Urban underground space water inflow process simulation method based on virtual connection technology

Abstract

The invention discloses an urban underground space water inflow process simulation method based on a virtual connection technology, and the method comprises the steps: obtaining data of hydro meteorology, ground surface and underground space topography and land utilization of a research region, and carrying out the processing of the data; based on the processed data, constructing a two-dimensional hydrodynamic model of the earth surface and underground integral area of the research area; the method comprises the following steps: initializing a two-dimensional hydrodynamic model, setting the full storage capacity and operation time of an underground space, virtually connecting a surface space and the underground space in the two-dimensional hydrodynamic model, setting boundary conditions of the two-dimensional hydrodynamic model, operating the two-dimensional hydrodynamic model, and judging whether the total water quantity of an underground space region reaches the set full storage capacity or not; and performing calculation and data updating according to the judgment result until the set operation time is reached, and outputting the ponding conditions of the earth surface and the underground space. The problem that an existing large underground space flood routing process is difficult to accurately simulate is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of urban water conservancy numerical simulation methods, and in particular relates to a method for simulating water inflow process in urban underground space based on virtual connection technology. Background Art

[0002] The rapid development of urbanization has changed the composition of urban underlying surfaces and local meteorological conditions. In addition, the rapid changes in the global climate have made urban water security issues more prominent. However, the inconsistency between urban infrastructure construction and the problems brought about by rapid urbanization and climate change has led to an increase in the frequency of flood risk disasters in cities. Accidents of underground garages, underground shopping malls, subway stations and other underground spaces being flooded in major cities at home and abroad are common, which not only causes huge economic losses and social impacts, but also poses a threat to people's lives and property. For example, on October 7, 2007, Hangzhou Huazhe Building was affected by Typhoon Rosa, and the underground garage was flooded, causing economic losses of more than 9 million yuan; the "7.20" heavy rain in Zhengzhou in 2021 caused water inflow to urban underground spaces such as subways and tunnels, causing heavy casualties and property losses. From 1992 to 2003, the London Underground in the UK suffered more than 1,200 flooding incidents, of which one flood alone caused significant losses of 740,000 pounds; in August 2021, Hurricane Ida's heavy rains caused the New York subway system to be completely paralyzed, resulting in huge casualties and property losses.

[0003] The development and utilization of underground space has increasingly become an important indicator of high-level urban development. While it provides convenience for urban life, it also poses great risks. When floods occur in cities, underground space is the first to be affected. In serious cases, it will affect the entire connected area, causing irreparable losses. At present, how to construct an integrated surface-to-underground space hydrodynamic model and accurately simulate the evolution of two-dimensional surface-to-underground space floods has become a major problem. With the rapid development of computer technology and computational fluid dynamics, and the in-depth study of free surface flow problems, the application of numerical simulation methods provides a path to solve the problem of floods in urban underground spaces.

[0004] Early numerical simulations of underground space mostly used generalization methods, generalizing underground space into "reservoirs" and their interconnected channels into pipes to simulate floods; such as the Link-Node method, which generalizes channels, underground tunnels and culverts into links, and underground shopping malls, subways and other underground space facilities into nodes, and uses open channel flow and empirical weir flow formulas to simulate the evolution of underground space floods. Such methods are not only relatively simple and less practical, but also increasingly difficult to adapt to the increasingly complex simulation of underground space. Summary of the invention

[0005] The object of the present invention is to provide a method for simulating the water inflow process of urban underground space based on virtual connection technology, which solves the problem that it is difficult to accurately simulate the flood evolution process of large underground spaces in the prior art.

