CN117436174A - Urban ventilation corridor construction method and system based on CFD and circuit theory - Google Patents

Abstract

The invention discloses an urban ventilation corridor construction method and system based on CFD and circuit theory, and belongs to the technical field of urban ecological environment planning. Including data acquisition and preprocessing, including urban wind speed background value and urban terrain and building distribution data acquisition and processing; surface temperature inversion, performing surface temperature inversion on the target area to obtain surface temperature distribution data; wind corridor construction suitability evaluation, Conduct multi-factor comprehensive evaluation of the suitability of ventilation corridor construction in the target area; circuit simulation, use circuit theory tools to conduct current simulation on the target area; and wind corridor construction, build the ventilation corridor system in the target area based on the current simulation diagram results. The advantages of this invention are: combining the laws of fluid motion and the random walk characteristics of electrons in circuits, constructing an urban ventilation corridor identification model based on fluid dynamics and circuit theory; constructing a "wind source-corridor-repair area" ventilation corridor system. It is more helpful to identify urban ventilation corridors and guide corridor construction practices.

Description

Urban ventilation corridor construction method and system based on CFD and circuit theory

Technical field

The present invention relates to the technical field of urban ecological environment planning, and more specifically, to an urban ventilation corridor construction method and system based on CFD and circuit theory.

Background technique

Since the 1990s, my country has entered a stage of rapid urbanization, and cities have maintained rapid development for nearly three decades. Since entering the new urbanization stage, the focus of my country's urbanization work has shifted from "quantitative" growth to "qualitative" improvement, and the improvement of human settlements has become the top priority of urban construction. Therefore, the construction of ventilation corridors to improve the urban ventilation environment, reduce the intensity of urban heat islands, improve thermal comfort levels, and alleviate haze weather has become an important means for urban managers to improve the living environment and improve urban livability.

The core of ventilation corridor construction is wind environment research. After more than 40 years of development, three physical measurement methods based on field measurements or wind tunnel experiments, direct simulation methods based on tools such as CFD and WRF, and indirect simulation methods based on ventilation potential evaluation and minimum cost path algorithms have gradually been formed at home and abroad. Technology System. Each of these three systems already has relatively mature technical processes, but the indirect simulation method based only on ventilation potential evaluation and minimum cost path algorithm is highly operable at the urban scale. This method currently has two main problems: First, the minimum cost path algorithm has problems such as insensitivity to low-level wind corridor identification, inability to represent corridor width information, and limited ability to identify potential wind corridor areas. It has great improvements. There is room for improvement; secondly, existing methods mostly conduct wind corridor simulations based on the prevailing urban wind direction, ignoring the impact of the complex built environment on urban wind conditions, and have limited ability to identify urban wind source areas, so they are not suitable for constructing more precise modernized urban ventilation corridor system. In summary, the development of ventilation corridor construction methods has important practical value, but the current mainstream technology system faces a dilemma between practicality and accuracy, and is in urgent need of improvement.

In related technologies, for example, Chinese patent document CN 114021303 A discloses an intelligent mining method for urban ventilation corridors based on high-precision oblique photography images, which includes the following steps: Step S1: Obtain the tilt of the target city through aircraft aerial photography using oblique photography technology Photograph the image to obtain the digital surface model DSM and the digital elevation model DEM; Step S2: Use the difference between DSM and DEM to extract the three-dimensional surface data of the target city; Step S3: Obtain multiple dominant wind direction information of the target city, and combine the steps The three-dimensional surface data obtained in S2 calculates the windward area density of each dominant wind direction; Step S4: Design a template based on the dominant wind direction information, and perform a template matching operation based on the windward area density of the dominant wind direction to find the windward area density interval. The numerically continuous area is used as the urban ventilation corridor; Step S5: Automatically excavate the urban ventilation corridor based on step S4 to extract the urban ventilation corridor that meets the preset requirements. It can be seen from the above that related technologies do not provide effective solutions to the problems of how to evaluate urban wind sources and how to identify potential ventilation corridors on a fine scale.

