Experimental study of fish-friendly angled bar racks with horizontal bars

This paper presents an experimental study of angled fish-friendly bar racks with horizontal bars, using a physical model in an open channel. Head losses are investigated for two bar shapes, three ratios between bar spacing and bar thickness and four angles of orientation of the racks. The Froude and bar-Reynolds numbers were respectively 0.275 and 3600. The head loss coefficients decrease as the blockage ratio and the angle of orientation of the rack decrease. They are well predicted by a formula produced previously for an inclined rack, with some adaptations. Velocity fields are characterized upstream and downstream of the racks, showing no effect of the angle of orientation and no heterogeneity over channel width. Consequently, the normal and tangential components of the velocity along the rack are in agreement with the theoretical values given by angular decomposition. These results serve to assess the compliance with biological criteria to avoid impingement risks and guide fish towards a bypass.