Road construction environment emission calculation method based on CFD simulation

Abstract

The invention discloses a CFD (computational fluid dynamics) simulation-based road construction environmental emission calculation method, and particularly relates to the technical field of environmental engineering and numerical simulation. The method comprises the following steps: establishing a three-dimensional physical model of a road construction environment emission system and determining a flow field computational domain; performing grid division on the three-dimensional physical model in a flow field calculation domain and establishing a grid structure internal association relationship; applying a mass conservation equation set, a momentum conservation equation set and an energy conservation equation set to the simulation model, and constructing a control equation system in combination with the turbulence model and the gas-solid two-phase flow model; setting boundary conditions such as an inlet, an outlet and a wall surface, and constructing an environmental emission simulation calculation model; actual data such as airflow velocity, temperature and particulate matter concentration of a road construction site emission source are collected and input into a simulation model for simulation calculation, a simulation result is compared with actually measured data through a relative error method, model verification is completed, and visual modeling and quantitative measurement and calculation of the road construction environment emission process are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental engineering and numerical simulation, and more particularly to a method for calculating environmental emissions from road construction based on CFD simulation. Background Art

[0002] With the acceleration of urbanization, the number of road construction projects continues to grow. The atmospheric pollutants generated during road construction have a certain impact on the surrounding air quality and human health.

[0003] Existing assessment methods for environmental emissions during the construction phase mostly rely on empirical formulas or emission factors, which make it difficult to accurately characterize the spatial diffusion process of pollutants in complex construction scenarios. They also lack the ability to dynamically simulate the coupled effects of multiple factors such as terrain, equipment layout, and meteorological conditions, resulting in large deviations in the assessment results. Summary of the Invention

[0004] In order to overcome the above-mentioned defects of the prior art, an embodiment of the present invention provides a method for estimating environmental emissions from road construction based on CFD simulation to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for calculating environmental emissions from road construction based on CFD simulation includes the following steps:

[0007] S1: Establish a CFD three-dimensional physical model of the road construction environmental emission system and determine the flow field calculation domain;

[0008] S2: Grid the established CFD simulation model according to the flow field calculation domain and establish internal connections;

[0009] S3: Assign fluid dynamics constraints to the CFD simulation model, including conservation of mass, momentum, energy, turbulence model, and gas-solid two-phase flow;

[0010] S4: Setting the boundary conditions of the CFD simulation model to form a calculation model for simulating environmental emissions of the road system; the boundary conditions include inlet conditions, outlet conditions, and wall conditions;

[0011] S5: Collect actual data from the construction site, perform simulation solutions based on the CFD simulation model, and verify the accuracy of the CFD simulation model using the relative error method.

[0012] In a preferred embodiment, S1 is specifically:

[0013] Collect 3D geometric information of the road construction environmental emission system, including road pavement shape, construction area boundaries, and locations of major emission sources;

[0014] A CFD three-dimensional physical model of the road construction environmental emission system is established based on road geometry information, construction equipment layout information, and surrounding terrain elevation information, including road structure, emission source geometry, and surrounding terrain;

[0015] Set the flow field calculation domain in the CFD three-dimensional physical model;

[0016] The flow field calculation domain is geometrically closed, and the inlet area, outlet area and wall area are divided on the boundary.

[0017] In a preferred embodiment, S2 is specifically:

[0018] Meshing the CFD three-dimensional physical model within the flow field calculation domain. The meshes include surface triangle meshes for representing the road structure and surrounding terrain, and tetrahedral meshes for representing the flow field volume information.

[0019] Apply localized mesh refinement at locations of major emission sources;

[0020] Apply a coarse mesh in the far-field boundary region;

[0021] Perform smoothing on the generated mesh to verify that the distortion and aspect ratio of the mesh elements meet the requirements of CFD simulation calculations;

[0022] A topological connection relationship between grid nodes and grid cells is established to form a grid data structure containing node coordinates and cell connection information.

