Author(s): Ismail Albayrak; Fiona Maager; Robert M. Boes
Keywords: Fish guidance structure; fish passage; head loss; horizontal bar rack; scale effect
Abstract: Horizontal bar racks are successfully used to protect downstream migrating fish and guide them to a bypass at a number of hydropower plants. However, there is no systematic study available on the hydraulic performance of such fish guidance structures. To fill this research gap, we experimentally investigated scale effects and hydraulic head losses of horizontal bar racks. The study involves two main rack angles, two bar shapes and depths, and three bar spacings as primary parameters characterizing the structure investigated as well as top, top & bottom, and bottom overlays as secondary parameters. The bar spacing was the most important factor determining the flow–rack interactions, followed by the rack angle, bar shape and depth, respectively. The overlay positions at the rack resulted in three distinct flow–rack interactions. A new head loss prediction formula was developed and compared with literature data. Recommendations for the optimum and economic rack design are given.