Urban flood simulation method based on unstructured grid coupling SWMM and FVCOM models

Abstract

The invention discloses an urban flood simulation method based on an unstructured grid coupling SWMM and FVCOM model, an inspection well simplification method is adopted to represent the exchange process of surface water flow and underground pipe network water flow, an unstructured grid FVCOM is used as a main program, and an SWMM is used as a subprogram to be called by the main program and the subprogram. The method comprises the steps that firstly, an underground pipe network water flow model and a surface water flow model are established through given basic data by means of an SWMM model and an unstructured grid FVCOM model; establishing a spatial topological relation between the SWMM pipe network nodes and the FVCOM grids; in the time step needing coupling, a pipe network water flow head and a surface water head of a pipe network inspection well node are obtained, the exchanged flow is calculated, and surface water and pipe network water flow are simulated according to the updated water head and flow; the time is progressive, and finally the whole city flood simulation process is completed. According to the invention, the coupling effect of urban pipe network water flow and surface water flow can be accurately simulated, and the simulation of urban flood with zigzag coastlines or complex building outlines is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of flood disaster prevention and control in urban areas with complex coastlines or complex building contours, and specifically relates to an urban flood simulation method that couples SWMM (Storm Water Management Model) and FVCOM (Finite Volume Coast and Ocean Model). Background Art

[0002] In order to study the problem of urban waterlogging, some methods for simulating urban waterlogging have been proposed in recent years. In the numerical simulation of the coupling between surface water flow and underground pipe network in the process of urban flooding, the use of dynamic bidirectional coupling model simulation has become a trend to simulate the coupling between surface water flow and pipe network. However, the current coupling models of surface water flow and pipe network flow mostly use structured grids. Structured grids cannot well describe the boundaries of tortuous coastlines or complex building contours. For urban areas with such boundaries, unstructured grids can better describe them and the surface water flow simulation results are more accurate. Summary of the invention

[0003] In response to the above-mentioned prior art, the present invention provides an urban flood simulation method based on unstructured grid coupling SWMM and FVCOM models, which can realize the simulation of urban flooding in urban areas with complex building boundaries or complex coastline boundaries, and can provide technical support for the accurate simulation of urban flooding in cities with irregular building contours or urban areas with complex coastline boundaries.

[0004] In order to solve the above technical problems, the present invention proposes an urban flood simulation method based on unstructured grid coupling SWMM and FVCOM model, which mainly adopts the inspection well simplification method to characterize the exchange process of surface water flow and underground pipe network water flow, and uses the unstructured grid FVCOM model as the main program, and uses the SWMM model as a subroutine for the main program to call, so as to perform real-time dynamic two-way data exchange between the surface water dynamic model and the pipe network hydrodynamic model, simulate the coupling effect of the underground pipe network water flow and the surface water flow, and finally realize the coupled simulation of urban floods with tortuous coastlines or complex building contours based on unstructured grids. The main process is: first, using the given basic data, use the SWMM model and the unstructured grid FVCOM model to respectively establish the models of underground pipe network water flow and surface water flow; establish the spatial topological relationship between the SWMM pipe network node and the FVCOM grid; at the time step that requires coupling, obtain the pipe network water flow head and surface water head of the pipe network inspection well node, determine the inflow or outflow of the inspection well node at the current time step, calculate the exchange flow, and the unstructured grid FVCOM model and SWMM model simulate the surface water and pipe network water flow respectively according to the updated head and flow; time is progressive, and finally the entire urban flood simulation process is completed. It specifically includes the following steps:

[0005] Step 1, obtaining basic data of the study area, wherein the basic data at least includes the distribution of the drainage network, the ground elevation data of the study area, the location of the inspection well, and the outline of the building;

[0006] Step 2, based on the above basic data, using the SWMM model and the unstructured grid FVCOM model, using the unstructured grid of the FVCOM model to respectively establish models of underground pipe network water flow and surface water flow, so as to describe the tortuous coastline or complex building contours;

