仿自然鱼道水动力特征及断面消能率研究

    Hydrodynamic characteristics and cross-sectional energy dissipation mechanisms in nature-like fishways

    • 摘要: 针对传统竖缝式鱼道存在的高速屏障、上溯通道固定、消能形式单一及回流区易导致鱼类迷失方向等问题,本研究聚焦交错石墙式仿自然鱼道,旨在探究其水动力特性优势及设计参数对消能率的影响,为优化设计提供指导方向。基于局部物理模型试验,沿水深方向垂直分层开展分析。得到如下研究结果:从水动力特性来看,通过水力条件分层协同优化,表层形成平稳顺直且可支持全断面过鱼的上溯通道;中、底层受绕流和孔隙过流的复合作用,形成低能耗、低曲率的“S”形通道,上溯方向明确。孔隙水流与绕流水体的相互作用,不仅消除了墙后回流区,还形成了低流速的休息区,从而有效规避了传统竖缝式鱼道因固定路径及回流现象导致上溯鱼类迷失方向的风险。在消能率调控方面,消能率(η)受过流量(Q)、断面底宽(B)及石墙高度(H)与水深(h)相对关系的三重调控:η与Q呈显著负相关,低流量时增大底宽可提升摩擦消能效率,且随着过流量的增加,增加断面底宽带来的消能效率优势加速衰退;墙高-水深关系对消能机制的影响可分为三个阶段:未淹没石墙阶段,消能率差异不显著;临界淹没石墙阶段,消能率与水深呈正相关;超淹没石墙阶段,堰流主导导致消能率衰减加剧。整体而言,交错石墙式仿自然鱼道分层协同的水动力特性与丰富的消能方式,避免了传统鱼道的固有缺陷,相关研究成果可为仿自然鱼道工程实践提供依据。

       

      Abstract: In response to the problems existing in traditional vertical-slot fishways, such as high-velocity barriers, fixed upstream channels, single energy dissipation forms, and backflow zones that tend to cause fish disorientation, this study focuses on the staggered stone wall-type nature-like fishway. It aims to explore its advantages in hydrodynamic characteristics and the influence of design parameters on the energy dissipation rate, so as to provide guidance for optimized design. Based on local physical model tests, an analysis was conducted with vertical stratification along the water depth direction. The research results are as follows: In terms of hydrodynamic characteristics, through hierarchical and coordinated optimization of hydraulic conditions, a stable and straight upstream channel capable of supporting fish passage across the entire cross-section is formed in the surface layer; in the middle and bottom layers, under the combined action of circumfluence and pore flow, an "S"-shaped channel with low energy consumption and low curvature is formed, with a clear upstream direction. The interaction between pore water flow and circumfluent water not only eliminates the backflow zone behind the wall but also forms a low-velocity resting area, thereby effectively avoiding the risk of upstream fish disorientation caused by fixed paths and backflow phenomena in traditional vertical-slot fishways. In terms of energy dissipation rate regulation, the energy dissipation rate (η) is regulated by three factors: flow rate (Q), cross-sectional bottom width (B), and the relative relationship between stone wall height (H) and water depth (h). Specifically, η is significantly negatively correlated with Q; increasing the bottom width at low flow rates can improve frictional energy dissipation efficiency, and as the flow rate increases, the advantage in energy dissipation efficiency brought by increasing the cross-sectional bottom width decays rapidly. The influence of the wall height-water depth relationship on the energy dissipation mechanism can be divided into three stages: in the unsubmerged stone wall stage, the difference in energy dissipation rate is not significant; in the critically submerged stone wall stage, the energy dissipation rate is positively correlated with water depth; in the over-submerged stone wall stage, the dominance of weir flow leads to intensified attenuation of the energy dissipation rate. Overall, the staggered stone wall-type nature-like fishway, with its hierarchically coordinated hydrodynamic characteristics and diverse energy dissipation modes, avoids the inherent defects of traditional fishways, and the relevant research results can provide a basis for the engineering practice of nature-like fishways.

       

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