Piano Key Weir Hydraulics: Experimental Study of Flow Patterns and Investigation of the Sloped Crest A-Type PKW

摘要

Piano Key Weir is a cost-effective and hydraulically performant solution for spillways, considered as a Climate Change adaptation as well. In order to enhance the understanding of the hydraulic behavior of the A-type PKW and to investigate the effects of introducing a crest slope, an experimental study has been performed. This new configuration aims to reduce the discharge capacity at low heads requested in some cases for flood management purposes, while keeping the same maximum reservoir level. In this paper, three models have been tested first in order to investigate the scale effects and the flow patterns in terms of discharge capacity, velocity field and nappe behavior. Then, seven PKW configurations with different crest slopes have been studied. Results confirm the relevant influence of the scale effect at low heads. The comparison of the experimental discharges with the ones predicted by the published analytical formulations, inside their validity fields, shows, a similar trend within ±15% but not identical results. Clinging, leaping, springing and drowned flow regimes ranges have been quantified. The velocity fields have also been analyzed. The results of the sloped crest PKW investigation reveal that the discharge capacity is significantly reduced at low relative heads H/P<0.35 but, it matches the standard model capacity for H/P>0.6 with a maximum deviation of 10%.