Urban surface and underground space flood simulation method based on hydrodynamic model

Abstract

The invention provides an urban surface and underground space flood simulation method based on a hydrodynamic model, and belongs to the technical field of urban flood disaster prevention and control and hydrological hydraulic engineering. The method comprises the steps of urban surface and underground space generalization processing, model element coupling association establishment, model element algorithm setting and model result calibration verification. The model established by the method has high-performance and high-precision computing power, can efficiently and accurately simulate the flowing form of flood in the urban complex underground space, and provides support for urban flood early warning.

Description

Technical Field

[0001] This invention belongs to the field of urban flood disaster prevention and control and hydrological and water conservancy engineering technology, and specifically relates to a method for simulating urban surface and underground space floods based on a hydrodynamic model. Background Technology

[0002] Against the backdrop of global warming and continuous urbanization, urban underlying surfaces are becoming increasingly complex and runoff generation and drainage processes are becoming distorted. The generation, evolution, and receding speeds of urban floods are accelerating significantly, leading to a marked increase in the difficulty of accurate and rapid simulation. Exploring methods for accurate simulation and rapid early warning and forecasting of urban flood disasters can effectively guide disaster prevention and emergency management, thereby mitigating the losses caused by floods. This has become a hot topic in hydrology, hydrodynamics, and hazard science.

[0003] Urban flood simulation is a crucial method for urban flood prevention and mitigation. The accuracy, breadth, and depth of simulation methods directly impact its application in this field. Current urban flood simulation and early warning systems suffer from problems such as insufficient accuracy in early warnings, overemphasis on above-ground aspects while neglecting underground ones, difficulties in simulating complex underground structures, and low computational efficiency. While there has been considerable research both domestically and internationally on surface two-dimensional, river, and drainage network simulation technologies, underground space flood simulation remains in a relatively early stage. Simulation methods for local structures often rely on coarse statistical calculations of underground flood flow changes, lacking systematic and refined methods for simulating underground flooding.

[0004] Against the backdrop of frequent urban flooding, the water conservancy industry has placed higher demands on the computational accuracy and efficiency of flood models. Numerical calculation models that can accurately and efficiently simulate floods in complex urban underlying surfaces and surface and underground spaces can improve the simulation and early warning level of urban surface and underground flooding, enhance the scientific nature of urban flood response decisions and flood disaster reduction capabilities, mitigate the impact of flood disasters on the socio-economic situation, and provide technical support for establishing an urban flood safety guarantee system.

[0005] Therefore, developing a method that can achieve high-precision and high-efficiency integrated simulation of urban surface and underground floods, solving the technical challenges of simulating floods in complex underground spaces, and improving the overall simulation and early warning capabilities of urban floods are urgent technical problems that need to be solved in this field. Summary of the Invention

[0006] To overcome the problems of existing technologies, this invention proposes a method for simulating urban surface and underground floods based on a hydrodynamic model. This method effectively solves the technical problems of existing urban flood simulations that emphasize surface flooding while neglecting underground flooding, making it difficult to simulate complex underground spaces, balancing computational accuracy and efficiency, and resulting in insufficient early warning accuracy.

[0007] The objective of this invention is achieved as follows:

[0008] This invention provides a method for simulating urban surface and underground flooding based on a hydrodynamic model, comprising the following steps:

[0009] Step 1, Generalization of urban surface and underground space:

[0010] We collect basic data including surface topography, underlying surface type, drainage network, urban river system, and underground space topography. Based on the spatial scale, spatial location, and flood movement characteristics of the study area, we generalize the urban surface and underground real space into model elements including one-dimensional space, two-dimensional space, zero-dimensional space, and connecting nodes.

[0011] Step 2, Establish coupling relationships between model elements

[0012] Based on the connectivity of each layer of space in the study area, and according to the spatial relative positions of each model element, the coupling calculation relationship between each model element is established.

[0013] The coupling methods are divided into two categories: vertical coupling uses connecting nodes to couple the upper and lower spaces, and planar coupling uses boundary conditions to calculate the water flow motion at adjacent points in the same space.

