Analysis On The Turbulent Characteristics Of Corrugated Steel Pipe Culvert Fishway

For centuries,people have controlled floods,provided irrigation and used potential energy by building hydraulic structures such as dams on rivers,but the construction of these hydraulic structures has cut off river connectivity and influenced the ecological environment of rivers.With the rapid development of society and economy,people's awareness of ecological protection has been gradually strengthened,and the restoration of river connectivity has become an inevitable trend.Fish passages play an important role in reducing the impact of barriers on sluice-dam projects and improving fish's ability to trace upstream,and fish channel is also one of the important techniques to maintain river connectivity.In this paper,the method of three-dimensional numerical simulation based on Fluent for corrugated steel pipe culverts is presented.The characteristics of turbulent flow such as velocity,turbulent kinetic energy,vortex and turbulent dissipation rate of corrugated steel pipe culverts with different slope and depth are analyzed.The main contents and conclusions are given as follows:(1)The velocity field of the culvert is simulated,contour map of longitudinal velocity at each section is established.It can be concluded that the flow velocity in the central area of the culvert exceeds the water section is large,and the flow velocity near the culvert side wall is small;the flow velocity near the midline of each section follows the distance.When the elevation of the bottom of the culvert increases,the velocity decreases near the surface of the water.When the flow rate is 0.07 m~3/s,the slope is 0.4m,the maximum velocity appears at0.198 m from the bottom of the culvert,and the maximum velocity is about 1.06m/s(except for the culvert inlet).With the increase of the slope,the velocity increases in the culvert,and the area of the higher velocity region increases.The embedded culvert can effectively reduce the internal velocity of the culvert and improve the effect of fish crossing.(2)Through numerical simulation analysis of the turbulent kinetic energy in the culvert,it can be seen that there is a large turbulent energy around the side wall of the culvert,and there is almost no turbulent kinetic energy near the water surface.With the increase of the water depth,the turbulent energy gradually increases to reach the maximum.After the values,they begin to become smaller and tend to be stable.When the flow rate is 0.07 m~3/s,the slope is 0.4m,the maximum turbulent kinetic energy near the culvert is about 0.026m~2/s~2;the distribution of turbulent kinetic energy in the culverts is compared under different slopes.The larger the slope,the smaller the area of the low turbulent kinetic energy area;the buried depth of the culvert can slow down the flow to a certain extent.The degree of fluctuation makes the flow more stable;the distribution of turbulence dissipation rate and turbulent energy in each section has a similar rule,that is,the turbulent dissipation rate is also high in areas with large turbulence energy,and vice versa.(3)By simulating the vortex distribution in the culvert,it can be concluded that due to the effect of the side wall,a certain vortex is generated near the side wall of the culvert,and the size and position of the vortex change with the flow of the water;the larger the slope,the higher the velocity of flow in the culvert.The larger the area of the flow affected by the vortex,the more unfavorable to the upstream migration of the fish;the depth of burying can improve the vortex state in the culvert,and the area affected by the vortex flow is gradually reduced.When fish pass through,they should try to avoid being close to the side wall of the culvert in order to avoid whirlpools and other effects.