Contents of the invention

1. Technical problems to be solved

In view of the problems existing in the existing technology such as difficulty in assessing urban wind sources and accurately identifying potential ventilation corridors on a fine scale, the present invention provides an urban ventilation corridor construction method and system based on CFD and circuit theory, which combines fluid dynamic characteristics and electronic random walk characteristics to provide more refined urban wind field information for the construction of ventilation corridors based on RS and GIS, thereby further improving the construction method of urban ventilation corridors and better realizing urban ventilation corridors on a fine scale. and identification of important nodes.

2.Technical solutions

The object of the present invention is achieved through the following technical solutions.

The urban ventilation corridor construction method based on CFD and circuit theory includes the following steps:

Data acquisition and preprocessing: Obtain data such as meteorological wind speed, terrain and building distribution in the target area, and perform preprocessing;

Urban wind field drawing: Import the obtained urban meteorological wind speed and simplified urban three-dimensional model into CFD software for wind field simulation to obtain the urban wind field situation;

Surface temperature inversion: Perform surface temperature inversion based on daytime remote sensing data to obtain the surface temperature distribution in the target area;

Suitability evaluation of ventilation corridor construction: Conduct a single-factor evaluation on the suitability of ventilation corridor construction in the target area, and superimpose the single-factor evaluation results to obtain a multi-factor comprehensive evaluation result;

Circuit simulation: Combined with the suitability results of urban wind fields and wind corridor construction, circuit theory tools are used to simulate the wind environment current in the target area;

Construction of ventilation corridor system: Based on the current simulation results, an urban ventilation corridor system of "wind source-corridor-repair area" is constructed. Further, data acquisition includes digital elevation model data, remote sensing image data, building base maps and height vector data, road network vector data, green space and water system vector data, and wind direction and speed multi-year observation data.

Furthermore, preprocessing involves projecting and cropping the acquired geographical information data in the GIS platform, removing null values from the acquired wind direction and speed data, calculating the annual average daily wind speed and wind frequency in each direction, and building a three-dimensional city Simplify the model.

Furthermore, the preprocessing steps are as follows:

Check data status;

Unify coordinates and range: Project and clip the acquired data in the GIS platform to unify the projection coordinate system and range of the data;

Calculate the wind frequency and average wind speed in each direction:

is the daily average wind speed over the years, N is the total number of days with wind speed and direction data, V _i is the daily average wind speed on the i-th day, f _α is the wind frequency in direction α, and n _α is the number of days in the wind direction data with direction α.

Furthermore, the specific steps to check the data situation are: check and process abnormal values of the obtained digital elevation model data; check remote sensing image data; check and process geometric errors in the vector data of buildings, green spaces, water systems and road networks; remove wind direction and speed data Null values and other outliers in . Furthermore, the steps to obtain the urban wind field include: establishing a simplified three-dimensional model of the city based on the building base map, height vector data and digital elevation model data, importing the simplified three-dimensional model of the city into CFD software for wind environment simulation, and obtaining stable wind conditions at a specific height. State wind speed distribution.

Furthermore, the specific steps for CFD software to simulate wind environment are:

Pre-processing: including importing the model, establishing the solution domain and dividing the mesh;

Solution: including establishing turbulence model, setting boundary conditions, solving for steady state and determining convergence;

Post-processing: Display simulation results using wind speed plots and vector plots.

Further, in the circuit simulation step, the circuit simulation results include obtaining accumulated current, current potential and normalized current.

Furthermore, the steps to construct a ventilation corridor system include: interpreting the cumulative current, normalized current, and current potential results obtained from circuit simulation; determining the wind sources, corridors, repair areas and their boundaries in the urban ventilation corridor system.

The system based on the above urban ventilation corridor construction method based on CFD and circuit theory includes:

Data acquisition and preprocessing module: Obtain data such as meteorological wind speed, terrain and building distribution in the target area, and perform preprocessing;

Urban wind field drawing module: Import the obtained urban meteorological wind speed and simplified urban three-dimensional model into CFD software for wind field simulation to obtain the urban wind field situation;

Surface temperature inversion module: perform surface temperature inversion based on daytime remote sensing data to obtain the surface temperature distribution in the target area;

Suitability evaluation module for ventilation corridor construction: conduct a single-factor evaluation on the suitability of ventilation corridor construction in the target area, and superimpose the single-factor evaluation results to obtain multi-factor comprehensive evaluation results;

Circuit simulation module: Combined with the suitability results of urban wind fields and wind corridor construction, circuit theory tools are used to simulate the wind environment current in the target area;

Ventilation corridor system building module: Based on the current simulation results, the "wind source-corridor-repair area" urban ventilation corridor system is constructed.

