Novel weir flow bottom hole combined fishway with diversion piers and vortex recognition method of novel weir flow bottom hole combined fishway

Abstract

The invention relates to a novel weir flow bottom hole combined fishway with diversion piers and a vortex recognition method of the novel weir flow bottom hole combined fishway, and belongs to the field of hydraulic engineering and ecological engineering. On the basis of a traditional weir flow bottom hole combined fishway, a traditional thin-walled weir is bent in the horizontal direction by improving the form of the weir, then the length of the overflow front edge is increased, and a diversion pier is additionally arranged at an outlet of a bottom hole. The combination of the weir and the bottom hole can effectively change the proportion of overflow on the weir and overflow at the bottom hole, and can effectively improve the water flow state in the fishway pool chamber. Besides, on the basis of the idea that the vorticity is larger than deformation, the vorticity is further decomposed into a rotating part and a non-rotating part through an omega vortex recognition method, and then vortexes in the fishway are effectively recognized. Physical model tests and numerical simulation prove that the device can effectively improve the water flow environment in the fishway pool chamber, and can be popularized and applied to actual engineering.

Description

Technical Field

[0001] The invention relates to the technical field of water ecological engineering, and specifically discloses a novel weir flow bottom hole combined fishway with diversion piers and a vortex identification method thereof. Background Art

[0002] my country is rich in fish resources and has many migratory fish. As human demand for water resources increases, the construction of water conservancy projects such as hydropower stations and sluice gates is increasing. However, these projects will inevitably cause certain damage to the continuity of the river ecosystem, especially to the survival and reproduction of fish. In order to protect fish resources, protect the river ecological environment, and maintain biological diversity, fishways have emerged as an important ecological construction project. Fishways are a kind of engineering construction that specifically provides a passage for fish. Its main function is to ensure the survival and reproduction of fish, so as to achieve the harmonious development of water conservancy projects and the ecological environment.

[0003] Engineering technology fishways are mainly built with hard materials such as concrete and steel. The basic principle is that a series of pools separated by a certain number of baffles provide an environment for fish to swim and rest. Generally, they can be divided into vertical slit type, weir flow type, orifice type and their combination fishways. The weir flow type fishway is suitable for fish that like to swim and jump on the surface, and its weir body is easily blocked by floating objects, resulting in low fish passing efficiency. The bottom hole type fishway is suitable for fish that like to swim on the bottom layer. Its orifice is set underwater and is easily blocked by large pieces of sediment, and is not suitable for fish with surface water level habits. Therefore, the weir hole combination fishway proposed in the present invention can better play the hydraulic characteristics of the two types of fish holes, flexibly control the flow rate and water flow structure of the pool chamber, and can meet the needs of fish with different habits, greatly improve the types and efficiency of fish passing, and help restore the river ecology, protect fish resources and river species diversity.

[0004] The vortex identification method is widely used in various fields of fluid mechanics research. It can be used to identify vortices in fishways and provide an important basis for the study of the hydraulic characteristics of fishways. Currently, the following typical methods are used to identify vortices. Q criterion: The Q criterion mistakenly identifies stretching, compression, and deformation shear as part of the vortex. It relies on the selection of thresholds but lacks a unified standard. λ2 criterion: The λ2 criterion ignores transient stress and viscosity terms and uses S 2 +Q 2 Obtaining the minimum pressure at the vortex center leads to errors and excludes points that do not meet the zero gradient condition. In addition, the small-scale vortices are mixed in and are also affected by the threshold. Δ criterion: This criterion is a weak criterion. Because although this criterion points out the area with vortices It has complex (imaginary) eigenvalues, but it is not clear whether the vortex-free region All eigenvalues ​​of are real numbers and are also affected by the threshold. Through a review of the research on the above methods, it is found that the above methods have some shortcomings in identifying fluid vortices, and the recognition effect is general. Therefore, it is necessary to establish a numerical simulation method that can effectively identify vortices in vertical slot fishways. Summary of the invention

[0005] The present invention provides a novel weir flow bottom hole combined fishway with diversion piers and a vortex identification method thereof, which plays an important role in optimizing the design of the fishway and expands the application of the vortex identification technology in the fluid field.

