CN110991822A - Three-dimensional hydrodynamic numerical simulation method based on oblique image modeling - Google Patents
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Abstract
The invention belongs to the field of urban flood disaster prevention and reduction, and discloses a three-dimensional hydrodynamic numerical simulation method based on oblique image modeling, which comprises the following steps of: 1) based on multi-view image data automatic modeling, a Geographic Information System (GIS) and a Building Information Model (BIM) are fused to construct a three-dimensional digital city model; 2) constructing a three-dimensional hydrodynamic model on the basis of the model, and applying boundary conditions and initial conditions to the numerical model according to historical disaster statistical data to realize high-precision flood routing numerical simulation in an urban range; 3) carrying out refined urban flood numerical simulation; 4) and carrying out flood risk analysis. According to the flood routing process in the city and the flood routing process in the building, the method can accurately reproduce the formation mechanism of the urban flood waterlogging, so that a basis is provided for disaster prevention and reduction.
Description
Technical Field
The invention belongs to the technical field of urban flood simulation numerical simulation, relates to process simulation of urban waterlogging formation after a coastal city encounters strong storm surge, and particularly relates to a three-dimensional hydrodynamic numerical simulation method based on oblique image modeling.
Background
Storm tides induced by extreme atmospheric disturbances expose coastal cities to flood disasters, especially when they are superimposed with astronomical tides, can cause a large amount of flood to flood over the dykes and flood into coastal cities. Flood incursions cause severe losses to local economies. The urban flood routing numerical simulation determines boundary conditions according to historical disaster statistical data, identifies flood routing paths according to topographic relief conditions, solves variable spatial distribution of each instantaneous flow field, analyzes flood waterlogging risks of coastal cities, and is important for preventing and reducing flood and observing cities.
The early research estimates flood risks according to historical disaster statistical information, omits the internal building structure and the water flow dynamics characteristics of the city, and has obvious defects in the application of the fast-changing city. Due to climate change and rapid urbanization, flooding becomes more and more frequent, the loss caused by the flooding and the influence of the flood on the society are increasing, and it is increasingly difficult to evaluate urban waterlogging by using historical disaster statistical information. In recent years, the numerical simulation of urban flood based on hydrodynamic models is becoming more mature, and becomes an important auxiliary tool for urban flood risk assessment. Demirkesen and the like are combined with GIS and DEM raster data, an intelligent algorithm is adopted to solve flood paths, urban flood flooding conditions are analyzed, flood risk maps in different recurrence periods are drawn, and support is provided for urban flood control risk control and decision-making. YIn and the like construct a high-resolution two-dimensional hydrodynamic model based on radar precipitation data to carry out urban flood analysis and vulnerability assessment. The flood evolution process under the real terrain can simulate the actual flooding process, thereby providing reference for flood control and disaster reduction and developing rapidly. Liang utilizes TVD-MacCormac and Standard MacCormac to solve the two-dimensional shallow water equation, and simulates the flood submerging process of urban areas by coupling actual terrains and buildings, thereby providing a design basis for upgrading and transforming cities. Sandra et al simulate the propagation process of water flow in an idealized city after an instantaneous dam break by using a finite volume method, respectively perform numerical simulation and physical model experiments by using two building layout modes, and capture complete water depth, flow velocity and pressure information in a flow field, thereby providing reference for the verification of a flood evolution model of a complex model. The Hubbard establishes a five-level analysis model of the vulnerability of the structure based on the terrain, flood submergence, building position, foundation elevation and road, applies historical flood to the campus to research the vulnerability of the building under extreme flood disasters, and makes emergency evacuation measures according to the calculation result. Bernhard Gems utilizes flow 3d to reproduce the submerging process in the waterfront building based on actual terrain, and makes flood risk analysis, evaluation and emergency measures, thereby reducing life and property loss to the maximum extent. The flood routing numerical simulation is essentially a three-dimensional process, three-dimensional flood numerical simulation needs to be carried out based on the fluctuation change characteristics of real landform, and the simulation result can really guide practice and the smooth operation of disaster prevention and reduction.