[0006] The technical solution adopted by the present invention is a method for simulating the water inflow process of urban underground space based on virtual connection technology, which obtains data on hydrometeorology, surface and underground space topography, and land use in the research area, and processes the data; constructs a two-dimensional hydrodynamic model for the overall surface and underground area of the research area based on the processed data; Initializes the two-dimensional hydrodynamic model, sets the full storage volume of the underground space and the operation time, virtually connects the surface space and the underground space in the two-dimensional hydrodynamic model, sets the boundary conditions of the two-dimensional hydrodynamic model, runs the two-dimensional hydrodynamic model and determines whether the total water volume in the underground space area reaches the set full storage volume, and performs calculations and data updates according to the judgment result until the set operation time is reached, and outputs the water accumulation situation on the surface and in the underground space.

[0007] The present invention is further characterized in that, Specifically, it includes the following steps: Step 1, obtain data on hydrometeorology, surface and underground space topography, and land use in the research area; Step 2, construct an integrated surface-underground space topography based on the data obtained in Step 1, and classify the land use of the integrated surface-underground space topography according to the topography of the research area; Step 3, construct a two-dimensional hydrodynamic model for the integrated surface and underground area of the research area based on the classification result in Step 3, initialize the two-dimensional hydrodynamic model, and set the full storage volume of the underground space and the operation time; Step 4, construct a virtual connection boundary to connect the surface space and the underground space in the two-dimensional hydrodynamic model, and set the boundary conditions of the two-dimensional hydrodynamic model; Step 5, determine whether the total water volume in the underground space area reaches the maximum storage volume. If it reaches the maximum storage volume, set the virtual connection boundary as a closed boundary and proceed to the next step; if it does not reach the maximum storage volume, directly proceed to the next step; Step 6, calculate the rainfall and infiltration source terms in the integrated surface and underground area of the two-dimensional hydrodynamic model to obtain the net rainfall in the integrated surface and underground area; Step 7, calculate the Riemann fluxes of water volume and momentum at each unit interface in the integrated surface and underground area through the HLLC approximate Riemann solver; Step 8, calculate the Riemann fluxes of mass and momentum obtained in Step 7 to obtain the final water volume and momentum channels; Step 9: Update the water depth, flow velocity, and momentum of the integrated surface and underground space area based on the net rainfall, water volume, and momentum channels obtained in Step 6 and Step 8; Step 10: Run Step 5 to Step 9 until the running time set in Step 3 is reached, and output the water accumulation situation of the surface and underground space.

[0008] In Step 1, data on hydrometeorology, surface and underground space topography, and land use of the research area are obtained by interpolating measured elevation points or using airborne lidar.

[0009] In Step 2, the construction of the integrated surface-underground space topography specifically involves moving the surface topography and the underground space topography to the same plane without connection, and discretizing the surface and underground topographies into grids of the same resolution so that they are in the same plane; In Step 2, land use classification is divided into roads, green spaces, houses, and underground spaces according to natural attributes, and the Manning coefficient and infiltration rate of each land use type are determined.

[0010] In Step 3, the two-dimensional hydrodynamic model is calculated by the two-dimensional shallow water equations, as shown in the following formula: ; ; where t is time, in seconds; is the variable vector; is the water depth, in meters; q x and q y are respectively x and y the unit-width flow rates in two directions, in m 2 / s; and are respectively x and y the flux vectors in the g is the gravitational acceleration, in m / s 2 ; u and v are respectively x and y the flow velocities in the is the source term vector; i is the infiltration source term; z b is the elevation of the riverbed bottom, in meters; is the Chezy coefficient, , where n is the Manning coefficient.

[0011] In Step 4, the virtual connection boundary is specifically to discretize the terrain grids of the surface and underground space in the two-dimensional hydrodynamic model, divide the grid numbers, and record the numbers of each upper, lower, left, and right grid; according to the specific position of the underground space entrance, determine the topological relationship between the surface terrain and the grid number of the underground space entrance, so that the network number of the underground space entrance corresponds to the surface terrain grid.

[0012] In Step 4, setting the boundary conditions of the two-dimensional hydrodynamic model is specifically that except for the virtual connection area, the boundaries of other areas in the integrated area of the surface and underground space are set as closed boundaries, and the no-slip condition is adopted for the closed boundary treatment, with the normal and tangential velocities being zero.