[0006] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a novel weir flow bottom hole combined fishway with diversion pier, comprising a bottom plate and a left wall 2 and a right wall 3 symmetrically distributed on both sides of the bottom plate, the bottom plate is stepped, and a plurality of steps 7 are arranged along the water flow direction, and a zigzag partition 4 is arranged at the corresponding position of each step 7, and the two sides of the zigzag partition 4 are tightly fitted with the left wall 2 and the right wall 3 respectively, and a bottom hole 5 is arranged in the middle of the zigzag partition 4, and a plurality of intervally distributed zigzag partitions 4 divide the fishway surrounded by the bottom plate, the left wall 2 and the right wall 3 into a plurality of continuously connected fishway pool chambers, and the entrance of the fishway is the upstream water inlet channel 1, and the exit is the downstream outlet 8.

[0007] Specifically, the folded line partition 4 is a symmetrical and tortuous trapezoidal shape, including a middle partition and a first left-side bent plate and a first right-side bent plate symmetrically distributed on both sides thereof, the left side of the first left-side bent plate is connected to the second left-side bent plate, and the right side of the first right-side bent plate is connected to the second right-side bent plate, and the bottom hole 5 is arranged in the middle and lower part of the middle partition, and the second left-side bent plate and the second right-side bent plate are tightly fitted to the left wall 2 and the right wall 3 respectively.

[0008] Preferably, the zigzag partition 4 bends downstream in the plane, and the horizontal distance from the left wall 2 to the first bending point is l1, the horizontal distance from the first bending point to the second bending point is l2, the horizontal distance from the second bending point to the third bending point is l3, the horizontal distance from the third bending point to the fourth bending point is l4, and the horizontal distance from the fourth bending point to the right wall 3 is l5, l1:l2:l3:l4:l5=1:2:4:2:1, the bending angle between the second bending plate on the left and the outer side of the first bending plate on the left is a0, the bending angle between the first bending plate on the left and the inner side of the middle partition is b0, the bending angle between the middle partition and the inner side of the first bending plate on the right is b1, and the bending angle between the first bending plate on the right and the outer side of the second bending plate on the right is a1, a0=b0=b1=a1=135°.

[0009] Preferably, except for the last fold line partition plate 4 , a diversion pier 6 is provided downstream of the bottom hole 5 of each of the preceding fold line partition plates 4 .

[0010] Preferably, the height of the fold line partition 4 is lower than the heights of the left wall 2 and the right wall 3 .

[0011] Preferably, the diverter pier 6 is cylindrical and located directly behind the bottom hole 5, and the horizontal distance between the center of the diverter pier 6 and the bottom hole 5 is twice its own diameter. The bottom hole 5 is a rectangular slot with an aspect ratio of 1:1, and the cross-sectional size of the diverter pier 6 in the direction perpendicular to the water flow is the same as the size of the bottom hole 5.

[0012] Preferably, the converted slope of the base plate is 3%.

[0013] A vortex identification method for a novel weir flow bottom hole combined fishway with diversion piers comprises the following steps:

[0014] Step 1: Establish a 3D geometric model: Use 3D geometric modeling software to create a 3D geometric model of the fluid calculation domain, and export a geometric file that meets the format requirements of the computational meshing software;

[0015] Step 2: Grid division of computational domain: Import the geometry file outputted in step 1 into the grid division software, divide the computational domain in detail, encrypt the grids for the side walls, top area and water flow area at the bottom hole 5 of the fishway, and after the grids are generated, export the corresponding grid files according to the grid files required by the numerical simulation calculation software;

[0016] Step 3, establishing a three-dimensional mathematical model: the fluid flowing through the fishway is assumed to be an incompressible Newtonian fluid, and the three-dimensional mathematical model includes a flow control equation, which is composed of a continuity equation, a momentum equation, and a k-ε equation;

[0017] Continuity equation:

[0018]

[0019] Momentum equation:

[0020]

[0021] Where: ρ is the fluid density, unit: kg / m 3 ; t is time, unit is s; x i 、x j represents the grid node coordinates in the x direction, i, j = 1, 2, 3; u i 、u j Then they are x i and x j The average velocity in the direction, in m / s; P represents the average pressure, in Pa; g i is the gravitational acceleration in different directions, in m / s 2 ; μ is the dynamic viscosity coefficient, unit N·s / m2 ;μ t is the turbulent viscosity coefficient, in N·s / m 2 ; k represents turbulent kinetic energy, unit J; ε is the turbulent kinetic energy dissipation rate, unitless;

[0022] The equations of turbulent kinetic energy k and turbulent kinetic energy dissipation rate ε of the RNGk-ε model are as follows:

