Dynamic boundary simulation method and system of hydrodynamic water quality model

Abstract

The invention discloses a dynamic boundary simulation method and system of a hydrodynamic water quality model, and relates to the technical field of hydrodynamic water quality simulation, and the dynamic boundary simulation method of the hydrodynamic water quality model mainly comprises the following steps: constructing the hydrodynamic water quality model and dividing a dynamic grid boundary into dynamic dry and wet grids; determining a dynamic convergence node according to the spatial relationship between the outermost boundary of the water body simulated by the hydrodynamic water quality model and the convergence branch; gradually searching from the grid at the node position to the wet grid at the lowest water level according to the bottom elevation represented by grids around the convergence node and the principle that the elevation is continuously reduced, and determining a dynamic convergence path; and dynamically determining a boundary convergence grid according to the dynamic convergence path and the grid water level change. By means of the dynamic boundary simulation method and system of the hydrodynamic water quality model, complex boundary conditions and various convergence types can be better processed.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrodynamic water quality simulation, and more specifically, to a moving boundary simulation method and system for a hydrodynamic water quality model. Background Art

[0002] Currently, hydrodynamic water quality models are increasingly widely used in environmental monitoring and water quality management. For example, models such as EFDC (Environmental Fluid Dynamics Code), DELFT3D, ECOMSED, MIKE, and WASP use methods such as the finite element method, finite difference method, and finite volume method for water body generalization. For example, currently widely used models such as DELFT3D and EFDC lack consideration of the dynamic changes of the input or discharge of coastal areas, tributaries, non-point sources, and point sources with the moving boundary. ECOMSED considers different types of discharges, but when facing high-altitude inland areas, especially places with gradients on the water surface and excessive water body oscillations, the simulation values are unstable.

[0003] The confluence of tributaries, as the most important boundary condition of the hydrodynamic water quality model, affects the simulation accuracy of the hydrodynamic water quality model. In order to improve the simulation effect of the hydrodynamic water quality model, various methods have been proposed. For example, Patent CN108009349A proposes a method for locally optimizing and encrypting grids for drawing, Patent CN110188483A proposes a method for constructing an adaptive grid for a hydrodynamic water quality model, and Patent CN118709388A proposes a method for dividing control units based on multi-level verification. However, these methods mainly focus on the division of grids and control units, and the tributary confluence process is usually static, that is, in the model, the grid position where the tributary confluence is located is fixed and cannot change with the change of the water level, which is difficult to accurately reflect the dynamic changes of hydrodynamic and pollutant transport during the confluence process. With the increasing demand for environmental protection and resource management, there is an urgent need for more accurate and real-time simulation technologies to effectively respond to the dynamic changes of tributary confluence. Summary of the Invention

[0004] The purpose of the present invention is to provide a moving boundary simulation method and system for a hydrodynamic water quality model, which can perform hydrodynamic simulation on the moving boundary and the change phenomenon of the discharge intersection position in complex waters, dynamically change the grid position where the confluent tributary is located with the change of the water level, accurately reflect the dynamic changes of hydrodynamic and pollutant transport during the confluence process, improve the calculation accuracy and speed, and can better handle complex boundary conditions and diverse confluence types.

[0005] The present invention provides a moving boundary simulation method for a hydrodynamic water quality model, comprising the following steps: S1. According to the hydrodynamic water quality model of the research area, perform water body grid division to obtain a grid matrix; S2. According to the grid matrix and the water film, obtain the water body dry-wet grid division equation; S3. According to the water body dry-wet grid division equation, utilize the spatial relationship between the outermost boundary of the water body and the incoming tributaries to obtain the coordinates of the dynamic incoming nodes and their corresponding grid numbers; S4. According to the dynamic incoming nodes and the grid matrix, obtain the set of tributary incoming paths; S5. According to the grid matrix, obtain the set of water body boundaries at the current water level; S6. According to the set of tributary incoming paths and the set of water body boundaries at the current water level, obtain the boundary incoming grids.