[0007] Step 3, read the inp format file generated by the SWMM model, obtain the location coordinates of the SWMM pipe network nodes, and establish a spatial topological relationship with the FVCOM of the surface water flow;

[0008] Step 4: Based on the SWMM network node water head and the FVCOM surface water flow head, the inspection well simplification method is used to characterize the exchange process between the surface water flow and the underground network water flow;

[0009] Step 5, using the unstructured grid FVCOM model as the main program and the SWMM model as a subroutine for the main program to call;

[0010] Step 6, start the model and start calculation;

[0011] Step 7, at the time step that requires coupling, the two models exchange data to realize dynamic real-time coupling, including: the SWMM model transmits the manhole node water head of the current time step to the unstructured grid FVCOM model, the FVCOM model obtains the coupling node water head and the network water head according to the manhole node water head and the surface water head, and calculates the exchanged flow flux, and then transmits the calculated flow to the SWMM model, thereby realizing the update of the water head and flow; the FVCOM model and the SWMM model simulate the surface water and pipe network water flow respectively according to the updated water head and flow;

[0012] Step 8: Repeat step 7 at the time step that requires coupling, and finally achieve the simulation of urban flooding with tortuous coastlines or complex building contours.

[0013] Furthermore, the urban flood simulation method of the present invention comprises:

[0014] In step 4, the inspection well simplification method is used to characterize the exchange process between surface water flow and underground pipe network water flow. According to the relationship between the surface water depth D1, the inspection well node head H2, and the surface elevation Z, the interaction between the surface water flow and the underground pipe network water flow includes the following situations:

[0015] (1) When D1 = 0, if H2 ≤ Z, the interaction state is that the inspection well has neither inflow nor outflow;

[0016] (2) When D1 = 0, if H2 > Z, the interaction state is outflow from the inspection well;

[0017] (3) When D1>0, if H2<Z, the interaction state is manhole inflow;

[0018] (4) When D1>0, if H2=Z, the interaction state is manhole inflow;

[0019] (5) When D1>0, if H2>Z and H2<Z+D1, the interaction state is manhole inflow;

[0020] (6) When D1>0, if H2>Z and H2=Z+D1, the interactive state is that the inspection well has neither inflow nor outflow;

[0021] (7) When D1>0, if H2>Z+D1, the interaction state is outflow from the inspection well.

[0022] In step 5, the specific steps of using the unstructured grid FVCOM model as the main program and the SWMM model as a subroutine for the main program to call are as follows:

[0023] Step 5-1, compare the SWMM network node head and the surface water head, add the mass source term to the continuity equation of the FVCOM model, and the continuity equation after vertical integration is as follows:

[0024]

[0025] In formula (1): ζ is the current water level of the control body; is the average flow velocity in the direction of the control volume; is the average flow velocity in the y direction of the control volume; Q sur is the overflow flow from the underground pipe network inspection well node; D is the water depth of the control body; δ sur is the Dirichlet function, where, under the node overflow state, δ sur The value is 1; under the node discharge state, δ sur The value is -1; when the node is neither overflowing nor leaking, δ sur The value is 0;

[0026] Step 5-2, the flow conservation equation at the node in the SWMM model is as follows:

[0027]

[0028] In formula (2): A j is the cross-sectional area of ​​the inspection well node; η j is the current water level of the inspection well node; t is the time; is the inflow flow of the kth pipeline connecting the inspection well node; Q laterin Inbound traffic added for external customization; Q sur is the overflow flow from the underground pipe network inspection well node; δ sur is the Dirichlet function, where, under the node overflow state, δ sur The value is 1; under the node discharge state, δ sur The value is -1; when the node is neither overflowing nor leaking, δ sur The value is 0.

