Streamwise bars in fish-friendly angled trashracks

Experimental results for fish-friendly trashracks placed in an open-water channel are presented. Eighteen angled trashracks were used to test different bar spacings, bar shapes and rack angles. Each model trashrack comprised two horizontal supports with regularly spaced slots adjusted to compensate for the trashrack angle, i.e. maintain the vertical bars “streamwise” (parallel to flow). Water depths and velocity profiles were acquired upstream and downstream of each rack configuration. The results reveal that the head-loss coefficient for angled racks with streamwise bars does not depend on the rack angle and can be calculated with equations for racks perpendicular to the channel. Upstream velocity profiles along the rack are not significantly affected by the rack angle and downstream transverse profiles are nearly uniform. A comparison with conventional angled trashracks with bars set perpendicular to the rack revealed the many advantages of streamwise bars.