One-dimensional-two-dimensional hydrodynamic model coupling method based on replacement backflow mechanism

Abstract

The invention relates to the field of hydrodynamic model coupling, in particular to a one-dimensional-two-dimensional hydrodynamic model coupling method based on a replacement backflow mechanism. According to the method, a uniform one-dimensional node structure elevation and a two-dimensional real surface elevation are introduced to form a water head judgment system, so that the flow direction is accurately judged; aiming at one-dimensional-two-dimensional water head difference abnormity caused by height system inconsistency, interpolation deviation or local terrain sudden change, the invention provides a replacement backflow mechanism, abnormal coupling flux is automatically replaced by a water head difference threshold value and a hydraulic exchange strength coefficient, exchange processes which do not conform to a physical mechanism, such as false backward flow and suspended overflow, are corrected, and the method has the advantages of high reliability and high reliability. The stability and continuity of the coupling process are guaranteed, the problems that in an existing coupling method, elevation data are not uniform, the coupling flow direction is misjudged, and overflow and backflow are unstable are effectively solved, the accuracy and reliability of urban flood simulation are greatly improved, and the method is suitable for popularization and application. And a more stable and credible technical support is provided for urban drainage system dispatching and waterlogging early warning.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of water power model coupling, in particular to a one-dimensional-two-dimensional water power model coupling method based on a replacement backflow mechanism. BACKGROUND

[0002] In the scenarios of urban flood simulation, drainage system scheduling and river-lake interaction analysis, the coupling of one-dimensional pipe network / river model and two-dimensional surface water power model is the core link to realize the complete water circulation representation in the city. The commonly used one-dimensional and two-dimensional coupling node flow generally directly transmits the overflow of the one-dimensional model to the two-dimensional model, or uses direct interpolation or average flux to complete data interaction, interpolates the water depth of the two-dimensional submerged unit as the equivalent water level, and then calculates the difference between the one-dimensional node water level to complete the calculation of the orifice flow formula, so as to realize the information transmission of pipe network, river network and surface water power. However, the differences in data processing methods, physical scales and numerical discretization between traditional one-dimensional and two-dimensional water power models will lead to inconsistent mass and momentum conservation in the pressure-free water surface switching, dry-wet over-processing and line-surface element flux mapping at the coupling node, thereby affecting the reliability of the simulation of key business scenarios such as runoff evolution, flood regulation and inundation analysis. SUMMARY

[0003] Due to the different requirements of models of different dimensions for data processing methods, the traditional coupling method uses artificial adjustment of the properties of coupling nodes one by one to meet the needs of the two models. The present application starts from the perspective of one-dimensional and two-dimensional water power model coupling process, uses the one-dimensional and two-dimensional properties of the coarsely processed coupling nodes, and combines the current initial state and driving conditions to execute the backflow mechanism of water exchange, thereby improving the simulation effect and accuracy of flood inundation.

