An experimental investigation on louvres and angled bar racks

Scale effects and hydraulic head losses are systematically investigated for fish guidance structures, i.e. louvres and angled bar racks. The experiments were conducted at 1:1 and 1:2 Froude-scaled models in a laboratory flume for a wide range of rack configurations under various hydraulic conditions. The study involves three main rack angles, three bar angles, and three bar openings as primary parameters characterizing the structure investigated, and two bar shapes, three bar depths and three relative rack submergences as secondary parameters. This study demonstrates that the above parameters are strongly interrelated with respect to the head loss, and the bar opening has a determinative effect on the flow–rack interactions. The analysis of functional relations among the parameters has led to a new head loss prediction formula. The implications of the findings for optimum engineering solutions in terms of head loss, fish guidance and project economy are also addressed.