[0006] The present invention also provides a moving boundary simulation system for a hydrodynamic water quality model. The moving boundary simulation system for a hydrodynamic water quality model comprises the following modules: a grid division module configured to perform water body grid division according to the hydrodynamic water quality model of the research area to obtain a grid matrix; a water body dry-wet grid division module configured to obtain the water body dry-wet grid division equation according to the grid matrix and the water film; a dynamic incoming node acquisition module configured to obtain the coordinates of the dynamic incoming nodes and their corresponding grid numbers according to the water body dry-wet grid division equation by utilizing the spatial relationship between the outermost boundary of the water body and the incoming tributaries; a tributary incoming path set module configured to obtain the set of tributary incoming paths according to the dynamic incoming nodes and the grid matrix; a water body boundary set module configured to obtain the set of water body boundaries at the current water level according to the grid matrix; and a boundary incoming grid acquisition module configured to obtain the boundary incoming grids according to the set of tributary incoming paths and the set of water body boundaries at the current water level.

[0007] Implementing the moving boundary simulation method and system for a hydrodynamic water quality model provided by the present invention has the following beneficial effects: The present invention takes into account the moving boundary and the rapid changes in various input conditions, and can be well applied to the moving boundary structure in waters with large water level fluctuations, and can effectively determine the dynamic changes in the incoming water and pollutant input positions of tributaries, point sources and non-point sources; it can be used for the hydrodynamic water quality simulation of water bodies with moving boundaries due to water level changes and multiple inlets; by using the moving boundary method to consider the moving boundary and emission phenomena, it can better meet the physical meanings of the momentum equation and the continuity equation of the hydrodynamic water quality model in the dry grid area, and reduce iterative fluctuations and numerical divergence; the basic formulas and principles constructed by the algorithm solve the problem of missing incoming boundaries in the hydrodynamic water quality model, realize the automatic determination of the incoming boundary of the hydrodynamic water quality model according to the water level change, and improve the model accuracy; The present invention takes into account the dynamic changes of inputs or emissions from coastal areas, tributaries, non-point sources, and point sources along with moving boundaries, the moving boundaries of the moving confluence paths of emissions, and also considers the moving confluence positions of emissions. It can help existing hydrodynamic water quality models accurately simulate the hydrodynamic processes and the transport and diffusion of pollutants in water bodies, provide accurate pollutant concentration distribution information, and contribute to optimizing water quality management and environmental protection decisions; The present invention has achieved the optimization of existing models technically, solved the limitations of traditional methods in dealing with the dynamic confluence of tributaries, and can improve the efficiency and accuracy of water quality management, having important application value and promotion prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The present invention will be further described below in conjunction with the drawings and embodiments. In the drawings: Figure 1 is a flowchart of the moving boundary simulation method of the hydrodynamic water quality model provided by the present invention; Figure 2 The algorithm flowchart of the moving boundary method of the hydrodynamic water quality model provided by the present invention; Figure 3 is the two-dimensional grid of the hydrodynamic water quality model and the distribution of confluence nodes. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0009] For a clearer understanding of the technical features, objectives, and effects of the present invention, the specific embodiments of the present invention will now be described in detail with reference to the drawings.

