An Experimental Study Of Turbulent Structures And Fish Movement In Oval Orifice Fishway

China is rich in fish resources,and there are many migratory and semi-migrating fishes,but the fish-passing effect is not ideal.In this paper,two sets of typical flow rates are selected as test flow rates.The turbulent flow structure of the oval orifice fishway is systematically studied in a large scale fishway tank,and a fish release test is performed.The acoustic Doppler velocimeter(ADV)was used to measure the three-dimensional flow velocity of each measuring point in the test pool,and the measuring points were arranged at different water depths(z = 49.5,45.5,41.5,37.5,33.5,29.5,25.5,21.5,17.5,13.5 cm),14 horizontal lines(x = 10,15,20,30,50,70,90,110,130,150,160,165,170,175cm)are arranged on each water depth plane,and 9 are arranged on each horizontal line Measuring points(y =-20,-12,-8,-4,0,4,8,12,20cm).In addition,with the relevant comparison of the rectangular orifice fishway measurement test,the velocity vector field,the three-dimensional time-averaged velocity distribution,the maximum longitudinal velocity of the section along the course,the turbulence intensity,and Reynolds were compared in the oval orifice fishway pool.The stress,velocity autocorrelation coefficient,and turbulence scales(micro-scale,integral scale)were systematically analyzed,and the characteristics of the turbulent structure of the oval orifice fishway were proposed.The main results of the test are as follows:1)After exiting from the oval orifice,the jet diffuses in the pool,expands on both sides of the orifice on the horizontal plane,expands up and down in the longitudinal section,and shows a tendency to gather in the downstream partition attachment.The longitudinal velocity is similar to the Gaussian distribution in the horizontal direction,but is different from the plane turbulent jet.The velocity is the largest at the long axis of the oval orifice and gradually decreases to the left and right sides of the non-orifice.The vertical distribution in the longitudinal section is different from the rectangular.Orifice,the longitudinal velocity of the oval orifice is saddle-shaped along the vertical direction,and there will be two wave crests;the lateral flow of the second half of the oval orifice and the downstream baffle blocking the return water turbulence will create a vertical vortex.Further increasing the lateral flow of the water body causes the lateral flow velocity to decrease first and then increase,and the larger the flow rate,the more obvious the increase trend in the second half;the vertical flow velocity decreases along the process,which is basically zero in the middle of the pool.2)The maximum longitudinal velocity of the oval orifice is attenuated along the horizontal plane and longitudinal section,and the variation of the maximum longitudinal velocity along the course of the rectangular orifice is about the same under the same water level.Most of the energy has been attenuated by the first half of the pool on the horizontal plane,and the larger the flow rate,the faster the attenuation,while the maximum longitudinal flow velocity change along the longitudinal section has little relationship with the flow rate.3)The turbulence intensity and Reynolds stress in the oval orifice area are greater than those in the non-orifice area.As the flow rate increases,the amplitude of the turbulence intensity and Reynolds stress increases.Large turbulence occurs at the junction of the non-orifice area,reaching a maximum value.4)The velocity of the jet in the orifice area is larger than that in the non-orifice area,and the turbulence is severe,which leads to a decrease in its correlation.With the increase of the flow rate,the amplitude of the correlation coefficient of the flow rate further decreases and the period is shorter.The size of the micro vortex in the orifice area is larger than that in the non-orifice area.At large flow rates,the micro vortex in the non-orifice area hardly develops with time,and disappears as it grows.The average size of the vortex body in the non-orifice area is larger than that of the orifice area,and the period is obvious.The vortex in the flow field develops well,and the curve of the orifice area fluctuates up and down,and the period is small.In general,the turbulence in the orifice area is severe,and the tiny vortex body is quickly destroyed after it is generated.The vortex generally develops in the non-orifice area.5)The fish release object will have a significant response to the turbulent structure in the oval orifice fishway.The turbulence structure in the pool affects the swimming behavior,retrograde response,and hole behavior of the fish release object.Fishes generally continue to track back only when they reach the on-street flow velocity when starting to swim.Generally,the water depth plane with a lower longitudinal flow velocity of the oval orifice is used to trace back to save their own energy.Vortex in the oval orifice fishway Rest in the area hovering.