Ecological conservation area arrangement analysis method and device

Abstract

The invention belongs to the technical field of river ecological conservation area design, and particularly relates to an ecological conservation area arrangement analysis method and device. The method comprises the following steps: S1, establishing a three-dimensional water flow mathematical model; s2, according to the three-dimensional water flow mathematical model, performing simulation analysis by adopting multi-stage flow working conditions of high flow, low flow and low flow; s3, the river reach ecological conservation areas are evenly arranged in the bent and straight section river channel; s4, after the canal is built, the flow velocity in the ecological conservation area is studied under the working conditions of all levels of flow; s5, the flow velocity of water flow in the ecological conservation area is increased, plug flow simulation of the ecological conservation area is carried out, and flow velocity distribution of the ecological conservation area is obtained.The novel ecological conservation area arrangement analysis method and device are used for guiding arrangement of the ecological conservation area during river channel design.

Description

Technical Field

[0001] The invention belongs to the technical field of river ecological conservation area design, and specifically relates to an ecological conservation area layout analysis method and device. Background Art

[0002] River ecological conservation areas refer to areas whose main functions are to protect biodiversity, maintain water and soil, and purify the air. These areas are usually located along rivers. Through measures such as vegetation restoration, wetland construction, and soil and water conservation, the ecological functions of rivers are improved, providing a high-quality ecological environment for surrounding areas.

[0003] The main functions of river ecological conservation areas include water conservation, soil conservation and biodiversity protection. During the river construction process, ecological conservation areas are usually constructed and managed through vegetation restoration, wetland construction, soil and water conservation and ecological restoration. Summary of the invention

[0004] In order to arrange ecological conservation areas and obtain the flow rate of the river during river design, the present invention proposes an ecological conservation area arrangement analysis method and device for guiding the setting of ecological conservation areas during river design.

[0005] In order to achieve the above objectives, the following technical solutions are proposed:

[0006] An ecological conservation area layout analysis method comprises the following steps:

[0007] S1, establish a three-dimensional water flow mathematical model;

[0008] S2, based on the three-dimensional water flow mathematical model, simulates and analyzes the multi-level flow conditions of flood, normal and dry seasons

[0009] S3, arrange the ecological conservation area of ​​the river section within the straightening section of the river;

[0010] S4, study the flow velocity in the ecological conservation area under various flow conditions after the canal is built;

[0011] S5, increasing the water flow velocity in the ecological conservation area, and conducting flow simulation in the ecological conservation area to obtain the flow velocity distribution in the ecological conservation area.

[0012] Furthermore, step S1 specifically includes: establishing a basic mathematical equation of three-dimensional water flow; performing discretization and spatial discretization of the equation; determining a definite solution condition; and terrain and grid division.

[0013] Furthermore, the discrete processing of the equation includes establishing an unstructured grid flow field model, using explicit-implicit alternating technology to integrate the mass conservation equation and the momentum conservation equation in time and space respectively, and the equation moments in each direction and on a single grid line are scanned and solved alternately in the x, y, and z directions using a double-precision scanning method.

[0014] Furthermore, the spatial discretization processing includes: establishing an unstructured grid flow field model; when spatially discretizing the calculation area in the model, using an unstructured grid finite volume method to spatially discretize the unified continuous system into a series of irregular and non-overlapping grid units, wherein an unstructured grid is used on the plane of the three-dimensional model and a structured grid is used vertically.

[0015] Furthermore, a structural grid is used in the vertical direction to form a vertical layered structure, including a uniform layering mode, a specified relative layering mode and a variable layering mode.

[0016] Furthermore, the solution conditions include initial conditions and boundary conditions. The initial conditions are to start the calculation initialization process based on measured data; the boundary conditions include assumed conditions and general boundary conditions. The assumed conditions do not involve the specific numerical values ​​of the water surface and flow velocity; the general boundary conditions include: a given flow rate at the inlet and a given corresponding water level at the outlet; for a non-sliding bank boundary, the flow velocity is taken as zero; for a sliding bank boundary, the flow velocity in the direction of the boundary normal is taken as zero; the given sediment content at the inlet of the sediment boundary changes with time, and there is no gradient change at the outlet boundary.

[0017] Furthermore, it also includes the determination of dry-wet boundary conditions, monitoring the water depth of each unit, and dividing the units into three categories according to the water depth: dry units, partially dry units and wet units, and determining the flood boundary based on the partially dry unit surface.