[0010] Figure 1 shows a schematic diagram of the moving boundary simulation method of the hydrodynamic water quality model of this embodiment. In this embodiment, the moving boundary method of the hydrodynamic water quality model includes the following steps: S1. According to the hydrodynamic water quality model of the study area, divide the water body into grids to obtain a grid matrix; In an exemplary embodiment, the grid matrix includes elements, and the elements include coordinate value attributes, wet-dry attributes, wet-dry dynamic attributes, water depth, water surface level, bottom elevation, and the projected coordinates of the grid center point; As an exemplary embodiment, in step S1, a hydrodynamic water quality model is constructed, the water body is divided into grids, and a grid matrix A is established. Specifically: the study area is divided into grids with m rows and n columns, and each grid cell represents an element a in matrix A i , where each element should have the following attributes: coordinate values (I, J); wet-dry attribute W (the value is 0 or 1, and only when it is 0 does it represent a dry grid); wet-dry dynamic attribute WD (when WD = 0, the grid is dry, and when WD = 1, the grid is wet) water depth H; water surface level WL; bottom elevation BE, etc.; S2. Obtain the water body wet and dry grid division equation based on the grid matrix and the water film; In an exemplary embodiment, the water body wet and dry grid division equation is as follows: , , where, is the wet and dry attribute, is the bottom elevation, is the highest water level, is the wet and dry dynamic attribute, is the water surface level, is the water film; As an exemplary embodiment, in step S2, determine the standard water film WTF for judging the dynamic wet and dry grids of the water body. The water film is used to determine the wet and dry dynamic attributes of the grids in the grid matrix. Specifically, the size of WTF is used as the judgment boundary for the wet and dry grids in the running state. (When the water depth H of the grid (i.e., WL - BE) exceeds the size of WTF, the wet and dry dynamic attribute WD value of the grid is 1); Based on the water body wet and dry grid division equation, modify the grid cells whose grid attribute WD = 1, but the WD of their four neighboring cells is 0, and set their grid WD attribute to 0 to eliminate the interference caused by local pits; Calculate the flow rate, velocity, water depth and all other hydrodynamic variables of the wet grid cells at the current time step; Before the next time step, if WD = 0, the flow rate, velocity, water depth and all other hydrodynamic variables will be set to zero first; For the dry grids in the four neighboring areas (up, down, left, right) of the wet grid, their hydrodynamic variables will be determined by linear interpolation between their adjacent wet cells; As an exemplary embodiment, in step S2, establish the water body wet and dry grid division equation according to WTF, which specifically includes: S21. Set the highest water level as MAX_WL and the lowest water level as MIN_WL. If BE > MAX_WL, then this grid will be defined as always dry, and at this time W = 0. If BE ≤ MAX_WL, then this grid may be a wet grid or a dry grid, and at this time W = 1. For these grids with W = 1, the next judgment is required; That is: , S22. Set the grid wet and dry dynamic variable WD to distinguish the wet and dry states of the grid when W = 1. The water surface level WL of all grids will be set to the initial water level INI_WL. If WL - BE < WTF, then the grid wet and dry dynamic variable WD = 0. When WL - BE ≥ WTF, then the grid wet and dry dynamic variable WD = 1; That is: , S23. Modify the grid cells with grid property WD = 1 but with four neighboring cells having WD = 0, and set their grid WD property to 0 to eliminate the interference caused by local pits. S24. Calculate the flow rate, flow velocity, water depth, and all other hydrodynamic variables for the wet grid cells at the current time step. S25. Before the next time step, if WD = 0, the flow rate, flow velocity, water depth, and all other hydrodynamic variables will first be set to zero; for the dry grids in the four neighboring areas (up, down, left, right) of the wet grid, their hydrodynamic variables will be determined by linear interpolation between their adjacent wet cells. S3. According to the water body wet-dry grid division equation, using the spatial relationship between the outermost boundary of the water body and the inflowing tributaries, obtain the coordinates of the dynamic inflow nodes and their corresponding grid numbers. In an exemplary embodiment, step S3 specifically includes: according to the water body wet-dry grid division equation, based on the spatial relationship between the outermost boundary of the water body and the inflowing tributaries, the intersection point of the two is the dynamic inflow node, calculate its projection coordinates, and calculate the Euclidean distance from each grid center. , where 、 are the abscissa and ordinate of the dynamic inflow node respectively, 、 are the projected abscissa and ordinate of the grid center point respectively; take the grid number corresponding to the minimum as the grid number of the dynamic inflow node. As an exemplary embodiment, in step S3, determine the position of the dynamic inflow node according to the spatial relationship between the outermost boundary of the water body and the inflowing tributaries, and