ABSTRACT
ABSTRACT: The Piano Key Weir (PKW) is a type of labyrinth weir with efficient hydraulic performance especially at low heads. For ten years, many experiments conducted in channels have contributed to identify the primary parameters influencing hydraulic performance and some secondary parameters like the dam height, the noses under the outlet keys or the crest shape. EDF has launched a new experimental program including the study of the crest shape effect on the discharge capacity under free flow conditions. This article presents the crest shapes testing on a typeA PKWwith flat-topped, half-rounded and quarter-rounded crests. Some crest configurations were tested at two damheights. The analyses confirmed that the crest shape influences the discharge capacity at lowheads and that the half-rounded and the quarter-rounded shapes have better hydraulic performance than the flat-topped shape. The present study highlighted that the discharge efficiency was mainly influenced by the lateral crest, and that with the rounded shapes, the gain in discharge (relative to the flat-topped crest) increased with the dam height and could reach from 10% to 20% at low heads when the scale effects became negligible.