In summary, the problems of the prior art are as follows:
1) the two-dimensional hydrodynamic numerical simulation is used for solving the urban flood evolution process based on a shallow water equation, neglects vertical flow velocity gradient change and adopts hydrostatic pressure to approximate urban pressure spatial distribution, is suitable for a water area with an open water surface, the horizontal dimension of the two-dimensional hydrodynamic numerical simulation is far larger than the vertical dimension, and the flow velocity is far smaller than the size and the change of the flow velocity in the vertical direction and the change of the flow velocity in the horizontal direction, so that the flow velocity in the vertical direction is represented by the average value of the flow velocity in the water depth. Therefore, in the urban range of variable terrain, dense building distribution and criss-cross streets, the accuracy of the calculation result is not high, and the practicability is not strong.
2) The fine landform has decisive influence on the water flow motion state, but the existing research does not pay enough attention to the landform data and does not bring the complete landform and landform into the calculation range, so that the simulation and the actual condition are disjointed, and the application of numerical simulation is restricted.
At present, researches for accurately showing flood dynamic processes in an urban area are few, and researches for applying an oblique photogrammetry technology to urban flood numerical simulation and solving a water flow process inside a building are few and few, so far, the method is not reported in the aspect in domestic and foreign documents, and is pioneering and challenging.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, and provides a city three-dimensional hydrodynamic numerical simulation based on oblique image modeling, a true three-dimensional digital city model is constructed on the basis of a city model created by oblique photography by combining BIM and GIS technologies, and the true three-dimensional digital city model has complete building space distribution information, complete street distribution and other landform and geomorphic details, so that high-precision flood numerical simulation is realized, the arrangement of coastal city disaster prevention and reduction projects is optimized, and the smooth development of emergency rescue measures is optimized.
The technical problem to be solved by the invention is realized by the following technical scheme:
a three-dimensional hydrodynamic force numerical simulation method based on oblique image modeling is characterized by comprising the following steps: the simulation method comprises the following steps:
1) building a three-dimensional digital city model based on oblique image modeling and combining technologies such as a building information model and a geographic information system;
2) according to historical disaster situation statistical data, combining with the landform and landform to apply boundary conditions and initial conditions which are in line with the reality for the digital city model;
3) carrying out refined urban flood numerical simulation, wherein the refined urban flood numerical simulation comprises solving a flood submerging process inside a local building, obtaining a space-time change rule of each physical variable in a flood evolution process, and displaying three-dimensional characteristics of the flood evolution process from different sides;
4) carrying out flood risk analysis, and analyzing population exposure and evaluating the flood risk of coastal cities by combining population distribution, field variable spatial distribution such as water depth, flow velocity and pressure intensity in a research area;
moreover, the step 1) digital city model creation method includes:
1) data integrity verification and data quality evaluation. On the premise of ensuring the completeness of data, deleting images with obvious defects of noise, dislocation and the like, and homogenizing the rest images to obtain images with uniform resolution;
2) and identifying image feature points and constructing a feature database. Carrying out feature point matching on the multi-view images and establishing the association of the homonymous control points of the multiple images;
3) iterative solving of highly redundant control points to obtain high-density spatial point cloud data and generation of an irregular triangulation network model (TIN) by adopting a multi-view image dense matching technology and a multi-view stereo matching (PMVS2) algorithm based on a feature database and a camera spatial orientation;
4) matching the texture image data with accurate coordinate information with the TIN model to finally generate a digital city model with complete landform and landform;
5) on the basis of the urban model, a three-dimensional model of the region of interest is constructed by combining GIS space positioning and BIM modeling technology, and the three-dimensional model comprises complete description of complete space information inside and outside the building.
