Three-Dimensional Modelling of Flow in a Vertical Slot Fishway

The flow characteristics of fishways constructed to facilitate fish migration bypassing barriers in rivers, depend on the fishway geometry and the layout. Hence, the selection of the baffles and pools arrangement within the channel is essential for an optimum design of a fishway. In this study, the suitability of flow characteristics of vertical slot fishway (VSF) with selected geometric design was assessed by both experimental study and numerical modelling. Three—dimensional computational fluid dynamic model was developed by using ANSYS CFX 17.2 software. Model validation was done based on the water depth and velocity measurements obtained from laboratory experiments. Suitability of flow characteristics were assessed for increasing slopes by developing CFD models for 7, 9, 11 and 13% slope cases. It was found that the maximum values of velocity, turbulent kinetic energy and energy dissipation rate in the fishway occur at the slots and they increase with the increasing slope. The low velocity pool volumes corresponding to each slope were computed to assess the adequacy of the resting zones for fish. The study concludes that the pool length of the VSF could be 43% larger than the recommended values with the fishway slope up to 13%, while ensuring favourable flow conditions for fish passage to economize the VSF design.