Analysis method and device based on tributary junction hydrographic characteristics

Abstract

The invention belongs to the technical field of water conservancy projects, and particularly relates to an analysis method and device based on branch manifold hydrographic characteristics. The method comprises the following steps: step 1, establishing a water flow model; 2, discretizing an equation set of the model; step 3, carrying out mesh generation on the model, and encrypting a mesh near a tributary junction; 4, water flow model verification is carried out, so that calculation parameters are obtained; and 5, applying the two-dimensional water flow model conforming to simulation precision to simulation calculation of actual engineering, analyzing the influence of factors in two aspects of tributary flood convergence and hub flood diversion on channel water flow conditions, and analyzing navigation conditions to obtain reasonable ranges of longitudinal flow velocity and transverse flow velocity in the channel. By deeply analyzing the water flow characteristics of the tributary junction, the processes of water flow dynamic, sediment movement, riverbed evolution and the like of a river system can be more comprehensively known.

Description

Technical Field

[0001] The invention belongs to the technical field of water conservancy projects, and in particular relates to an analysis method and device based on the hydrological characteristics of a tributary confluence. Background Art

[0002] The confluence of tributaries is an important part of the river system, and its flow characteristics are affected by the complex effects of mutual support, squeezing and mixing between the main stream and the tributaries. By analyzing the flow characteristics of tributary confluences, we can have a deeper understanding of how these interactions affect the structure, velocity and energy distribution of the flow, so as to more comprehensively grasp the overall flow dynamics of the river system. First, by analyzing the flow characteristics of tributary confluences, we can establish corresponding mathematical models to predict the changes in flow characteristics under different conditions (such as rainfall intensity, reservoir flood discharge, etc.), providing a scientific basis for river management and flood prevention and disaster reduction. Secondly, by analyzing the flow characteristics of tributary confluences, we can evaluate the navigation conditions of the area, including parameters such as water depth, flow velocity, and flow state, providing an important reference for shipping planning and management. Thirdly, the confluence area of ​​rivers is often prone to riverbed siltation and riverbank erosion, which affect the stability and navigation conditions of the river. By analyzing the flow characteristics of tributary confluences, we can understand the laws of riverbed evolution and sediment movement, and provide a scientific basis for river regulation projects. Through reasonable regulation measures, the navigation conditions at the confluence of tributaries can be improved and the stability and safety of the river can be enhanced. Summary of the invention

[0003] The present invention aims at the unique waterway conditions of the Pinglu Canal from Pingtangjiangkou to Madou hub section, considers the influence of tributary flood inflow and hub flood diversion on the waterway flow conditions, and proposes an analysis method and device based on the hydrological characteristics of tributary confluence, so as to obtain more accurate flow velocity statistics in the navigation channel of tributary confluence and obtain the navigation conditions of tributary confluence.

[0004] In order to achieve the above objectives, the following technical solutions are proposed:

[0005] The analysis method based on the hydrological characteristics of tributary confluence includes the following steps:

[0006] Step 1: Establish a one-dimensional water flow model and a two-dimensional water flow mathematical model according to the waterway conditions;

[0007] Step 2: Discretize the model equations;

[0008] Step 3: Use a combination of triangular mesh and quadrilateral mesh to encrypt the mesh near the confluence of the tributaries;

[0009] Step 4: verify the one-dimensional water flow model and the two-dimensional water flow mathematical model to obtain calculation parameters;

[0010] Step 5. Apply the two-dimensional water flow model that meets the simulation accuracy to the simulation calculation of the actual project, and analyze the impact of tributary flood inflow and hub flood diversion on the waterway flow conditions, so as to obtain a reasonable range of longitudinal and lateral flow velocities in the waterway for navigation condition analysis.

[0011] As a preferred solution, in step 4, the verification of the one-dimensional water flow model includes roughness calibration and water surface line verification, and the water surface line verification includes pre-project water surface line verification, pre-project water surface line review and post-project water surface line review.

[0012] As a preferred solution, the boundary conditions for the one-dimensional water flow model verification include:

[0013] Inlet boundary: flow inlet boundary conditions are used to give the inlet section flow and inlet water flow direction; when there are tributaries, flow boundary conditions are set at the tributary confluence point;

[0014] Outlet boundary: Use water level outlet boundary condition.