[0029] In step 7, the FVCOM model obtains the coupling node head and network head according to the inspection well node head and the surface water head, and calculates the exchange flow flux Q exc for:

[0030]

[0031] H1=D1+Z (4)

[0032] H2=D2 (5)

[0033] In formula (3) to formula (5), c0 is the flow coefficient, ranging from [0-1], A is the effective flow area of ​​the inspection well, g represents the gravity acceleration, H1 and H2 are the average water head of the grid unit and the water head of the inspection well node, respectively, D1 represents the surface water depth, D2 is the water depth in the inspection well, and Z is the surface elevation.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The present invention couples the underground pipe network water flow model SWMM and the surface water flow model FVCOM based on unstructured grids. In the past, the coupling models of surface water flow and underground pipe network water flow mostly used structured grids. When the outline of urban buildings is complex, or there are complex coastline boundaries near urban areas, structured grids cannot well describe the complex boundaries. The present invention couples SWMM and FVCOM in real time and dynamically based on unstructured grids, which can describe the changes of complex boundaries. After verification by physical models, the model calculation values ​​are in good agreement with the experimental values, and can be used to simulate floods in urban areas with complex building outlines or coastline boundaries. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a flow chart of the urban flood simulation method of the present invention coupling SWMM and FVCOM models;

[0037] Figure 2 It is the physical coupling process of the pipe network water flow and the surface water flow of the present invention;

[0038] Figure 3 It is a schematic diagram of the interaction between the surface water flow and the underground pipe flow of the present invention;

[0039] Figure 4 It is a schematic diagram of the arrangement of the physical model experiment verified by the present invention;

[0040] Figure 5-1 and Figure 5-2 is a comparison chart of the errors between the experimental value and the simulation value in the physical model experiment verified by the present invention, wherein: Figure 5-1 This is a comparison chart of the error between the interactive flow experimental value and the simulation value. Figure 5-2 It is a comparison chart of the error between the experimental value and the simulated value of the water depth at the measuring point. DETAILED DESCRIPTION

[0041] The design concept of the urban flood simulation method proposed in the present invention is: in the past, the coupling model of surface water flow and underground pipe network water flow mostly adopted structured grids. When the outline of urban buildings is relatively complex, or there are complex coastline boundaries near the urban area, the structured grid cannot well describe the complex boundaries. The present invention is based on unstructured grids to perform real-time dynamic coupling of the underground pipe network water flow model SWM and the surface water flow model FVCOM, which can describe the changes of complex boundaries. After verification by the physical model, the model calculation value is consistent with the experimental value. It can be used for simulating urban floods with complex building outlines or coastline boundaries, and provide technical support for accurate simulation of urban flooding in cities with irregular building outlines or urban areas with complex coastline boundaries. The method mainly includes: using the inspection well simplification method to characterize the exchange process of surface water flow and underground pipe network water flow, using the rewritten unstructured grid FVCOM model as the main program, and SWMM as a subroutine for calling. First, the models of underground pipe network water flow and surface water flow are established respectively using SWMM and FVCOM with given basic data; at the time step that requires coupling, the water head of the inspection well node pipe network and the surface water head are obtained and the exchange flow is calculated; time is progressive, and finally the entire urban flood simulation process is completed. The present invention can realize the real-time dynamic data exchange of the two models, can accurately simulate the coupling effect of urban pipe network water flow and surface water flow, and realizes the simulation of urban floods with tortuous coastlines or complex building contours based on the unstructured grid coupling model.

[0042] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the following embodiments are by no means intended to limit the present invention in any way.