[0018] Furthermore, the terrain and grid division include: processing the river section in the three-dimensional water flow model: using quadrilateral coupled triangular grids for grid division on the plane, the grid scale does not exceed 5m in the downstream direction and does not exceed 3m in the cross-flow direction, and local encryption is performed at the confluence of the bends and straightening points, and the grid spacing is encrypted to 0.5m~1m; the vertical direction perpendicular to the water depth is divided into 5 layers.

[0019] Furthermore, the analysis result in step S4 is:

[0020] The average annual flow and water consumption for navigation is 24m 3 / s condition, each ecological conservation area is almost still water, the surface velocity is in the range of 0.00m / s~0.006m / s, the bottom velocity is in the range of 0.00m / s~0.004m / s, and the hydrodynamic conditions are weak;

[0021] The average annual flow and water consumption for navigation is 40m3 / s condition, each ecological conservation area is almost still water, the surface velocity is in the range of 0.00m / s~0.014m / s, the bottom velocity is in the range of 0.00m / s~0.010m / s, and the hydrodynamic conditions are weak;

[0022] The annual flood flow and navigation water volume is 24m 3 / s condition, the hydrodynamic conditions in each ecological conservation area are enhanced, the surface velocity is in the range of 0.002m / s~0.152m / s, and the bottom velocity is in the range of 0.01m / s~0.106m / s;

[0023] The annual flood and navigation water volume is 40m 3 / s condition, the hydrodynamic conditions in each ecological conservation area were slightly enhanced, the surface velocity was in the range of 0.003m / s~0.141m / s, and the bottom velocity was in the range of 0.01m / s~0.092m / s;

[0024] The dry season flow and navigation water consumption is 24m 3 / s condition, each ecological conservation area is almost still water, the surface velocity is in the range of 0.00m / s~0.010m / s, the bottom velocity is in the range of 0.00m / s~0.007m / s, and the hydrodynamic conditions are weak;

[0025] The dry season flow and the water consumption for navigation at the Madao hub is 40m 3 / s conditions, each ecological conservation area is almost still water, the surface flow velocity is in the range of 0.00m / s ~ 0.017m / s, the bottom flow velocity is in the range of 0.00m / s ~ 0.012m / s, and the hydrodynamic conditions are weak.

[0026] Based on the same concept, an ecological conservation area layout analysis device is also proposed, comprising at least one processor and a memory communicatively connected to the at least one processor; the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute an ecological conservation area layout analysis method described in any one of claims 1 to 9.

[0027] Based on the scheme of the present invention, the beneficial effect is: the present invention proposes a new ecological conservation area layout analysis method and device, which are used to guide the setting of ecological conservation areas during river channel design. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flow chart of the method for analyzing the layout of ecological conservation areas;

[0029] Figure 2 is the grid configuration diagram of the three-dimensional numerical model;

[0030] Figure 3 It is a schematic diagram of horizontal mixed stratification with sigma / z value applied vertically;

[0031] Figure 4 It is a three-dimensional water flow mathematical model and grid layout diagram;

[0032] Figure 5 It is a schematic diagram of the location of the flow velocity comparison section;

[0033] Figure 6 It is a schematic diagram of the arrangement of flow velocity sampling points;

[0034] Figure 7 This is the velocity distribution cloud map of the ecological conservation area under condition 1, the multi-year average flow, and the horse trail diversion of 24m3 / s;

[0035] Figure 8 This is the velocity distribution cloud map of the ecological conservation area under condition 2, the multi-year average flow, and the horse trail diversion of 40m3 / s;

[0036] Fig. 9 This is the velocity distribution cloud map of the ecological conservation area under condition 3, annual flood flow, and horse trail diversion of 24m3 / s;

[0037] Fig.10 This is the velocity distribution cloud map of the ecological conservation area under condition 4, annual flood flow, and horse trail diversion of 40m3 / s;

[0038] Fig.11 This is the velocity distribution cloud map of the ecological conservation area under condition 5, dry season flow, and horse trail diversion of 24m3 / s;

[0039] Fig.12 This is the velocity distribution cloud map of the ecological conservation area under condition 6, dry season flow, and horse trail diversion of 40m3 / s;

[0040] Fig.13 This is a schematic diagram of the arrangement of the S10 flow velocity sampling points;

[0041] Fig.14 It is the cloud map of flow velocity distribution before the ecological conservation area project;

[0042] Fig.15 This is the velocity distribution cloud map after the S10 ecological conservation area project. DETAILED DESCRIPTION

[0043] The present invention is further described in detail below in conjunction with test examples and specific implementation methods. However, this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments, and all technologies realized based on the content of the present invention belong to the scope of the present invention.