[0004] In order to achieve the above purpose, the present application provides a one-dimensional-two-dimensional water power model coupling method based on a replacement backflow mechanism, and the specific steps are as follows: S1, constructing a one-dimensional water power model and a two-dimensional water power model; based on the terrain, pipe network, river and other basic data of the region, a one-dimensional pipe network / river water power model and a two-dimensional surface water power model are established, the initialization calculation of the structured nodes is completed, and the spatial properties of the nodes are obtained, including the parameters of elevation, connectivity relationship; S2, identifying the coupling nodes and their spatial properties: in the established one-dimensional and two-dimensional models, according to the node spatial position, pipe bottom elevation, maximum well depth, two-dimensional grid elevation and other information, the minimum distance between the coupling nodes is calculated, the node pairs satisfying the distance threshold are screened, and their structural elevation, ground elevation, well bottom elevation and instantaneous water depth are extracted; S3, calculating the theoretical exchange flux of the coupling process; based on the vertical coupling (pipe network-surface) and the lateral coupling (river-surface), the orifice flow formula, the weir flow formula or the gradient-driven exchange model is used to calculate the theoretical flux between the coupling nodes, so as to obtain the initial overflow or return flow; S4, constructing a unified water head discrimination system of one-dimensional structure elevation and two-dimensional surface elevation; by comparing the one-dimensional node structure elevation (well bottom elevation+maximum well depth) with the two-dimensional real surface elevation, the actual water head difference is calculated, which is used to judge the effectiveness of the flow direction of the theoretical coupling flux and identify whether there is an abnormal water head difference caused by interpolation error, inconsistent elevation system or local terrain mutation; S5, judging whether the replacement return flow mechanism is triggered; if the calculated water head difference meets the conditions of "two-dimensional water head being significantly higher than one-dimensional structure water head" or "theoretical flux direction being inconsistent with actual terrain", it is determined that the abnormal coupling state is triggered, and the replacement return flow mechanism is triggered; otherwise, the theoretical coupling flux is directly used; S6, performing replacement return flow flux calculation; when the replacement return flow mechanism is triggered, the vertical replacement return flow flux and the lateral replacement return flow flux are calculated according to the water head difference, the two-dimensional surface water depth, the structure elevation and the hydraulic exchange intensity coefficient, which replace the original theoretical flux, wherein the replacement return flow flux meets the stability limit of the minimum water head difference threshold; S7, updating the final coupling flux and completing the one-dimensional-two-dimensional hydrodynamic model coupling; the replacement return flow flux or the theoretical flux is used as the final exchange flux, which is written into the corresponding boundary conditions of the one-dimensional model and the two-dimensional model, so as to realize the bidirectional water exchange of the coupling nodes, and thus the one-dimensional pipe network / river network and the two-dimensional surface hydrodynamic model are coupled and solved.

[0005] Preferably, step S1 is preceded by step S0, which comprises: S01, target city area pipe network model generalization: collecting city drainage pipe network data, arranging and standardizing the inspection well, rain and sewage separation structure, pipe segment connection relationship and terrain elevation in the region; redundant nodes are merged, dense nodes are thinned, and abnormal or defective pipe segments are repaired to obtain initial data of the pipe network in the research area; S02, preliminary construction of hydrodynamic model database: collecting digital elevation data (DEM), land use data, pipe network / road / river network distribution data, building distribution data and rainfall data of the target basin, and uniformly interpolating these data to unify the spatial or temporal resolution to preliminarily construct the hydrodynamic model database.

[0006] Preferably, the step S2 further comprises the following steps: S21, using a spatial search algorithm based on geometric distance, the coordinates of the node units (inspection well nodes, drainage outlet nodes, structure nodes, river section nodes, etc.) in the one-dimensional model and the corresponding relationship between the discrete grid node coordinates in the two-dimensional model are established; the constrained nearest neighbor matching algorithm is used to establish the connection between them, and the calculation formula is as follows: ; Constraints: ; In the formula: and are the horizontal and vertical coordinates of the one-dimensional model nodes, respectively; and are the horizontal and vertical coordinates of the two-dimensional model grid nodes, respectively; is the minimum distance between the two nodes; is the search range set, which can be set to 2-5 times the grid distance of the two-dimensional model to simplify the global search range; S22, extract the one-dimensional spatial attributes of the node pair under the coupling connection, including node coordinates ( , ), pipe bottom elevation , maximum well depth , node real-time water depth after coupling model running , and the corresponding ground elevation and real-time water level of the one-dimensional node: ; ; Extract the spatial attributes of the two-dimensional model grid, including grid node coordinates ( , ), serial number, and node ground elevation .