3. Beneficial effects

Compared with the existing technology, the advantage of the present invention is that: this solution combines the characteristics of fluid motion and the random walk characteristics of electrons in the circuit to construct an urban ventilation corridor identification model based on fluid dynamics and circuit theory; this solution uses CFD simulation The results evaluate the wind conditions in the target area, which can effectively obtain the range and relative intensity of the main wind sources in the target area; this plan introduces circuit theory into the simulation of potential ventilation corridors, which can better simulate the secondary wind corridors in the target area and visually display the wind Corridor width and identification of ventilation obstruction points; the urban ventilation corridor system thus constructed has more application value and is more conducive to the formulation of relevant construction plans.

Description of the drawings

Figure 1 is a flow chart of an urban ventilation corridor construction method based on CFD and circuit theory according to an embodiment of the present invention;

Figure 2 is a simplified schematic diagram of the mountain body according to an embodiment of the present invention;

Figure 3 is an example diagram of a simplified three-dimensional model of a city according to an embodiment of the present invention;

Figure 4 is an example of a pedestrian height and wind speed diagram obtained from CFD simulation according to an embodiment of the present invention;

Figure 5 is an example diagram of surface temperature inversion results according to an embodiment of the present invention;

Figure 6 is an example diagram of multi-factor evaluation results of ventilation corridor construction suitability according to an embodiment of the present invention;

Figure 7 is an example diagram of circuit simulation results (accumulated current) according to an embodiment of the present invention;

Figure 8 is an example diagram of circuit simulation results (current potential) according to an embodiment of the present invention;

Figure 9 is an example diagram of circuit simulation results (normalized current) according to an embodiment of the present invention;

Figure 10 is an example diagram of extracting potential wind source distribution in a ventilation corridor based on circuit simulation results according to an embodiment of the present invention;

Figure 11 is an example diagram of extracting potential corridor ranges of ventilation corridors based on circuit simulation results according to an embodiment of the present invention;

Figure 12 is a schematic diagram of a ventilation corridor system according to an embodiment of the present invention.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

Combined with Figure 1, the urban ventilation corridor construction method of the present invention based on CFD and circuit theory includes data acquisition and preprocessing, urban wind field drawing, surface temperature inversion, wind corridor construction suitability evaluation, circuit simulation and ventilation corridor System building.

Specific steps are as follows:

Data acquisition and preprocessing:

Obtain geographical information and meteorological data of the target area and perform preprocessing.

Specifically, during implementation, the data includes acquisition of digital elevation model data, remote sensing image data, building base maps and height vector data, road network vector data, green space and water system vector data, and multi-year observation data of wind direction and speed. Preprocessing involves unified projection and cropping of the acquired geographical information data in the GIS platform, and operations such as removing null values from the acquired wind direction and speed data, calculating the annual average daily wind speed and wind frequency in each direction.

More specifically, preprocessing includes the following work:

Check the data:

Check and process abnormal values of the acquired digital elevation model data; check whether the remote sensing image data is a clear and cloudless daytime image of the target area in summer in recent years; check and process geometric errors in the vector data of buildings, green spaces, water systems and road networks; remove wind direction Null values and other outliers in wind speed data.

Unify coordinate systems and extents:

In the GIS platform, the acquired digital elevation model, remote sensing images, buildings, green spaces, water systems, and road network data are projected and cropped to unify the projection coordinate system and range of the data.

Calculate the wind frequency and average wind speed in each direction:

As an optional implementation, calculate the annual average daily wind speed and wind frequency in all directions (excluding calm wind days, that is, the wind speed is less than 0.1m/s). The specific calculation formulas are as follows: Formulas 1 and 2:

in is the daily average wind speed over the years, N is the total number of days with wind speed and direction data, V _i is the daily average wind speed on the i-th day, f _α is the wind frequency in direction α, and n _α is the number of days in the wind direction data with direction α. Depending on the accuracy of the data, you can choose to calculate eight-way or sixteen-way wind frequency.

Urban wind field drawing:

Use CFD simulation to obtain urban wind field conditions.