[0014] Step 3, Model Feature Algorithm Settings

[0015] For different model elements, configure matching internal flood calculation equations, and configure corresponding coupling calculation algorithms for coupling elements and coupling boundaries; combine the model elements in step 1 with the coupling relationship in step 2 to construct an integrated flood simulation model.

[0016] Step 4, Model Result Calibration and Validation

[0017] Based on monitoring data or survey information including rainfall, water level, and water depth in the surface and underground spaces, the parameters of the constructed integrated flood simulation model are calibrated and the results are verified.

[0018] Furthermore, in step 1, the one-dimensional space is a space with long channel characteristics and internal flood flow characteristics of open channel flow or pipeline flow; the two-dimensional space is a space with obvious planar characteristics and internal flood flow direction is planar; the zero-dimensional space is a space with small size and small difference in water depth at various points inside.

[0019] Furthermore, in step 2, the connectivity relationships of the various spatial layers include:

[0020] (a) indicates the connection between the canal and both banks, (b) the connection between the inlet and outlet of the pipeline network, (c) the connection between the upper and lower steps, and (d) the connection between the doors and windows of the enclosed space; among them, the calculation of (a) / (b) / (d) uses the coupled boundary, and the calculation of (c) uses the connecting node element. The flow transmission of the connecting node is only realized through a fixed position, while the flow transmission of the coupled boundary is realized at any contact position in the adjacent space. Moreover, the calculation of the coupled boundary needs to take into account the changes in water level and flow velocity in the two spaces at the same time.

[0021] Furthermore, in step 3, the internal flood calculation equations for the one-dimensional space, two-dimensional space, and zero-dimensional space are the Saint-Venant equation, the shallow water equation, and the reservoir equation, respectively; the coupled calculation algorithm for the vertical connection node is the stepped flow model, and the coupled calculation algorithm for the planar coupled boundary is the weir flow model.

[0022] Furthermore, in step 4, the parameters involved in model calibration include confluence parameters and inflow / outflow boundary conditions, wherein the confluence parameter is roughness; the calculation conditions for model calibration and verification include: selecting measured data from rain gauge stations as rainfall input based on the principle of closest spatial distance, finely adjusting the terrain conditions based on survey data, using the surveyed flood level as the lower boundary condition of the drainage channel hydrodynamic model, and using the water level-discharge relationship of typical cross sections as the lower boundary condition of the hydrodynamic model.

[0023] The advantages and beneficial effects of this invention are:

[0024] 1. The method described in this invention realizes integrated flood simulation of urban surface and underground spaces. Through unified model element generalization and spatial coupling processing, it accurately restores the interactive flow and propagation process of floods in multiple layers of surface and underground spaces, filling the technical gap in flood inundation simulation of complex underground spaces.

[0025] 2. This invention balances high accuracy and high efficiency in simulation. It matches corresponding hydrodynamic algorithms according to the characteristics of different model elements and sets exclusive calculation rules for vertical and planar coupling scenarios. This not only achieves refined simulation of complex underlying surfaces and underground structures, but also avoids redundant calculations, thus meeting the engineering needs of rapid early warning of urban flooding.

[0026] 3. The model of this invention has strong practicality and adaptability. It is based on actual basic data for modeling. After calibration and verification with monitoring data, the water volume error is controllable. The calculation results are highly consistent with the actual working conditions. It can be flexibly adapted to the spatial structure characteristics of different cities. The simulation results can provide accurate support for urban flood early warning and emergency management.

[0027] 4. The modeling steps of the method described in this invention are standardized and highly operable. The process logic of spatial generalization, element coupling, algorithm matching, and calibration verification is clear, which is convenient for those skilled in the art to implement. It is conducive to its application in urban disaster prevention and mitigation, water conservancy projects and other fields, effectively improving the city's flood disaster reduction capabilities and providing technical support for building an urban flood safety guarantee system. Attached Figure Description

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] Figure 1 This is a flowchart of the calculation process for the urban surface and underground space flood simulation method based on a hydrodynamic model as described in this invention.