[0023] In a preferred embodiment, S3 is specifically:

[0024] Based on the established grid data structure, the fluid dynamics control equations, including the mass conservation equation, momentum conservation equation and energy conservation equation, are applied to the CFD three-dimensional physical model;

[0025] A turbulence model is selected to describe the flow characteristics of the airflow, and the Reynolds-averaged Navier-Stokes equation method is used to close the turbulent momentum term;

[0026] Set up a computational model for gas-solid two-phase flow and define the interaction between the gas and solid phases, including the coupling relationship between the gas and solid phases, particle motion trajectories, and interaction forces;

[0027] Set the physical property parameters of the fluid during the calculation process.

[0028] In a preferred embodiment, S4 is specifically:

[0029] Based on the grid data structure of the flow field calculation domain and the fluid mechanics control equations, the boundary conditions of the CFD three-dimensional physical model are set, including the boundary conditions of the inlet area, the outlet area and the wall area;

[0030] The setting of the boundary conditions of the inlet area includes determining the velocity magnitude, airflow direction, temperature and particle concentration distribution of the inlet boundary;

[0031] The setting of the boundary conditions of the outlet area includes specifying the pressure conditions of the outlet boundary and the distribution of the outflow fluid parameters;

[0032] The setting of the boundary conditions in the wall area includes the no-slip velocity condition at the wall, the wall temperature condition, and the boundary limitation conditions for the interaction between particles and the wall.

[0033] In a preferred embodiment, S5 is specifically:

[0034] Obtain actual emission data at road construction sites, including the location of construction equipment emission sources, emission air velocity, emission gas temperature, and particulate matter concentration;

[0035] The actual emission data is used as the boundary condition data of the import area to input into the CFD three-dimensional physical model to perform environmental emission simulation calculations;

[0036] Compare the airflow velocity, temperature, pressure and particulate matter concentration results obtained from the environmental emission simulation with the actual emission data;

[0037] By calculating the relative error between the simulation results and the actual measurement results, it is verified whether the calculation accuracy of the CFD three-dimensional physical model meets the requirements for environmental emission measurement.

[0038] The technical effects and advantages of the road construction environmental emission measurement method based on CFD simulation of the present invention are as follows:

[0039] By establishing a CFD three-dimensional physical model of the road construction environmental emission system, combined with the actual geometric structure and terrain information of the construction site, the distribution of emission sources and the characteristics of the surrounding spatial environment can be accurately reflected; through grid division and internal topological structure establishment, high-resolution simulation of flow field details in complex construction environments can be achieved; the mass conservation, momentum conservation, and energy conservation equations are introduced, and the turbulence model and gas-solid two-phase flow model are integrated to comprehensively characterize the migration and diffusion behavior of pollutants in the flow field; by setting multiple types of boundary conditions including inlets, outlets and walls, the physical rationality of the model boundary response is improved; the actual emission data of the construction site is collected and simulated and solved, and the relative error method is used for accuracy verification, thus achieving dynamic consistency between the CFD simulation model and the measured data, and improving the credibility and engineering applicability of the simulation and measurement evaluation results of road construction environmental emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a schematic diagram of a method for calculating environmental emissions from road construction based on CFD simulation according to the present invention. DETAILED DESCRIPTION

[0041] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0042] Example

[0043] Figure 1 The present invention provides a method for calculating environmental emissions from road construction based on CFD simulation, which includes the following steps:

[0044] S1: Establish a CFD three-dimensional physical model of the road construction environmental emission system and determine the flow field calculation domain;

[0045] S2: Grid the established CFD simulation model according to the flow field calculation domain and establish internal connections;

[0046] S3: Assign fluid dynamics constraints to the CFD simulation model, including conservation of mass, momentum, energy, turbulence model, and gas-solid two-phase flow;

[0047] S4: Setting the boundary conditions of the CFD simulation model to form a calculation model for simulating environmental emissions of the road system; the boundary conditions include inlet conditions, outlet conditions, and wall conditions;

[0048] S5: Collect actual data from the construction site, perform simulation solutions based on the CFD simulation model, and verify the accuracy of the CFD simulation model using the relative error method.