[0013] In Step 6, the spatial non-uniform rainfall method is used for the calculation of rainfall and infiltration source terms, and no rainfall calculation is performed on the underground space part in the integrated area of the surface and underground space.

[0014] Step 7 is specifically to use the HLLC Riemann solver to calculate the water volume flux and momentum flux on the virtual connection boundary, as shown in the following formula: ; Among them, , , and are the intermediate wave numerical fluxes, and the calculation formulas are as shown below: ; ; Among them, and are the left and right tangential velocity components; 、 and are the left, middle, and right wave speeds respectively.

[0015] In Step 8, the calculation of the Riemann flux of mass and momentum is specifically to perform the treatment of the bottom slope source term and the friction source term, and the bottom slope source term method and the explicit-implicit method are respectively adopted for the treatment of the bottom slope source term and the friction source term.

[0016] The beneficial effects of the present invention are: The method for simulating the water inflow process of urban underground space based on the virtual connection technology of the present invention realizes the calculation of the flood evolution process from the surface to the underground space in the overall area by establishing a virtual connection boundary from the surface to the underground space and directly calculating the flux at the virtual connection grid boundary using the Riemann solver, and finely simulates the calculation of the integrated flood process of the surface and underground space.

[0017] At the same time, virtual connection technology is used to carry out numerical simulation of the integrated flood evolution process of the surface and underground space to meet the needs of actual simulation, realizing a detailed simulation of the flood evolution process of large-scale underground space under various extreme design rainfall conditions, and timely early warning and forecast of underground flood disasters. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a flow chart of a method for simulating water inflow process in an urban underground space based on virtual connection technology of the present invention; Figure 2 is a schematic diagram of the structure of the water tank model of Example 2; Figure 3 is a schematic diagram of the total water volume curve of the simulation results in Example 2; Figure 4 It is the topographic map of the surface and underground garage of Tianfuhe Garden in Example 4; Figure 5 It is a schematic diagram of the water inflow curve of the simulation results of the underground space A and B areas in Example 4. DETAILED DESCRIPTION

[0019] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] Example 1 The method for simulating the water inflow process of urban underground space based on virtual connection technology in the present invention obtains data on hydrological meteorology, surface and underground space topography, and land use in the study area, and processes the data; a two-dimensional hydrodynamic model of the entire surface and underground area of ​​the study area is constructed based on the processed data; Initialize the two-dimensional hydrodynamic model, set the underground space storage capacity and operation time, virtually connect the surface space and underground space in the two-dimensional hydrodynamic model, set the boundary conditions of the two-dimensional hydrodynamic model, run the two-dimensional hydrodynamic model and determine whether the total water volume in the underground space area has reached the set storage capacity, perform calculations and update data based on the determination results until the set operation time is reached, and output the water accumulation conditions of the surface and underground space.

[0021] like Figure 1 As shown, the specific steps include: Step 1: Obtain high-resolution digital elevation data (DEM) of the surface and underground space of the study area by interpolation of measured elevation points or by using unmanned aerial vehicle laser radar, namely, data on hydrological meteorology, surface and underground space topography, and land use; Step 2, constructing the surface-underground space integrated terrain based on the data obtained in step 1, specifically, moving the surface terrain and the underground space terrain to the same plane but not connected, and discretizing the surface and underground terrain into grids of the same resolution so that they are in the same plane.

[0022] According to the terrain conditions of the research area, the integrated surface-underground space terrain is classified for land use. According to natural attributes, it is mainly divided into 4 different land use types: roads, green spaces, houses, and underground spaces. The Manning coefficient and infiltration rate of each land use type are determined.