[0030] Figure 2 This is a schematic diagram of the model mesh and connection elements in an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of the model space layering in an embodiment of the present invention;

[0032] Figure 4 This is a spatial distribution map of water depth calculated by flood simulation in the study area in this embodiment of the invention;

[0033] Figure 5 This is a comparison chart of the model calculation results and monitoring data in an embodiment of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments disclosed herein will be described in further detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0035] Example:

[0036] This embodiment takes an urban area including an upper-level parking lot, the surface (including drainage channels), and underground tunnels as the research area (e.g., Figure 2 , Figure 3 As shown in the figure, a method for simulating urban surface and underground flooding based on a hydrodynamic model is presented, such as... Figure 1 As shown, it includes the following steps:

[0037] Step 1, Generalization of urban surface and underground space:

[0038] Collect basic data such as surface topography, underlying surface type, drainage network, urban river system, and underground space topography. Based on the spatial scale, spatial location, and flood movement characteristics of the study area, divide the real space of the study area into different types of model elements, including one-dimensional space, two-dimensional space, zero-dimensional space, and connecting nodes.

[0039] Specifically, the study area is divided into spatial types such as surface plane, surface channels, underground drainage networks, large underground passages (such as subway tunnels), large underground spaces (such as parking lots), and small underground spaces (such as basements). Spaces with long passage characteristics and internal flood flow characteristics of open channel flow or pipe network flow are classified as one-dimensional spatial elements; spaces with obvious planar characteristics and internal flood flow direction with planar characteristics are classified as two-dimensional spatial elements; and spaces with small dimensions (such as small basements of 5-20 cm²) are classified as two-dimensional spatial elements. The characteristics of very small differences in water depth at various internal points (1~5 cm) are classified as zero-dimensional spatial elements. The dimensions of underground space are the basis for spatial classification and need to be determined based on design data or site survey data.

[0040] In this embodiment, as Figure 2 , Figure 3 As shown, the surface drainage channel is divided into a one-dimensional space for calculating flood movement within the channel; the upper parking lot, surface plane, and underground tunnel are divided into two-dimensional spaces for calculating planar flood flow; small underground ancillary spaces within the modeling area are divided into zero-dimensional spaces; and the connecting stairs between the upper parking lot and the surface, and the subway entrances / connecting points between the surface and the underground tunnel are defined as connection nodes, serving as core elements for vertical coupling. Simultaneously, in the parameter settings for the two-dimensional and zero-dimensional model elements of the underground space, a vertical dimension upper limit parameter is added to adapt to the limited water storage capacity of the underground space.

[0041] Step 2, Establish coupling relationships between model elements

[0042] Combination Figure 2 The model space hierarchical structure of the study area shown, Figure 3 Based on the distribution of the model mesh and connecting elements, and according to the connectivity relationships of each layer of space in the study area (step connectivity, tunnel entrance connectivity, and flood discharge channel connectivity with both banks), and the spatial relative positions of each model element, the coupling calculation relationship between each model element is established.

[0043] Coupling methods are divided into two categories. Vertical coupling uses connection nodes to couple upper and lower spaces, i.e., between the upper parking lot and the ground surface, or between the ground surface and the underground tunnel. A coupling calculation relationship for flood transmission is established through pre-set connection nodes, and the flow is transmitted only through these fixed nodes. Planar coupling uses boundary conditions to calculate the water flow movement at adjacent points in the same space, i.e., between adjacent areas on the ground plane. A coupling calculation relationship for flood flow is established through coupling boundaries (e.g., ...). Figure 3 (The coupling boundary) allows flow to be transmitted at any contact point in adjacent spaces, and the calculation of the coupling boundary synchronously references the changes in water level and flow velocity on both sides.

[0044] The above method completes the overall coupling of the three-layer spatial model elements in the modeling area, such as... Figure 3As shown.

[0045] Step 3, Model Feature Algorithm Settings

[0046] For different model elements, configure matching internal flood calculation equations, and configure corresponding coupling calculation algorithms for coupling elements and coupling boundaries; combine the model elements in step 1 with the coupling relationship in step 2 to construct an integrated flood simulation model.