[0015] As a preferred solution, the specific steps of roughness calibration include: adjusting the parameters of the model, obtaining the change of the river water level according to the change of the parameters, so as to ensure that the simulated value of the water level is consistent with the measured value; the riverbed roughness of the one-dimensional water flow model of the natural river before the project is between 0.03 and 0.04, and the riverbed roughness of the one-dimensional water flow model of the waterway after the project is between 0.015 and 0.03.

[0016] As the preferred solution, the water surface line verification before the project, the water level-flow relationship of the model control section is: the calculated flow of the model river section is 23m 3 / s, the water level at the river mouth is 60.8m;

[0017] The water level line was reviewed before the project. The relationship between the water level and flow rate of the model control section is: When the flood frequency of the model river section is P = 5%, the peak flow rate is 2140m 3 / s, the river mouth water level is 63.40m; when the flood frequency of the model river section is P = 20%, the peak flow is 1110m 3 / s, the water level at the river mouth is 62.90m;

[0018] After the project, the water level line was reviewed. The relationship between the water level and flow rate of the model control section is: When the flood frequency of the model river section is P = 5%, the peak flow rate is 1260m 3 / s, the river mouth water level is 63.40m; when the flood frequency of the model river section is P = 20%, the peak flow is 672m 3 / s, the water level at the estuary is 62.90m.

[0019] As the preferred solution, after taking the downstream flood diversion hub into consideration, the calculation conditions are:

[0020]

[0021] As a preferred solution, the verification of the two-dimensional water flow model includes water level verification and cross-sectional flow velocity verification; the water level verification boundary conditions include: the upper boundaries are all flow boundary conditions, the lower boundaries are all water level boundary conditions, and when tributaries merge, flow boundary conditions are set at the confluence of tributaries, and each boundary condition is established by a one-dimensional mathematical model; when verifying the water level, the initial water level uses the lower boundary water level, and the initial flow velocity is set to 0m / s; the roughness value of the two-dimensional water flow mathematical model in the main channel of the canal ranges from 0.015 to 0.03, and the roughness value of the straightening section or ecological conservation area ranges from 0.030 to 0.040.

[0022] As a preferred solution, in step five, the calculation conditions include: when there is no flood diversion downstream, the flow of the main river channel is the flood flow once in two years; when there is flood diversion downstream, the flow of the main river channel is the flood flow once in 20 years.

[0023] As a preferred solution, the longitudinal and transverse flow velocities within 500m upstream and downstream of the tributaries such as the confluence are statistically analyzed:

[0024] Without considering downstream flood diversion, when encountering tributary floods of once in 5 years, once in 10 years, and once in 20 years, the maximum longitudinal flow velocity in the channel near the confluence of the river is 0.68m / s, 0.88m / s, and 1.08m / s respectively, and the maximum transverse flow velocity is 0.19m / s, 0.23m / s, and 0.28m / s respectively;

[0025] When the downstream flood diversion is 1000m3 / s, when the tributaries encounter floods once in 5 years, once in 10 years, and once in 20 years, the maximum longitudinal flow velocities in the waterway near the confluence of Shaping River are 0.98m / s, 0.99m / s, and 1.00m / s respectively, and the maximum lateral flow velocities are 0.36m / s, 0.41m / s, and 0.44m / s respectively.

[0026] Based on the same concept, an analysis device based on the hydrological characteristics of tributary confluences 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 any of the above-mentioned analysis methods based on the hydrological characteristics of tributary confluences.

[0027] The scheme of the present invention has the following beneficial effects: the method of the present invention takes into account the influence of tributary flood inflow and hub flood diversion on the water flow conditions of the waterway, and through in-depth analysis of the flow characteristics of tributary confluence, a more comprehensive understanding of the water flow dynamics, sediment movement and riverbed evolution of the river system can be obtained. This helps to deepen the understanding of the overall operation mechanism of the river system and provide a scientific basis for river management and protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flow chart of the analysis method based on the hydrological characteristics of tributary confluence;

[0029] Figure 2 It is a schematic diagram of variable arrangement;

[0030] Figure 3 This is the calculated cross-section layout of the natural river channel of Shaping River before the project;

[0031] Figure 4 This is the calculation section layout diagram of the Pingtangjiangkou to Madao hub section;

[0032] Figure 5 It is the computational grid diagram of the Pingtangjiangkou to Madao hub section;

[0033] Figure 6 It is a schematic diagram of the location of the flow velocity comparison section;

[0034] Figure 7 This is the distribution map of flow measurement sections downstream of the confluence of Qin River;

[0035] Figure 8 Condition 1: Yujiang River flow is once in two years, Shaping River flow is once in five years, and Pingtang River estuary flow distribution map;