[0044] Example 1

[0045] An ecological conservation area layout analysis method, the flow chart is as follows Figure 1 As shown, the following steps are included:

[0046] S1, establish a three-dimensional water flow mathematical model;

[0047] S2, based on the three-dimensional water flow mathematical model, adopts the flood, normal and dry multi-level flow conditions for simulation analysis;

[0048] S3, arrange the ecological conservation area of ​​the river section within the straightening section of the river;

[0049] S4, study the flow velocity in the ecological conservation area under various flow conditions after the canal is built;

[0050] S5, increasing the water flow velocity in the ecological conservation area, and conducting flow simulation in the ecological conservation area to obtain the flow velocity distribution in the ecological conservation area.

[0051] 1.1. Establishment of three-dimensional water flow mathematical model

[0052] 1.1.1. Basic equations

[0053] The mathematical basis of the MIKE3 model is the Reynolds-averaged Navier-Stokes equations, which include the effects of turbulence and density changes. The governing equations of the three-dimensional hydrodynamic module are as follows:

[0054] (1) Continuity equation of water flow:

[0055]

[0056] (2) Momentum equation in the X direction:

[0057]

[0058] (3) Momentum equation in the Y direction:

[0059]

[0060] Where:

[0061] is the fluid acceleration; is the horizontal velocity gradient; f v 、f u is the Coriolis acceleration; is the surface water level acceleration; is the atmospheric pressure gradient; is the buoyancy effect acceleration; is the wave radiation stress; is the vertical stress generated by the Bousinesq approximation; u s S、vs S is the acceleration generated by the source inflow. u 、F v is the horizontal stress, and the velocity gradient-stress relationship is used.

[0062] The velocity boundary conditions of the water surface and the riverbed bottom can be expressed as follows:

[0063] (1) At the water surface, that is, z = η:

[0064]

[0065] Where: (τ sx , τ sy ) is the shear force produced by the wind on the water surface.

[0066] (2) Riverbed bottom, i.e. z = -d:

[0067]

[0068] Where: (τ bx , τ by ) is the riverbed shear stress, which can be related to water depth and average flow velocity by using the Schertz formula:

[0069]

[0070] Where: C is the Xie Cai coefficient.

[0071] 1.1.2. Discretization of equations

[0072] The MIKE3 model uses an explicit-implicit alternating technique to integrate the mass conservation equation and momentum conservation equation in time and space respectively. The moments of the equations in each direction and on individual grid lines are solved by scanning alternately in the x, y, and z directions using a double-precision scanning method.

[0073] 1.1.3. Spatial Discretization

[0074] The basic idea of ​​spatial discretization of the unstructured grid flow model MIKE3 Flow Model FM is: when the calculation area is spatially discretized, the unstructured grid finite volume method is used to discretize the unified continuous system into a series of irregular and non-overlapping grid units in space. The three-dimensional model uses an unstructured grid on the plane and a structured grid in the vertical direction, that is, a hierarchical structure is used in the vertical direction. The grid configuration diagram of the three-dimensional numerical model is shown in the figure. Figure 2 shown.

[0075] Two different types of grid composition can be applied in the vertical space domain: Sigma layering and Sigma / z-value level mixed layering.

[0076] (1) Sigma stratification

[0077]

[0078] MIKE3 Flow Model is based on relative layered grid technology in the vertical direction. The vertical position of each layered grid can be configured according to three Sigma coordinate transformation methods:

[0079] 1) Uniform layering mode

[0080] Vertically, the ratio of the spacing between any two layers of grids to the total water depth is equal, and the distribution of each layer along the water depth is uniform.

[0081] 2) Specify relative layering mode

[0082] 3) Variable layering mode

[0083] In this layering mode, three Sigma coordinate parameters need to be specified. This mode can produce the effect of stretching the table and the thickness of the bottom layer. Three setting parameters are required:

[0084] ①sigmac(σ c )

[0085] σ c is the harmonic weight coefficient of the uniform distribution mode and the stretching mode, and its value range is 0≤σ c ≤1. When the value is 1, the vertical grid configuration in this mode is the same as that in the uniform layering mode; when the value is 0, the vertical grid configuration in this mode is the same as that in the stretched layering mode.

