Numerical Simulation Of Hydraulic Characteristics Of Fishway

As an ecological compensation facility for river blocking structures of water conservancy projects,fishway plays an important role in maintaining the long-term development of river ecosystem.However,there are many thorny problems in the construction and operation of the fishway,such as fish can not find the fishway entrance,the fish passing rate is not high,and even if they reach the upstream,the fish body has been damaged to some extent,and so on.The key to these problems is that the hydraulic characteristics of the flow field in different types of fishways are not well understood.This paper compared and analyzed the hydraulic characteristics of the flow fields of vertical slot fishway,overflow weir fishway and orifice fishway through the method of numerical simulation.By comparing the measured data of the physical model with the calculated values of the mathematical model,the reliability of the selected turbulence model was verified.A total of 15 working conditions are designed for the three types of fishways.The hydraulic characteristics of flow pattern,velocity,turbulent kinetic energy and dissipation rate of the three types of fishways are compared and analyzed.The flow field characteristics of each type of fishway and the applicability of fishway based on hydraulic characteristics are analyzed.The main research contents and achievements of this paper are as follows:(1)By extracting the velocity distribution nephogram,the flow pattern changes of three types of fishways were compared.By calculating the mainstream area of the upper,middle and lower layers of the vertical slot fishway,it is concluded that the mainstream area of the surface layer of the vertical slot fishway is higher than that of the bottom layer.By changing the inlet flow of the overflow weir fishway and the depth of the pool chamber of the model,it is concluded that the overflow weir fishway presents three different flow patterns: drop flow,transition flow and sliding flow.By extracting the velocity distributions in the x-y direction and x-z direction at the center of the large orifice and the center of the small orifice respectively,the law of the interaction between the large orifice and the small orifice is obtained.(2)By extracting the maximum velocity along the typical tank chamber under various working conditions,the specific distribution of velocity in the tank chamber is obtained.By extracting the velocity vector diagram,the distribution of main flow area and reflux area in the tank is obtained.Combined with the data analysis of the indoor velocity and direction of the pool,the preferred swimming speed range of the fish corresponding to the fish migration and the required explosive swimming speed of the fish are obtained.(3)By extracting turbulent kinetic energy and dissipation rate,we can understand whether the designed fishway under this working condition can be used for fishway operation and the energy dissipation effect of this type of fishway.For the 15 working conditions in this paper,a total of 7 working conditions are selected for fishway operation.(4)Based on the hydraulic characteristics of various types of fishways,this paper makes a comprehensive analysis from the aspects of fish passing position,corresponding favorite swimming speed range,corresponding explosive swimming speed,adaptability to changes in incoming water flow,fishway energy dissipation effect,and selects typical fish to match their swimming characteristics with fishways to study the applicability of various types of fishways.