[0036] Fig. 9 Condition 2: Yujiang River flow is once in two years, Shaping River flow is once in ten years, and Pingtang River estuary flow field distribution map;

[0037] Fig.10 Condition 3: Yujiang River flow is once in two years, Shaping River flow is once in 20 years, and Pingtang River estuary flow field distribution map;

[0038] Fig.11 Condition 4: Yujiang River flow is once in 10 years, Shaping River flow is once in 5 years, and Pingtang River estuary flow field distribution map;

[0039] Fig.12 Condition 5: Yujiang River flow is once in 10 years, Shaping River flow is once in 10 years, and Pingtang River estuary flow field distribution map;

[0040] Fig.13 It is working condition 6, the flow of Yujiang River is once in 20 years, the flow of Shaping River is once in 2 years, the Madou hub diverts flood, and the flow field distribution map of Pingtang River estuary. DETAILED DESCRIPTION

[0041] 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.

[0042] Example 1

[0043] The analysis method based on the hydrological characteristics of tributary confluence is shown in the flowchart below: Figure 1 As shown, the following steps are included:

[0044] Step 1: Establish a one-dimensional water flow model and a two-dimensional water flow mathematical model according to the waterway conditions;

[0045] Step 2: Discretize the model equations;

[0046] Step 3: Use a combination of triangular mesh and quadrilateral mesh to encrypt the mesh near the confluence of the tributaries;

[0047] Step 4: verify the one-dimensional water flow model and the two-dimensional water flow mathematical model to obtain calculation parameters;

[0048] Step 5. Apply the two-dimensional water flow model that meets the simulation accuracy to the simulation calculation of the actual project, and analyze the impact of tributary flood inflow and hub flood diversion on the waterway flow conditions, so as to obtain a reasonable range of longitudinal and lateral flow velocities in the waterway for navigation condition analysis.

[0049] Furthermore, when establishing a one-dimensional water flow model, the basic equations used include the water flow continuity equation and the water flow motion equation, among which:

[0050] The continuity equation for water flow is:

[0051]

[0052] The equation of motion is:

[0053]

[0054] Where: x is the process (m); Q is the flow (m 3 / s); Z is the water level (m); g is the acceleration due to gravity; t is the time (s); q l is the lateral injection flow per unit length m 2 / s; is the cross-sectional area of ​​water flow (m 2 ), R is the hydraulic radius of the section, β is the kinetic energy correction coefficient, and n is the roughness coefficient.

[0055] The boundary conditions in the one-dimensional water flow model calculation usually include the inlet and outlet boundaries of the river. In this model, the above boundary conditions are processed as follows:

[0056] 1) Inlet boundary: Use flow inlet boundary conditions, that is, give the inlet cross-section flow and inlet water flow direction. When there are tributaries, set the flow boundary conditions at the tributary confluence.

[0057] 2) Outlet boundary: adopt water level outlet boundary condition.

[0058] According to the above theoretical analysis, the model building process is as follows:

[0059] First, the topographic data adopts the 1:2000 river topographic map measured in the project river section in 2022.

[0060] Secondly, Shaping River merges into Yujiang River at its estuary, which belongs to the Xijin Reservoir area. The water level-flow relationship at the estuary section can be calculated through the backwater surface line of the Xijin Reservoir area. Therefore, Pingtangjiangkou section is selected as the control section of the one-dimensional water flow model of Shaping River natural river.

[0061] Finally, the river section and cross-section layout are calculated.

[0062] Before the project, the Pinglu Canal from Pingtang River Mouth to Madao Hub was mainly excavated from the natural river channel of Shaping River. Therefore, the section from Pingtang River Mouth to Shaping Town was selected for calculation. The calculated river length is about 33km, the section spacing is 500m, and a total of 67 sections are arranged. The selected calculation area and section distribution are shown in Figure 3 .

[0063] After the project

[0064] The river section selected for calculation is from Pinglu Canal Pingtang River Mouth to Madao Hub Dam, with a channel mileage of K0+000~K28+100, a section spacing of 500m, and a total of 58 sections. The selected calculation area and section distribution are shown in Figure 4 .

[0065] Furthermore, when establishing a two-dimensional water flow model, the basic equations include the water flow continuity equation, the X-direction momentum equation, and the Y-direction momentum equation.

