Suppressed by the up passage vortex at upstream side of blade, the intensity and scale of the tip clearance leakage vortex is decreased.

渐缩型间隙在叶片前半轴弦受到上通道涡的抑制，减少了叶顶间隙泄漏涡的强度和范围；

youdao

The Environment Agency said while the passage of tagged fish over the barrage had been low, it had found the numbers of young salmon upstream had increased, which underlined the complexity of the issue.

BBC: Fears over Tees Barrage impact on fish