正挑丁坝区鱼类栖息地水力生境指标分布特征数值模拟

Numerical Simulation of Distribution Characteristics of Hydraulic Fish Habitat Index in 90°Spur Dike Areas

丁坝区鱼类栖息地研究对河流生态保护具有重要意义,基于三维水流数学模型,探讨了正挑丁坝区鱼类栖息地水力生境指标的分布特征,结果表明:①水流流速随弗劳德数Fr的增大而增大,坝后回流区宽度逐渐减小,主流区沿程从急变流变为渐变流,并逐渐恢复为均匀流;②主流区和回流区流速梯度G较小,G>2的区域主要集中在水槽左右两岸和丁坝坝头附近,横断面上G随弗劳德数Fr的增大而减小;③丁坝上游至下游剖面动能梯度M的分布特征与G相似,M高值区出现在水槽右岸及坝头附近相对槽宽B^(+)=0.25~0.40区段,但水槽左岸的M值较小且沿程变化不大;④丁坝上游流速适宜度S_(u)随Fr的增大而减小,丁坝和丁坝下游断面S_(u)随Fr的增大而增大;丁坝下游回流区的S_(u)较小,一般不超过0.3,而主流区的S_(u)可能超过0.8,表明该区域鱼类产卵栖息条件较好。研究结果可为丁坝区鱼类资源保护和生态航道工程建设提供参考。

The study of fish habitat in spur dike areas is of great significance to the ecological protection of rivers.In this paper,the distribution characteristics of the hydraulic fish habitat index in a spur dike area are discussed by a three-dimensional(3D)mathematical model for water flow.The results reveal that①the flow velocity increases with the Froude number Fr;the width of the back flow area behind the dike decreases gradually,and the main flow area changes from rapidly varied flow to gradually varied flow and gradually returns to uniform flow.②The flow velocity gradient G in the main flow and back flow areas is small;the areas with G>2 are mainly concentrated on the left and right banks of the water channel and near the spur dike head,and on the cross-section,G declines as Fr grows.③The distribution characteristics of the kinetic energy gradient M on the section of the spur dike from upstream to downstream are similar to those of G.The high-value areas of M appear on the right bank of the water channel and in the section with the relative channel width B^(+) of 0.25~0.40 near the spur dike head,but M is small on the left bank of the water channel and has little change along the way.④With the increase in Fr,the velocity suitability S_(u) in the upstream of the spur dike decreases,while S_(u) at the spur dike and in the downstream cross-section of the spur dike increases.S_(u) of the back flow area in the downstream of the spur dike is small,generally not more than 0.3,while S_(u) in the main flow area may exceed 0.8,which indicates that the spawning habitat of fish in this area is better.The research results can provide a reference for the protection of fish resources in spur dike areas and the construction of ecological waterway projects.