[0086] ②theta(θ)

[0087] θ is the control parameter of the surface layer thickness, and its value range is 0<θ≤20.

[0088] ③b

[0089] b is the bottom layer thickness control parameter, and its value range is 0 <b≤1。

[0090] (2) Sigma / z value level mixing stratification

[0091] Sigma / z value horizontal mixed stratification means that Sigma coordinates are used for stratification between the free surface and the user-specified water level (sigma critical water level, in meters), and z value absolute coordinates are used for stratification below the user-specified water level. The Sigma coordinate stratification settings in the upper water body are as described above. The z value absolute coordinate stratification settings in the lower water body are divided into the following two types: equidistant stratification and specified stratification. The illustration of applying Sigma / z value horizontal mixed stratification vertically is shown in Figure 3 .

[0092] 1.1.4. Definite solution conditions

[0093] (1) Determination of initial conditions

[0094] Because the river model calculation is a non-steady flow that changes continuously over time, initial conditions need to be given first. When the model starts to calculate, the water surface and flow field are generally not coordinated with each other. It is necessary to let the model run for a period of time from any initial conditions, and gradually adjust the water surface and flow field in the calculation area to make them coordinated with each other and match them with the boundary conditions. The initialization process can start from a cold start (flow rate is zero) state. However, sometimes in order to speed up the completion of the initialization process and avoid instability, the general model starts calculation based on measured data.

[0095] Once the initialization process is completed, all variables will be coordinated with each other, and the calculation results can be stored as initial conditions for future formal calculations.

[0096] (2) Determination of boundary conditions

[0097] In the process of numerical simulation calculation, boundary condition processing is very important. If it is not handled properly, it will easily cause numerical solution distortion and local instability. Since the water surface elevation and flow velocity must satisfy the internal connection specified by the control equation, the water surface and flow velocity conditions cannot be given at the same time on the boundary in the numerical solution of the discrete equation. Therefore, in the actual numerical solution, it is often necessary to make additional assumptions on the boundary. These additional numerical boundary conditions do not involve the specific numerical values ​​of the water surface and flow velocity. General boundary conditions: the flow rate is given at the inlet and the corresponding water level is given at the outlet; for the non-sliding bank boundary, the flow velocity is taken as zero; for the sliding bank boundary, the flow velocity in the direction of the boundary normal is taken as zero. The given sediment content at the inlet of the sediment boundary changes with time, and there is no gradient change at the outlet boundary.

[0098] (3) Treatment of dry and wet boundaries

[0099] Natural river channels are narrow and changeable, with winding boundaries and large fluctuations in water levels due to non-constant water flows. The boundary position of the river bank will move with the rise and fall of the water level. When the water level rises, the beach flows through and the grid points on the beach are within the boundary. When the water level drops, the beach emerges from the water. From a physical point of view, when the beach emerges from the water, the water depth on the grid should be zero and the flow rate should also be zero. However, in the iterative calculation process, when the water depth is zero or small, computer numerical overflow or calculation divergence will occur. Therefore, a moving boundary problem occurs, which must be considered in the calculation.

[0100] This model uses the method of determining the flooding point and introducing the moving boundary processing method to solve the problem of continuous flooding. The water depth of each unit is monitored and the units are divided into three categories according to the water depth: dry units, partially dry units and wet units. The flood boundary can be determined according to the partially dry unit surface.

[0101] ① The cells are identified as dry, semi-dry or wet cells. The boundaries of each cell are also checked during the calculation to establish the flooding boundaries.

[0102] ② The unit boundary is defined as a flooded boundary if the following two conditions are met: first, the water depth on one side of the unit must be less than hdry, and the water depth on the other side must be greater than hflood. Second, the static water depth of the unit with a water depth less than hdry plus the surface elevation water level of the other unit must be greater than zero.

[0103] ③ A cell will be defined as dry if it meets the following two conditions: first, the water depth in the cell must be less than the dry water depth hdry, and second, none of the three boundaries of the cell is a flooded boundary. Cells defined as dry will be ignored in the calculation.

[0104] ④ The cell is defined as semi-dry: if the cell water depth is between hdry and hwet, or when the water depth is less than hdry but one of the boundaries is flooded, the momentum flux is set to 0 and only the mass flux is calculated.

[0105] ⑤ The cell is defined as wet: if the water depth of the cell is greater than hwet, then both momentum flux and mass flux will be considered in the calculation.