establish a mapping equation from the dynamic inflow node to the water body grid with the water body grid matrix, then the water body grid number corresponding to the dynamic inflow node can be obtained according to the coordinates of the tributary dynamic inflow node, that is, the water body grid number IJ at the start of the discharge path of the inflowing tributary; specifically, consider the lateral inflows such as tributaries and sewage outfalls as tributaries uniformly, and take the intersection position of the outer boundary corresponding to the highest water level of the water body simulated by the hydrodynamic water quality model and the inflowing tributary as the dynamic inflow node of the tributary. From the coordinates (x n , y n ) of the projection coordinate system of the inflow node, obtain the IJ number of the corresponding water body grid, calculate the Euclidean distance between the inflow node and the center point of each grid respectively , where 、 are the abscissa and ordinate of the dynamic inflow node respectively, 、 are the projected abscissa and ordinate of the grid center point respectively; take the grid number corresponding to the minimum as the grid number of the dynamic inflow node. S4. Obtain the tributary inflow path set according to the dynamic inflow node and the grid matrix; In an exemplary embodiment, step S4 specifically includes: S41. Determine the starting grid of the tributary inflow into the river according to the grid matrix; S42. Determine the limiting direction of the wet grid with respect to the starting grid according to the river tributary inflow starting grid number corresponding to the dynamic inflow node; S43. Search according to the limiting direction of the wet grid with respect to the starting grid to obtain the tributary inflow path set; As an exemplary embodiment, in step S4, determine the tributary inflow path set P (including the IJ numbers of all inflow path grids), that is, according to the bottom elevation represented by the grid, following the principle of continuously decreasing elevation, start from the starting grid corresponding to the dynamic inflow node position O(I o , J o ) and gradually search towards the wet grid at the lowest water level to form the tributary inflow path; in step S41, the starting grid of the tributary inflow into the river is the grid corresponding to the dynamic inflow node, and the tributary inflow path starts from the dynamic inflow node, that is, at the intersection grid of the tributary and the MAX_WL line, and ends at the grid cell where the tributary intersects the MIN_WL line; in step S42, first determine the direction of the grid cell with BE ≤ MIN_WL with respect to the starting grid, compare the IJ numbers of the starting grid and all grid cells intersecting the MIN_WL. If the I number of the grid cell intersecting the MIN_WL is greater than the I number of the starting grid, the wet grid is on the right side of the starting grid. If the I number of the grid cell intersecting the MIN_WL is less than the I number of the starting grid, the wet grid is on the left side of the starting grid; if the J number of the grid cell intersecting the MIN_WL is greater than the J number of the starting grid, the wet grid is above the starting grid. If the J number of the grid cell intersecting the MIN_WL is less than the J number of the starting grid, the wet grid is below the starting grid; in step S43, during the process of the tributary inflow path from start to end, the grid cells should be arranged in descending order of BE. Starting from the inflow starting grid, within the range of the direction defined in step S42, search the four directions of up, right, down, and left in sequence, and select the grid with the lowest surrounding bottom elevation as the next grid of the tributary inflow path until it reaches the grid cell where it intersects the MIN_WL, and record the selected grid IJ numbers in order to form the inflow path set P; S5. Obtain the water body boundary set at the current water level according to the grid matrix; As an exemplary embodiment, in step S5, determining the water body boundary set B at the current water level specifically includes: S51. Determining whether the grid is in set B by judging the WD attribute values of the grid and its four neighboring grids at the current time step. If the WD of the grid itself is 1 and at least one of the four neighboring grids has WD = 0, the IJ number of the grid will be saved in set B; S52. Updating set B after each time step starts. S6. Obtaining the boundary inflow grids according to the tributary inflow path set and the water body boundary set at the current water level. As an exemplary embodiment, in step S6, according to the tributary inflow path set and the water body boundary set at the current water level, that is, dynamically determining the boundary inflow grids through the tributary inflow paths and the grid water level changes, specifically includes: Taking the intersection of set P obtained in S4 and set B obtained in S5 to get that the grid cell is a tributary boundary inflow grid; Sometimes the sewage outfall of the point source may be built inside the lake or reservoir. In this case, if BE ≤ MIN_WL at the sewage outfall, the boundary inflow grid cell is fixed, that is, the grid cell corresponding to the location of the sewage outfall; After resetting WD each time, recalculating the boundary inflow grid cells in the tributary inflow paths.