Specifically, a simplified three-dimensional model of the city is established based on the building base map, height vector data and digital elevation model data. The simplified three-dimensional model of the city is imported into CFD software for wind environment simulation, and the steady-state wind field conditions at a specific height are obtained.

In implementation, the undulating terrain and large number of buildings need to be simplified and represented by limited patches. In order to avoid unreasonable patch division while reducing modeling nodes, as an optional implementation method, the simplified method is as follows:

Simplify special terrains and buildings such as mountains in the target area respectively.

As shown in Figure 2, the mountain is simplified into a stepped multi-layered right-edge geometry based on contour lines. The contour spacing is determined based on the height of the mountains in the study area. The higher the mountains, the greater the spacing. If there is a large height difference between different mountains in the target area, different contour spacing can be selected for the mountains in different height ranges.

For buildings, the GIS platform is used to generate new building patches with a tolerance of 80m and roads and main water systems as obstacle surfaces, and unnecessary modeling nodes are removed. The above process will inevitably cause the model to flatten, so the patch height needs to be stretched to a certain extent. As an optional implementation, the stretching formula is:

H＝H _e +H _b (1)

Where H is the height of each patch, He _e is the average elevation of the patch, H _b is the assigned height of the patch building, h _i is the height of the i-th building in the patch, S _i is the i-th building in the patch The base area of the building, S is the total base area of the building in patch i. Convert the architectural vector base map into a three-dimensional model in CAD. After adjustment by combining the simplified mountain model and the simplified building model, the final simplified model of the target area is formed as shown in Figure 3.

The steps for simulating the wind environment part of CFD software are as follows:

Pre-processing: including importing the model, establishing the solution domain, and dividing the mesh. Importing the model means importing the building, terrain and other models of the area to be simulated in a format that can be recognized by the CFD software. Establishing the solution domain determines the calculation range of the CFD software to solve the fluid flow. Since the turbulence formed when the airflow passes through buildings and mountains requires space to develop, the solution domain requires a certain expansion of the model range. According to the recommendations of the Japanese Academy of Architectural Design (AIJ) on the building wind environment, the expansion range is 3-5H at the entrance of the solution domain, 4H in thickness, 3-5H in width on both sides, 5-7H in the exit, and H is the model maximum height. Meshing is to use a discretized grid to reflect the geometric characteristics of the model and serve as a unit for subsequent calculation and storage of data. Too fine a mesh will lead to low computational efficiency, and too coarse a mesh will affect the reliability of CFD simulation results.

Solution: including establishing a turbulence model, setting boundary conditions, solving for steady state, and determining convergence. To establish a turbulence model is to select the model equations used by CFD software to solve the steady state of fluid flow. Setting boundary conditions means determining the wind speed, wind pressure and other conditions at the inlet, outlet, side, top surface and model wall of the solution domain, so that the CFD simulation can correctly reflect the climate characteristics of the target area. To solve for the steady state, it is to iteratively calculate the steady state of the flow field in the solution domain under the aforementioned settings until the calculation residual is reduced to an acceptable level and the calculation results can be judged to be convergent.

Post-processing: Result visualization and output, using wind speed cloud diagrams, vector diagrams and other readable methods to display simulation results.

In this embodiment, scSTREAM software is used for simulation. The specific process is as follows:

In the preprocessing step, the aforementioned target area in stl format is first imported to finally simplify the model, and it is expanded in the software to obtain the solution domain.

Considering the calculation efficiency of the city-scale model, the expansion range in this embodiment is set as follows: model entrance 3H, thickness 4H, both sides 3H, exit 5H, where H is the highest height of the model.

In order to reduce the amount of calculation while ensuring the reliability of the results, the structured grid is divided by limiting the minimum grid size and inputting the ideal number of grids. The minimum grid size is used to ensure that the geometric features of key areas of the model are well preserved. The scSTREAM software will automatically stretch the grid size of the blank areas of the model based on the ideal number of grids.

In the solution step, in the scSTREAM software, you only need to set the basic boundary type to external flow field, and enter the wind direction and inlet wind speed to complete the boundary condition settings. Regarding the turbulence model, this embodiment selects the RNG k-ε model in the Reynolds Average Navier-Stokes (RANS) equation to solve the steady state of the incompressible fluid. The RANS equation performs Reynolds averaging processing on the flow field physical quantities in the time domain, and then solves the resulting time-averaged governing equations. Its calculation efficiency is high and its accuracy can basically meet the needs of routine research and industrial design. It is a widely used steady-state turbulence model.