[0106] The actual boundary activity is in accordance with the kinematic principle and is continuous, so the artificial "activity boundary" will introduce numerical errors. In order to avoid continuous interference, the boundary is judged every few time steps in the simulation (but it must be ensured that the rise and fall of the water level within these time steps will not exceed the dry boundary).

[0107] 1.1.5. Terrain and grid division

[0108] In order to further analyze the hydrodynamic conditions of the straightening section and ecological conservation area of ​​the Pinglu Canal Project from Pingtang River Mouth to Madou Hub, this report simulates and analyzes the key straightening sections and river sections in the ecological conservation area where the hydrodynamic conditions vary greatly seasonally using multi-level flow conditions of flood, normal and dry seasons. The three-dimensional water flow mathematical model is used for segmented calculation. The calculation range is shown in the table below.

[0109] Table 1 Scope of the three-dimensional water flow mathematical model for the ecological conservation area and the straightening section

[0110] Model segmentation Model length Contains ecological conservation areas Number of grid divisions K8+100~K11+100 3.0km Ecological Conservation Area S1~Ecological Conservation Area S2 157394 1BDK0+000~1BDK4+900 4.9km Ecological conservation area S3 to ecological conservation area S9 193345 1BDK4+900~1BDK8+800 3.9km Ecological Conservation Area S10 128913

[0111] In order to accurately simulate the hydrodynamic conditions of the straightening section and ecological conservation area in the river section of this study, the three-dimensional water flow mathematical model is used to refine the simulated river section: quadrilateral coupled triangular grids are used for grid division on the plane, and the grid scale does not exceed 5m in the downstream direction and 3m in the cross-flow direction. For the straightening confluence, local encryption is performed, and the grid spacing is encrypted to 0.5m~1m; the vertical direction is divided into 5 layers perpendicular to the water depth. There are three straightening sections and key river sections in the ecological conservation area from Pingtangjiangkou to Madao Hub, including 10 ecological conservation areas. A total of about 120,000 to 190,000 grids are generated in the simulation area. The three-dimensional water flow mathematical model and grid layout diagram are shown in Figure 4 .

[0112] Model Validation

[0113] The upper boundaries of the three-dimensional water flow mathematical model are all flow boundary conditions, and the lower boundaries are all water level boundary conditions. Each water level boundary condition is determined by the one-dimensional mathematical model of the long river section. The roughness is verified in sections by calculating the water level according to the one-dimensional model in the simulated river section. At the same time, in view of the lack of measured data in the engineering river section, the S10 model of the ecological conservation area is selected, and the cross-sectional flow velocity of the three-dimensional water flow mathematical model of this section is verified by citing the relevant scheme design and flow field distribution results of the special topic of the physical model of the tributary confluence of Shaping River in the "Study on Mathematical Models or Physical Models of Important Tributaries Confluence"

[0114] (1) Water level verification and calculation parameter selection

[0115] The roughness is verified in sections according to the water level calculated by the one-dimensional model in the river section. From the verification results, the water level difference between the one-dimensional model and the three-dimensional model is within the range of ±0.02m, and the accuracy of the three-dimensional model can be guaranteed. The water surface line verification of the three-dimensional water flow mathematical model is shown in Table 2. After the water surface line verification, the roughness value of the main channel of the canal of the three-dimensional water flow mathematical model is generally in the range of 0.015-0.03, and the roughness value of the straightening section or ecological conservation area is generally in the range of 0.030-0.040.

[0116] Table 2 Verification of water surface line of three-dimensional water flow mathematical model

[0117]

[0118] (2) Cross-sectional flow velocity verification

[0119] ① The report cited the "Study on Mathematical Models or Physical Models of Important Tributaries" and the results of the design of the physical model of the Shaping River tributary confluence and the flow field distribution to verify the flow velocity of the three-dimensional water flow mathematical model (taking the S10 section of the ecological conservation area as an example). The verification condition was selected from the Shaping River tributary confluence into the 20-year flood (Q = 1260m 3 / s), Xijin Reservoir and Madao Hub Dam are at normal water level. Figure 5 The comparison of velocity distribution between the two-dimensional water flow mathematical model and the physical model test is shown in Table 3.