[0007] Preferably, step S3 further comprises the following steps: S31, using vertical coupling to calculate the flux of the coupling nodes of the one-dimensional pipe network hydrodynamic model and the two-dimensional hydrodynamic model; When the inspection well overflows, and the corresponding surface grid node has no water level, the overflow occurs, and the orifice flow formula is used to calculate the overflow: ; When the inspection well node water level is lower than the ground grid node water level under the corresponding latitude and longitude, the surface water flows into the underground drainage pipe network through the inspection well connection facility to form backflow: ; When the current node corresponds to the overflow and the two-dimensional surface water level is not 0, whether the overflow or the backflow of the coupling node is determined by the positive and negative of ; wherein is the vertical coupling flux of the model, ; is the node overflow amount, ; is the orifice flow coefficient; is the water storage area at the inspection well, ; the positive and negative signs are used to distinguish the node overflow and the node backflow; S32, the lateral coupling is used to calculate the flux of the coupling node of the one-dimensional river network hydrodynamic model and the two-dimensional hydrodynamic model; The lateral coupling calculation formula is as follows: ; ; ; wherein is the lateral coupling flux of the model, ; and are water level values connected with the river and the surface, ; is the river bank elevation, ; is the bank length, ; generally, it is the boundary length of the unit connected with the river section.

[0008] Preferably, the step S4 further comprises the following steps: S41, the judgment of the replacement backflow mechanism is further divided into vertical coupling judgment and lateral coupling judgment according to the coupling type, and whether the replacement backflow is executed is independently determined according to the corresponding water head difference ( - ); Vertical coupling replacement backflow: ( ); Lateral coupling replacement backflow: ); In the formula: is a water head difference of a two-dimensional water dynamic model, ; is a hydraulic exchange intensity coefficient, generally 0.01~0.05; is a vertical coupling replacement backflow flux, ; is a lateral coupling replacement backflow flux, ; is a water storage area at a manhole, ; is a river embankment elevation, ; is an embankment length, ; is a two-dimensional surface water depth, ; is a water head difference calculated in a current step, ; is a minimum water head difference threshold value, generally 0.01~0.05, ; S42, after determining the theoretical flux and the replacement backflow between the coupling nodes, the exchange water amount of the coupling nodes is uniformly updated to form a final coupling flux, and the judgment mode is as follows:

[0009] In the formula: is a final flux of the coupling node, ; is a theoretical flux under a corresponding coupling mode, ; is a two-dimensional surface water depth, ; is a water head difference calculated in a current step, ; is a minimum water head difference threshold value, generally 0.01~0.05, .

[0010] The one-dimensional-two-dimensional water dynamic model coupling method based on the replacement backflow mechanism realizes the coupling of one-dimensional and two-dimensional water dynamics, including: By uniformly updating the theoretical flux or the replacement backflow flux, the final coupling flux is applied to the corresponding boundary term or source-sink term of the one-dimensional pipe network model and the two-dimensional surface model, so that the two models realize bidirectional water exchange and synchronous iteration at each time step, and the coupling solution of the one-dimensional-two-dimensional water dynamic field is completed.

[0011] The present application has the following beneficial effects: 1. The application constructs a vertical-lateral double-path hydraulic exchange system, which can simultaneously process the two-way water dynamic process of surface-pipe network and surface-river channel, so that the coupling mechanism can cover multiple types of water flow exchange situations in urban drainage systems. This system significantly improves the physical consistency of the coupling process and provides more stable support for the simulation of complex terrain and multi-source flooding.

[0012] 2. The application proposes a unified water head discrimination framework, using "one-dimensional node structure elevation (well bottom elevation + maximum well depth)" and "two-dimensional real ground surface elevation" as the comparison benchmark, which avoids the flow direction misjudgment caused by resolution difference, interpolation error and inconsistent elevation system. This mechanism ensures that the coupling direction judgment is more accurate and reliable, reducing manual parameter adjustment.

[0013] 3. The application introduces a replacement backflow mechanism, which automatically replaces the coupling flux when detecting abnormal water head difference, and timely corrects false backflow, suspended overflow and other non-physical behaviors. This mechanism improves the numerical stability of the coupling process, avoids model collapse and abnormal flow fluctuations, thereby significantly enhancing the simulation accuracy and reliability of engineering applications. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is a one-dimensional-two-dimensional hydrodynamic model coupling method flow chart based on the replacement backflow mechanism of the application; Figure 2 is a model verification result graph of the traditional coupling method and the coupling method based on the replacement backflow mechanism; Figure 3 is a model flooding situation result graph of the traditional coupling method and the coupling method based on the replacement backflow mechanism. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical scheme and advantages of the application clearer and more apparent, the following embodiments are used to further describe the application. It should be understood that the specific embodiments described herein are only used to explain the application and do not limit the application.

