Numerical Simulation And Optimization Of Hydraulic Characteristics Of Xiajiang Fishway

In recent years,with the environmental effects of water conservancy and hydropower projects receiving more and more attention in China,more and more ecological corridors such as fish passages have been put into operation.Ensuring the traceability of migratory fish to complete the traceability of spawning behavior is a concentrated embodiment of the ecological value of the fishway,and the structure of the fishway is the key factor determining the flow pattern of the fishway,which has an important impact on whether the migratory fish can successfully complete the traceability.As important indicators reflecting the flow pattern of the fishway mainstream area and the turbulent energy field of the fishway,the flow velocity field and turbulent energy field distribution of the fishway play an important role in effectively evaluating the effect of the fishway crossing the fish.To this end,this paper relies on the example of Xiajiang Water Conservancy Hub Project in Ji’an,Jiangxi Province,takes the Xiajiang Fishway as the research object,and uses the research method combining numerical simulation calculation and on-site monitoring of the fishway to carry out the optimization research of the hydraulic characteristics of the vertical seam fishway,the main contents are as follows:(1)Aiming at the feasibility and reliability of the numerical simulation method of the hydraulic characteristics of the fishway,on the basis of analyzing and determining the numerical simulation theory and method of the hydraulic characteristics of the fishway,the measured data of the Xiajiang Fishway obtained by arranging the speed sensor and water level gauge are compared with the numerical simulation calculation results based on the RNG6)- turbulence model,so as to verify the effectiveness of the numerical simulation method of the proposed hydraulic characteristics of the fishway.The result shows that the flow potential distribution and mainstream trajectory line of the two are in good agreement,and the deviations in the water level along the overflow of the fish channel and the distribution of lateral longitudinal flow velocity are within 15%.(2)In view of the problem that the local flow velocity of the fishway exceeds the design flow rate of the fishway shown in the measured data of the fishway flow velocity,this paper combines the reference system of the design index of the Xiajiang Fishway to propose measures to add the fishway guide plate,and compares a total of 12 optimization schemes for different vertical joint sizes,horizontal partition and guide plate layout forms of the standard pool section and rest pool section in fishway,and the distribution of the fishway streamline,the flow field distribution of the mainstream area of the pool chamber and the reflux area,as well as the turbulent energy,the hydraulic characteristics of the fishway such as the distribution of turbulent energy dissipation rate to evaluate whether the optimized results fit the requirements of the fishway or not.The results show that:1)Compared with the ipsilateral arrangement of the traditional fishway diaphragm,the heterolateral arrangement of the cross-diaphragm of the Xiajiang Fishway can reduce the overall turbulent energy of the fishway while improving the turbulent energy dissipation rate,and reduce the maximum flow rate of the mainstream by more than15%;2)After adjusting the relative width of the vertical gap of the fishway and the vertical gap of the fish passage diaphragm to 0.20,it can effectively reduce the flow rate and optimize the flow state,compared with the original fishway pool room,the maximum flow rate of the mainstream decreases by 5.83%,the maximum turbulent energy decreases by 19.86%,the distribution of the mainstream area and the reflux area is more uniform,which meets the maximum design flow rate of the fishway,and at the same time the overall turbulence energy value is small,it can ensure that there is a small range of high turbulence energy areas to promote fish upward tracing;3)Add a guide plate in the section of the fishway rest pool,when the guide plate is located at the length of 1/2 of the rest pool room,the size is 1.0m×3.5m,and the guide angle is 30°,compared with the original fishway pool room,the maximum flow rate of the mainstream drops by 7.27%,and 3 suitable size and moderate speed reflux areas can be formed in the rest pool room,and can meet the smooth transition from the rest pool section to the standard pool section,compared with other working conditions,this arrangement can achieve the highest efficiency of turbulent energy dissipation rate growth.