| The response relationship between migration behaviors of fish and water flow structure is the core of fishway design.Choose Schizothorax prenanti as the representative of the coldwater fish in the southwest of China.Three kinds of scaled vertical slot fishway model with different baffle plate pier head types are adopted to study the migration behaviors of juvenile Schizothorax prenanti.The purpose of this study was to explore the response relationship between the migration behavior of Schizothorax prenanti and the water flow structure.The main research work and achievements of this paper are as follows:(1)The water flow structures of the fishway in pier head type I(hooked pier head),pier head type II(broken line pier head),and pier head type III(streamline pier head)are calculated and compared by numerical simulation method.The results show that: the total areas of the back-flow area of three types of fishways with pier heads are similar,the total areas of the left back-flow area were larger than that of the right back-flow area.There is only one back-flow area on the left side of the mainstream of the fishway in pier head types II and III.There are two back-flow areas,one large and one small,on the left side of the mainstream of fishway in pier head type I.The vertical slot velocity of a fishway in pier head type III is slightly larger than that of a fishway in pier head type I and II,and the distribution is more uniform.The distribution of turbulent kinetic energy in the pool is similar.The size and distribution range of turbulent kinetic energy in fishway of pier head type III near the vertical slot are slightly larger than those in fishway of pier head type I and II.The total hydraulic strain distributions of three types of fishways with pier heads are similar.(2)The pier head types I and II were divided into experimental group A,the pier head types II and III were divided into experimental group B.The control experiment of Schizothorax prenanti was carried out.Taking the passing rate and passing time recorded in the fish passage test as the evaluation indexes,the Schizothorax prenanti passage effects of three vertical slot fishway with different pier head types were compared.The results showed that the Schizothorax prenanti passing effect of fishway in pier head type II and III was similar and better than that of fishway in pier head type I.Because the shape of pier head type III is better than that of pier head type II to protect the fish object,so pier head type III is the most suitable type of vertical slot fishway baffle plate pier for Schizothorax prenanti.(3)In the fish passing experiment,the migration trajectory of Schizothorax prenanti was recorded and the hot spot map was drawn.The statistical results show that most Schizothorax prenanti prefer to pass through the back-flow area on the right side of the pool,a few Schizothorax prenanti will rest on the back surface of the guide plate and then continue to swim up.Most of the Schizothorax prenanti prefer to pass through the side of the baffle plate at the vertical slot.Based on the statistical analysis of the migration trajectory and hydraulic indexes,it is found that most of Schizothorax prenanti in the pool will avoid the areas with high velocity,high turbulent kinetic energy,and high total hydraulic strain.The correlation between the migration trajectories of Schizothorax prenanti and the hydraulic indexes,such as velocity,turbulent kinetic energy and velocity gradient,are Spearman rank correlation analyzed.There is a negative correlation between velocity,turbulent kinetic energy,velocity gradient and passing number.Most Schizothorax prenanti prefer areas with lower velocity,lower turbulent kinetic energy and larger velocity gradient when passing through the vertical slot.(4)The influence of guide plate length change(△P)and guide plate position change(△L)on plane water flow structure is studied by numerical simulation,and the influence of vertical slot width change(△b)on water line is studied by physical model test.It is found that when the length of guide plate changes in the range of △P=±0.1P and the position of guide plate changes in the range of △L=±0.15 P,there is no substantial influence on the plane water flow structure.Backwater phenomenon of different degrees appeared in the upstream side of the vertical slot narrow position,and water drop phenomenon of different degrees appeared in the downstream side of the vertical slot narrow position.The influence of a narrow vertical slot on the water line of the upstream side pool is larger than that of the downstream side pool.The range of upstream influence pool and maximum variation of water line at high water depth is larger than those at a low water depth. |
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