[0016] The present application aims at the problems of interface flux interruption, weak water head difference misjudgment and water quantity non-conservation in the existing one-dimensional-two-dimensional coupled hydrodynamic model, and proposes a replacement backflow coupling method which can maintain the continuity of water exchange under different working conditions of critical elevation. Due to the significant differences in elevation source, discrete method and physical expression between the one-dimensional pipe network model and the two-dimensional surface model, the traditional weir or orifice flow formula based on water head difference often cannot correctly trigger overflow or backflow in scenes such as shallow water, pipe network full-flow criticality, river counter-pressure, etc., thereby leading to the lack of backflow, the expansion of local stagnant water and the deviation of overall water quantity balance. In order to overcome the above technical bottlenecks, the present application builds a replacement backflow mechanism to dynamically compensate the interface flux under the condition of weak water head difference, so that the water quantity transmission can be stable, continuous and meet the principle of mass conservation under various complex topography and dynamic water level conditions when the one-dimensional and two-dimensional models are coupled, thereby significantly improving the precision and engineering applicability of urban flood simulation and drainage analysis.

[0017] All other embodiments obtained by those skilled in the art based on the embodiments in the present application without making creative efforts fall within the scope of protection of the present application.

[0018] The technical solutions of the present application will be further described below through specific embodiments. In each of the following embodiments, the method is a conventional method unless otherwise specified; and the reagents and materials can be purchased on the market unless otherwise specified.

[0019] A one-dimensional-two-dimensional hydrodynamic model coupling method based on a replacement backflow mechanism, comprising the following steps: Embodiment one: starting from building one-dimensional and two-dimensional hydrodynamic models of urban drainage systems, the present embodiment realizes the bidirectional hydrodynamic coupling between them by identifying coupling nodes, calculating theoretical coupling flux, building a unified water head discrimination system and triggering the replacement backflow mechanism under abnormal water head difference conditions. The present embodiment is used to verify the coupling stability and simulation precision of the present application under complex topography conditions. The method of the present application includes the following parts: I. City basic data processing and model preliminary construction This part corresponds to steps S1, S2 and S3. First, collect the DEM data, underground drainage pipe network survey data, river network structure, inspection well attributes, rainfall and water level monitoring data of the target city area, and interpolate and align the above data to the same spatial coordinate system to preliminarily build the basic database of one-dimensional and two-dimensional hydrodynamic models.

[0020] II. Coupling node identification and attribute extraction This part corresponds to step S4. By reading the pipe network node coordinates, well bottom elevation, maximum well depth, and two-dimensional grid center point coordinates and ground surface elevation information, the grid threshold Screening node pairs meeting the spatial proximity condition. Attribute extraction is performed on the identified node pairs, including structural elevation, one-dimensional water depth, two-dimensional water depth, and ground surface elevation, to provide basic parameters for subsequent coupling calculations.

[0021] III. Theoretical flux calculation This part corresponds to step S5. Vertical coupling (inspection well-ground surface) and lateral coupling (river-ground surface) are performed according to the attributes of the coupling nodes. Vertical coupling uses orifice flow or seepage flux model based on water head difference, and lateral coupling uses weir flow or river bank overflow model, to calculate the theoretical overflow or return flow between node pairs.

[0022] IV. Construction of unified water head discrimination system and triggering of replacement return flow mechanism This part corresponds to step S6. To eliminate the misjudgment of coupling direction caused by the inconsistency between one-dimensional structural elevation and two-dimensional actual ground surface elevation system, this embodiment constructs a unified water head discrimination system, in which one-dimensional node water head is represented by the superposition of well bottom elevation and maximum well depth, and two-dimensional node water head is represented by the superposition of ground surface elevation and grid water depth. The water head difference is calculated and the rationality of the theoretical coupling direction is judged.