The RNG k-ε model is an improved version of the standard k-ε model. It has the advantages of improved accuracy of rapid strain flow and improved accuracy of eddy currents, and has good performance in simulating the external wind environment of buildings. Other solution settings include: setting the calculation step size to 500, and the convergence criterion is that the turbulence dissipation rate, turbulence energy, and velocity residuals are all less than 0.001.

As shown in Figure 4, a wind speed cloud map at pedestrian height (about 1.5m) in the target area should be produced during post-processing. The height of the wind speed cloud chart in this embodiment is 1.5m above the average altitude of the target area. The Magnitude of Velocity in Figure 4 is the velocity magnitude.

Perform surface temperature inversion for the target area:

As shown in Figure 5, this embodiment selects Landsat 8 remote sensing images in summer with less cloud cover in recent years to perform surface temperature inversion to obtain the surface temperature distribution in the target area.

Conduct a multi-factor comprehensive evaluation of the suitability of ventilation corridor construction in the target area:

Since buildings and high-altitude, high-undulation, and large-slope terrain are the two most important factors hindering wind flow in urban environments, the present invention selects terrain conditions and building environment as negative factors for ventilation corridor suitability. Open space is a natural component of air ducts in the city, and roads are built spaces that can be planned and constructed at low cost. Therefore, open space and road ventilation performance are selected as positive factors for the suitability of ventilation corridors.

These four elements basically cover the natural and man-made influencing factors that affect the suitability of ventilation corridor construction, can make a more comprehensive evaluation, and can take into account the existing urban built environment and ventilation planning needs. The popular evaluation ideas in the past were mainly to calculate urban morphological parameters such as windward area index and sky openness, and to evaluate the suitability of ventilation corridor construction based on surface roughness.

This idea can more objectively quantify the degree of wind blocking by urban features. However, ventilation corridors, as a highly practical and multi-functional planning tool, often need to make full use of existing conditions and coordinate with the current status and development intentions of urban construction. . The urban morphological method focuses too much on mechanical wind resistance indicators and ignores urban characteristics in other dimensions. The evaluation method adopted in the present invention strives to take into account both the objectivity and comprehensiveness of the evaluation to strengthen the ability of the evaluation results to guide ventilation corridor planning.

The specific indicators for each factor selection should be flexibly selected according to the characteristics of the target area. The indicators selected in this embodiment are as shown in Table 1:

Table 1. Factors and indicators for suitability evaluation of ventilation corridor construction

For each evaluation indicator, the target area indicator performance is scored according to five levels, namely high (9), higher (7), medium (5), lower (3), and low (1). The road direction (X ₃₁ ) and road grade (X ₃₂ ) need to be weighted and averaged to obtain the single-factor evaluation results of road ventilation performance, and the patch direction (X ₄₂ ) and patch width (X ₄₃ ) need to be weighted and averaged to obtain the open space strip For the plaque evaluation results, in this embodiment, multiple experts were consulted, and the index weights were determined based on the characteristics of the target area as X ₃₁ :X ₃₂ =1.3:1 and X ₄₂ :X ₄₂ =1:1.2.

The single-factor evaluation results need to be superimposed according to certain rules to obtain the multi-factor evaluation results. In this embodiment, the evaluation results of terrain conditions and building environment are superimposed and the minimum value is obtained to obtain the negative factor evaluation result. The evaluation results of road ventilation performance and open space are superimposed and the maximum value is obtained to obtain the positive factor evaluation result. A pairwise discriminant matrix is used method to superimpose the evaluation results of positive and negative factors. The specific discriminant matrix is shown in Table 2, and the final multi-factor evaluation results of the suitability of ventilation corridor construction are shown in Figure 6.