[0023] Step 3: Based on the classification results in Step 2, construct a two-dimensional hydrodynamic model for the integrated surface-underground area of the research area, initialize the two-dimensional hydrodynamic model, and set the full storage volume and operation time of the underground space. Step 4: Construct a virtual connection boundary to connect the surface space and the underground space in the two-dimensional hydrodynamic model, discretize the terrain grids of the surface and the underground space, divide the grid numbers, and record the numbers of each upper, lower, left, and right grid; according to the specific location of the underground space entrance, determine the topological relationship between the surface terrain grid number and the underground space entrance grid number, so that the network number of the underground space entrance corresponds to the surface terrain grid.

[0024] Set the boundary conditions of the two-dimensional hydrodynamic model. Specifically, except for the virtual connection area, set the boundaries of other areas in the integrated surface-underground area as closed boundaries. The closed boundary treatment adopts the no-slip condition, and the normal and tangential velocities are zero.

[0025] Step 5: Judge whether the total water volume in the underground space area reaches the maximum water storage capacity. If it reaches the maximum water storage capacity, set the virtual connection boundary as a closed boundary and enter the next step; if it does not reach the maximum water storage capacity, directly enter the next step. Step 6: Use the spatially non-uniform rainfall method to calculate the rainfall and infiltration source terms for the integrated surface-underground area in the two-dimensional hydrodynamic model, and obtain the net rainfall in the integrated surface-underground area; no rainfall calculation is performed on the underground space part in the integrated surface-underground area.

[0026] Step 7: Calculate the Riemann fluxes of water volume and momentum at each unit interface in the integrated surface-underground area through the HLLC approximate Riemann solver. Step 8: Process the bottom slope source term and friction source term for the Riemann fluxes of mass and momentum obtained in Step 7. Specifically, the bottom slope source term method and the explicit-implicit method are used for the bottom slope source term and friction source term processing respectively to obtain the final water volume and momentum channels.

[0027] Step 9: Update the water depth, flow velocity, and momentum of the integrated surface-underground area based on the net rainfall, water volume, and momentum channels obtained in Step 6 and Step 8. Step 10: Run Steps 5 to 9 until the operation time set in Step 3 is reached, and output the water accumulation situation of the surface and the underground space.

[0028] Example 2 AsFigure 2 As shown, it consists of two ideal water tanks. The concave water tank is 300 m long, 175 m wide in total, with slopes of 15° on both sides, and a surface area of 210,000 m 2 ; The flat water tank is 150 m long and 25 m wide, with a surface area of 15,000 m 2 , the Manning roughness coefficient is 0.014, and the grid size is 2 m.

[0029] For the working condition simulation, the right outlet of the concave water tank and the left inlet of the flat water tank are connected by a virtual boundary. The rainfall time is set to 2 h, the rainfall intensity is 10 mm / h, the infiltration of each part is 0, and rainfall only occurs on the concave water tank. The simulation duration is 5 h, and theoretically, 4200 m 3 of water volume is generated.

[0030] This embodiment mainly tests the water volume balance of the virtual connection boundary. Through simulation, the water flows converge at the bottoms of the two tanks respectively, and the total water volume process is as Figure 3 . Finally, the total water volume in the two water tanks is statistically 4200 m 3 , which is the same as the theoretical value, indicating that the water volume of the virtual connection boundary has good conservation.

[0031] Embodiment 3 On the basis of Embodiment 1, in the method for simulating the urban underground space water intake process based on the virtual connection technology of the present invention, the two-dimensional hydrodynamic model solves the two-dimensional shallow water equations (abbreviated as SWEs), ignoring the kinematic viscosity term, turbulent viscosity term, wind stress, and Coriolis force. The two-dimensional shallow water equations are shown as the following formulas: ; ; where t is time, with the unit of s; is the variable vector; is the water depth, with the unit of m; q x and q y are respectively x and y the unit-width discharges in the two directions, with the unit of m 2 / s; and are respectively x and y the flux vectors in the g direction; 2 is the gravitational acceleration, with the unit of m / s u and v are respectively x and y the flow velocities in the direction, with the unit of m / s; iis the infiltration source term; z b is the riverbed bottom elevation, in m; is Xie Cai coefficient, ,in n is the Manning coefficient.