[0011] This embodiment provides a moving boundary simulation system for a hydrodynamic water quality model. The moving boundary simulation system for a hydrodynamic water quality model includes the following modules: A grid division module configured to: perform water body grid division according to the hydrodynamic water quality model of the research area to obtain a grid matrix; A water body wet-dry grid division module configured to: obtain the water body wet-dry grid division equation according to the grid matrix and the water film; A dynamic inflow node acquisition module configured to: obtain the coordinates of the dynamic inflow nodes and their corresponding grid numbers according to the water body wet-dry grid division equation and using the spatial relationship between the outermost boundary of the water body and the inflowing tributaries; A tributary inflow path set module configured to: obtain the tributary inflow path set according to the dynamic inflow nodes and the grid matrix; A water body boundary set module configured to: obtain the water body boundary set at the current water level according to the grid matrix; A boundary inflow grid acquisition module configured to: obtain the boundary inflow grids according to the tributary inflow path set and the water body boundary set at the current water level.

[0012] In an exemplary embodiment, the grid matrix includes elements, and the elements include coordinate value attributes, wet-dry attributes, wet-dry dynamic attributes, water depth, water surface level, bottom elevation, and grid center point projection coordinates.

[0013] In an exemplary embodiment, the water body wet-dry grid division equation is as follows: , , Among them, is the dry-wet property, is the bottom elevation, is the highest water level, is the dry-wet dynamic property, is the water surface level, is the water film.

[0014] In an exemplary embodiment, the dynamic inflow node acquisition module is specifically configured as follows: According to the water body dry-wet grid division equation, based on the spatial relationship between the outermost boundary of the water body and the tributary inflow, the intersection point of the two is the dynamic inflow node, calculate its projection coordinates, and calculate the Euclidean distance from the center of each grid , where , are the abscissa and ordinate of the dynamic inflow node respectively, , are the projected abscissa and ordinate of the grid center point respectively; Take the grid number corresponding to the minimum as the grid number of the dynamic inflow node.

[0015] In an exemplary embodiment, the tributary inflow path set module is specifically configured as follows: According to the grid matrix, determine the starting grid for the tributary inflow of the river; According to the grid number of the starting grid for the tributary inflow of the river corresponding to the dynamic inflow node, determine the limiting direction of the wet grid with respect to the starting grid; Search according to the limiting direction of the wet grid with respect to the starting grid to obtain the tributary inflow path set.

[0016] In some embodiments, the moving boundary simulation method of the above hydrodynamic water quality model can also be implemented in the following manner. This example takes the Weihe River in Xi'an as an example to propose a moving boundary method for the hydrodynamic water quality model. For the technical process, please refer to Figure 2 , the moving boundary simulation method of the hydrodynamic water quality model includes: Step 1: Construct a hydrodynamic water quality model, divide the water body grid, and establish a grid matrix A: Regarding the establishment of matrix A and its related characteristics, the study area is divided into a grid of m rows and n columns, and each grid unit represents the element a in matrix A i , where each element should have the following attributes: number value (I, J), dry-wet property W (the value is 0 or 1, and only when it is 0 does it represent a dry grid), dry-wet dynamic property WD (when WD = 0, the grid is dry, and when WD = 1, the grid is wet), water depth H, water surface level WL, bottom elevation BE, projected coordinates of the grid center point, etc.; In this example, the Weihe River in Xi'an is selected. The flow rates during the dry season and the wet season of the Weihe River in Xi'an differ by dozens of times, and the water body boundary changes significantly. A two-dimensional hydrodynamic and water quality model of the main stream of the Weihe River in Xi'an and its tributary, the Zaohe River, is established, which is divided into 301×253 grid cells in total, and the number of available grid cells is 3,221, as Figure 3 shown. The numbering starts from the lower left corner of the grid. I increases sequentially from left to right, and J increases sequentially from bottom to top. Other attributes are obtained through the digital elevation model (DEM) and measured data; Step 2: Determine the standard water film WTF for judging wet and dry grids of the water body; Use the size of WTF as the judgment boundary for wet and dry grids in the initial state. (When the water depth H of the grid (i.e., WL - BE) exceeds the size of WTF, the wet and dry attribute W of the grid is 1); In this example, WTF is set to 0.05 meters; Step 3: Establish an equation for dividing wet and dry grids of the water body based on WTF in Step 2;

[0017]