[0047] The equation for calculating internal floods in one-dimensional space (surface drainage channels) is the Saint-Venant equation:

[0048]

[0049]

[0050] In the formula, Flow rate at cross-section; It is the cross-sectional area; The width of the cross section; This refers to the water level at the cross-section. It is the acceleration due to gravity; It is a side inflow; This is the component of the lateral inflow velocity in the direction of water flow, which is generally approximately zero; The flow modulus reflects the actual flow capacity of the river channel. t is the momentum correction coefficient, which reflects the uniformity of the flow velocity distribution across the river cross section; t is time, and x is the spatial coordinate along the direction of water flow.

[0051] The internal flood calculation equation for a two-dimensional space (upper parking level, ground surface, underground tunnel) is the shallow water equation:

[0052]

[0053]

[0054]

[0055] In the formula, Let t be the water depth and t be the time. for Flow velocity in the direction; for Flow velocity in the direction; The atmospheric pressure at the water surface; The elevation of the bottom of the bed surface; , The force of wind load, , For the Coriolis force of geotransformation, It is the acceleration due to gravity. This represents the density of the water.

[0056] The equation for calculating internal floods in zero-dimensional space is the reservoir equation:

[0057]

[0058]

[0059] In the formula, A is the bottom area of ​​the reservoir, h is the water depth, and t is time. The inflow rate is the flow rate between adjacent planar spaces. The inflow rate in the vertical space; Let L be the cross-sectional area between adjacent planar spaces, L be the distance between adjacent spaces, and Q be the inflow rate between adjacent planar spaces. The difference in water level between adjacent spaces in a plane. This is the momentum correction factor, which is usually related to the Manning coefficient.

[0060] The coupling calculation algorithm for vertical connection nodes is a stepped flow model, and the formula for the stepped flow model is derived from the three basic equations describing open channel flow:

[0061]

[0062] In the formula, E is the mechanical energy per unit weight of water across the cross-section, h is the water depth, v is the average flow velocity across the cross-section, and E s It refers to the cross-sectional specific energy, where A is the cross-sectional area of ​​the water passage and B is the cross-sectional width of the water passage. Still water is deep. The critical water depth, This is the kinetic energy correction factor. This is the acceleration due to gravity.

[0063] The coupling calculation algorithm for the planar coupled boundary is based on the weir flow model:

[0064]

[0065] In the formula, Q is the flow rate, B is the width of the weir crest, and h is the head of water above the weir. denoted as the weir flow coefficient, and g is the acceleration due to gravity.

[0066] Step 4, Model Result Calibration and Validation

[0067] Based on monitoring data or survey information, including rainfall and water levels in the surface and underground spaces, the parameters of the constructed integrated flood simulation model are calibrated and the results are verified.

[0068] Specifically, measured rainfall data from rain gauges near the study area were selected as rainfall input. Based on the survey data, the topographic conditions such as retaining walls and water-blocking heights within the modeling area were finely adjusted. The surveyed flood level was used as the lower boundary condition of the hydrodynamic model of the surface drainage channel (one-dimensional space). The confluence parameters (roughness) and inflow / outflow boundary conditions were selected as core calibration parameters, and simulation calculations were carried out using heavy rain conditions.

[0069] The model calculation results were compared with the measured water depth data at key locations such as the water ingress point of the subway tunnel in the modeling area. Figure 4 The results showed that the simulated water depth at monitoring point 1 was 1.3m, while the actual water depth in the field was 1.2m; the simulated water depth at monitoring point 2 was 1.05m, while the actual water depth in the field was 1.0m. The model water volume error was controlled within 10%, and the spatial distribution of the simulated water depth highly matched the actual survey results (e.g., ...). Figure 4 (Water depth classification distribution).