[0023]

[0024]

[0025] Where: G k represents the turbulent kinetic energy generated due to the mean velocity gradient; G b It is used to generate turbulent kinetic energy caused by buoyancy; Y M The influence of compressible velocity turbulent pulsation expansion on the total dissipation rate; σ k and σ ε are the reciprocals of the effective turbulent Prandtl number of the turbulent kinetic energy k and the turbulent kinetic energy dissipation rate ε, respectively, and σ k =1.0,σ ε =1.3, in FLUENT, as the default value constant, C 1ε =1.44, C 2ε =1.92, C μ =0.09;

[0026] The Euler multiphase flow VOF model is used to track the free surface of the water flow. In the VOF model, all fluids share a set of momentum equations, and the volume integral of each fluid in each computational unit is tracked throughout the domain in order to accurately describe the behavior of multiple fluids. The equation form is:

[0027]

[0028] Where: α w is the volume fraction of the liquid phase, the sum of the volume fractions of the gas phase and the liquid phase is 1,

[0029] Step 4: According to the actual operating conditions of the object under study, the corresponding boundary conditions and initial conditions are set to perform numerical calculations of the three-dimensional flow field. The volume fraction of the velocity inlet water is set to 1, and the turbulence is set to the default value of 5%. In order to simulate the actual situation more realistically, a gas inlet is set on the upper surface of the computational fluid domain to simulate an open-top channel; the side walls, baffles, and bottom plates are set as side walls. Based on the mathematical model established in step 3, the three-dimensional flow field is numerically simulated using CFD calculation software;

[0030] Step 5: post-processing, using CFD post-processing software to obtain the flow field information of the fishway;

[0031] Step six, vortex identification is performed based on the Ω criterion, and the isosurface of Ω=0.52 is used to identify the vortex surface, thereby displaying the three-dimensional vortex structure in the flow field.

[0032] Specifically, the step six is ​​as follows:

[0033] The application of Ω criterion in discrete vector field data is written to identify vortices. The third generation vortex identification method is adopted, and the parameter Ω is introduced. Ω represents the ratio of the vorticity of the rotating part to the total vorticity. Ω is equal to the square of vorticity divided by the sum of the square of vorticity and the square of deformation. According to the relationship between rotational motion and deformation in flow, the mathematical definition and identification method of vortices are proposed. When Ω is greater than 0.5 and the vorticity exceeds the deformation, it is considered that a vortex is formed. The isosurface of Ω=0.52 is used to identify the vortex surface, thereby displaying the three-dimensional vortex structure in the flow field.

[0034] The Ω criterion further decomposes the vorticity ω into a rotating part and a non-rotating part, namely:

[0035] ω=R+S(7)

[0036] Where: R is the vorticity of the rotating part, S is the vorticity of the non-rotating part, that is, pure shear, R and ω have different directions, and the estimation formula is:

[0037]

[0038] Where: A is the velocity gradient symmetric tensor, representing the deformation effect, B is the velocity gradient antisymmetric tensor, representing the rotation effect, || || F Represents the Forbenius norm of the matrix;

[0039] Any point in the non-uniform flow field can generate a velocity gradient tensor in a specific coordinate system (x, y, z), that is, a 3×3 matrix. According to the Cauchy-Stokes decomposition, this matrix can be decomposed into a symmetric tensor and an antisymmetric tensor:

[0040]

[0041] Where: represents the velocity gradient tensor; (u, v, w) represents the velocity in the coordinate system (x, y, z);

[0042] In actual use, in order to prevent the problem of zero division, a positive number γ less than 0.01 is added to the denominator, so that the expression of Ω becomes:

[0043]

[0044] Preferably, the 3D geometry software in step 1 is Solidworks and AutoCAD, the meshing software in step 2 is ANSYS mesh, the CFD calculation software in step 4 is ANSYS FLUENT, the CFD post-processing software in step 5 is Tecplot, and the vortex identification in step 6 is performed based on the Ω criterion, and the software used is Tecplot.