[0049] S1: Establish a CFD three-dimensional physical model of the road construction environmental emission system and determine the flow field calculation domain, including:

[0050] Collect 3D geometric information of road construction environmental emission systems;

[0051] The three-dimensional geometric information of the road construction environmental emission system includes the shape of the road surface, the boundaries of the construction area, and the locations of major emission sources. The three-dimensional geometric information in the road construction environmental emission system involves spatial shape information related to the road structure and construction area, as well as spatial position information of construction equipment related to the emission process. The data that needs to be collected includes the geometric dimensions of the road surface, the longitudinal and transverse slopes of the road surface, the radius of road curves, the location coordinates of the construction area boundary line, the location and appearance of important buildings or temporary facilities within the construction area, the type and spatial location of construction equipment, and the spatial positioning information of major emission sources during the road construction process, such as construction vehicles, construction machinery, mixing plants, excavators, and pavers. Surveying and mapping instruments such as total stations, three-dimensional laser scanners, or drones can be used for on-site mapping and aerial surveys to collect on-site conditions and generate accurate three-dimensional spatial coordinate data, recording the spatial location of each piece of construction equipment and emission source and the corresponding detailed geometric outline. For example, if there is a 500-meter-long and 20-meter-wide urban road widening and reconstruction project at the construction site, it is necessary to record the road widening area and the geometric dimensions of the original road through on-site measurement, including the road thickness, slope, curve radius and edge contour. The boundary of the construction area is determined as the location of the temporary fence outside the area, and the position of construction equipment such as excavators, bulldozers, loaders and transport vehicles in the construction area is mapped to determine the location coordinates of the emission sources of each construction equipment, providing real and reliable basic data for the establishment of the CFD three-dimensional physical model.

[0052] A CFD three-dimensional physical model of the road construction environmental emission system is established based on road geometry information, construction equipment layout information, and surrounding terrain elevation information;

[0053] The CFD 3D physical model includes the road structure, emission source geometry, and surrounding terrain. Using previously collected data on the road pavement shape, construction area boundaries, construction equipment location and outlines, and terrain elevation data surrounding the construction site, a comprehensive CFD 3D physical model is established using professional 3D modeling software such as CATIA, SolidWorks, or similar 3D geometric modeling tools. The CFD 3D physical model reflects the 3D geometric shape of the road structure, including the road pavement structure and its extended spatial area. Furthermore, based on the construction equipment layout information, the 3D geometric outlines of the construction equipment are drawn and integrated into the overall model as the emission source geometry. Based on actual terrain data, the actual terrain elevation information surrounding the construction area is constructed, presenting the terrain undulations and related terrain contours. For example, for a road construction site located in hilly terrain, there may be a certain height of slope near the construction site. When establishing the 3D physical model, the surrounding terrain height differences, slope angles, and hill positions are accurately modeled, thus fully presenting the 3D physical environment of the actual construction area. Determine the size and structure of each emission device, paved road surface, and road environment in the road environment emission system, use pre-processing software to establish a three-dimensional physical model, and constitute the flow field calculation domain; wherein, the emission equipment includes at least one of a paver, a roller, and a milling machine.

[0054] Set the flow field calculation domain in the CFD three-dimensional physical model;

[0055] Based on a fully constructed three-dimensional physical model of the road structure, emission source geometry, and surrounding terrain, the spatial extent of the computational flow field area is determined to accurately analyze environmental emissions during road construction. The computational flow field domain is typically defined as the spatial extent encompassing emission sources, construction equipment, and their impact areas. The computational domain boundaries are determined based on the site scale and emission source location. For example, they typically extend at least 500 meters outward from major construction emission sources and at least 50 meters vertically upward from the top of the source to fully capture the entire process of pollutant emission diffusion in the surrounding space. The computational flow field domain must encompass all road structures and construction equipment within the construction area, fully accounting for the influence of surrounding terrain so that the computational domain boundaries meet the physical requirements of actual emission propagation. For example, if the actual construction site is a road widening project within an urban area, the computational flow field domain should fully encompass the spatial extent between the construction section and the surrounding buildings, ensuring that all areas potentially affected by construction emissions are included within the computational flow field domain.