[0043] like Figure 1 As shown, the urban flood simulation method proposed in the present invention based on unstructured grid coupling SWMM and FVCOM model is implemented in the following steps:

[0044] Step 1, obtaining basic data of the study area, wherein the basic data at least includes the distribution of the drainage network, the ground elevation data of the study area, the location of the inspection well, and the outline of the building;

[0045] Step 2, based on the basic data, using SWMM and unstructured grid FVCOM model, using FVCOM's unstructured grid to describe the tortuous coastline or complex building contours;

[0046] Step 3: Read the inp format file generated by SWMM, obtain the location coordinates of the SWMM pipe network nodes, and establish a spatial topological relationship with the surface water flow model FVCOM. Figure 2 As shown in the figure, under the framework of FVCOM as the main program, the real-time dynamic bidirectional coupling between FVCOM and SWMM is realized by calling the SWMM subroutine;

[0047] Step 4: Based on the SWMM network node water head and surface water flow head, Figure 3 The simplified inspection well method is used to characterize the exchange process between surface water flow and underground pipe network. According to the different states of surface water flow and pipe network flow, the interaction states between surface water flow and pipe network flow are divided into seven types.

[0048] Step 5, use the unstructured grid FVCOM model as the main program and the SWMM model as a subroutine for the main program to call;

[0049] Step 6: Start the model and start calculation.

[0050] Step 7: At the time step that requires coupling, the two models exchange data to achieve dynamic real-time coupling. SWMM passes the manhole node head of the current time step to the unstructured grid FVCOM model. FVCOM calculates the flow flux exchanged between the two models based on the manhole node head and the surface water head. FVCOM passes the calculated flow to SWMM.

[0051] In step 8, FVCOM and SWMM simulate surface water and pipe network water flow respectively according to the updated head and flow, and repeat step 7 at the time step that requires coupling, finally realizing the simulation of urban flooding with tortuous coastline or complex building contours.

[0052] The present invention is also characterized in that step 4 is based on the different states of surface water flow and canal water flow, such as Figure 3 The interaction between surface water flow and canal water flow is divided into seven states as shown below:

[0053] ((1) When D1 = 0, if H2 ≤ Z, the interaction state is that the inspection well has neither inflow nor outflow;

[0054] (2) When D1 = 0, if H2 > Z, the interaction state is outflow from the inspection well;

[0055] (3) When D1>0, if H2<Z, the interaction state is manhole inflow;

[0056] (4) When D1>0, if H2=Z, the interaction state is manhole inflow;

[0057] (5) When D1>0, if H2>Z and H2<Z+D1, the interaction state is manhole inflow;

[0058] (6) When D1>0, if H2>Z and H2=Z+D1, the interactive state is that the inspection well has neither inflow nor outflow;

[0059] (7) When D1>0, if H2>Z+D1, the interaction state is outflow from the inspection well.

[0060] Where D1 is the surface water depth, H2 is the inspection well node head, and Z is the surface elevation.

[0061] Step 5 is as follows:

[0062] Step 5-1, compare the SWMM network node head and the surface water flow head. In order to consider the impact of the underground pipe network on the surface water flow, it is necessary to add a mass source term to the FVCOM continuity equation. The continuity equation after vertical integration is improved as follows:

[0063]

[0064] Where: ζ is the current water level of the control body; is the average flow velocity in the direction of the control volume; is the average flow velocity in the y direction of the control volume; Q sur is the overflow flow from the underground pipe network inspection well node; D is the water depth of the control body; δ sur is the Dirichlet function, which takes the value of 1 when the node is in overflow state, -1 when it is in leakage state, and 0 when it is neither overflowing nor leakage state.

[0065] Step 5-2: To reflect the flow exchange between the pipe network and the surface water flow, the flow conservation equation at the node in SWMM is rewritten as:

[0066]

[0067] Where: A j is the cross-sectional area of ​​the inspection well node; η j is the current water level of the inspection well node; t is the time; is the inflow flow of the kth pipeline connecting the inspection well node; Q laterin Inbound traffic added for external customization; Q sur is the overflow flow from the underground pipe network inspection well node; δ sur is the Dirichlet function, which takes the value of 1 when the node is in overflow state, -1 when it is in leakage state, and 0 when it is neither overflowing nor leakage state.