[0045] The beneficial effect of the present invention is that in the weir flow bottom hole combined fishway, the water head on the weir needs to reach a certain height to satisfy the migration of fish that prefer surface activities. However, this will increase the pressure head of the bottom hole, resulting in an increase in the flow rate of the bottom hole, which brings great challenges to fish that prefer bottom activities. The present invention proposes a new type of weir flow bottom hole combined fishway. On this basis, based on the concept of eco-friendliness, a zigzag partition and a diversion pier structure are arranged inside the pool chamber. While providing multiple migration channels for fish, it effectively changes the ratio of flow over the weir and flow through the bottom hole, which can effectively improve the flow state of the water in the fishway pool chamber. It provides a reference for the structural design of the fishway pool chamber and can be promoted and applied to actual projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is a flow chart of the method adopted by the present invention;

[0047] Figure 2 It is a schematic diagram of the two-dimensional model structure of the present invention,

[0048] Figure 3 It is a schematic diagram of the structure of the three-dimensional model of the present invention;

[0049] Figure 4 This is a partial schematic diagram of the folding line partition of the present invention;

[0050] Figure 5 is a top view of the folded line partition of the present invention;

[0051] Figure 6 It is a plan view of the physical test model of the present invention;

[0052] Figure 7 is a fluid calculation domain grid diagram of an implementation case of the present invention;

[0053] Figure 8 is a flow field distribution diagram of a single pool chamber cross section of an implementation case of the present invention;

[0054] Fig. 9 It is a vortex extraction diagram of a cross section of a single pool chamber of an implementation case of the present invention.

[0055] The numbers in the figure are: 1-upstream water inlet channel, 2-left wall, 3-right wall, 4-broken line partition, 5-bottom hole, 6-cylindrical diversion pier, 7-step, 8-downstream outlet. DETAILED DESCRIPTION

[0056] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and the invention content.

[0057] Example 1: Figure 1-9 As shown, a novel weir flow bottom hole combined fishway with diversion piers includes a bottom plate and a left wall 2 and a right wall 3 symmetrically distributed on both sides of the bottom plate. The bottom plate is stepped, and a plurality of steps 7 are arranged along the water flow direction. A zigzag partition 4 is arranged at the corresponding position of each step 7. The two sides of the zigzag partition 4 are tightly fitted with the left wall 2 and the right wall 3 respectively. A bottom hole 5 is arranged in the middle of the zigzag partition 4. Several zigzag partitions 4 distributed at intervals divide the fishway surrounded by the bottom plate, the left wall 2 and the right wall 3 into a plurality of continuously connected fishway pool chambers. The entrance of the fishway is the upstream water inlet channel 1, and the exit is the downstream outlet 8.

[0058] Furthermore, the folded line partition 4 is a folded line weir, which is formed by symmetrically bending a flat thin-walled weir in space, and is in a trapezoidal shape as a whole, including a middle partition and a first left bending plate and a first right bending plate symmetrically distributed on both sides thereof, the left side of the first left bending plate is connected to the second left bending plate, the right side of the first right bending plate is connected to the second right bending plate, the bottom hole 5 is arranged in the middle and lower part of the middle partition, and the second left bending plate and the second right bending plate are closely attached to the left wall 2 and the right wall 3 respectively. The weir body divides the fishway into multiple continuous pools, i.e., fishway pool chambers, and a fishway bottom hole 5 is arranged in the middle of the bottom of the weir body, and the fishway bottom hole 5 connects the multiple pools.

[0059] Furthermore, the folded-line partition 4 bends downstream in the plane, and the horizontal distance from the left wall 2 to the first bending point is l1, the horizontal distance from the first bending point to the second bending point is l2, the horizontal distance from the second bending point to the third bending point is l3, the horizontal distance from the third bending point to the fourth bending point is l4, and the horizontal distance from the fourth bending point to the right wall 3 is l5, l1:l2:l3:l4:l5=1:2:4:2:1, the bending angle between the second bending plate on the left and the outer side of the first bending plate on the left is a0, the bending angle between the first bending plate on the left and the inner side of the middle partition is b0, the bending angle between the middle partition and the inner side of the first bending plate on the right is b1, and the bending angle between the first bending plate on the right and the outer side of the second bending plate on the right is a1, a0=b0=b1=a1=135°. The angle of the broken-line weir can effectively increase the length of the overflow front edge and reduce the flow velocity of the water flowing over the weir. It also controls the ratio of the flow over the weir and the flow over the bottom hole, thereby regulating the water flow characteristics of the fishway.

[0060] Furthermore, except for the last zigzag baffle 4, a diversion pier 6 is provided downstream of the bottom hole 5 of each of the preceding zigzag baffles 4. The diversion pier 6 is used to create obstacles to the water flow and can reduce the flow rate of the water flow in the bottom hole.