Moreover, the method for constructing the three-dimensional hydrodynamic model by the digital city model in the steps 2) and 3) comprises the following steps:
1) setting boundary conditions and initial conditions of a research area according to historical disaster situation statistical data;
2) setting the size of the grid to ensure that the grid can accurately capture hydrodynamic characteristics, and verifying the independence of the grid;
3) the Reynolds average N-S equation and the RNG k-epsilon turbulence model are adopted to solve the dam-crossing water flow motion and turbulence condition, and the continuous equation is as follows:
wherein: ui represents the average velocity, xi is the dimension, t is the time, p is the pressure, ρ is the fluid density, gi is the gravitational acceleration component, v is the molecular kinematic viscosity, and vt is the vortex kinematic viscosity.
Turbulent vortex viscosity is calculated from the turbulence energy k and the turbulence dissipation factor epsilon in the form:
wherein C is a constant, the RNG k epsilon model adopts a modified turbulent dissipation ratio to represent the turbulent intensity, and the transport equation of k epsilon is as follows:
wherein R isεFor the shear performance of turbulent flow, G is the velocity of turbulent kinetic energy, and the coefficients in the model take the following values:
Cμ＝0.085，Cε1＝1.42，Cε2＝1.68，σk＝σε＝0.7194，β＝0.012，η＝4.38
the time step is determined according to the Courant-Friedrichs-Lewy (CFL) condition, and the CFL condition in the three-dimensional model has the following form:
wherein C is a dimensionless constant whose value depends on the particular equation to be solved; and (3) solving by adopting a display time advancing format, setting the value C to be 1, determining a time step according to the CFL condition, wherein the time step adopted in the calculation process is smaller than the time step determined by the CFL, and the convergence stability of the numerical simulation can be ensured with higher probability.
The VOF (volume of fluid) method is used to solve for free surface motion; the tracking of the gas and liquid free surfaces is solved by a continuous equation of the form:
any finite control volume is filled with gas or liquid or a mixture of both, depending on the volume fraction α of liquidw，
Based on solving the control equation, dam flood discharge and flood routing numerical simulation can be smoothly carried out, and numerical dispersion is carried out on the control equation by adopting a finite volume method; in each control volume, the calculation is performed according to the volume average of variables, including pressure, volume fraction, density, viscosity, turbulence energy and turbulence dissipation rate, is solved one by one, and the surface flux, surface stress and volume force on the control body are solved by a conservation equation.
The invention has the advantages and beneficial effects that:
1. the method is based on the urban surface constructed by oblique photography, combines a geographic information system and a building information model technology, constructs a three-dimensional model of the region of interest and integrates the two, and realizes the creation of the three-dimensional urban model of the region of interest.
2. According to the invention, three-dimensional hydrodynamic numerical simulation is carried out on the basis of a high-precision three-dimensional urban digital model, boundary conditions and initial conditions can be applied more truly and effectively, the consistency between simulation and actual conditions is ensured, and the accuracy of numerical simulation is greatly improved.
3. The high-precision flood numerical simulation method can take the complex dynamic characteristics formed by the relief of the terrain, the collision of the building and the like in the flood routing process into consideration, realize higher-precision flood numerical simulation, and accurately present the flood process in the building.
Drawings
FIG. 1 is a schematic frame diagram of the present invention;
FIG. 2 is a flow chart of digital city model construction fusing BIM and GIS technologies;
FIG. 3 is a water depth and submergence range distribution diagram of the hydrodynamic model;
FIG. 4 is a perspective view of a three-dimensional hydrodynamic model;
FIG. 5 is a diagram of a flood routing process inside a building;
fig. 6 is a chart of risk assessment of the study area.
Detailed Description
The present invention is further illustrated by the following specific examples, which are intended to be illustrative, not limiting and are not intended to limit the scope of the invention.