[0066] 1) Continuity equation of water flow:

[0067]

[0068] 2) Momentum equation in the X direction:

[0069]

[0070] 3) Momentum equation in the Y direction:

[0071]

[0072] In the above formulas, t is time, x, y are spatial coordinates, z is water level, h is water depth, h = zz b , z b is the riverbed elevation, u and v are the vertical average flow velocities along the x and y directions, g is the gravitational acceleration, n is the roughness coefficient, ν t is the turbulent kinetic energy diffusion coefficient.

[0073] The boundary conditions of the two-dimensional water flow model are:

[0074] In a two-dimensional water flow model, boundary conditions usually include the river inlet and outlet boundaries, bridge pier boundaries, bank boundaries, and moving boundaries. In this model, the above boundary conditions are handled as follows:

[0075] 1) Inlet boundary: The flow inlet boundary condition is adopted, that is, the inlet section flow rate and the inlet water flow direction are given, and the lateral distribution of the inflow at the inlet section is given.

[0076] 2) Outlet boundary: adopt water level outlet boundary condition.

[0077] 3) Bank boundary: The bank boundary is a non-slip boundary and its velocity is given as zero.

[0078] 4) Moving boundary: This model uses the “freezing” method to deal with the moving boundary, that is, judging whether the grid unit is exposed above the water surface based on the riverbed elevation at the water level node. If not, the roughness takes a normal value, otherwise, the roughness takes a positive number close to infinity.

[0079] 5) Modeling terrain data: The terrain data of the river section to be regulated in 2022 will be used.

[0080] Furthermore, in step 2, discretizing the equation group of the model includes discretizing the one-dimensional water flow model and the two-dimensional water flow model.

[0081] The one-dimensional water flow model is discretized. The numerical method used in the model is the finite volume method. The specific discretization process is as follows:

[0082] The first step is variable arrangement:

[0083] The finite volume method first divides the solution area into discrete control volumes, such as Figure 2 As shown in Figure 1, the computational river section is divided into similar control volumes. The vector Q and scalar A are arranged alternately at nodes that differ by half a grid, and a point is arranged at the center of each control volume. The region boundary is the outer boundary of the control volume.

[0084] The second step is to solve the equation discretely:

[0085] The finite volume method uses control volumes to discretize equations. Based on the grids obtained in the first step, equations (1) and (2) are integrated in different control volumes and discretized based on control nodes to obtain the following discrete equations:

[0086] Continuity equation

[0087]

[0088] Equations of motion

[0089]

[0090] The two-dimensional water flow model is discretized and the finite volume method (FVM) is used to discretize equations 5-1 to 5-3. The finite volume method is also called the control volume method. Its basic idea is:

[0091] The computational domain is divided into a series of non-repeating control volumes, with one control volume surrounding each grid point.

[0092] The differential equation to be solved is integrated for each control volume to obtain a set of discrete equations, where the unknowns are the values ​​of the dependent variables at the grid points.

[0093] In order to find the integral of the control volume, it is necessary to assume that the values ​​vary between the grid points, that is, the segmented distribution profile of the set values.

[0094] From the perspective of the selection method of the integral region, the finite volume method belongs to the subregion method of the weighted residual method; from the perspective of the approximate method of the unknown solution, the finite volume method belongs to the discrete method using local approximation. In short, the subregion method plus discretization is the basic method of the finite volume method.

[0095] The basic idea of ​​the finite volume method is easy to understand and can be directly interpreted physically. The finite volume method is actually the inverse process of deriving differential equations using the concept of microelement in fluid mechanics. The grid is equivalent to the enlarged microelement. The physical meaning of the discrete equation is the conservation principle of the dependent variable in a finite control volume, just as the differential equation represents the conservation principle of the dependent variable in an infinitely small control volume.

[0096] The discrete equations derived from the finite volume method require that the integral conservation of the dependent variable is satisfied for any set of control volumes, so it is naturally satisfied for the entire calculation area. Therefore, the discrete equations derived from the finite volume method can be guaranteed to be conservative, and the adaptability to the regional shape is better than that of the finite difference method. This is the attractive advantage of the finite volume method. Some discretization methods, such as the finite difference method, only satisfy the integral conservation of the discrete equations when the grid is extremely fine; while the finite volume method shows accurate integral conservation even in the case of coarse grids.

[0097] Furthermore, step three includes terrain and grid division. Network encryption methods include encryption based on terrain changes, continuous multiple single-layer encryption, and regional encryption. In order to study the water flow conditions of the Pinglu Canal from Pingtangjiangkou to Madao Hub, the model uses underwater terrain data measured in 2022. According to the river channel topography and the layout of the canal waterway engineering, the focus of the two-dimensional water flow and sediment mathematical model research is the section where each tributary converges into the main channel.