[0056] The flow field calculation domain is geometrically closed and the inlet area, outlet area and wall area are divided on the boundary;

[0057] To ensure the feasibility of CFD simulations, the defined flow field computational domain must be geometrically enclosed, defining the computational domain as a completely enclosed spatial region. Specifically, geometric enclosure is performed around the boundaries of the defined flow field computational domain, forming a completely enclosed spatial volume. After enclosure, different types of boundary regions are identified, including inlet, outlet, and wall regions. The inlet region is defined as the location upstream of the construction emission source or where the primary airflow enters the computational domain. It is used to input the airflow velocity, temperature, airflow direction, and particulate matter concentration. The outlet region is defined as the downstream boundary of the flow field and is used to define the pressure or flow characteristics of the fluid exiting the computational domain. The wall region is defined as the solid surface boundary of construction equipment, road surfaces, the ground, and surrounding buildings or terrain. These areas are restricted to fluid flow and are set to no-slip boundary conditions to reflect the restrictive effects of real physical surfaces. For example, when geometrically enclosing an urban road construction site, the inlet region can be set upstream of the wind direction, the outlet region at the downstream boundary of the construction site, and the wall region encompasses the road surface, the exterior surfaces of construction equipment, and the facades of surrounding buildings. By defining the characteristics of these boundary regions, accurate boundary conditions can be defined during CFD simulations.

[0058] S2: Grid the established CFD simulation model according to the flow field calculation domain and establish internal connections, including:

[0059] Mesh the CFD three-dimensional physical model within the flow field calculation domain;

[0060] Meshing is a crucial step in CFD simulations. By creating a large number of tiny spatial cells within three-dimensional space, a continuous flow problem is transformed into a discrete computational problem. First, the established three-dimensional CFD physical model of the road construction environmental emissions system must be spatially discretized within the defined flow field computational domain. The three-dimensional physical model is a complete three-dimensional model based on on-site data collected from the road surface geometry, construction area boundaries, construction equipment layout, and surrounding terrain elevation. This includes the road structure, emission source geometry, and surrounding terrain.

[0061] Specifically, meshing involves two types of meshes: surface triangular meshes and volume tetrahedral meshes. Surface triangular meshes describe the spatial shape of the road surface and surrounding terrain. Volume tetrahedral meshes describe the spatial distribution and flow characteristics of the fluid within the entire flow field computational domain, reflecting the spatial characteristics of pollutant diffusion and transport.

[0062] For example, in the project of urban road reconstruction, the widened area of the road surface and the original road structure surface are represented by a series of triangular mesh elements, and the spatial coordinates of the vertices of each triangular mesh element are derived from the three-dimensional physical model. The three-dimensional outer surface of the soil slope, roadbed or retaining wall structure existing on both sides of the road is also divided into triangular mesh elements, representing the complex curved surface of the terrain and structure. Tetrahedral mesh is automatically generated inside the model, extending and filling from the road structure and terrain surface mesh to the interior of the space, forming a volume discrete element without gaps, which is used to solve the fluid parameters in the CFD calculation process.

[0063] Applying local encryption grid at the location of the main emission source;

[0064] Local encryption grid refers to the use of smaller grid size around the main emission source in the road construction site, thereby improving the spatial resolution of the area to ensure the fine simulation of fluid flow and pollutant diffusion in the emission source area. The main emission source is generally a location with high emission air flow speed, high concentration or significant temperature difference during construction, such as the exhaust port of the paver, the exhaust pipe of the mixing station, the exhaust port of the excavator and the dust raising area of the on-site material pile.