A three-dimensional hydrodynamic force numerical simulation method based on oblique image modeling is characterized by comprising the following steps: the simulation method comprises the following steps:
1) building a three-dimensional digital city model based on oblique image modeling and combining technologies such as a building information model and a geographic information system;
2) according to historical disaster situation statistical data, combining with the landform and landform to apply boundary conditions and initial conditions which are in line with the reality for the digital city model;
3) carrying out refined urban flood numerical simulation, wherein the refined urban flood numerical simulation comprises solving a flood submerging process inside a local building, obtaining a space-time change rule of each physical variable in a flood evolution process, and displaying three-dimensional characteristics of the flood evolution process from different sides;
4) carrying out flood risk analysis, and analyzing population exposure and evaluating the flood risk of coastal cities by combining population distribution, field variable spatial distribution such as water depth, flow velocity and pressure intensity in a research area;
step 1) the digital city model creating method comprises the following steps:
1) data integrity verification and data quality evaluation. On the premise of ensuring the completeness of data, deleting images with obvious defects of noise, dislocation and the like, and homogenizing the rest images to obtain images with uniform resolution;
2) and identifying image feature points and constructing a feature database. Carrying out feature point matching on the multi-view images and establishing the association of the homonymous control points of the multiple images;
3) iterative solving of highly redundant control points to obtain high-density spatial point cloud data and generation of an irregular triangulation network model (TIN) by adopting a multi-view image dense matching technology and a multi-view stereo matching (PMVS2) algorithm based on a feature database and a camera spatial orientation;
4) matching the texture image data with accurate coordinate information with the TIN model to finally generate a digital city model with complete landform and landform;
5) on the basis of the urban model, a three-dimensional model of the region of interest is constructed by combining GIS space positioning and BIM modeling technology, and the three-dimensional model comprises complete description of complete space information inside and outside the building. FIG. 2 is a digital city model construction process integrating BIM and GIS technologies.
The method for constructing the three-dimensional hydrodynamic model by the digital city model in the steps 2) and 3) comprises the following steps:
1) setting boundary conditions and initial conditions of a research area according to historical disaster situation statistical data;
2) setting the size of the grid to ensure that the grid can accurately capture hydrodynamic characteristics, and verifying the independence of the grid;
3) the Reynolds average N-S equation and the RNG k-epsilon turbulence model are adopted to solve the dam-crossing water flow motion and turbulence condition, and the continuous equation is as follows:
wherein: ui represents the average velocity, xi is the dimension, t is the time, p is the pressure, ρ is the fluid density, gi is the gravitational acceleration component, v is the molecular kinematic viscosity, and vt is the vortex kinematic viscosity.
Turbulent vortex viscosity is calculated from the turbulence energy k and the turbulence dissipation factor epsilon in the form:
wherein C is a constant, the RNG k epsilon model adopts a modified turbulent dissipation ratio to represent the turbulent intensity, and the transport equation of k epsilon is as follows:
wherein R isεFor the shear performance of turbulent flow, G is the velocity of turbulent kinetic energy, and the coefficients in the model take the following values:
Cμ＝0.085，Cε1＝1.42，Cε2＝1.68，σk＝σε＝0.7194，β＝0.012，η＝4.38
the time step is determined according to the Courant-Friedrichs-Lewy (CFL) condition, and the CFL condition in the three-dimensional model has the following form:
wherein C is a dimensionless constant whose value depends on the particular equation to be solved; and (3) solving by adopting a display time advancing format, setting the value C to be 1, determining a time step according to the CFL condition, wherein the time step adopted in the calculation process is smaller than the time step determined by the CFL, and the convergence stability of the numerical simulation can be ensured with higher probability.
The VOF (volume of fluid) method is used to solve for free surface motion; the tracking of the gas and liquid free surfaces is solved by a continuous equation of the form:
any finite control volume is filled with gas or liquid or a mixture of both, depending on the volume fraction α of liquidw，
Based on solving the control equation, dam flood discharge and flood routing numerical simulation can be smoothly carried out, and numerical dispersion is carried out on the control equation by adopting a finite volume method; in each control volume, the calculation is performed according to the volume average of variables, including pressure, volume fraction, density, viscosity, turbulence energy and turbulence dissipation rate, is solved one by one, and the surface flux, surface stress and volume force on the control body are solved by a conservation equation.
The model verification in the step 3) comprises the following steps:
lack of actual measurement data of urban inland inundation induced by storm surge for one hundred years, and limited precision of in-situ observation and capture of complex hydrodynamic phenomena restricts verification of flood evolution numerical simulation. At present, most research achievements adopt a flood submerging range to verify the accuracy of numerical simulation. For this reason, the accuracy of the model is verified by adopting an urban flood physical model experiment with water depth data and the flood tide process and the submerging range thereof observed in 2019, 4, 16 days.