[0120] Table 3 Comparison of flow rates between three-dimensional digital model and physical model (m / s)

[0121]

[0122] It can be seen that the difference between the flow velocity calculated by the three-dimensional digital model and the measured flow velocity on the surface of the logistics model is within ±0.1m / s, and the difference is positive and negative, which is consistent with the measured value of the physical model. Simulation calculations can be carried out for application in actual engineering.

[0123] 1.2. Preparation of simulation conditions

[0124] According to the design requirements, the report uses flood, normal and dry multi-level flow conditions for simulation analysis. The flood flow uses the annual flood flow of Shaping River and Shizi River, the medium water flow uses the multi-year average flow of Shaping River and Shizi River, and the dry flow uses the dry season flow of Shaping River and Shizi River. The typical flow of each level is considered to be combined with the Madao hub diversion 24m 3 / s (recent water consumption for navigation), 40m 3 / s (long-term shipping water consumption), there are 6 combined operating conditions in total, and the simulated operating conditions are shown in the table.

[0125] Table 4 Calculation conditions of the three-dimensional water flow mathematical model in the ecological conservation area and the straightening section

[0126]

[0127] 1.3. Results Analysis

[0128] In general, the ecological conservation areas of the studied river sections are all arranged within the original Shaping River channel of the straightening section. After the canal was built, the mainstream returned to the main channel of the canal under various flow conditions. The flow velocity in the ecological conservation area (straightening section) was generally very small, almost in a static water state. In order to further quantify the flow velocity in the ecological conservation area (straightening section), 29 flow velocity sampling points were used. Figure 6 The surface velocity and bottom flow of each sampling point are shown in Table 5. The velocity distribution cloud map of the ecological conservation area is shown in Figure 7 to Figure 12 . From the statistical results:

[0129] (1) Multi-year average flow

[0130] The average annual flow and water consumption for navigation at the Madao hub is 24m 3 / s conditions, each ecological conservation area (straightening section) is almost still water, the surface flow velocity is in the range of 0.00m / s to 0.006m / s, the bottom flow velocity is in the range of 0.00m / s to 0.004m / s, and the hydrodynamic conditions are weak.

[0131] The average annual flow and water consumption for navigation at the Madao hub is 40m 3 / s conditions, each ecological conservation area (straightening section) is almost still water, with surface velocity ranging from 0.00m / s to 0.014m / s and bottom velocity ranging from 0.00m / s to 0.010m / s, and the hydrodynamic conditions are weak.

[0132] (2) Annual flood flow

[0133] The annual flood flow and the water consumption for navigation at the Madao hub are 24m 3 / s conditions, the hydrodynamic conditions in each ecological conservation area (straightening section) were slightly enhanced, the surface flow velocity was in the range of 0.002m / s to 0.152m / s, and the bottom flow velocity was in the range of 0.01m / s to 0.106m / s.

[0134] The annual flood and navigation water demand of Madao hub is 40m 3 / s conditions, the hydrodynamic conditions in each ecological conservation area (straightening section) were slightly enhanced, the surface flow velocity was in the range of 0.003m / s to 0.141m / s, and the bottom flow velocity was in the range of 0.01m / s to 0.092m / s.

[0135] (3) Dry season flow

[0136] The dry season flow and the water consumption for navigation at the Madao hub is 24m 3 / s conditions, each ecological conservation area (straightening section) is almost still water, the surface flow velocity is in the range of 0.00m / s to 0.010m / s, the bottom flow velocity is in the range of 0.00m / s to 0.007m / s, and the hydrodynamic conditions are weak.

[0137] The dry season flow and the water consumption for navigation at the Madao hub is 40m 3 / s conditions, each ecological conservation area (straightening section) is almost still water, the surface flow velocity is in the range of 0.00m / s to 0.017m / s, the bottom flow velocity is in the range of 0.00m / s to 0.012m / s, and the hydrodynamic conditions are weak.

[0138] According to the design principles of the design unit for arranging ecological conservation areas, the hydrodynamic conditions in the above-mentioned ecological conservation areas (straightening sections) are relatively low, and algal blooms are prone to occur, so ecological measures need to be taken to reduce algae growth.

[0139] Table 5 Statistics of flow velocity at measuring points in the ecological conservation area (straightening section)

[0140]

[0141] Table 5 Flow velocity statistics at the measuring points in the ecological conservation area (straightening section) continued

[0142]

[0143] 1.4. Flow simulation in ecological conservation areas

[0144] According to the above simulation results, many ecological conservation areas are almost still water under the conditions of multi-year average flow and dry season flow, with weak hydrodynamic conditions and high risk of algal bloom. To further alleviate the risk of algal bloom, the design unit installed a solar push flow aerator at the turning point of the S10 ecological conservation area to increase the water flow velocity in the ecological conservation area.