Table 2. Positive and negative elements superimposed pairwise discriminant matrix

Circuit simulation:

Circuit theory can draw on the process of random walks of electrons in circuits to simulate the flow of wind in different urban spaces. Like the minimum path, it has the advantages of less data requirements and simple process. When encountering a branch route, the minimum path method will only choose the one with the smallest cumulative cost, while in circuit theory the current on the branch circuit is inversely proportional to the respective resistance. That is, when circuit theory is used to simulate the flow of urban wind, wind at obstacle points will be distributed in proportion to the ventilation potential (conductance) of different branch paths like current, which is more consistent with the result of airflow concentrating on one path than simulated by the minimum path method. The actual situation. Circuit theory analysis can simultaneously solve for single path and global connectivity benefits. Just as the increase of branch circuits in a parallel circuit will reduce the total resistance of the circuit and increase the total current, the increase in downwind flow routes of this algorithm will also improve the global ventilation capacity. , which is very consistent with the network connectivity pursued in the construction of ventilation corridors. In addition, circuit theory solution results can provide ventilation possibilities (cumulative current flow) for the entire study area, making it possible to identify the width of ventilation corridors and key points in areas without potential ventilation corridors. Therefore, circuit theory is more suitable for modeling potential wind corridors than the minimum path method commonly used in existing wind corridor simulations.

Use the above CFD simulation, surface temperature inversion and ventilation corridor construction suitability evaluation results to conduct circuit simulations in the target area. Specifically, the Omniscape program developed based on the Julia language is used to perform circuit theory calculations. The CFD simulation results at 1.5m above the average altitude of the simplified city model (i.e., at pedestrian height) are used as the source surface. The wind speed is the power intensity; local circulation is considered. The operating rules and the construction purpose of ventilation corridors to reduce urban heat islands are set to only allow connections to sources whose temperature is no higher than it; the conductivity surface is based on the comprehensive evaluation results of the suitability of ventilation corridor construction.

As shown in Figures 7 to 9, the circuit simulation results include three items: cumulative current, current potential (flow potential), and normalized current flow (normalized current flow). The current potential is the cumulative current output when the resistance of the entire study area is 1, which can characterize the ability of the power supply to generate current. The cumulative current is the current result of the study area output by the Omniscape program, which represents the current size. The normalized current is the ratio of the cumulative current to the current potential, which is used to evaluate the impact of conductance on the current after excluding power intensity factors; its high value indicates that the current is significantly higher than expected, and the area is highly channelized because the resistance is significantly smaller than that of nearby pixels. .

Ventilation corridor system construction:

Based on the simulation results, a ventilation corridor system in the target area is constructed.

Specifically, this step first requires interpreting the cumulative current, normalized current, and current potential results obtained from circuit simulation, and determining the types and specific ranges of each element in the ventilation corridor system in the target area.

In this embodiment, the current potential represents the ability to generate wind and can be used to extract important wind sources in the ventilation corridor system. The accumulated current represents the ventilation condition of the target area and can be used to identify the ventilation corridor network. The normalized current represents the influence of terrain, buildings, roads and open space factors on urban ventilation after excluding wind source intensity factors. The normalized current high value area indicates that the nearby area is high in altitude or has dense buildings, the number of paths that can be selected when the air flow passes is severely reduced, or there is a high-quality wind corridor with significantly better ventilation conditions than the nearby area; a low value indicates that the current is here It is significantly smaller than expected, indicating the existence of areas with blocked ventilation; the normalized current can be used to extract high-quality wind corridor areas, severely blocked ventilation areas and key blocking points in the wind corridor. Based on this, this embodiment establishes a conversion framework between output results and ventilation corridor construction strategies, as shown in Table 3:

Table 3. Circuit Theory-Ventilation Corridor Conversion Framework

As shown in Figures 10 and 11: Three levels of potential wind source ranges are extracted based on the current potential value, three types of potential wind corridor ranges are extracted based on the cumulative current value, and the normalized current values are divided into highly channelized areas and lightly channelized areas. There are five categories: area, general area, area with mild obstruction of wind corridor, and area with severe obstruction of wind corridor. In this embodiment, the boundaries of the potential wind source range are: wind source core area (current potential ≥ 2000), wind source buffer area (1500 ≤ current potential < 2000), wind source edge area (1200 ≤ current potential < 1500) ; The potential wind corridor division range is: wind source area (cumulative current ≥ 1600), high air volume corridor area (800 ≤ cumulative current < 1600), wind volume corridor area ( 300 ≤ cumulative current < 800); normalized current The value classification boundaries are: highly channelized area (normalized current value greater than 1.3), lightly channelized area (normalized current value between 1.1 and 1.3), general area (normalized current value between 0.9 and 1.1 between), the wind corridor is slightly blocked (normalized current value is between 0.7 and 0.9), and the wind corridor is severely blocked (normalized current value is less than 0.7).