[0098] The two-dimensional mathematical model mainly uses a combination of triangular grids and quadrilateral grids to discretize the calculation area. The density of the grid varies along the river channel and the width of the river. At the same time, in order to adapt to the current status of the river channel and the layout of the engineering plan, and to improve the calculation accuracy of the waterway flow conditions, the grid near the confluence of the tributaries is locally encrypted. Figure 5 The grid size of the calculated river section is generally 5m along the flow direction and 5m perpendicular to the flow direction. For the confluence area of ​​tributaries, the encrypted grid size is generally 3m along the flow direction and 3m perpendicular to the flow direction. The total length of the calculated river section is about 28km, and 365,487 grids are divided.

[0099] Furthermore, the one-dimensional water flow model is verified, including water level verification and cross-sectional flow velocity verification.

[0100] Water level verification determines the selection of calculation parameters. The upper boundary of the river section model is the flow boundary condition, and the lower boundary is the water level boundary condition. When tributaries are involved, the flow boundary condition is set at the confluence of the tributaries. Each boundary condition is established by the one-dimensional mathematical model of the long river section.

[0101] The initial water level is the lower boundary water level, and the initial flow velocity is set to 0 m / s. Since the deviation of the initial conditions will gradually disappear during the calculation process, the given initial flow velocity and initial water level will not affect the calculation accuracy.

[0102] 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 two-dimensional model is within the range of ±0.02m, and the accuracy of the two-dimensional model can be guaranteed. After the water surface line verification, the roughness value of the two-dimensional water flow mathematical model in the main channel of the canal 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.

[0103] In the cross-section velocity verification, the verification condition is selected as the Shaping River tributary into the 20-year flood (Q = 1260m 3 / s), Xijin Reservoir and Madao Hub Dam are at normal water level. Figure 6 ,The velocity distribution comparison of the two-dimensional water flow mathematical model and the physical model test is shown in Table 1.

[0104] Table 1 Comparison of flow rates between two-dimensional digital model and physical model (m / s)

[0105]

[0106] It can be seen that the difference between the flow velocity calculated by the digital model and the actual measured flow velocity of the logistics model is within ±0.1m / s, and the difference is positive and negative, which is consistent with the actual measured value of the physical model. Simulation calculations can be carried out for application in actual engineering.

[0107] On the other hand, the flow velocity data of four sections measured on April 20, 2022 were collected. The sections are located downstream of the confluence of Qinjiang River, at the channel mileage of K52+500~K53+500 (see Figure 7 ), the flow of the Qin River mainstream was 26.14m 3 / s. The above data are used to verify the cross-sectional flow velocity of the two-dimensional water flow model of the Qishi hub ~ Qingnian hub section, which can also serve as a side evidence of the simulation accuracy of the two-dimensional water flow mathematical model in this section (Pingtangjiangkou ~ Madao hub section). The verification results are shown in Table 2.

[0108] Table 2 Comparison of the two-dimensional model and the measured flow velocity of Qin River

[0109]

[0110] Judging from the verification results, the measured cross-sectional flow velocity is basically consistent with the calculated flow velocity distribution law, the cross-sectional flow velocity difference is within ±0.05m / s, the difference is alternating between positive and negative, and the calculated cross-sectional flow velocity is relatively close to the measured cross-sectional flow velocity results, which meets the simulation accuracy requirements of the two-dimensional water flow mathematical model.

[0111] Further, step five mainly includes the analysis of water flow characteristics in the navigation channel and the analysis of water flow characteristics at the confluence of tributaries. In particular, the present invention mainly discusses the analysis of water flow characteristics at the confluence of tributaries. The analysis of water flow characteristics at the confluence of tributaries includes the statistics of flow velocity in the navigation channel at the confluence of tributaries and the analysis of navigation conditions at the confluence of tributaries.

[0112] The statistics of flow velocity in the navigation channel at the confluence of tributaries are as follows: There are two tributaries converging into the Pinglu Canal from Pingtangjiangkou to Madou hub, namely Shaping River and Shizi River. In order to analyze the impact of tributary confluence on the water flow conditions in the canal waterway, the statistical results of longitudinal and transverse flow velocities within 500m upstream and downstream of the tributary confluence are listed, see Tables 3 and 4.