[0018] The specific judgment steps are as follows: Step 3.1: Set the highest water level as MAX_WL and the lowest water level as MIN_WL. If BE > MAX_WL, then this grid will be defined as a dry grid all the time, and at this time W = 0. If BE ≤ MAX_WL, then this grid may be a wet grid or a dry grid, and at this time W = 1. For these grids with W = 1, the next step of judgment is required; Step 3.2: Set the grid wet and dry dynamic variable WD to distinguish the wet and dry states of the grid when W = 1. The water surface level WL of all grids will be set to the initial water level INI_WL. If H < WTF, then the grid wet and dry dynamic variable WD = 0. When WL - BE ≥ WTF, then the grid wet and dry dynamic variable WD = 1; Step 3.3: Modify those grid cells with WD = 1 but WD = 0 in their four neighboring cells, and set their grid WD attribute to 0 to eliminate the interference caused by local pits; Step 3.4: Calculate the flow rate, flow velocity, water depth, and all other hydrodynamic variables of the wet grid cells at the current time step; Step 3.5: Before the next time step, if WD = 0, the flow rate, flow velocity, water depth, and all other hydrodynamic variables will first be set to zero; for those dry grids in the four neighboring areas (up, down, left, right) of the wet grid, their hydrodynamic variables will be determined by linear interpolation between their adjacent wet cells; In this example, the maximum water level MAX_WL at the downstream outlet is set to 314 m, the minimum water level MIN_WL is 303.4 m, and the initial water level INI_WL is 306.7 m. The wet / dry attributes of the grids constructed for the Weihe River in Xi'an are judged through the wet / dry grid division equation of the water body, and the WD value of 1 modified due to local pits is changed to 0; the dry area and the wet / dry dynamic area of the basin can be obtained, and the numerical calculation of the model is carried out on the grids with WD = 1 in the wet / dry dynamic area. Step 4: Determine the position of the dynamic inflow node according to the spatial relationship between the outermost boundary of the water body and the tributary inflow, and establish a mapping equation from the dynamic inflow node to the water body grid in the water body grid matrix; that is, the lateral inflows such as tributaries and sewage outfalls are uniformly regarded as tributaries. According to the position where the outermost boundary corresponding to the maximum water level of the water body simulated by the hydrodynamic water quality model intersects the tributary inflow, it is used as the dynamic inflow node of the tributary. From the coordinates (x n , y n ) of the projection coordinate system of the inflow node, the IJ numbers of the corresponding water body grids are obtained, and the Euclidean distances between the inflow node and the center points of each grid are calculated respectively , where , are the abscissa and ordinate of the dynamic inflow node respectively, , are the projected abscissa and ordinate of the grid center point respectively. The grid number corresponding to the minimum is used as the grid number of the dynamic inflow node.