Combining the characteristics of the target area and the simulation results of circuit theory, the three-element ventilation corridor system of "wind source-corridor-repair area" was determined. Wind source refers to the space that can produce clean and cool air, including core wind source and secondary wind source; corridor refers to the space that transports clean and cool air, including main corridor and secondary corridor; repair area refers to the area that affects the wind source to spread the breeze or In areas where the corridor is blocked or even broken, measures need to be taken to reduce wind resistance and repair the wind corridor system. Finally, the results of the urban ventilation corridor planning system in the target area are obtained as shown in Figure 12.

Compared with related technologies, it is too costly and difficult to directly use tools such as CFD and WRF models to simulate ventilation corridors. Direct interpretation of ventilation corridors is only based on planning experience, or indirect simulation of ventilation corridors using minimum path algorithms is difficult due to relatively rough wind conditions. It is not accurate enough due to the lack of condition assessment and aerodynamic foundation. This plan takes into account the achievability of the process and the reliability of the results, and is helpful for planning practice.

Combining Figures 1 to 12, the urban ventilation corridor construction system based on CFD and circuit theory includes:

Data preprocessing module, used to obtain geographical information and meteorological data of the target area and perform preprocessing;

The urban wind field drawing module is used to obtain the urban wind speed distribution background, build a simplified three-dimensional model of the city, and import it into the software to simulate the wind environment and draw the urban wind field;

The surface temperature inversion module is used to perform surface temperature inversion and obtain the surface temperature distribution in the target area;

The construction suitability evaluation module is used to conduct a single-factor evaluation on the suitability of ventilation corridor construction in the target area, and superimpose the single-factor evaluation results to obtain a multi-factor comprehensive evaluation result;

The circuit simulation module is used to perform circuit simulation and use the circuit simulation results to construct a ventilation corridor system in the target area;

The ventilation corridor system building module is used to construct a "wind source-corridor-repair area" urban ventilation corridor system based on circuit simulation results.

In related technologies, the simulation of potential ventilation corridors mostly uses the minimum path method, which is insensitive to low-level potential ventilation corridors, does not have width information, and has limited ability to guide wind environment improvement strategies in areas lacking potential ventilation corridors. This plan introduces circuit theory into the simulation of potential ventilation corridors, which can better simulate the secondary wind corridors in the target area, visually display the width of the wind corridors, and identify ventilation obstruction points. The urban ventilation corridor system thus constructed is more scientific and effective.

In addition, in related technologies, most of the wind condition assessment links only use a single prevailing wind direction or wind frequency map in all directions. However, this solution uses CFD simulation results to evaluate the wind conditions in the target area, which can effectively obtain the range and relative position of the main wind sources in the target area. Strength helps determine ventilation corridors and formulate subsequent planning policies.

The invention and its implementation have been schematically described above. This description is not limiting. The invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the invention. What is shown in the drawings is only one embodiment of the present invention, and the actual structure is not limited thereto. Any reference signs in the claims shall not limit the claims involved. Therefore, if a person of ordinary skill in the art is inspired by the invention and without deviating from the purpose of the invention, can design a similar structural method and embodiment to the technical solution without creativity, they shall all fall within the protection scope of this patent. Furthermore, the word "comprising" does not exclude other elements or steps, and the word "a" before an element does not exclude the inclusion of "a plurality" of that element. Multiple elements stated in a product claim may also be implemented by one element through software or hardware. Words such as first and second are used to indicate names and do not indicate any specific order.

