Structure of Flow in Vertical Slot Fishway

This paper presents the results of an experimental study on the structure of flow in a vertical slot fishway of an effective and simple design. The flow at the slot could be treated as a plane jet, but there are a number of differences from the plane jet. It was found that for a slope of 5%, the main flow travels from one slot to the next through the pool as a 2D curved jet with two recirculation regions—one on each side. For slopes of 10 and 20%, the main flow is 3D. Water flows toward the side wall between the long baffles near the bed and piles up along the sidewall; part of the flow rises to the surface and then travels to the outlet. The decay of longitudinal velocity in the pool is much larger than that of the plane jet. The volume averaged velocity head of the water in the pool was found to be ∼12% of Δh, the head drop per pool. The volume of the recirculation region between the short baffles was ∼28% of the volume of the pool for all three slopes and all discharges whereas the corresponding volume of the horizontal eddy just downstream of the long baffles for the two larger slopes was ∼10%. The relative volume of the two recirculation regions was ∼73% for the 5% slope and ∼38% for the 10 and 20% slopes.