[0113] Table 3 Statistics of flow velocity in the channel at the confluence of tributaries from Pingtang River estuary to Madao hub (without considering Madao flood diversion)

[0114]

[0115] Table 4 Statistics of flow velocity in the channel at the confluence of tributaries from Pingtang River estuary to Madao hub (taking Madao flood diversion into account)

[0116]

[0117] The navigation conditions at the confluence of tributaries are analyzed as follows:

[0118] According to the "Canal Navigation Standards" (JTS180-2-2011): Pinglu Canal is a Class I canal. The vertical flow velocity in the waterway of the canal's intakes, discharges and other confluent waters should not exceed 2m / s, and the horizontal flow velocity should not exceed 0.3m / s. From the statistical results:

[0119] (1) When flood diversion at Madao hub is not considered

[0120] When encountering floods with a return period of 5 years, 10 years, and 20 years, the maximum longitudinal flow velocity in the waterway near the confluence of Shaping River was 0.68m / s, 0.88m / s, and 1.08m / s, respectively, and the maximum transverse flow velocity was 0.19m / s, 0.23m / s, and 0.28m / s, respectively. The maximum longitudinal flow velocity in the waterway near the confluence of Shizi River was 0.70m / s, 0.94m / s, and 1.16m / s, respectively, and the maximum transverse flow velocity was 0.06m / s, 0.12m / s, and 0.17m / s, respectively. It can be seen that when the Madao hub does not divert floodwaters, the longitudinal and transverse flow velocities at the confluence of Shaping River and Shizi River do not exceed the standard.

[0121] (2) Considering flood diversion at the Madao hub

[0122] Dangmadao Hub Flood Diversion 1000m 3 / s, when encountering tributary floods of once in 5 years, once in 10 years, and once in 20 years, the maximum longitudinal flow velocity in the channel near the confluence of Shaping River was 0.98m / s, 0.99m / s, and 1.00m / s, respectively, and the maximum transverse flow velocity was 0.36m / s, 0.41m / s, and 0.44m / s, respectively, and the transverse flow velocity was slightly exceeded. The maximum longitudinal flow velocity in the channel near the confluence of Shizi River was 0.38m / s, 0.12m / s, and 0.38m / s, respectively, and the maximum transverse flow velocity was 0.04m / s, 0.06m / s, and 0.07m / s, respectively, and both longitudinal and transverse flow velocities were within the standard.

[0123] In summary, when the Madao hub does not divert floodwaters, the flow conditions at the confluence of the tributaries of the Pinglu Canal from Pingtangjiangkou to the Madao hub are good, and the longitudinal and lateral flow velocities are within the standard. After the Madao hub diverts floodwaters for the Xijin Reservoir, the lateral flow velocity at the confluence of the Shaping River slightly exceeds the standard, and the lateral flow velocity exceeds the standard by 0.14 m / s.

[0124] Furthermore, it also includes the analysis of water flow conditions at the Pingtang River estuary. In order to further analyze the distribution of flow velocity in the navigation channel under various conditions when Shaping River encounters Yujiang River at the Pingtang River estuary, and provide supporting data for the design of the waterway plan, supplementary calculations are performed considering the different flood flow conditions of Shaping River and Yujiang River. The calculation conditions are shown in Table 5.

[0125] Table 5 The supplementary conditions of the flow from Shaping River and Yujiang River

[0126]

[0127] After the supplementary working conditions were formulated, the calculation results were analyzed as follows: The velocity statistics in the channel under each working condition and the flow field distribution map of Pingtang River Estuary are shown in Table 6 and Figure 8 to Figure 13 , from the statistical results point of view:

[0128] (1) Under the condition of once-in-two-year flow of Yujiang River

[0129] ① When the flow of Shaping River returns once in five years, the area within K0+000~K0+400 is greatly affected by the flow of Yujiang River, and the flow velocity in the navigation channel is distributed in the range of 0.46m / s~1.89m / s. Affected by the oblique intersection of the channel axis and the flow direction, the maximum lateral flow velocity is in the range of 0.50m / s~0.92m / s. The area within K0+500~K0+800 is greatly affected by the runoff of Shaping River, and the flow velocity in the navigation channel is distributed in the range of 0.26m / s~0.79m / s, and the maximum lateral flow velocity is in the range of 0.03m / s~0.12m / s, and the lateral flow velocity is relatively small.

