Author(s): M. Oertel
Linked Author(s): Mario Oertel
Keywords: Piano Key Weir; PKW; In-channel; State-of-the-art; Future challenges; Labyrinth weir
Abstract: Piano Key Weirs (PKW) are non-linear weir structures, which were developed in the late 1990s. In the following years several structures were investigated in experimental as well as numerical models and were also built in prototypes, especially in France. Thereby, PKWs represent an improvement and further development of so called Labyrinth weir, but with an additional increase of discharge capacities and a reduced footprint. Two main PKW applications can be separated in research projects: (1) ontopofdams (floodreleasestructures) and (2) in-channelapplications (replacementofregularweirs). Themaindifference between Labyrinth and Piano Key Weirs can be found in basic geometry components. While for Labyrinth Weirs the geometry follows a kind of accordion shape with vertical weir walls (velocity distribution close to the flow surface), the PKW design is more complex and includes sloped inlet and outlet keys, placed on a small footprint area. In this context, the general flow characteristics are also modified because the inlet and outlet keys can reach flow areas close to the river bed (for in-channel application). Hence, the velocity distribution differs majorly from those found in Labyrinth weirs -- and with it resulting phenomena like scouring or sediment transport. The present paper summarizes and highlights current research investigations and state-of-the-art solutions for PKWdesignsandcalculations -- especiallyforin-channelapplications. Basedonthiscomprehensiveliteraturereview, future challenges for PKW research projects are specified. Topics like general flow characteristics, scale effects, downstream scouring, sediment transport, drift wood log jams, fish climb capability, or concrete abrasion will be discussed in detail to identify current and further research needs in small-scaled and large-scaled experimental and numerical models.