| With the rapid development of social economy in recent years,the demand for hydropower and other resources is also increasing.To satisfy people's demand for resources,a large number of sluice-dam projects have been constructed on rivers Although the construction and operation of water conservancy projects have made great economic and social benefits in flood control,power generation,shipping and water supply,the river ecosystem has been destroyed.For example,the fragmentation of the river habitat,the truncation of the migratory passage of fish,and the decrease of the biological diversity of fish,etc.As an eco-compensation project,fish passes satisfies people's requirements for restoration of water ecosystems,and also meet the sustainable requirements for the harmonious development of man and nature.Its construction has improved river connectivity and connectivity,greatly improved river ecological restoration,coordinated the relationship between dam construction and the ecological environment,and met the requirements of people to restore water ecosystems.Combining historical data with the characteristics of imitation of natural fish passes,preliminary selection of rare fish species,endemic fish species,and economic fishes are objects of passing fish.Such as Elongate loach,Myxocyprinusasiaticus,Onychostoma sima,Brass gudgeon,Leiocassis longirostris,Beaufortialeveretti,Pseudorasbora parva,Ctenopharyngodon idellus,Rhinogobio ventralis Savage et Dabry,Prenant's schizothoracin,Procyprisrabaudi,etc.According to the swimming capability of some subjects,the flow rate of the pool chamber is not more than 1.0m/s,and the flow rate at the contraction section of the inlet and the chamber is not greater than 1.30m/s.In this study,the numerical simulation method was used to study the hydraulic characteristics of natural fishways,and the effects of changes in the shape of natural fish passages and the arrangement of drift stones on the addition of rough slopes were investigated.These effects on flow patterns,velocity distribution,and flow fields in the pool were affected.Based on the results of the model calculation combined with the requirements of the fish's upstream swimming ability,the main results of selecting a natural fish pass type structure suitable for retrospective fishes are as follows:(1)Numerical simulation of numerical simulation of natural fish passages with rough rampsAs the slope increases,the water levels in the pool rooms become relatively low,i=4%,i=5%,and the water level fluctuates.The slope i=2%,i=3%,the water depth in the pool room is relatively stable,and the flow state of the water in the fish pond pool is good.There is no excessive and severe vortex and water jump area,which is suitable for fish tracing.The i=3%relative to the i=2%cross-section flow rate and the fishway inlet flow rate is 1.7?2.3 m/s,and the import turbulence intensity is relatively large,causing the retroactive disorientation.Therefore,the gradient i=2%is selected in this study.(2)Optimization of two kinds of rough ramps for imitation of natural fish passagesThe structure of the regular code-passing structure mimics the natural conditions of the fishway with better hydraulic conditions.The water depth along the route fluctuates in the range of 0.35-0.60m,and the water level gradually decreases along the course.The average ratio is reduced to 5%,and the change is relatively gentle.The flow rate from the surface to the bottom of the mainstream is decreasing.The flow velocity at the bottom is 0.6?0.8m/s,the middle is 0.6?1.0m/s,and the surface velocity is 1.0?1.2m/s.The flow velocity from the bottom to the surface gradually increases.At the bottom of the mainstream speed in the 0.2?0.6m/s larger area of low velocity area.The streamline in the middle is relatively smooth,and the mainstream and low-flow recirculation zones are distinct.The maximum turbulent kinetic energy range from top to bottom for different water depths is:0.06?0.23m~2/s~2,0.05?0.073m~2/s~2,0.04?0.0643m~2/s~2.The maximum surface layer and the bottom layer show a decreasing trend from top to bottom.The area affected by kinetic energy also gradually decreases.(3)Structural optimization of existing hydraulic problemsThe partial structure is optimized to increase the length of the boulders to 0.25m,the length of the pool room is 1.20m,and a group of energy dissipation tooth piers are set at the entrance of the fishway.The mainstream is not significantly compressed,the streamline is relatively straight,the mainstream and the low-velocity recirculation zone are clearly distinguished,the mainstream streamline extends downstream and the distance increases.The mainstream is in the middle of the fishway,and the velocity of the pool chamber is similar to the central axis of Y=0.55m.Symmetrical distribution,near the edge of the boulders forming a low flow velocity area of 0.2 m/s?0.6 m/s,accounting for nearly 2/3 of the cross-section,cross-section at the flow rate exceeds the fish standard 1.2m/s section increased;pool room water depth range It is 0.59?0.39m and the average ratio is 3.3%.The maximum import flow rate is less than 1.3m/s,which meets the requirement of overfishing,and the maximum turbulent energy is 0.09 m~2/s~2,which indicates that the water body blended with strong energy dissipation effect is better,and it can meet the standard requirements for imitating the natural fishway. |
PDF Full Text Request