[0145] In order to simulate the flow conditions in the ecological conservation areas after improvement measures were taken, a three-dimensional water flow mathematical model was used for supplementary simulation, and the results are as follows.

[0146] 1.4.1. Simulation working conditions

[0147] According to the design requirements, the report uses flood, normal and dry multi-level flow conditions for simulation analysis. The flood flow uses the annual flood flow, the medium water flow uses the multi-year average flow, and the low water flow uses the dry season flow of Shaping River and Shizi River. The typical flow of each level is considered to be combined with the upper hub diversion 24m 3 / s (recent shipping water consumption), there are 3 combined operating conditions in total, and the simulated operating conditions are shown in the table.

[0148] Table 6 Calculation conditions of three-dimensional water flow mathematical model in S10 ecological conservation area

[0149]

[0150] 1.4.2. Results analysis

[0151] In general, under all levels of flow conditions, the mainstream returns to the main channel of the canal. The flow velocity in the ecological conservation area is generally small, almost in a still water state. After the installation of flow-pushing facilities and the connection of ditches, the flow velocity is slightly improved, but the increase in flow velocity is small and the impact range is relatively limited.

[0152] In order to further quantify the flow velocity in the ecological conservation area, multiple flow velocity sampling points were selected in each ecological conservation area. Fig.13 , the surface velocity and bottom flow of each sampling point are counted, see Table 6, and the velocity distribution cloud map of the ecological conservation area is shown in Figure 14-15 . From the statistical results:

[0153] (1) Multi-year average flow

[0154] S10 ecological conservation area: After taking measures of flow-pushing facilities, the surface flow velocity is in the range of 0.011m / s to 0.019m / s, and the bottom flow velocity is in the range of 0.006m / s to 0.011m / s. Compared with before taking measures, the maximum increase in surface flow velocity is 0.019m / s, and the maximum increase in bottom flow velocity is 0.011m / s.

[0155] (2) Annual flood flow

[0156] S10 ecological conservation area: After taking measures of flow-pushing facilities, the surface flow velocity was in the range of 0.003m / s to 0.034m / s, and the bottom flow velocity was in the range of 0.003m / s to 0.019m / s. Compared with before taking measures, the maximum increase in surface flow velocity was 0.031m / s, and the maximum increase in bottom flow velocity was 0.018m / s.

[0157] (3) Dry season flow

[0158] S10 ecological conservation area: After taking measures of flow-pushing facilities, the surface flow velocity is in the range of 0.011m / s to 0.019m / s, and the bottom flow velocity is in the range of 0.007m / s to 0.011m / s. Compared with before taking measures, the maximum increase in surface flow velocity is 0.019m / s, and the maximum increase in bottom flow velocity is 0.011m / s.

[0159] Table 7 Statistics of flow velocity before and after the implementation of measures in ecological conservation areas

[0160]

[0161] The flow velocity statistics before and after the implementation of measures in the ecological conservation area are shown in Table 7.

[0162] Finally, it should be noted that the embodiments described in detail above are only the best practices of the invention and cannot be used to limit the scope of rights of the invention. Equivalent replacement of the technical solutions recorded in the aforementioned embodiments does not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the invention, and they should all be included in the scope of the claims and description of the invention.

Claims

1. A method for analyzing the layout of an ecological conservation area, characterized in that: The following steps are involved: S1, establish a three-dimensional water flow mathematical model; S2, based on the three-dimensional water flow mathematical model, adopts the flood, normal and dry multi-level flow conditions for simulation analysis; S3, arrange the ecological conservation area of ​​the river section within the straightening section of the river; S4, study the flow velocity in the ecological conservation area under various flow conditions after the canal is built; S5, increasing the water flow velocity in the ecological conservation area, and conducting flow simulation in the ecological conservation area to obtain the flow velocity distribution in the ecological conservation area.

2. The method for analyzing the layout of an ecological conservation area according to claim 1, characterized in that: Step S1 specifically includes: establishing a basic mathematical equation for three-dimensional water flow; performing discretization and spatial discretization of the equation; determining a definite solution condition; and terrain and grid division.