[0032] The two-dimensional hydrodynamic model of the present invention uses a dynamic wave method to simulate the flood evolution process and adopts a finite volume method in a Godunov format to perform spatial discretization to solve the two-dimensional shallow water equation.

[0033] Step 7 specifically uses the Godunov type HLLC Riemann solver to calculate the water flux and momentum flux on the virtual connection boundary to deal with the rapid flow and discontinuity problems, as shown in the following formula: ; in, , , and is the intermediate wave numerical flux, and the calculation formula is as follows: ; ; in, and is the left and right shear velocity component; , and They are left, center and right wave speeds respectively.

[0034] Example 4 Tianfuheyuan was selected as the research area. The community has complete surface and underground garage digital elevation (DEM) data, such as Figure 4 As shown, the surface area is 6.72hm 2 The underground garage area is 5.89hm 2 , where the elevation of area B is 0.2m higher than that of area A.

[0035] The underlying surface attributes of the terrain include roads, green spaces, and roofs. The stable infiltration rate of green spaces is 2.65 mm / h, and the stable infiltration rates of roads and roofs are 0. The Manning coefficients of roads, green spaces, and roofs are 0.015, 0.06, and 0.014, respectively. The stable infiltration rate of underground space is set to 0, and the Manning coefficient is set to 0.015.

[0036] The rainfall data used was the “July 20” rainstorm in Zhengzhou, and the simulation lasted for 32 hours. In the model, the surface underground garage entrance and the underground garage were connected using a virtual connection, and the water volume threshold was set according to the volume of the underground garage. The evolution of underground space floods was simulated in detail. The water inflow process of areas A and B is shown in the figure. Figure 5As shown, according to the simulation results, water starts to enter Area A of the underground garage in the community 1 hour after rainfall, and Area B starts to get waterlogged 4 hours later. The waterlogging process increases with the increase in rainfall, and the increasing trend changes with the change in rainfall, which is in line with the actual situation. The total water inflow into the community garage reaches the peak value of 36,104 m 3 .

Claims

1. A method for simulating water inflow in urban underground space based on virtual connection technology, characterized in that: Obtain data on hydrology and meteorology, surface and underground topography, and land use in the study area, and process the data; construct a two-dimensional hydrodynamic model of the entire surface and underground area of ​​the study area based on the processed data; Initialize the two-dimensional hydrodynamic model, set the underground space storage capacity and operation time, virtually connect the surface space and underground space in the two-dimensional hydrodynamic model, set the boundary conditions of the two-dimensional hydrodynamic model, run the two-dimensional hydrodynamic model and determine whether the total water volume in the underground space area has reached the set storage capacity, perform calculations and update data based on the determination results until the set operation time is reached, and output the water accumulation conditions of the surface and underground space.

2. The method for simulating water inflow in urban underground space based on virtual connection technology according to claim 1 is characterized in that: The specific steps include: Step 1: Obtain data on hydrology and meteorology, surface and underground topography, and land use in the study area; Step 2: construct the surface-underground space integrated terrain based on the data obtained in step 1, and classify the land use of the surface-underground space integrated terrain according to the terrain conditions of the study area; Step 3, based on the classification results of step 3, construct a two-dimensional hydrodynamic model of the surface and underground integrated area of ​​the study area, initialize the two-dimensional hydrodynamic model, and set the underground space storage capacity and operation time; Step 4, constructing a virtual connection boundary to connect the surface space and the underground space in the two-dimensional hydrodynamic model, and setting the boundary conditions of the two-dimensional hydrodynamic model; Step 5, determine whether the total water volume in the underground space area reaches the maximum water storage volume. If the maximum water storage volume is reached, set the virtual connection boundary as a closed boundary and proceed to the next step; If the maximum water storage capacity has not been reached, go directly to the next step; Step 6, calculating rainfall and infiltration source terms in the integrated area of ​​the surface and underground space in the two-dimensional hydrodynamic model to obtain the net rainfall in the integrated area of ​​the surface and underground space; Step 7, using the HLLC approximate Riemann solver to calculate the Riemann flux of water and momentum at each unit interface in the integrated area of ​​the surface and underground space; Step 8, calculating the Riemann flux of mass and momentum obtained in step 7 to obtain the final water volume and momentum channel; Step 9, updating the water depth, flow velocity, and momentum of the integrated area of ​​the surface and underground space based on the net rainfall, water volume, and momentum channels obtained in steps 6 and 8; Step 10, run steps 5 to 9 until the running time set in step 3 is reached, and output the water accumulation conditions on the surface and underground space.

