Energy dissipation on a stepped spillway downstream of a Piano Key Weir - Experimental study

Piano Key Weir (PKW) is a new type of weir showing appealing hydraulic capacities. Its specific geometric features create different interacting flows and jets downstream of the structure. This suggests that the use of a PKW to control the flow upstream of a stepped spillway may help in enhancing energy dissipation on the downstream channel. The first results of an experimental study carried out at the Laboratory of Engineering Hydraulics – HACH in the scope of a Coyne & Bellier – Tractebel Engineering project are presented in the paper. The goal of the study was to compare the energy dissipation on a stepped spillway downstream of a PKW with the one which takes place on the same spillway equipped with a standard ogee-crested weir. Despite similar global energy dissipation rates whatever the weir type due to the relative important height of the spillway, significant differences in the aeration of the flow along the spillway have been shown. This paves the way to further investigations.