| As an engineering measure to assist fish to cross the dam,fishway alleviates the negative impact of dam construction on fish resources to a certain extent.In order to help fish quickly find the location of fishway entrance,it is often necessary to provide favorable auxiliary measures for the built fish passage entrance.The construction of water recharge facilities is one of the effective measures to improve the effect of fish passage.How different hydration forms change the fish the swimming behavior strategy to attract its entry into the fishway entrance is a hot topic at home and abroad.Based on the generalized model of fish passage import,this study used Schizothorax prenanti as the research object,and explored the effects of different flow rates and water supplement distances on the upstream behavior of target fish near the fish passage import by using three forms of internal side water supplement,bypass water supplement and top water supplement.Through the fine simulation of the hydraulic field around the fish and the combination of the fish tracing trajectory,the hydrodynamic characteristics after water replenishment are explored.The main conclusions are as follows:(1)The internal side of the fish passage inlet can effectively increase the inlet velocity of the fish passage and maximize the radiation range of the main flow under the limit velocity of the fish.However,excessive velocity will form a velocity barrier,which will hinder the fish upstream to a certain extent.Compared with the top supplement of the bypass,the outflow velocity of the bypass is not high,but will not cause greater turbulence.The high top flow velocity has a strong attraction effect on fish.Fish will be attracted to the vicinity of the top flow velocity,and the turbulence will significantly change the trajectory of fish in the upstream.The form of bypass recharge can provide steady flow and steady flow velocity.Compared with the top recharge of bypass,under the same flow rate,the flow velocity of the outlet of recharge is very small and the attraction to fish is not enough,but the smooth outflow will not produce strong turbulence is its advantage of recharge,so the bypass recharge form needs sufficient flow rate to play its role in attracting fish.The top recharge of bypass can increase the flow velocity by falling water,which can produce high flow velocity and sufficient attraction range in the direction of recharge outlet,but falling water will cause greater turbulence.Therefore,in order to ensure that the top of the bypass has a higher attraction rate and passing efficiency for fish,it is essential to select the reasonable recharge flow and recharge water level.Therefore,in order to ensure that the top of the bypass has a higher attraction rate and passing efficiency for fish,it is essential to select the reasonable recharge flow and recharge water level.Therefore,in this experiment,it is verified that the bypass recharge distance of 100 cm and the top of the bypass recharge water of 65 cm have higher passing efficiency than the experiment without recharge water.(2)Analyzing some laws of velocity and turbulent kinetic energy factors around fish,we can find that with the increase of velocity,the distribution proportion presents a normal distribution law.With the increase of velocity,the distribution proportion increases,reaching the maximum value at 0.6-0.8 m.s-1,and then declines when the velocity is higher than 0.8 m.s-1.One-way ANOVA showed that the distribution ratio of0.6-0.8 m.s-1 was significantly higher than that of other flow velocities.By analyzing the proportion of turbulent kinetic energy distribution in fish,we can see that with the increase of turbulent kinetic energy,the time of fish appearing in its region will decrease obviously.Fish avoid turbulent kinetic energy exceeding 0.04 m2.s-2and rarely enter turbulent kinetic energy exceeding 0.06 m2.s-2.By analyzing the distribution track of turbulent kinetic energy in fish,we find turbulent kinetic energy and its distribution time.There was a significant negative correlation between them.(3)Analyzing the distribution of resistance and energy consumption in the process of fish tracing,we can see that although the resistance from the two ends of fish tracing up the entrance is about 0.2 N,the overall resistance and energy consumption from the left wall are higher.From the cumulative energy consumption of fish tracing up,we can see that the total energy consumption of different tracing up is very different.In fish tracing up the entrance of fish tracing,the total energy consumption varies greatly.When backtracking is carried out near the wall,the maximum energy consumption of water recharge at the inner side of the fish passage inlet is 62.75×10-2 J.When backtracking is not done,the longer the backtracking distance is,the higher the energy consumption is.The energy consumption of backtracking from the right end of the fish passage inlet is34.4×10-2 J,and the energy consumption of backtracking from the wall end is 48.27×10-2 J.The top of the bypass can effectively guide fish to enter from the right end of the fish passage inlet to reduce the energy consumption of fish backtracking.The upstream energy consumption of fish can be reduced to 10.9×10-2 J,even if the long upstream path,the energy consumption is only 28.89×10-2 J.(4)By analyzing the advantages and disadvantages of the three types of recharge,it can be found that side recharge can keep the best flow pattern at the inlet of the fishway by increasing the flow rate when the inlet velocity of the fishway is low.Bypass recharge can help fish locate the entrance of the fishway accurately by using the velocity difference between the inlet and the outflow.The top water of the bypass can attract fish entrance to the vicinity of the entrance of the fishway by using the high velocity drop.It can also guide fish to enter the entrance of the fishway with low energy consumption.However,it is necessary to design reasonable recharge distance and flow rate according to different types of fish entrance. |
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