[0023] When the theoretical coupling flux does not meet the water head difference relationship or abnormal phenomena such as false backflow and suspended overflow occur, the system triggers the replacement return flow mechanism. The replacement return flow flux is calculated according to the water head difference, two-dimensional water depth, and hydraulic exchange intensity coefficient to replace the original theoretical flux, so that the coupling condition returns to a physically reasonable state.

[0024] According to the coupling type, it is further divided into vertical coupling judgment and lateral coupling judgment, which respectively determines whether to perform replacement return flow according to the corresponding water head difference

[0025] Vertical coupling replacement return flow: ) Lateral coupling replacement return flow: ) In the formula: is the water head difference of one-dimensional and two-dimensional hydrodynamic model, ​​​​​is the hydraulic exchange intensity coefficient, generally taken as 0.01-0.05; is the vertically coupled replacement backflow flux, ; is the laterally coupled replacement backflow flux, ; is the impoundment area at the inspection well, ; is the river embankment elevation, ; is the embankment length, ; is the minimum water head difference threshold value, generally taken as 0.01-0.05, .

[0026] Five, final coupling flux updating and model synchronous iteration This part corresponds to steps S7, S8. The replacement backflow flux or the theoretical flux is uniformly taken as the final coupling flux, and is written into the boundary flow of the one-dimensional hydrodynamic model and the source and sink term of the two-dimensional hydrodynamic model, so that the water level, water depth and flow field of the two models are updated synchronously in the same time step, and the one-dimensional-two-dimensional hydrodynamic coupling solution is completed.

[0027] The final coupling node flux is updated as:

[0028] In the formula, is the final coupling node flux, ; is the theoretical flux under the corresponding coupling mode, ; is the two-dimensional surface water depth, ; is the water head difference calculated in the current step, ; is the minimum water head difference threshold value, generally taken as 0.01-0.05, .

[0029] Example two: In this embodiment, the main urban area of Kunming is taken as an example to illustrate the execution process of the method, and the specific process is as follows: S1, basic data acquisition and processing. ASTER GDEM digital elevation is obtained from the geographic spatial data cloud (http: / / www.gscloud.cn / ) network, the spatial resolution is 30m, the DEM data is cut according to the boundary of the main urban area of Kunming, the road generalization method is used to build the one-dimensional pipe network model and the one-dimensional river model (.inp) of the main urban area, the non-uniform triangular grid is used to build the two-dimensional land grid file (.slf), and the resolution is 15m.

[0030] S2, One-dimensional hydrodynamic model construction. The one-dimensional hydrodynamic model adopts dynamic wave method to solve Saint-Venant equation, which is used to simulate complex flow state such as pipeline water storage, downstream water level jacking, import and export loss and pressure flow, and mainly includes the following forms of pipeline control equation and node control equation: ①The pipeline control equation includes continuity equation and momentum equation as follows: Continuity equation:

[0031] Momentum equation:

[0032] In the formula, is the flow rate, ; is the cross-sectional area, ; is the gravitational acceleration, 9.81 ; is the water head, ; is the horizontal coordinate length, ; is the time, is the; friction slope is obtained by Manning formula:

[0033] ②The node control equation is as follows:

[0034] In the formula, is the node water head, ; is the flow rate into and out of the node, ; is the number of pipelines or channels connected to the node; is the node bottom area, .

[0035] Convert to full difference format:

[0036] Solve the equations simultaneously to obtain the pipeline flow rate and node water head in any time step.

