竖缝式鱼道桩柱结构过鱼效果探究

Optimizing Vertical Slot Fishway Hydraulics with a Pool Cylinder

为优化鱼道池室结构,提升鱼类洄游效果,以常规竖缝式鱼道为原型,以齐口裂腹鱼(Schizothorax prenanti)为试验对象,通过数值模拟和对照性过鱼试验,比较分析了4种池室内部增加与未增加桩柱的水流结构。结果表明,在鱼道主流中间增设桩柱结构,可以有效减小回流区面积,减幅达49%,并可减小竖缝处的紊动能,最大减少18%;增加鱼类上溯路线分布,提高了池室空间利用率。2种结构的上溯轨迹分析发现,齐口裂腹鱼多选择回流区外侧上溯,避免进入回流区中心,即选择较高的水力应变与紊动能区域作为上溯方向,且上溯路线中偏好较低水力因子区域,上溯偏好流速为0.01~0.09 m/s,紊动能为0.001~0.008 m^(2)/s^(2),水力应变为0.2~3.0/s。体型Ⅱ鱼道通过在主流位置增加桩柱结构,形成了多股水流,有效减小回流区的占比,提高了鱼道池室空间利用率,为鱼类的上溯路径提供了更多选择。

The vertical slot fishway is widely used to assist upstream fish migration and increase river connectivity.However,the fish passage efficiency of most fishways is not satisfactory and the pool struc-ture in particular has potential for improvement.In this study,we used numerical simulations to analyze the pool flow structure after cylinders were placed in various configurations in the pool between the slots of a vertical slot fishway.Fish swimming behavior and preferences were then observed as the hydraulic parameters were varied in controlled fish passage experiments.Our aim was to provide theoretical evi-dence for improving fish passage design and efficiency.Four cylinder configurations(Ⅰ,Ⅱ,Ⅲ,andⅣ)were compared to determine which arrangement gave the best flow regime and fish passing efficiency.Then,Schizothorax prenanti was selected for experiments on fish passing through pools modified with cylinders and the pools of a standard vertical slot structure and upstream swimming behavior was ob-served.Results show that a single cylinder at mid-pool of the mainstream(configurationⅡ)reduced the reflux zone by 49%and the turbulent kinetic energy at the vertical slot by 18%,which increased upstream swimming routes and available pool space.Analysis of upstream swimming trajectories in the experi-ments shows that S.prenanti prefer swimming outside the recirculation zone,and used the higher hydrau-lic strain in the turbulence energy area to adjust swimming direction.The preferred upstream swimming trajectory of S.prenanti was significantly related to the velocity,turbulence energy,and hydraulic strain(P≤0.01),with a preferred flow velocity range of 0.01-0.09 m/s,turbulent kinetic energy range of 0.001-0.008 m^(2)/s^(2),and hydraulic strain range of 0.2-3.0/s.In conclusion,adding a cylinder mid-pool main-stream of the fishway(configurationⅡ)produces multiple streams of water,reduces recirculation zone size,increases useable pool space,and provides more upstream swimming trajectories.