| Large and medium-sized pump stations play an important role in the time-conditioning and flood control of water resources.Among them,axial pumps are the most common engineering equipment in pump station systems due to their large flow rate,low head,and high specific speed.However,the operation of the unit will inevitably threaten the living environment of aquatic organisms in the basin,especially the high mortality rate of overfish.In order to reduce the probability and mortality of fishes passing through the pumping station system and overcurrent components.In this paper,based on the CFD-DEM coupling method,the spherical particles are used to knead the three-dimensional structure of the outer contour of the fish to simulate the movement of the fish in the axial pump of the pump station.Combined with the mathematical model of blade impact,the probability of impact of fish through the pump station machinery is studied.By analyzing the speed,surface pressure fluctuations and shear rate changes of the fish in the flow field,the fish damage and mortality rate are studied to provide certain data support for further optimization of the blade design.The main research work carried out in this paper and the main research results obtained are as follows:(1)Through a lot of literature reading,analysis of the theoretical results of domestic and foreign experts and scholars on the mathematical model of blade impact and the mechanism of fish damage.Aiming at the current situation that the actual movement characteristics of fish in the flow field are few,the CFD-DEM coupling method is used to simulate the movement law of fish in the axial flow field of the axial flow and the stress and pressure on the surface of the fish.(2)Aiming at the characteristics that the fish model accounts for less than 10% of the total integral of the flow field and the large particle size,the Euler-Lagrangian method is selected to simulate the movement characteristics of fish in the flow field.In addition to the effects of gravity,buoyancy,drag force,virtual mass force and pressure gradient force on particles,the effects of collisions between particles and the rotation of particles on the calculation results are considered.(3)Using the Bosman company BVOP125-?-140 axial flow pump as a prototype,its hydraulic performance was simulated and compared with the experimental results,the feasibility of the numerical simulation method was verified,and the reasons for the simulation errors were systematically explained.The relative distance between the threedimensional coordinates of the fish model and the monitoring point is used to determine whether the fish collides with the blade,and the probability of fish collision is counted.Then compared with the impact probability data of the blade impact mathematical model,the credibility of the CFD-DEM method to simulate the impact probability of fish is verified.(4)The impact probability of fish in a fish-friendly axial flow pump is studied.Based on the mechanism of fish damage,the changes in the movement speed,acceleration,surface pressure fluctuation and shear rate of fish in the flow field are analyzed.The results show that: The collision between fish and the leading edge of the blade is the main cause of fish damage.The surface pressure fluctuation and shear rate due to the small effect area and short time,except for the impact at the blade rim,will not cause substantial damage to the fish body.(5)By discussing the flow field characteristics of fish-friendly pumps at different flow inlets or different pump shaft speeds.The pressure and velocity streamline distribution in the blade field in the flow field and the pressure distribution in the cross section of the space spiral volute diversion component are analyzed to study the passing performance of fish under different operating conditions.The results show that the fish have a low probability of impact under high flow rate and low speed,and have a strong passing performance.The research results have been applied in engineering practice. |
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