[0061] Furthermore, the height of the fold line partition 4 is lower than the heights of the left wall 2 and the right wall 3 .

[0062] Furthermore, the diverter pier 6 is cylindrical and is located directly behind the bottom hole 5, and the horizontal distance between the center of the diverter pier 6 and the bottom hole 5 is twice its own diameter. The bottom hole 5 is a rectangular slot with an aspect ratio of 1:1, and the cross-sectional size of the diverter pier 6 in the direction perpendicular to the water flow is the same as that of the bottom hole 5.

[0063] Furthermore, the converted slope of the bottom plate is 3%. The fishway design with this slope can effectively promote the reasonable distribution of water flow and provide a suitable habitat and migration environment for fish.

[0064] The working principle of the novel weir flow bottom hole combined fishway with diversion piers described in the present invention is: after the water flows into the fishway through the water inlet channel 1, it flows through the bottom hole 5 and the weir top at the same time to the fishway outlet. When the water flows through the fishway through the bottom hole 5, due to the difference in flow velocity on both sides behind the bottom hole 5, two horizontal reflow areas will appear inside the pool room, distributed on both sides of the pool room. These reflow areas have a certain influence on the distribution of water flow and at the same time alleviate the flow velocity of the water flow in the pool room, and also provide a diverse environment for the activities of fish; after the water flow encounters the obstacle diversion pier 6, it forms a wall-adhering flow along the surface of the cylinder. This flow effectively reduces the influence of the flow velocity difference, and flows around to the back of the cylinder to merge. The arrangement of the obstacle diversion pier 6 effectively reduces the area of ​​the reflow area inside the pool room, and to a certain extent reduces the possibility of fish entering the vortex and getting lost.

[0065] A vortex identification method for a novel weir flow bottom hole combined fishway with diversion piers comprises the following steps:

[0066] Step 1: Establish a 3D geometric model: Use 3D geometric modeling software Solidworks and AutoCAD to create a 3D geometric model of the fluid calculation domain, and export the geometric file that meets the format requirements of the computational meshing software;

[0067] Step 2: Calculation domain meshing: Import the geometry file output in step 1 into the meshing software ANSYSmesh, use the hexahedral structured mesh scheme to divide the calculation area in detail, and perform mesh encryption processing on the side wall, top area and water flow area at the bottom hole 5 of the fishway. After the mesh is generated, export the corresponding mesh file according to the mesh file required by the numerical simulation software for subsequent numerical simulation use;

[0068] Step 3, establishing a three-dimensional mathematical model: the fluid flowing through the fishway is assumed to be an incompressible Newtonian fluid, and the three-dimensional mathematical model includes a flow control equation, which is composed of a continuity equation, a momentum equation, and a k-ε equation;

[0069] Continuity equation:

[0070]

[0071] Momentum equation:

[0072]

[0073] Where: ρ is the fluid density, unit: kg / m 3 ; t is time, unit is s; x i 、x j represents the grid node coordinates in the x direction (i, j = 1, 2, 3); u i 、u j Then they are x i and x j The average velocity in the direction, in m / s; P represents the average pressure, in Pa; g i is the gravitational acceleration in different directions, in m / s 2 ; μ is the dynamic viscosity coefficient, unit N·s / m 2 ;μ t is the turbulent viscosity coefficient, in N·s / m 2 ; k represents turbulent kinetic energy, unit J; ε is the turbulent kinetic energy dissipation rate, unitless;

[0074] The equations of turbulent kinetic energy k and turbulent kinetic energy dissipation rate ε of the RNGk-ε model are as follows:

[0075]

[0076]

[0077] Where: G k represents the turbulent kinetic energy generated due to the mean velocity gradient; G b It is used to generate turbulent kinetic energy caused by buoyancy; Y M The influence of compressible velocity turbulent pulsation expansion on the total dissipation rate; σ k and σ ε are the reciprocals of the effective turbulent Prandtl number of the turbulent kinetic energy k and the turbulent kinetic energy dissipation rate ε, respectively, and σ k =1.0,σ ε =1.3, in FLUENT, as the default value constant, C 1ε =1.44, C 2ε =1.92, C μ =0.09;

[0078] The Euler multiphase flow VOF model is used to track the free surface of the water flow. In the VOF model, all fluids share a set of momentum equations, and the volume integral of each fluid in each computational unit is tracked throughout the domain in order to accurately describe the behavior of multiple fluids. The equation form is:

[0079]

[0080] Where: α w is the volume fraction of the liquid phase, the sum of the volume fractions of the gas phase and the liquid phase is 1,

[0081] In this case, the volume fraction of water at the inlet is set to 1, and the turbulence is set to the default value of 5%. In order to simulate the actual situation more realistically, a gas inlet is set on the upper surface of the computational fluid domain to simulate an open-top channel. The mathematical model established based on the above step 3 is simulated using the CFD calculation software ANSYS.

