Size-scale Effects of an A-type Piano Key Weir

Piano Key Weirs (PKW) are non-linear weir structures with the benefit of an increased discharge capacity, compared to regular, linear weirs. While the structure’s footprint is very small, PKWs can be placed on top of dams for flood release purposes. But also, in-channel approaches are possible. Compared to regular weirs with movable elements, PKWs are more complex hydraulic structures, but with less maintenance necessity. PKW research is very young and nowadays frequently discussed within the hydraulic structure community. When analyzing experimental model data, scale effects are of major interest, because small scaled models might be affected by viscosity and surfaced tension influences. For other non-linear weir types, e.g. labyrinth weirs, size-scale effects have been analyzed comprehensively during the last years. For PKWs, only a few investigations are available in the literature. The present paper pics up this research topic and presents a study on size-scale effects of an A-type PKW. Therefore, experimental models with various scale sizes were conducted in the TH Luebeck’s hydraulic laboratory to identify the influence of scale effects on resulting nape behaviors and consequently, on resulting discharge coefficients. A surface tension correction function is presented.