3. The method for analyzing the layout of an ecological conservation area according to claim 2, characterized in that: The discrete processing of the equations includes establishing an unstructured grid flow field model, using explicit-implicit alternating technology to integrate the mass conservation equation and the momentum conservation equation in time and space respectively, and the equation moments in each direction and on a single grid line are scanned and solved alternately in the x, y, and z directions using a double-precision scanning method.

4. The method for analyzing the layout of an ecological conservation area according to claim 2, characterized in that: The spatial discretization process includes: establishing an unstructured grid flow field model; when performing spatial discretization on the calculation area in the model, using an unstructured grid finite volume method to spatially discretize a unified continuous system into a series of irregular and non-overlapping grid units, wherein an unstructured grid is used on the plane of the three-dimensional model and a structured grid is used vertically.

5. The method for analyzing the layout of an ecological conservation area according to claim 4, characterized in that: A structural grid is used vertically to form a vertical layered structure, including a uniform layering mode, a specified relative layering mode and a variable layering mode.

6. The method for analyzing the layout of an ecological conservation area according to claim 2, characterized in that: The solution conditions include initial conditions and boundary conditions. The initial conditions are to start the calculation initialization process based on measured data; the boundary conditions include assumed conditions and general boundary conditions. The assumed conditions do not involve the specific numerical values ​​of the water surface and flow velocity; the general boundary conditions include: a given flow rate at the inlet and a given corresponding water level at the outlet; for a non-sliding bank boundary, the flow velocity is taken as zero; for a sliding bank boundary, the flow velocity in the direction of the boundary normal is taken as zero; the given sediment content at the inlet of the sediment boundary changes with time, and there is no gradient change at the outlet boundary.

7. The method for analyzing the layout of an ecological conservation area according to claim 6, characterized in that: It also includes the determination of dry-wet boundary conditions, monitoring the water depth of each cell, and dividing the cells into three categories according to the water depth: dry cells, partially dry cells and wet cells, and determining the flood boundary based on the partially dry cell surface.

8. The method for analyzing the layout of an ecological conservation area according to claim 2, characterized in that: The terrain and grid division include: processing the river section in the three-dimensional water flow model: using quadrilateral coupled triangular grids for grid division on the plane, the grid scale does not exceed 5m in the downstream direction and 3m in the cross-flow direction, and local encryption is performed at the confluence of the bends and straightening points, and the grid spacing is encrypted to 0.5m~1m; the vertical direction is divided into 5 layers perpendicular to the water depth.

9. The method for analyzing the layout of an ecological conservation area according to claim 1, characterized in that: The analysis result in step S4 is: The average annual flow and water consumption for navigation is 24m 3 / s condition, each ecological conservation area is almost still water, the surface velocity is in the range of 0.00m / s~0.006m / s, the bottom velocity is in the range of 0.00m / s~0.004m / s, and the hydrodynamic conditions are weak; The average annual flow and water consumption for navigation is 40m 3 / s condition, each ecological conservation area is almost still water, the surface velocity is in the range of 0.00m / s~0.014m / s, the bottom velocity is in the range of 0.00m / s~0.010m / s, and the hydrodynamic conditions are weak; The annual flood flow and navigation water volume is 24m 3 / s condition, the hydrodynamic conditions in each ecological conservation area are enhanced, the surface velocity is in the range of 0.002m / s~0.152m / s, and the bottom velocity is in the range of 0.01m / s~0.106m / s; The annual water volume for flood and navigation is 40m 3 / s condition, the hydrodynamic conditions in each ecological conservation area were slightly enhanced, the surface velocity was in the range of 0.003m / s~0.141m / s, and the bottom velocity was in the range of 0.01m / s~0.092m / s; The dry season flow and navigation water consumption is 24m 3 / s condition, each ecological conservation area is almost still water, the surface velocity is in the range of 0.00m / s~0.010m / s, the bottom velocity is in the range of 0.00m / s~0.007m / s, and the hydrodynamic conditions are weak; The dry season flow and the water consumption for navigation at the Madao hub is 40m 3 / s conditions, each ecological conservation area is almost still water, the surface flow velocity is in the range of 0.00m / s~0.017m / s, the bottom flow velocity is in the range of 0.00m / s~0.012m / s, and the hydrodynamic conditions are weak.

10. An ecological conservation area layout analysis device, characterized in that: It includes at least one processor and a memory that is communicatively connected to the at least one processor; the memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute an ecological conservation area layout analysis method as described in any one of claims 1 to 9.

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