[0068] In step 6, the coupling node water head and network water head are obtained and the exchanged flow flux is calculated as:

[0069]

[0070] H1=D1+Z (4)

[0071] H2=D2 (5)

[0072] Where: c0 is the flow coefficient, ranging from [0-1], A is the effective flow area of ​​the inspection well, g represents the acceleration of gravity, H1 and H2 are the average water head of the grid unit and the water head of the inspection well node, D1 represents the surface water depth, D2 is the water depth in the inspection well, and Z is the surface elevation.

[0073] Verification experiment of the method described in the present invention:

[0074] The FVCOM-SWMM coupling method was validated using the physical test data of the interaction between surface water flow and underground pipe network water flow in the publicly published literature (Rubinato, et al. Experimental calibration and validation of sewer / surface flow exchange equations in steady and unsteady flow conditions. Journal of Hydrology, 2017, 552: 421-432.). The model layout diagram is shown in Figure 4 The length and width of the test flume are 8m and 4m respectively, with a slope of 1:1000. There is an open inspection well 2.5m away from the midpoint of the upstream boundary. The size is circular with an inner diameter of 240mm. A circular pipe with an inner diameter of 75mm is connected to the inspection well. The bottom of the flume is 0.478m away from the bottom of the pipe. A head pressure gauge is arranged 480mm upstream from the center of the inspection well. The roughness of the flume is 0.02, and the roughness of the pipe is 0.009. The initial water depth in the flume and the pipe is zero. The numerical model is consistent with the experimental model. In the model simulation, the downstream boundary of the surface water flow and the downstream outlet boundary of the drainage system are free outflow open boundaries, and the upstream is a constant inflow boundary.

[0075] The simulated water depth and interaction flow values ​​at the measuring point can be obtained by calculation and compared with the experimental values ​​in the literature, such as Figure 5-1 and Figure 5-2 As shown in the figure, the simulation values ​​are in good agreement with the experimental values, which verifies the accuracy of the coupling method.

[0076] Although the present invention has been described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can make many improvements and changes without departing from the purpose of the present invention, which are all within the protection of the present invention.

Claims

1. A method for simulating urban floods based on unstructured grid coupling SWMM and FVCOM model, characterized in that: The inspection well simplification method is used to characterize the exchange process of surface water flow and underground pipe network water flow, and the unstructured grid FVCOM model is used as the main program, and the SWMM model is used as a subroutine for the main program to call, so as to perform real-time dynamic two-way data exchange between the surface water dynamic model and the pipe network hydrodynamic model, simulate the coupling effect of underground pipe network water flow and surface water flow, and finally realize the coupled simulation of urban flooding with tortuous coastline or complex building outline based on unstructured grid. The process is as follows: Firstly, the SWMM model and the unstructured grid FVCOM model are used to respectively establish the models of underground pipe network water flow and surface water flow through the given basic data; the spatial topological relationship between the SWMM pipe network nodes and the FVCOM grid is established; at the time step that requires coupling, the pipe network water flow head and the surface water head of the pipe network inspection well node are obtained, the inflow or outflow of the inspection well node in the current time step is determined, and the exchange flow is calculated. The unstructured grid FVCOM model and the SWMM model respectively simulate the surface water and pipe network water flow according to the updated head and flow; time is progressive, and finally the entire urban flood simulation process is completed.

