An Experimental Study Of Turbulent Structures And Fish Movement In Combined Fishway Of Notch Weir,Rectangular Central Orifice And Vertical Slot

There are many migratory fishes in China's coastal areas,and a single fish pass is difficult to meet the design requirements of different fishes to swim upstream.The combined fish pass can better display the hydraulic characteristics of various fish crossings and improve fish passing efficiency.However,there are more numerical simulation studies on the combined fishway,and less experimental studies.For this,a combined fishway consisted of notch weir,rectangular mesopore and vertical seam is designed and a more systematic experimental study is carried out in this paper.And an acoustic Doppler velocimeter(ADV)was used to measure the three-dimensional instantaneous flow velocity of each point in the combined fishway pool on the same and different sides.Based on measured data,the flow characteristics,time-averaged flow velocity,turbulent intensity,Reynolds stress,spectral characteristics,correlation functions,and turbulence scales of the combined fishway were analyzed.And Some hydraulic characteristics in the fishway were simulated by FLOW 3D software.addition,through the fish release experiment,the reaction of the fish passing object to the arrangement of the same side and the other side was observed by using high speed camera and 3d photography,and the relationship between the fish passing object and the turbulent structure in the fish passage was analyzed.The main research work of this paper is as follows:?(1)Based on the measured data,a vector diagram of the flow field in the fishway was drawn,and the three-dimensional time-averaged flow velocity was analyzed.The combined fishway is highly tridimensional,and the main flow area is obvious.Due to the staggered outflow,there is a greater lateral velocity and a distinct downwash flow and the vortex is more likely to form on each water layer on the opposite side.(2)Combined with the measured data,the turbulence intensity in three directions at the characteristic position of the fishway was analyzed.Extreme and turbulent intensity points appear in the first half of the pool on the same and opposite side.The jet meeting area and the back flow section on the opposite sidearea strong turbulence area,and the opposite side is more obvious than the same.Turbulence intensity generally decreases with increasing water depth.(3)Combined with the measured data,the Reynolds stress in three planes at the characteristic position of the fishway was analyzed.The extreme points of Reynolds stress appear at the side wall and the velocity mixing area,the same side is dominated by the Reynolds stress in the xoy plane,and the values on the three sides are not significantly changed on the opposite side,especially in the second half of the pool.(4)Combined with the measured data,the longitudinal pulsation velocity spectrum of the characteristic points on the fish pass through the fish position is analyzed.It is found that the opposite side has more high-frequency pulsation energy than the same side.The pulse energy decreases along the way.(5)Based on the measured data,the autocorrelation coefficient of the longitudinal pulsating velocity of the characteristic points at the fish pass position is analyzed.The longitudinal pulsations of the water flow particles show a correlation with time,and are: notch weir> orifice> seam,and the fluctuation period along the process is extended;Integral and differential transformation of autocorrelation coefficients,and found that characteristic location There are vortices with different scales,and the integral scale is: notch weir> orifice> l seam.Differential-scale vortices are easily formed on the same and different sides near the upstream partition,and then decay along the way.(6)FLOW3D was used to select the RNG model to simulate the flow velocity,turbulence intensity,and Reynolds stress in the fishway.In the analysis of the flow velocity of the fishway,a better conclusion can be obtained,which is in line with the actual measurement.There are still deficiencies in the analysis of other disturbance scales.(7)Combining the numerical values with the measured conclusions,through fish release experiments,different fish species have different sensitivity levels to the flow velocity and turbulent structure in the pond.The location where the Reynolds stress changes drastically is the key area for fish to get induction.Avoiding strong turbulence areas,middle and upper tier fish prefer a larger flow velocity,and have greater tolerance to strong turbulence areas.