[0130] ② When the Shaping River flow returns once in 10 years, the area within K0+000~K0+400 is greatly affected by the flow from the Yujiang River, and the flow velocity in the navigation channel is distributed in the range of 0.54m / s~1.96m / s. Affected by the oblique intersection of the channel axis and the flow direction, the maximum lateral flow velocity is in the range of 0.32m / s~0.95m / s; the area within K0+500~K0+800 is greatly affected by the runoff of the Shaping River, and the flow velocity in the navigation channel is distributed in the range of 0.41m / s~0.77m / s, and the maximum lateral flow velocity is in the range of 0.04m / s~0.12m / s, and the lateral flow velocity is relatively small.

[0131] ③ When the flow of Shaping River returns once in 20 years, the area within K0+000~K0+400 is greatly affected by the flow of Yujiang River, and the flow velocity in the navigation channel is distributed in the range of 0.79m / s~2.02m / s. Affected by the oblique intersection of the channel axis and the flow direction, the maximum lateral flow velocity is in the range of 0.50m / s~0.98m / s; the area within K0+500~K0+800 is greatly affected by the runoff of Shaping River, and the flow velocity in the navigation channel is distributed in the range of 0.74m / s~1.00m / s, and the maximum lateral flow velocity is in the range of 0.06m / s~0.15m / s, and the lateral flow velocity is relatively small.

[0132] (2) Under the condition of Yujiang River flow once in 10 years

[0133] ① When the flow of Shaping River occurs once every two years, the area within K0+000~K0+400 is greatly affected by the flow of Yujiang River, and the flow velocity in the navigation channel is distributed in the range of 0.49m / s~2.73m / s. Affected by the oblique intersection of the channel axis and the flow direction, the maximum lateral flow velocity is in the range of 0.75m / s~1.28m / s. The area within K0+500~K0+800 is greatly affected by the runoff of Shaping River, and the flow velocity in the navigation channel is distributed in the range of 0.32m / s~0.69m / s, and the maximum lateral flow velocity is in the range of 0.03m / s~0.10m / s, and the lateral flow velocity is relatively small.

[0134] ② When the flow of Shaping River returns once in five years, the area within K0+000~K0+400 is greatly affected by the flow of Yujiang River, and the flow velocity in the navigation channel is distributed in the range of 0.53m / s~2.79m / s. Affected by the oblique intersection of the channel axis and the flow direction, the maximum lateral flow velocity is in the range of 0.76m / s~1.32m / s; the area within K0+500~K0+800 is greatly affected by the runoff of Shaping River, and the flow velocity in the navigation channel is distributed in the range of 0.44m / s~0.79m / s, and the maximum lateral flow velocity is in the range of 0.05m / s~0.12m / s, and the lateral flow velocity is relatively small.

[0135] ③ When the Shaping River flow returns once in 10 years, the area within K0+000~K0+400 is greatly affected by the flow from the Yujiang River, and the flow velocity in the navigation channel is distributed in the range of 0.92m / s~2.84m / s. Affected by the oblique intersection of the channel axis and the flow direction, the maximum lateral flow velocity is in the range of 0.37m / s~1.35m / s; the area within K0+500~K0+800 is greatly affected by the runoff of the Shaping River, and the flow velocity in the navigation channel is distributed in the range of 0.13m / s~1.04m / s, and the maximum lateral flow velocity is in the range of 0.04m / s~0.16m / s, and the lateral flow velocity is relatively small.

[0136] In general, during the flood season, the range of K0+000~K0+400 in the designed channel at the mouth of Pingtang River is greatly affected by the flow of Yujiang River, and the flow velocity and lateral flow velocity in the channel are relatively large. However, given that this section of the channel is a trumpet-shaped widening section, the channel width gradually widens from about 300m at K0+400 to about 1000m at K0+000, providing a large operating space for ships entering and exiting the canal.

[0137] 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. The analysis method based on the hydrological characteristics of tributary confluence is characterized by: The following steps are involved: Step 1: Establish a one-dimensional water flow model and a two-dimensional water flow mathematical model according to the waterway conditions; Step 2: Discretize the model equations; Step 3: Use a combination of triangular mesh and quadrilateral mesh to encrypt the mesh near the confluence of the tributaries; Step 4: verify the one-dimensional water flow model and the two-dimensional water flow mathematical model to obtain calculation parameters; Step 5. Apply the two-dimensional water flow model that meets the simulation accuracy to the simulation calculation of the actual project, and analyze the impact of tributary flood inflow and hub flood diversion on the waterway flow conditions, so as to obtain a reasonable range of longitudinal and lateral flow velocities in the waterway for navigation condition analysis.