[0019] In this example, the grid length is between 60 and 500 m, and the width is between 50 and 260 m; the watershed hydrological model (SWAT) is used to simulate the land runoff, and 36 inflow nodes are obtained, and their distribution is as Figure 3 shown; among them, there is 1 point source inflow node, which is the sewage outfall of the sewage treatment plant, and its distribution is Figure 3 the leftmost inflow node in; according to the mapping equation from the tributary inflow to the water body grid, the water body grid numbers corresponding to these 36 inflow nodes are obtained; Step 5: Determine the set P of tributary inflow paths (including the IJ numbers of all inflow path grids); that is, according to the bottom elevation represented by the grid, following the principle of continuously decreasing elevation, gradually search from the grid at the inflow node position O(I o , J o ) to the wet grid at the lowest water level to form the tributary inflow path; The specific steps are as follows: Step 5.1: Determine the starting grid of the river tributary inflow. The tributary inflow path starts from the dynamic inflow node, that is, the intersection grid between the tributary and the MAX_WL line, and ends at the grid cell where the tributary intersects the MIN_WL line; Step 5.2: First, determine the direction of the grid cell where BE = MIN_WL in the starting grid. Compare the IJ numbers of the starting grid and all grid cells intersecting with MIN_WL. If there is a grid cell intersecting with MIN_WL whose I number is greater than that of the starting grid, the wet grid is to the right of the starting grid; if there is a grid cell intersecting with MIN_WL whose I number is less than that of the starting grid, the wet grid is to the left of the starting grid; if there is a grid cell intersecting with MIN_WL whose J number is greater than that of the starting grid, the wet grid is above the starting grid; if there is a grid cell intersecting with MIN_WL whose J number is less than that of the starting grid, the wet grid is below the starting grid. Step 5.3: During the process of the tributary inflow path from start to end, the grid cells should be arranged in descending order of BE. Starting from the starting grid of the inflow, within the direction range defined in Step 5.2, search the four directions of up, right, down, and left in sequence, and select the grid with the lowest bottom elevation among the surrounding grids as the next grid of the tributary inflow path until reaching the grid cell intersecting with MIN_WL. Record the IJ numbers of the selected grids in order to form the inflow path set P. In this example, there are 36 inflow nodes in total. Starting from the grid where each inflow node is located, search according to the principle of continuously decreasing elevation towards the grid where the lowest water level is located until reaching the grid at the lowest water level. Store the IJ numbers of the grids corresponding to the paths formed during the search process into the set P (including all IJ numbers of the inflow path grids). There are 36 paths in this example. Step 6: Determine the water body boundary set B at the current water level. The specific steps are as follows: Step 6.1: Determine whether the grid is in the set B by judging the WD attribute values of the grid and its four neighboring grids at the current time step. If the WD of the grid itself is 1 and there is at least one grid among the four neighboring grids with WD = 0, the IJ number of this grid will be saved in the set B. Step 6.2: Update the set B after each time step starts. In this example, the water body boundary grid set is updated once for each calculation time step. Step 7: Determine the dynamic boundary inflow grids. According to Steps 5 and 6, that is, determine the tributary boundary inflow grids dynamically based on the tributary inflow path and the grid water level change. The specific steps are as follows: Step 7.1: Find the intersection of the set P obtained in Step 5 and the set B obtained in Step 6 to get that the grid cell is a tributary boundary inflow grid. Step 7.2: Sometimes, the sewage outlet of a point source may be built inside a lake or reservoir. In this case, if BE ≤ MIN_WL at the sewage outlet, the boundary inflow grid cell is fixed, that is, the grid cell corresponding to the location of the sewage outlet; Step 7.3: After resetting WD each time, recalculate the boundary inflow grid cells in the tributary inflow path.

[0020] In this example, the set of tributary inflow paths is intersected with the set of water body boundary grids in each calculation step to obtain the dynamic boundary inflow grids of the tributaries. The hydrodynamic and water quality model constructed according to this method successfully simulates the complex phenomena of water level changes and wet-dry cell conversions. This method can dynamically change the grid position where the tributary inflows according to the change of water level, accurately reflect the hydrodynamic conditions at the tributary inflow, accurately reflect the dynamic transport and distribution of pollutants during the inflow process, solve the limitations of traditional methods in dealing with dynamic tributary inflows, help the existing hydrodynamic and water quality models accurately simulate the transport and diffusion process of pollutants in the water body, provide accurate pollutant concentration distribution information, improve the efficiency and accuracy of water quality management, and contribute to optimizing water quality management and environmental protection decisions.

[0021] The embodiments of the present invention have been described above in conjunction with the accompanying drawings. However, the present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many forms without departing from the purpose of the present invention and the scope protected by the claims. All of these fall within the protection scope of the present invention.

Claims

1. A moving boundary simulation method for a hydrodynamic water quality model, characterized in that: The following steps are involved: S1. Divide the water body grid according to the hydrodynamic and water quality model of the study area to obtain the grid matrix; S2. Obtaining a dry-wet grid partition equation for a water body according to the grid matrix and the water film; S3, according to the water body dry-wet grid division equation, using the spatial relationship between the outermost boundary of the water body and the inflow tributary, obtain the dynamic inflow node coordinates and their corresponding grid numbers; S4, obtaining a set of tributary inflow and outflow paths according to the dynamic inflow node and the grid matrix; S5. Obtaining a water body boundary set at a current water level according to the grid matrix; S6. Obtain a boundary inflow grid according to the tributary inflow path set and the water body boundary set at the current water level.

2. The moving boundary simulation method of the hydrodynamic water quality model according to claim 1 is characterized in that: The grid matrix includes elements, and the elements include coordinate value attributes, dry and wet attributes, dry and wet dynamic attributes, water depth, water surface level, bottom elevation and grid center point projection coordinates.