[0082] Step 4: According to the actual operating conditions of the object under study, the corresponding boundary conditions and initial conditions are set to perform numerical calculations of the three-dimensional flow field. The volume fraction of the velocity inlet water is set to 1, and the turbulence is set to the default value of 5%. In order to simulate the actual situation more realistically, a gas inlet is set on the upper surface of the computational fluid domain to simulate an open-top channel; the side walls, baffles, and bottom plates are set as side walls. Based on the mathematical model established in step 3, the CFD calculation software ANSYS FLUENT is used to perform numerical simulations of the three-dimensional flow field;

[0083] Step 5: Post-processing: CFD post-processing software Tecplot is used to obtain the flow field information of the fishway to facilitate the subsequent vortex identification;

[0084] Step 6: Use Tecplot software to identify vortices based on the Ω criterion, use the isosurface of Ω=0.52 to identify the vortex surface, and then display the three-dimensional vortex structure in the flow field. Specifically:

[0085] The application of Ω criterion in discrete vector field data is written to identify vortices. The third generation vortex identification method is adopted, and the parameter Ω is introduced. Ω represents the ratio of the vorticity of the rotating part to the total vorticity. Ω is equal to the square of vorticity divided by the sum of the square of vorticity and the square of deformation. According to the relationship between rotational motion and deformation in flow, the mathematical definition and identification method of vortices are proposed. When Ω is greater than 0.5 and the vorticity exceeds the deformation, it is considered that a vortex is formed. The isosurface of Ω=0.52 is used to identify the vortex surface, thereby displaying the three-dimensional vortex structure in the flow field.

[0086] The Ω criterion further decomposes the vorticity ω into a rotating part and a non-rotating part, namely:

[0087] ω=R+S(7)

[0088] Where: R is the vorticity of the rotating part, S is the vorticity of the non-rotating part, that is, pure shear, R and ω have different directions, and the estimation formula is:

[0089]

[0090] Where: A is the velocity gradient symmetric tensor, representing the deformation effect, B is the velocity gradient antisymmetric tensor, representing the rotation effect, || || F Represents the Forbenius norm of the matrix;

[0091] Any point in the non-uniform flow field can generate a velocity gradient tensor in a specific coordinate system (x, y, z), that is, a 3×3 matrix. According to the Cauchy-Stokes decomposition, this matrix can be decomposed into a symmetric tensor and an antisymmetric tensor:

[0092]

[0093] Where: represents the velocity gradient tensor; (u, v, w) represents the velocity in the coordinate system (x, y, z);

[0094] In actual use, in order to prevent the problem of zero division, a positive number γ less than 0.01 is added to the denominator, such as γ = 0.001, which not only prevents the problem of zero division but also has little effect on the result. In this way, the expression of Ω becomes:

[0095]

[0096] Figure 6 It is a plan view of the physical test model proposed in the present invention. The water flows out from the upstream water measuring weir and passes through the rectifier to dissipate unnecessary vortex and turbulent kinetic energy before entering the fishway. After flowing out of the fishway, the water flows into the circulating water tank through the tailwater gate.

[0097] Figure 8 It is a flow field distribution diagram of a single chamber cross section obtained by numerical simulation of the present invention, wherein X represents the water flow direction, Y represents the horizontal vertical water flow direction, Figure a represents a chamber without a diverter pier, and Figure b represents a chamber with a diverter pier, both of which are the second chambers in the fishway; in Figure a, a high velocity area appears directly behind the bottom hole 5, exceeding 1 m / s, with a length of about 0.4 m and a width of about 0.1 m; in Figure b, a high velocity area appears 0.2 m directly behind the bottom hole 5 and on both sides of the water-facing surface of the diverter pier, and both are less than 1 m / s, and the return swimming area on both sides of the pool is obvious; comparison of the two figures shows that setting the diverter pier can effectively reduce the water flow velocity behind the bottom hole; increasing the return flow area in two horizontal directions inside the chamber is helpful to improve the fishway migration efficiency, and can provide guidance for the construction of fishway projects.