2. The urban flood simulation method according to claim 1, characterized in that: The specific steps include: Step 1, obtaining basic data of the study area, wherein the basic data at least includes the distribution of the drainage network, the ground elevation data of the study area, the location of the inspection well, and the outline of the building; Step 2: Based on the above basic data, the SWMM model and the unstructured grid FVCOM model are used to respectively establish the models of underground pipe network water flow and surface water flow, so as to describe the tortuous coastline or complex building contours; Step 3, read the inp format file generated by the SWMM model, obtain the location coordinates of the SWMM pipe network nodes, and establish a spatial topological relationship with the FVCOM of the surface water flow; Step 4: Based on the SWMM network node water head and the FVCOM surface water flow head, the inspection well simplification method is used to characterize the exchange process between the surface water flow and the underground network water flow; Step 5, using the unstructured grid FVCOM model as the main program and the SWMM model as a subroutine for the main program to call; Step 6, start the model and start calculation; Step 7, at the time step that requires coupling, the two models exchange data to realize dynamic real-time coupling, including: the SWMM model transmits the manhole node water head of the current time step to the unstructured grid FVCOM model, the FVCOM model obtains the coupling node water head and the network water head according to the manhole node water head and the surface water head, and calculates the exchanged flow flux, and then transmits the calculated flow to the SWMM model, thereby realizing the update of the water head and flow; the FVCOM model and the SWMM model simulate the surface water and pipe network water flow respectively according to the updated water head and flow; Step 8: Repeat step 7 at the time step that requires coupling, and finally achieve the simulation of urban flooding with tortuous coastlines or complex building contours.

3. The urban flood simulation method according to claim 1, characterized in that: In step 4, the inspection well simplification method is used to characterize the exchange process between surface water flow and underground pipe network water flow. According to the relationship between the surface water depth D1, the inspection well node head H2, and the surface elevation Z, the interaction between the surface water flow and the underground pipe network water flow includes the following situations: (1) When D1 = 0, if H2 ≤ Z, the interaction state is that the inspection well has neither inflow nor outflow; (2) When D1 = 0, if H2 > Z, the interaction state is outflow from the inspection well; (3) When D1>0, if H2<Z, the interaction state is manhole inflow; (4) When D1>0, if H2=Z, the interaction state is manhole inflow; (5) When D1>0, if H2>Z and H2<Z+D1, the interaction state is manhole inflow; (6) When D1>0, if H2>Z and H2=Z+D1, the interactive state is that the inspection well has neither inflow nor outflow; (7) When D1>0, if H2>Z+D1, the interaction state is outflow from the inspection well.

4. The urban flood simulation method according to claim 1, characterized in that: In step 5, the specific steps of using the unstructured grid FVCOM model as the main program and the SWMM model as a subroutine for the main program to call are as follows: Step 5-1, compare the SWMM network node head and the surface water head, add the mass source term to the continuity equation of the FVCOM model, and the continuity equation after vertical integration is as follows: In formula (1): ζ is the current water level of the control body; is the average flow velocity in the direction of the control volume; is the average flow velocity in the y direction of the control volume; Q sur is the overflow flow from the underground pipe network inspection well node; D is the water depth of the control body; δ sur is the Dirichlet function, where, under the node overflow state, δ sur The value is 1; under the node discharge state, δ sur The value is -1; when the node is neither overflowing nor leaking, δ sur The value is 0; Step 5-2, the flow conservation equation at the node in the SWMM model is as follows: In formula (2): A j is the cross-sectional area of ​​the inspection well node; η j is the current water level of the inspection well node; t is the time; is the inflow flow of the kth pipeline connecting the inspection well node; Q laterin Inbound traffic added for external customization; Q sur is the overflow flow from the underground pipe network inspection well node; δ sur is the Dirichlet function, where, under the node overflow state, δ sur The value is 1; under the node discharge state, δ sur The value is -1; when the node is neither overflowing nor leaking, δ sur The value is 0.

5. The urban flood simulation method according to claim 1, characterized in that: In step 7, the FVCOM model obtains the coupling node head and network head according to the inspection well node head and the surface water head, and calculates the exchange flow flux Q exc for: H1=D1+Z (4) H2=D2 (5) In formula (3) to formula (5), c0 is the flow coefficient, ranging from [0-1], A is the effective flow area of ​​the inspection well, g represents the gravity acceleration, H1 and H2 are the average water head of the grid unit and the water head of the inspection well node, respectively, D1 represents the surface water depth, D2 is the water depth in the inspection well, and Z is the surface elevation.

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