3. The method for simulating water inflow in urban underground space based on virtual connection technology according to claim 2 is characterized in that: In step 1, the data on hydrology and meteorology, surface and underground topography, and land use of the study area are obtained by interpolation of measured elevation points or by drone-mounted lidar.

4. The method for simulating water inflow in urban underground space based on virtual connection technology according to claim 2 is characterized in that: In step 2, the construction of the integrated surface-underground space terrain is specifically to move the surface terrain and the underground space terrain to the same plane but not connected, and discretize the surface and underground terrain into grids of the same resolution so that they are in the same plane; The land use classification described in step 2 is divided into roads, green spaces, houses, and underground spaces according to natural attributes, and the Manning coefficient and infiltration rate of each land use type are determined.

5. The method for simulating water inflow in urban underground space based on virtual connection technology according to claim 2 is characterized in that: The two-dimensional hydrodynamic model in step 3 is calculated by the two-dimensional shallow water equation, as shown in the following formula: ； ； Where, t is time, unit is s; is a variable vector; is the water depth in m; q x and q y They are x and y Single-width flow in both directions, in m 2 / s; and They are x and y Flux vector in direction; g is the acceleration due to gravity, in m / s 2 ; u and v They are x and y Flow velocity in direction, in m / s; is the source term vector; i is the infiltration source term; z b is the riverbed bottom elevation, in m; is Xie Cai coefficient, ,in n is the Manning coefficient.

6. The method for simulating water inflow in urban underground space based on virtual connection technology according to claim 2 is characterized in that: The virtual connection boundary in step 4 is specifically to discretize the surface and underground space terrain grids in the two-dimensional hydrodynamic model, divide the grid numbers, and record the numbers of each upper, lower, left and right grid; according to the specific location of the underground space entrance, determine the topological relationship between the surface terrain and the underground space entrance grid number, so that the network number of the underground space entrance corresponds to the surface terrain grid.

7. The method for simulating water inflow in urban underground space based on virtual connection technology according to claim 2 is characterized in that: In step 4, the boundary conditions of the two-dimensional hydrodynamic model are set as follows: except for the virtual connection area, the boundaries of other areas in the integrated area of ​​the surface and underground space are set as closed boundaries. The closed boundary treatment adopts the no-slip condition, and the normal and tangential velocities are zero.

8. The method for simulating water inflow in urban underground space based on virtual connection technology according to claim 2 is characterized in that: In step 6, the spatial non-uniform rainfall method is used to calculate rainfall and infiltration source items, and rainfall calculation is not performed on the underground space in the integrated area of ​​the surface and underground space.

9. The method for simulating water inflow in urban underground space based on virtual connection technology according to claim 2 is characterized in that: Step 7 specifically uses the HLLC Riemann solver to calculate the water flux and momentum flux on the virtual connection boundary, as shown in the following formula: ； in, , , and is the intermediate wave numerical flux, and the calculation formula is as follows: ； ； in, and is the left and right shear velocity component; , and They are left, center and right wave speeds respectively.

10. The method for simulating water inflow in urban underground space based on virtual connection technology according to claim 2 is characterized in that: The calculation of the Riemann flux of mass and momentum in step 8 specifically involves processing the bottom slope source term and the friction source term, wherein the bottom slope source term and the friction source term are processed using the bottom slope source term method and the explicit and implicit method, respectively.

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