The physical model test is constructed by Italian researchers, a 1: 100 scale is adopted to remold city prototypes, 18 cubes are arranged in a staggered mode to represent building distribution, and referring to the figure 3, water level changes are dynamically observed at 10 measuring points through water level gauges, so that the method is widely used for hydrodynamic model verification. And (3) constructing urban terrain by using the data provided by the physical model, and then constructing a three-dimensional hydrodynamic numerical simulation to solve the time-varying process of the water depth at the position of the 10 measuring point, so as to verify the applicability and accuracy of the hydrodynamic model.
Comparing the water depth variation test values with the simulation values at 10 measuring points shows that the average water depth error of each point is within 15% referring to fig. 4.
The flood risk analysis in step 4) comprises:
FIG. 3 shows the water depth and the spatial distribution of the submerging range of the hydrodynamic model. The three-dimensional hydrodynamic numerical simulation can accurately capture elevation gradient changes, so that flood can be guaranteed to submerge in a larger range along the depth of a flow channel to the inside of a city according to hydrodynamic features. The flood routing numerical simulation based on the digital city model can reproduce the flood routing process in the city with high precision, and the disaster prevention capability is improved.
Fig. 4 reveals the spatial distribution characteristics of the flow field from different angles. When the flood lands, the flood firstly invades the low-level region of the terrain and gradually pushes the urban area along roads and bare land. Because the topography in the city rises gradually, and because the stopping of building leads to rivers motion to be slowed down, flood can't continue to go deep into inside the city, therefore flood mainstream is to diffusion all around, causes the submergence of wider scope. Storm surge causes that the general increase of water in coastal areas leads to that the flood in cities can not be discharged into gulf by oneself, and meanwhile, the continuous flood continuously floods the interior of the cities, so that the streets are submerged, the buildings are submerged, and the damage of urban waterlogging is further aggravated.
Fig. 5 illustrates a building interior flood routing process. The water flow reaches the outside of the building after 58s of simulation and starts to enter the house interior through doors, windows, etc., and the floor is completely flooded after 70 s. Due to the blocking of the wall surface, the vertical velocity component of flood inside the building is obvious. The complex flow state characteristics and the flow field are instantaneous change characteristics, the necessity of three-dimensional hydrodynamic simulation is highlighted, and the digital city model provides basic data for the three-dimensional hydrodynamic simulation, and the complex flow state characteristics and the flow field are dense and indistinct. The building has a large influence on flood, not only can change a flood path by collision and blocking flood movement, but also can provide a flow passage for the flood, so that complete building space description is very important for more accurately knowing urban flood space distribution characteristics.
Fig. 6 is a study area flood risk assessment. Urban waterlogging caused by storm surge in one hundred years is concentrated within the range of 200m along the shore, and the energy of flood is greatly weakened by the coastal dike. The water depth is more than 0.2m, the submerged area reaches 0.38km2, the water depth occupies 16.9% of the research area, the normal production and life of 400 persons in the area are seriously influenced, and the population distribution is influenced by flood water as shown in figure 6.
Although the embodiments of the present invention and the accompanying drawings are disclosed for illustrative purposes, those skilled in the art will appreciate that: various substitutions, changes and modifications are possible without departing from the spirit and scope of the invention and the appended claims, and therefore the scope of the invention is not limited to the disclosure of the embodiments and the accompanying drawings.
Claims (3)
1. A three-dimensional hydrodynamic force numerical simulation method based on oblique image modeling is characterized by comprising the following steps: the simulation method comprises the following steps:
1) building a three-dimensional digital city model based on oblique image modeling and combining technologies such as a building information model and a geographic information system;
2) according to historical disaster situation statistical data, combining with the landform and landform to apply boundary conditions and initial conditions which are in line with the reality for the digital city model;
3) carrying out refined urban flood numerical simulation, wherein the refined urban flood numerical simulation comprises solving a flood submerging process inside a local building, obtaining a space-time change rule of each physical variable in a flood evolution process, and displaying three-dimensional characteristics of the flood evolution process from different sides;
4) and carrying out flood risk analysis, and analyzing population exposure and evaluating the flood risk of coastal cities by combining population distribution, field variable spatial distribution such as water depth, flow velocity and pressure in a research area.