[0098] Fig. 9This is a vortex extraction diagram of a single pool cross section of an implementation case of the present invention. Two strong vortices are identified at the corner of the second pool partition, and the vortex core is located at the connection between the middle partition and the bent plates on both sides. Two ribbon-shaped vortices are also identified directly below the bottom hole 5, and the vortex strength is not high; a circle of mixed strong and weak vortices are identified on the water-facing surface of the diverter pier 6, and reverse vortices of the symmetrical diverter pier 6 are identified on both sides of the back water surface. Through the calculation process proposed by the present invention, the vortex structure of the fishway flow field can be better extracted, and the results can provide guidance for the study of fish ecology and ecohydraulics.

[0099] Table 1 is a comparison chart of the model test and numerical analysis data of the implementation case of the present invention, combined with Figure 8 In the absence of diversion piers, both the test and simulation in Table 1 show that the maximum flow rate is after the bottom hole of the second pool chamber. The test measurement data and simulation data are consistent with each other, and the accuracy is acceptable.

[0100] Table 1

[0101]

[0102] Hydraulic model tests and numerical simulation studies have shown that the novel weir flow bottom hole combined fishway with diversion piers proposed in the present invention can provide a good migration channel for fish and create a good migration environment for fish.

[0103] The contents described in the above embodiments should be understood as these embodiments are only used to more clearly illustrate the present invention, and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention made by those skilled in the art all fall within the scope defined by the claims attached to this application.

Claims

1. A novel weir flow bottom hole combined fishway with diversion pier, characterized by: The invention comprises a bottom plate and a left wall (2) and a right wall (3) symmetrically distributed on both sides of the bottom plate. The bottom plate is in a stepped shape and is provided with a plurality of steps (7) along the water flow direction. A folded line partition (4) is provided at a corresponding position of each step (7). The two sides of the folded line partition (4) are respectively tightly fitted with the left wall (2) and the right wall (3). A bottom hole (5) is provided in the middle of the folded line partition (4). A plurality of folded line partitions (4) distributed at intervals divide the fishway surrounded by the bottom plate, the left wall (2) and the right wall (3) into a plurality of continuously connected fishway chambers. The entrance of the fishway is an upstream water inlet channel (1), and the exit is a downstream outlet (8).

2. A novel weir flow bottom hole combined fishway with diversion pier according to claim 1, characterized in that: The fold line partition (4) is in a symmetrical and curved trapezoidal shape, comprising a middle partition and a first left-side bent plate and a first right-side bent plate symmetrically distributed on both sides thereof, the left side of the first left-side bent plate being connected to the second left-side bent plate, and the right side of the first right-side bent plate being connected to the second right-side bent plate, the bottom hole (5) being arranged in the middle and lower part of the middle partition, and the second left-side bent plate and the second right-side bent plate being tightly fitted to the left-side wall (2) and the right-side wall (3) respectively.

3. A novel weir flow bottom hole combined fishway with diversion pier according to claim 2, characterized in that: The fold line partition (4) bends downstream on a plane, and the horizontal distance from the left side wall (2) to the first bending point is l1, the horizontal distance from the first bending point to the second bending point is l2, the horizontal distance from the second bending point to the third bending point is l3, the horizontal distance from the third bending point to the fourth bending point is l4, and the horizontal distance from the fourth bending point to the right side wall (3) is l5, l1:l2:l3:l4:l5=1:2:4:2:1, the bending angle between the second bending plate on the left side and the outer side of the first bending plate on the left side is a0, the bending angle between the first bending plate on the left side and the inner side of the middle partition is b0, the bending angle between the middle partition and the inner side of the first bending plate on the right side is b1, and the bending angle between the first bending plate on the right side and the outer side of the second bending plate on the right side is a1, a0=b0=b1=a1=135°.

4. The novel weir flow bottom hole combined fishway with diversion pier according to claim 1 is characterized by: Except for the last fold line partition plate (4), a diversion pier (6) is provided downstream of the bottom hole (5) of each of the preceding fold line partition plates (4).

5. The novel weir flow bottom hole combined fishway with diversion pier according to claim 1 is characterized by: The height of the fold line partition (4) is lower than the height of the left wall (2) and the right wall (3).

