Flow measurement for the design optimization of fish pass entries in a run of river hydropower plant

The International Commission for the Protection of the Rhine (ICPR) has set the objective of guarantying the upstream migration of the salmons up to Basel, Switzerland, at horizon 2020. One of the last dams to be equipped is the one of Rhinau, in France. The large turbined discharges and the specificities of the hydroelectric facility require a detailed study of the flow in the tailrace channel to guaranty a proper visibility of the fishway entries for the fish. The study is not intended to the design of the fish pass itself, but to assure that fish can find its entries located in the tailrace channel within a highly fluctuation and structured flow field. Therefore, a physical model has been built at LCH-EPFL, on which the flow in the tailrace is assessed under different turbining configurations with the help of UVP transducers. Two transducers are used to create 2D representations of the measured flow field. The transducers are mounted on a robot capable of moving in all X, Y and Z directions within an area of 2x2 meters and able to manage the triggering of the UVP at each new robot location. Three types of datasets are recorded with this system: surface flow (longitudinal and lateral velocities), sections across each fishway entry (longitudinal and vertical velocities) and temporal variations of the longitudinal jet velocities. A last numerical step filters and interpolates the raw data to render clearly interpretable plots.