Claims (10)

1. The city ventilation corridor construction method based on CFD and circuit theory comprises the following steps:

data acquisition and preprocessing: acquiring data such as meteorological wind speed, topography, building distribution and the like of a target area, and preprocessing;

and (3) urban wind field drawing: the acquired urban meteorological wind speed and the simplified urban three-dimensional model are imported into CFD software to simulate a wind field, so that urban wind field conditions are obtained;

inversion of surface temperature: performing earth surface temperature inversion based on daytime remote sensing data to obtain earth surface temperature distribution conditions of a target area;

evaluation of wind tunnel construction suitability: carrying out single factor evaluation on the construction suitability of the ventilation gallery of the target area, and superposing the single factor evaluation results to obtain a multi-factor comprehensive evaluation result;

and (3) circuit simulation: combining the city wind field and wind tunnel construction suitability results, and using a circuit theoretical tool to simulate wind environment current of a target area;

and (3) constructing a ventilation gallery system: and constructing an urban ventilation corridor system of a wind source-corridor-repair area according to the current simulation result.

2. The method of constructing a ventilation gallery in a city of claim 1,

the data acquisition comprises digital elevation model data, remote sensing image data, building base map and altitude vector data, road network vector data, green land and water system vector data and wind direction and wind speed years of observation data.

3. The method of constructing a ventilation gallery in a city of claim 1,

the preprocessing is to project and cut the obtained geographic information data in a GIS platform, remove null values of the obtained wind direction and wind speed data, calculate the annual average wind speed and wind frequencies, and build a three-dimensional simplified model of the city.

4. A method of urban ventilation gallery construction according to claim 1 or 3, characterized in that,

the pretreatment steps are as follows:

checking the data condition;

unified coordinates and ranges: performing projection and cutting operation on the acquired data in a GIS platform, and unifying a projection coordinate system and a range of the data;

calculating the wind frequency and average wind speed of each direction:

for the average wind speed of the accumulated year, N is the total number of days of wind speed and wind direction data, V _i For the average daily wind speed on the i th day, f _α For wind frequency in direction alpha, n _α Days with direction alpha in the wind direction data.

5. The method of constructing a ventilation gallery in a city of claim 4,

the data condition checking step specifically comprises the following steps: checking and processing the obtained abnormal value of the digital elevation model data; checking remote sensing image data; checking and processing geometric errors in building, green land, water system and road network vector data; and removing null values and other abnormal values in the wind direction and wind speed data.

6. The method of constructing a ventilation gallery in a city of claim 1,

the step of obtaining the urban wind field comprises the following steps: and establishing a city simplified three-dimensional model according to the building base map, the altitude vector data and the digital elevation model data, and importing the city simplified three-dimensional model into CFD software for wind environment simulation to obtain steady-state wind speed distribution at a specific altitude.

7. The method of constructing a ventilation gallery in a city of claim 6,

the CFD software simulation wind environment comprises the following steps:

pretreatment: the method comprises the steps of importing a model, establishing a solving domain and dividing grids;

solving: the method comprises the steps of establishing a turbulence model, setting boundary conditions, solving steady state and convergence judgment;

post-treatment: the simulation results are displayed using wind speed cloud and vector diagrams.

8. The method of constructing a ventilation gallery in a city of claim 1,

in the circuit simulation step, the circuit simulation result includes acquiring an accumulated current, a current potential, and a normalized current.

9. The method of constructing a ventilation gallery in a city of claim 1,

the steps of constructing the ventilation gallery system comprise: reading accumulated current, normalized current and current potential results obtained by circuit simulation; and determining wind sources, galleries and repair areas in the urban ventilation gallery system and boundaries thereof.

10. A system based on the CFD and circuit theory-based urban ventilation gallery construction method according to any of the claims 1-9,

the method comprises the following steps of: acquiring data such as meteorological wind speed, topography, building distribution and the like of a target area, and preprocessing;

urban wind field drawing module: the acquired urban meteorological wind speed and the simplified urban three-dimensional model are imported into CFD software to simulate a wind field, so that urban wind field conditions are obtained;

the earth surface temperature inversion module: performing earth surface temperature inversion based on daytime remote sensing data to obtain earth surface temperature distribution conditions of a target area;

and a wind tunnel construction suitability evaluation module: carrying out single factor evaluation on the construction suitability of the ventilation gallery of the target area, and superposing the single factor evaluation results to obtain a multi-factor comprehensive evaluation result;

and a circuit simulation module: combining the city wind field and wind tunnel construction suitability results, and using a circuit theoretical tool to simulate wind environment current of a target area;

the ventilation gallery system building module: and constructing an urban ventilation corridor system of a wind source-corridor-repair area according to the current simulation result.