2. The analysis method based on the hydrological characteristics of tributary confluence according to claim 1, characterized in that: In step 4, the verification of the one-dimensional water flow model includes roughness calibration and water surface line verification, and the water surface line verification includes pre-project water surface line verification, pre-project water surface line review and post-project water surface line review.

3. The analysis method based on the hydrological characteristics of tributary confluence according to claim 2, characterized in that: The boundary conditions for the one-dimensional water flow model verification include: Inlet boundary: flow inlet boundary conditions are used to give the inlet section flow and inlet water flow direction; when there are tributaries, flow boundary conditions are set at the tributary confluence point; Outlet boundary: Use water level outlet boundary condition.

4. The analysis method based on the hydrological characteristics of tributary confluence according to claim 2, characterized in that: The specific steps of roughness calibration include: adjusting the parameters of the model, obtaining the change of the river water level according to the change of the parameters, so as to ensure that the simulated value of the water level is consistent with the measured value; the riverbed roughness of the one-dimensional water flow model of the natural river before the project is between 0.03 and 0.04, and the riverbed roughness of the one-dimensional water flow model of the waterway after the project is between 0.015 and 0.

03.

5. The analysis method based on the hydrological characteristics of tributary confluence according to claim 2, characterized in that: Verification of water surface line before the project, the relationship between water level and flow rate of the model control section is: the calculated flow rate of the model river section is 23 m 3 / s, the water level at the river mouth is 60.8m; The water level line was reviewed before the project. The relationship between the water level and flow rate of the model control section is: When the flood frequency of the model river section is P=5%, the peak flow rate is 2140 m 3 / s, the river mouth water level is 63.40m; when the flood frequency of the model river section is P=20%, the peak flow is 1110 m 3 / s, the water level at the river mouth is 62.90m; After the project, the water level line was reviewed. The relationship between the water level and flow rate of the model control section was as follows: When the flood frequency of the model river section was P=5%, the peak flow rate was 1260 m 3 / s, the river mouth water level is 63.40m; when the flood frequency of the model river section is P=20%, the peak flow is 672m 3 / s, the water level at the estuary is 62.90m.

6. The analysis method based on the hydrological characteristics of tributary confluence according to claim 5, characterized in that: Taking the downstream flood diversion hub into consideration, the calculation condition is: 。 7. The analysis method based on the hydrological characteristics of tributary confluence according to claim 5, characterized in that: The verification of the two-dimensional water flow model includes water level verification and cross-sectional flow velocity verification; the water level verification boundary conditions include: the upper boundaries are all flow boundary conditions, the lower boundaries are all water level boundary conditions, and when tributaries merge, flow boundary conditions are set at the confluence of tributaries, and each boundary condition is established by a one-dimensional mathematical model; when verifying the water level, the initial water level uses the lower boundary water level, and the initial flow velocity is set to 0m / s; the roughness value of the two-dimensional water flow mathematical model in the main channel of the canal ranges from 0.015 to 0.03, and the roughness value of the straightening section or ecological conservation area ranges from 0.030 to 0.

040.

8. The analysis method based on the hydrological characteristics of tributary confluence according to claim 1, characterized in that: In step five, the calculation conditions include: when there is no flood diversion downstream, the flow of the main river channel is the flood flow once in two years; when there is flood diversion downstream, the flow of the main river channel is the flood flow once in 20 years.

9. The analysis method based on the hydrological characteristics of tributary confluence according to claim 8, characterized in that: Statistics are collected on the longitudinal and transverse flow velocities within 500m upstream and downstream of the confluence of tributaries: Without considering downstream flood diversion, when encountering tributary floods of once in 5 years, once in 10 years, and once in 20 years, the maximum longitudinal flow velocity in the channel near the confluence of the river is 0.68m / s, 0.88m / s, and 1.08m / s respectively, and the maximum transverse flow velocity is 0.19m / s, 0.23m / s, and 0.28m / s respectively; When the downstream flood diversion is 1000m3 / s, when the tributaries encounter floods once in 5 years, once in 10 years, and once in 20 years, the maximum longitudinal flow velocities in the waterway near the confluence of Shaping River are 0.98m / s, 0.99m / s, and 1.00m / s respectively, and the maximum lateral flow velocities are 0.36m / s, 0.41m / s, and 0.44m / s respectively.

10. An analysis device based on the hydrological characteristics of tributary confluence, characterized in that: It includes 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 the analysis method based on the hydrological characteristics of tributary confluence as described in any one of claims 1 to 9.

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