[0037] S3, Two-dimensional hydrodynamic model construction. The two-dimensional hydrodynamic method is to divide the area within the two-dimensional land boundary into grid or raster data, assign digital elevation data, and simulate the surface flow process. The two-dimensional hydrodynamic model adopts finite volume method to solve shallow water equation. The shallow water equation is divided into continuity equation and momentum equation, and the specific equation is as follows:

[0038] wherein: is the water depth, ; is the time, ; and are the flow velocities in the and directions, respectively, ; is the source / sink term of the two-dimensional hydrodynamic model for the inflow or outflow; is the gravitational acceleration, 9.81 ; and are the horizontal and vertical coordinates, respectively, ; is the free surface elevation, ; and are the and directions, respectively, the Coriolis force, the wind drag, the bottom friction and other source / sink terms, ; is the momentum diffusion coefficient, .

[0039] The Coriolis force and the wind drag are not considered in the calculation, and the Manning formula is used to calculate the bottom friction, and thus the calculation formula is as follows:

[0040]

[0041] wherein: is the slope angle, degree; is the Manning coefficient, dimensionless number.

[0042] S4, after the modeling of the one-dimensional and two-dimensional hydrodynamic models in the main urban area of Kunming is completed, the corresponding relationship of the nodes between the two models is determined through the spatial search algorithm of geometric distance, and the coupling interface is formed. Specifically, the "J" / "T" type nodes in the one-dimensional hydrodynamic model are connected respectively, wherein "J" represents the inspection well node, and "T" represents the river section node, and the grid resolution of 15m is brought into , the nearest neighbor search is performed around the node, and the process does not depend on manual calibration and assignment.

[0043] S5, "J_100" and "T_401" are selected in the example, and the implementation effect of the application is shown, and the calculation is carried out taking the 122th step of the model running as an example. The spatial attributes of the nodes corresponding to the one-dimensional and two-dimensional are extracted respectively: the node coordinates ( , ), grid node coordinates (X, Y, Z) , ), pipe bottom elevation , maximum well depth , node ground surface elevation , node real-time water depth after coupling model running , and establish coupling relationship and identify coupling node interface.

[0044] The attributes of “J_100” are respectively:

[0045]

[0046]

[0047] Match valid

[0048]

[0049]

[0050]

[0051] Set the minimum water head difference threshold:

[0052] The attributes of “T_401” are respectively:

[0053]

[0054]

[0055] Match valid

[0056]

[0057]

[0058]

[0059]

[0060] S6, adopt vertical coupling and lateral coupling to calculate node foundation coupling flux, respectively denoted as , .

[0061] From S2, the node “J_100” meets the vertical coupling condition, and the current step has no overflow, and satisfies , the vertical coupling replacement backflow rule. Wherein, the hydraulic intensity exchange coefficient is 0.04, the effective water storage area at the top of the inspection well . The replacement backflow flux of the node is .

[0062] The node “T_401” meets the lateral coupling condition, and is calculated according to the traditional weir flow formula, and satisfies , , so the node executes the lateral coupling backflow mechanism .

[0063] S7, update the coupling node flux. The final coupling flux of “J_100” is , and the final coupling flux of “T_401” is , the positive and negative signs represent the node overflow and the node backflow S8, realize the coupling of one-dimensional and two-dimensional hydrodynamic models. In order to verify the promotion effect of the coupling method of the present application, the measured rainfall data of No. 20220815 and No. 20220923 are used as input, and the Nash efficiency coefficient of the water depth in the inspection well under the monitoring point is improved from 0.886 and 0.814 to 0.955 and 0.948, as shown in Figure 2 . At the same time, the design rainfall scenario of 5-year frequency is used as the model input to observe the submergence effect of the traditional method, as shown in Figure 3 . The present application can effectively eliminate the deviation caused by the error of elevation processing and the instability of coupling direction judgment in the traditional coupling method, and significantly improve the accuracy and stability of one-dimensional and two-dimensional coupled hydrodynamic simulation.