6. The novel weir flow bottom hole combined fishway with diversion pier according to claim 4 is characterized by: The diverter pier (6) is cylindrical and is located directly behind the bottom hole (5). The horizontal distance between the center of the diverter pier (6) and the bottom hole (5) is twice its own diameter. The bottom hole (5) is a rectangular notch with a length-to-width ratio of 1:

1. The size of the cross section of the diverter pier (6) in the direction perpendicular to the water flow is the same as that of the bottom hole (5).

7. The novel weir flow bottom hole combined fishway with diversion pier according to claim 1 is characterized by: The converted slope of the base plate is 3%.

8. A vortex identification method for a novel weir flow bottom hole combined fishway with diversion piers, characterized in that: The steps include: Step 1: Establish a 3D geometric model: Use 3D geometric modeling software to create a 3D geometric model of the fluid calculation domain, and export a geometric file that meets the format requirements of the computational meshing software; Step 2: Grid division of computational domain: Import the geometry file outputted in step 1 into grid division software, divide the computational domain in detail, perform grid encryption processing on the side wall, top area and water flow area at the bottom hole (5) of the fishway, and after the grid is generated, export the corresponding grid file according to the grid file required by the numerical simulation calculation software; Step 3, establishing a three-dimensional mathematical model: the fluid flowing through the fishway is assumed to be an incompressible Newtonian fluid, and the three-dimensional mathematical model includes a flow control equation, which is composed of a continuity equation, a momentum equation, and a k-ε equation; Step 4: According to the actual operating conditions of the object under study, the corresponding boundary conditions and initial conditions are set to perform numerical calculations of the three-dimensional flow field. The volume fraction of the velocity inlet water is set to 1, and the turbulence is set to the default value of 5%. In order to simulate the actual situation more realistically, a gas inlet is set on the upper surface of the computational fluid domain to simulate an open-top channel. The side walls, partitions and bottom plates are set as side walls, and based on the mathematical model established in step 3, the three-dimensional flow field is numerically simulated using CFD calculation software; Step 5: post-processing, using CFD post-processing software to obtain the flow field information of the fishway; Step six, vortex identification is performed based on the Ω criterion, thereby displaying the three-dimensional vortex structure in the flow field.

9. The vortex identification method of a novel weir flow bottom hole combined fishway with diversion pier according to claim 8 is characterized by: The step six is ​​specifically as follows: The application of Ω criterion in discrete vector field data is written to identify vortices. The third generation vortex identification method is adopted, and the parameter Ω is introduced. Ω represents the ratio of the vorticity of the rotating part to the total vorticity. Ω is equal to the square of vorticity divided by the sum of the square of vorticity and the square of deformation. According to the relationship between rotational motion and deformation in flow, the mathematical definition and identification method of vortices are proposed. When Ω is greater than 0.5 and the vorticity exceeds the deformation, it is considered that a vortex is formed. The isosurface of Ω=0.52 is used to identify the vortex surface, thereby displaying the three-dimensional vortex structure in the flow field. The Ω criterion further decomposes the vorticity ω into a rotating part and a non-rotating part, namely: ω=R+S(7) Where: R is the vorticity of the rotating part, S is the vorticity of the non-rotating part, that is, pure shear, R and ω have different directions, and the estimation formula is: Where: A is the velocity gradient symmetric tensor, representing the deformation effect, B is the velocity gradient antisymmetric tensor, representing the rotation effect, || || F Represents the Forbenius norm of the matrix; Any point in the non-uniform flow field can generate a velocity gradient tensor in a specific coordinate system (x, y, z), that is, a 3×3 matrix. According to the Cauchy-Stokes decomposition, this matrix can be decomposed into a symmetric tensor and an antisymmetric tensor: Where: represents the velocity gradient tensor; (u, v, w) represents the velocity in the coordinate system (x, y, z); In actual use, in order to prevent the problem of zero division, a positive number γ less than 0.01 is added to the denominator, so that the expression of Ω becomes:

10. The vortex identification method of a novel weir flow bottom hole combined fishway with diversion pier according to claim 8, characterized in that: The 3D geometry software in step 1 is Solidworks and AutoCAD, the meshing software in step 2 is ANSYS mesh, the CFD calculation software in step 4 is ANSYS FLUENT, the CFD post-processing software in step 5 is Tecplot, and the vortex identification in step 6 is performed based on the Ω criterion, and the software used is Tecplot.

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