3. The moving boundary simulation method of the hydrodynamic water quality model according to claim 1 is characterized in that: The water body dry and wet grid division equation is as follows: ， ， in, For dry and wet properties, is the bottom elevation, is the highest water level, is the wet and dry dynamic property, is the water surface level, A water film.

4. The moving boundary simulation method of the hydrodynamic water quality model according to claim 1 is characterized in that: Step S3 specifically includes: according to the water body dry-wet grid division equation, according to the spatial relationship between the outermost boundary of the water body and the inflow tributary, the intersection of the two is the dynamic inflow node, and its projection coordinates are calculated, and the Euclidean distance from each grid center is calculated. ,in , They are the horizontal and vertical coordinates of the dynamically imported nodes. , Divided into the horizontal coordinate and vertical coordinate of the grid center point projection; The grid number corresponding to the minimum is used as the grid number of the dynamic inflow node.

5. The moving boundary simulation method of the hydrodynamic water quality model according to claim 1 is characterized in that: Step S4 specifically includes: S41, determining the starting grid for the confluence of river tributaries according to the grid matrix; S42, determining a limiting direction of the wet grid with respect to the starting grid according to the river tributary confluence starting grid number corresponding to the dynamic confluence node; S43, searching the limited direction of the starting grid according to the wet grid to obtain a set of tributary confluence paths.

6. A moving boundary simulation system for a hydrodynamic water quality model, characterized in that: The moving boundary simulation system of the hydrodynamic water quality model includes the following modules: The grid division module is configured as follows: according to the hydrodynamic and water quality model of the study area, water body grid division is performed to obtain a grid matrix; A water body dry-wet grid division module is configured to: obtain a water body dry-wet grid division equation according to the grid matrix and the water film; The dynamic inflow node acquisition module is configured to: obtain the dynamic inflow node coordinates and their corresponding grid numbers according to the water body dry-wet grid division equation and by utilizing the spatial relationship between the outermost boundary of the water body and the inflow tributary; A branch inflow and confluence path collection module is configured to: obtain a branch inflow and confluence path collection according to the dynamic confluence node and the grid matrix; The water body boundary set module is configured to: obtain a water body boundary set at a current water level according to the grid matrix; The boundary inflow and confluence grid acquisition module is configured to obtain a boundary inflow and confluence grid according to the tributary inflow and confluence path set and the water body boundary set at the current water level.

7. The moving boundary simulation system of the hydrodynamic water quality model according to claim 6, characterized in that: The grid matrix includes elements, and the elements include coordinate value attributes, dry and wet attributes, dry and wet dynamic attributes, water depth, water surface level, bottom elevation and grid center point projection coordinates.

8. The moving boundary simulation system of the hydrodynamic water quality model according to claim 6, characterized in that: The water body dry and wet grid division equation is as follows: ， ， in, For dry and wet properties, is the bottom elevation, is the highest water level, is the wet and dry dynamic property, is the water surface level, A water film.

9. The moving boundary simulation system of the hydrodynamic water quality model according to claim 6, characterized in that: The dynamic inflow node acquisition module is specifically configured as follows: according to the water body dry-wet grid division equation, according to the spatial relationship between the outermost boundary of the water body and the inflow tributary, the intersection of the two is the dynamic inflow node, and its projection coordinates are calculated, and the Euclidean distance from the center of each grid is calculated. ,in , They are the horizontal and vertical coordinates of the dynamically imported nodes. , Divided into the horizontal coordinate and vertical coordinate of the grid center point projection; The grid number corresponding to the minimum is used as the grid number of the dynamic inflow node.

10. The moving boundary simulation system of the hydrodynamic water quality model according to claim 6, characterized in that: The specific configuration of the tributary confluence path collection module is: According to the grid matrix, determining the starting grid for the confluence of the river tributaries; Determine the limiting direction of the wet grid with respect to the starting grid according to the river tributary confluence starting grid number corresponding to the dynamic confluence node; A search is performed based on the wet grid in the limited direction of the starting grid to obtain a set of tributary inflow and confluence paths.

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