[0070] This implementation case, in conjunction with the appendix Figure 1-4 Flood simulations were successfully completed across multiple surface and underground spaces in the modeled area, accurately recreating the cross-spatial propagation and interactive flow of floodwater between the upper parking lot, the surface, and underground tunnels, thus verifying the accuracy and efficiency of the method proposed in this invention. The model constructed using this method can accurately simulate flood flow patterns on complex urban underlying surfaces. The simulation results can provide scientific numerical support for flood early warning and emergency response in the modeled area. Furthermore, the modeling process is standardized and highly operable, and can be widely applied to various urban surface and underground flood simulation scenarios.

[0071] Finally, it should be noted that the above is only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention (such as the application of various formulas, the order of steps, etc.) without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for simulating urban surface and underground flooding based on a hydrodynamic model, characterized in that, The method includes the following steps: Step 1, Generalization of urban surface and underground space: Collect basic data including surface topography, underlying surface type, drainage network, urban river system, and underground space topography. Based on the spatial scale, spatial location, and flood movement characteristics of the study area, the urban surface and underground real space are generalized into model elements including one-dimensional space, two-dimensional space, zero-dimensional space, and connecting nodes. Step 2, Establish coupling relationships between model elements Based on the connectivity of each layer of space in the study area, and according to the spatial relative positions of each model element, the coupling calculation relationship between each model element is established. Coupling methods are divided into two categories: vertical coupling uses connecting nodes to couple the upper and lower spaces, and planar coupling uses boundary conditions to calculate the water flow motion at adjacent points in the same space. Step 3, Model Feature Algorithm Settings For different model elements, configure matching internal flood calculation equations, and configure corresponding coupling calculation algorithms for coupling elements and coupling boundaries; combine the model elements in step 1 with the coupling relationship in step 2 to construct an integrated flood simulation model; Step 4, Model Result Calibration and Validation Based on monitoring data or survey information including rainfall, water level, and water depth in the surface and underground spaces, the parameters of the constructed integrated flood simulation model are calibrated and the results are verified.

2. The method for simulating urban surface and underground space flooding based on a hydrodynamic model according to claim 1, characterized in that, In step 1, the one-dimensional space is a space with long channel characteristics and internal flood flow characteristics of open channel flow or pipeline flow; the two-dimensional space is a space with obvious planar characteristics and internal flood flow direction is planar; the zero-dimensional space is a space with small size and small difference in water depth at various points inside.

3. The method for simulating urban surface and underground space flooding based on a hydrodynamic model according to claim 1, characterized in that, In step 2, the connectivity relationships of the various spatial layers include: (a) indicates the connection between the canal and both banks, (b) the connection between the inlet and outlet of the pipeline network, (c) the connection between the upper and lower steps, and (d) the connection between the doors and windows of the enclosed space; among them, the calculation of (a) / (b) / (d) uses the coupled boundary, and the calculation of (c) uses the connecting node element. The flow transmission of the connecting node is only realized through a fixed position, while the flow transmission of the coupled boundary is realized at any contact position in the adjacent space. Moreover, the calculation of the coupled boundary needs to take into account the changes in water level and flow velocity in the two spaces at the same time.

4. The method for simulating urban surface and underground space flooding based on a hydrodynamic model according to claim 1, characterized in that, In step 3, the internal flood calculation equations for the one-dimensional space, two-dimensional space, and zero-dimensional space are the Saint-Venant equation, the shallow water equation, and the reservoir equation, respectively; the coupled calculation algorithm for the vertical connection node is the stepped flow model, and the coupled calculation algorithm for the planar coupled boundary is the weir flow model.

5. The method for simulating urban surface and underground space flooding based on a hydrodynamic model according to claim 1, characterized in that, In step 4, the parameters involved in model calibration include confluence parameters and inflow / outflow boundary conditions, wherein the confluence parameter is roughness. The calculation conditions for model calibration and verification include: selecting measured data from rain gauge stations as rainfall input based on the principle of closest spatial distance; refining the terrain conditions based on survey data; using the surveyed flood level as the lower boundary condition of the drainage channel hydrodynamic model; and using the water level-discharge relationship of typical cross sections as the lower boundary condition of the hydrodynamic model.

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