2. The method according to claim 1, wherein the method comprises: the step 1) digital city model creating method comprises the following steps:
1) data integrity verification and data quality evaluation. On the premise of ensuring the completeness of data, deleting images with obvious defects of noise, dislocation and the like, and homogenizing the rest images to obtain images with uniform resolution;
2) and identifying image feature points and constructing a feature database. Carrying out feature point matching on the multi-view images and establishing the association of the homonymous control points of the multiple images;
3) iterative solving of highly redundant control points to obtain high-density spatial point cloud data and generation of an irregular triangulation network model (TIN) by adopting a multi-view image dense matching technology and a multi-view stereo matching (PMVS2) algorithm based on a feature database and a camera spatial orientation;
4) matching the texture image data with accurate coordinate information with the TIN model to finally generate a digital city model with complete landform and landform;
5) on the basis of the urban model, a three-dimensional model of the region of interest is constructed by combining GIS space positioning and BIM modeling technology, and the three-dimensional model comprises complete description of complete space information inside and outside the building.
3. The method according to claim 1, wherein the method comprises: the method for constructing the three-dimensional hydrodynamic model by the digital city model in the steps 2) and 3) comprises the following steps:
1) setting boundary conditions and initial conditions of a research area according to historical disaster situation statistical data;
2) setting the size of the grid to ensure that the grid can accurately capture hydrodynamic characteristics, and verifying the independence of the grid;
3) the Reynolds average N-S equation and the RNG k-epsilon turbulence model are adopted to solve the dam-crossing water flow motion and turbulence condition, and the continuous equation is as follows:
wherein: ui represents the average velocity, xi is the dimension, t is the time, p is the pressure, ρ is the fluid density, gi is the gravitational acceleration component, v is the molecular kinematic viscosity, and vt is the vortex kinematic viscosity.
Turbulent vortex viscosity is calculated from the turbulence energy k and the turbulence dissipation factor epsilon in the form:
wherein C is a constant, the RNG k epsilon model adopts a modified turbulent dissipation ratio to represent the turbulent intensity, and the transport equation of k epsilon is as follows:
wherein R isεFor the shear performance of turbulent flow, G is the velocity of turbulent kinetic energy, and the coefficients in the model take the following values:
Cμ＝0.085，Cε1＝1.42，Cε2＝1.68,σk＝σε＝0.7194，β＝0.012，η＝4.38
the time step is determined according to the Courant-Friedrichs-Lewy (CFL) condition, and the CFL condition in the three-dimensional model has the following form:
wherein C is a dimensionless constant whose value depends on the particular equation to be solved; and (3) solving by adopting a display time advancing format, setting the value C to be 1, determining a time step according to the CFL condition, wherein the time step adopted in the calculation process is smaller than the time step determined by the CFL, and the convergence stability of the numerical simulation can be ensured with higher probability.
The VOF (volume of fluid) method is used to solve for free surface motion; the tracking of the gas and liquid free surfaces is solved by a continuous equation of the form:
any finite control volume is filled with gas or liquid or a mixture of both, depending on the volume fraction α of liquidwBased on solving the control equation, dam flood discharge and flood routing numerical simulation can be smoothly carried out, and numerical dispersion is carried out on the control equation by adopting a finite volume method; in each control volume, the calculation is performed according to the volume average of variables, including pressure, volume fraction, density, viscosity, turbulence energy and turbulence dissipation rate, is solved one by one, and the surface flux, surface stress and volume force on the control body are solved by a conservation equation.
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| CN117852449B (en) * | 2024-03-06 | 2024-05-14 | 天津市气象科学研究所 | Fine ponding treatment method based on large-scale city rainstorm waterlogging model |
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