge capacity can be 25-35%.
• To disseminate knowledge of developments in the field to the hydropower industry.
• To provide a basis for cost-effective design options in renovation projects in the Sweden.