[0064] The above is only a preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A coupling method for a one-dimensional to two-dimensional hydrodynamic model based on a displacement backflow mechanism, characterized in that, Includes the following steps: S1. Construct a one-dimensional hydrodynamic model and a two-dimensional hydrodynamic model; Based on the basic data of the region's topography, pipeline network, and river channels, establish a one-dimensional pipeline network / river channel hydrodynamic model and a two-dimensional surface hydrodynamic model respectively, complete the initial calculation of the gridded and structured nodes of the model, and obtain the spatial attributes of the nodes, including parameters such as elevation and connectivity. S2. Identify the coupled nodes and their spatial attributes: In the established one-dimensional and two-dimensional models, based on the spatial location of the nodes, the bottom elevation of the pipe, the maximum well depth, the two-dimensional grid elevation, and other information, calculate the minimum distance between the coupled nodes, screen the node pairs that meet the distance threshold, and extract their structural elevation, surface elevation, bottom elevation of the well, and instantaneous water depth. S3. Calculate the theoretical exchange flux of the coupling process; based on two methods, vertical coupling (pipeline-surface) and lateral coupling (river channel-surface), the theoretical flux between coupling nodes is calculated using the orifice flow formula, weir flow formula or gradient-driven exchange model, respectively, to obtain the initial overflow or return flow. S4. Construct a unified head discrimination system for one-dimensional structural elevation and two-dimensional surface elevation; By comparing the one-dimensional node structure elevation (bottom elevation + maximum well depth) with the two-dimensional real surface elevation, the actual head difference is jointly calculated to determine the effectiveness of the theoretical coupled flux flow direction and identify whether there is an abnormal head difference caused by interpolation error, inconsistency of elevation system or sudden change in local topography. S5. Determine whether the displacement backflow mechanism is triggered; if the calculated head difference meets the conditions of "two-dimensional head is significantly higher than one-dimensional structural head" or "the theoretical flux direction is inconsistent with the actual topography", it is determined to be an abnormal coupling state and the displacement backflow mechanism is triggered; otherwise, the theoretical coupling flux is used directly. S6, perform displacement return flow calculation; when the displacement return mechanism is triggered, calculate the vertical displacement return flow and the lateral displacement return flow respectively based on the head difference, two-dimensional surface water depth, structural elevation and hydraulic exchange intensity coefficient, to replace the original theoretical flux, wherein the displacement return flow satisfies the stability constraint of the minimum head difference threshold. S7. Update the final coupled flux and complete the coupling of the one-dimensional and two-dimensional hydrodynamic models; use the displacement return flux or theoretical flux as the final exchange flux and write it into the corresponding boundary conditions of the one-dimensional and two-dimensional models to realize the bidirectional water exchange of the coupled nodes, thereby completing the coupled solution of the one-dimensional pipe network / river network and the two-dimensional surface hydrodynamic model.

2. The one-dimensional-two-dimensional hydrodynamic model coupling method based on the displacement reflux mechanism according to claim 1, characterized in that, Step S0, which precedes step S1, includes: S01. Generalization of the target city area pipe network model: Collect urban drainage pipe network data, organize and standardize the inspection wells, rainwater and sewage separation structure, pipe segment connectivity and topographic elevation in the area; merge redundant nodes, thin out overly dense nodes, and repair abnormal or defective pipe segments to obtain the initial pipe network data in the study area. S02. Preliminary Construction of Hydrodynamic Model Database: Collect digital elevation data (DEM), land use data, pipeline / road / river network distribution data, building distribution data, and rainfall data of the target watershed, and interpolate these data to a unified spatial or temporal resolution to initially construct a hydrodynamic model database.

3. The one-dimensional-two-dimensional hydrodynamic model coupling method based on the displacement backflow mechanism according to claim 1, characterized in that: Step S2 further includes the following steps: S21. A spatial search algorithm based on geometric distance is used to establish the correspondence between the coordinates of node elements (inspection well nodes, drainage outlet nodes, structure nodes, river cross-section nodes, etc.) in the one-dimensional model and the coordinates of discrete grid nodes in the two-dimensional model; a constrained nearest neighbor matching algorithm is used to establish the connection between the two, and its calculation formula is as follows: ； Constraints: ； In the formula: and These are the x and y coordinates of a node in a one-dimensional model, respectively. and These are the x and y coordinates of the mesh nodes in the two-dimensional model, respectively. This is the minimum distance between the two aforementioned nodes; The search range can be set to 2 to 5 times the mesh distance of the 2D model to simplify the global search range; S22. Extract the one-dimensional spatial attributes corresponding to the nodes under this coupling relationship, including node coordinates ( , ), Pipe bottom elevation , maximum well depth Real-time water depth at nodes after the coupled model is run Based on the ground elevation and real-time water level corresponding to this one-dimensional node: ； ； Extracting the spatial properties of the 2D model mesh, including mesh node coordinates ( , ), serial number, node surface elevation .

4. The one-dimensional-two-dimensional hydrodynamic model coupling method based on the displacement backflow mechanism according to claim 1, characterized in that: Step S3 also includes the following steps: S31. The flux calculation of the coupled node of the one-dimensional pipe network hydrodynamic model and the two-dimensional hydrodynamic model is adopted by vertical coupling. When an inspection well overflows and there is no water level at the corresponding surface grid node, the overflow rate is calculated using the orifice flow rate formula: ； When the water level at the inspection well node Water levels below the corresponding latitude and longitude of the surface grid nodes At that time, surface water flows into the underground drainage network through the inspection well connection facilities, forming a backflow: ； When an overflow occurs at the current node and the 2D surface water level is not zero, whether the overflow or backflow at the coupled node depends on... Positive and negative: ； In the formula: For the vertical coupling flux of the model, ; For node overflow, ; The orifice flow coefficient; The water storage area at the inspection well. Positive and negative signs are used to distinguish between node overflow and node backflow. S32. The flux calculation of the coupled nodes of the one-dimensional river network hydrodynamic model and the two-dimensional hydrodynamic model is adopted by lateral coupling. The formula for calculating lateral coupling is as follows: ； ； ； In the formula: For the lateral coupling flux of the model, ; and These represent the water level values ​​connecting the river channel and the land surface. ; Elevation of the riverbank ; The length of the embankment It is generally the boundary length of the unit connected to the river section.

5. The one-dimensional-two-dimensional hydrodynamic model coupling method based on the displacement backflow mechanism according to claim 1, characterized in that: Step S4 also includes the following steps: S41. The determination of the displacement reflux mechanism is further divided into vertical coupling determination and lateral coupling determination according to the coupling type, based on the corresponding head difference. ( - Independently decide whether to perform replacement backflow; Vertical coupling displacement reflux: （ ）； Lateral coupling displacement reflux: ）； In the formula: For the head difference in one-dimensional and two-dimensional hydrodynamic models, ; This is the hydraulic exchange intensity coefficient, typically taken as 0.01~0.05; For vertically coupled displacement return flux, ; For lateral coupling displacement return flow, ; The water storage area at the inspection well. ; Elevation of the riverbank ; The length of the embankment ; For two-dimensional surface water depth, ; The head difference is calculated for the current step size. ; This is the minimum head difference threshold, typically set to 0.01~0.

05. ; S42. After determining the theoretical flux and displacement return flow between the coupled nodes, update the exchange water volume of the coupled nodes uniformly to form the final coupled flux. The determination method is as follows: ； In the formula: For the final flux of the coupled node, ; This corresponds to the theoretical flux under the coupling mode. ; For two-dimensional surface water depth, ; The head difference is calculated for the current step size. ; This is the minimum head difference threshold, typically set to 0.01~0.

05. .

6. The coupling method for one-dimensional and two-dimensional hydrodynamic models based on the displacement reflux mechanism as described in any one of claims 1-5, characterized in that, include: By uniformly updating the theoretical flux or the displacement return flux, the final coupled flux is simultaneously applied to the corresponding boundary terms or source-sink terms of the one-dimensional pipe network model and the two-dimensional surface model, enabling the two models to achieve bidirectional water exchange and synchronous iteration at each time step, thus completing the coupled solution of the one-dimensional and two-dimensional hydrodynamic fields.

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