[0065] For example, when simulating the road construction site, the grid element size near the paver exhaust port is usually set to no more than 0.05 meters to fully resolve the initial diffusion process of the emission pollutants and the turbulent structure in the emission source area. The grid element size in the area away from the main emission source can be set to 0.5 meters to several meters to optimize the balance between calculation resources and precision requirements. The local encryption method of the grid can be realized through the grid size control tool in the pre-processing software, and the grid size of the area around the emission source is explicitly set in the three-dimensional modeling interface.

[0066] Applying coarse grid in the far-field boundary area;

[0067] The coarse grid technique features that in the location away from the emission source and the main influence area of pollutant diffusion in the road construction site, larger size grid elements are used in the grid division to reduce the total number of grid elements and improve the overall calculation efficiency. The grid element size near the boundary area or far-field area in the flow field calculation domain is usually set larger.

[0068] For example, in the process of emission simulation of urban road construction environment, the grid element size in the far-field area more than 500 meters away from the construction emission source is generally set to 5 meters or even larger to save the number of grid elements and calculation resources. There is a clear gradient transition between the size of the coarse grid elements in the far-field area and the size of the local encryption grid in the near-field, to avoid the instability caused by local mutation, and the gradient can be explicitly controlled through software settings to ensure that the grid size gradually increases from the emission source to the boundary area.

[0069] Perform smoothing on the generated mesh to verify that the distortion and aspect ratio of the mesh elements meet the requirements of CFD simulation calculations;

[0070] Mesh smoothing is a mesh optimization method used to adjust the shape of irregular mesh cells caused by the complexity of the geometric model to avoid severe distortion, excessive length or shortness of the mesh cells. Distortion and aspect ratio are two key indicators to describe the quality of mesh cells. Mesh cells with excessive distortion may cause instability in the numerical solution, and mesh cells with unreasonable aspect ratio may cause inaccurate calculation results. The calculation domain uses the layer-laying method to technically process the dynamic mesh, and the entire flow field area adopts a two-layer nested structure. The static area and the physical model area of ​​the emission equipment use a hexahedral structured mesh, and the rest use a tetrahedral unstructured mesh. The interface type of each area is set to Interior for connection, and the interface of the large rectangular and small rectangular channels is set to Interface for connection.

[0071] For example, in CFD simulations of urban road widening construction, after the initial mesh generation, mesh processing software such as ICEM CFD, HyperMesh, or similar mesh optimization tools should be used to automatically check and correct unit geometry defects. Using the software's mesh quality evaluation function, maximum allowable distortion and unit aspect ratio thresholds are set, such as distortion not exceeding 0.3 and aspect ratio not exceeding 5.0. Built-in algorithms are then used to automatically adjust and smooth mesh units that exceed these quality requirements, ensuring the stability and accuracy of the CFD simulation process.

[0072] Establishing the topological connection relationship between grid nodes and grid cells, forming a grid data structure containing node coordinates and cell connection information;

[0073] Topological connectivity records the positional relationship between each grid node and the surrounding grid cells, as well as the connection relationship between grid cells. The grid data structure contains the spatial coordinate information of all grid nodes and the grid node numbers to which each grid cell is connected, thus forming a grid file that can be recognized and used by numerical calculation programs.

[0074] For example, in CFD simulations at construction sites, the mesh files generated by the pre-processing software usually contain two parts of data. The first part is a list of node coordinates, such as node numbers and spatial coordinates (x, y, z). The second part is the unit connection relationship, such as the numbering sequence of the nodes contained in each triangular or tetrahedral unit, thereby defining the topological structure of the unit.

[0075] S3: Assign fluid dynamics constraints to the CFD simulation model, including conservation of mass, momentum, energy, turbulence model, and gas-solid two-phase flow, including:

[0076] Based on the established grid data structure, the fluid dynamics control equations, including the mass conservation equation, momentum conservation equation and energy conservation equation, are applied to the CFD three-dimensional physical model;

[0077] Based on the established mesh data structure, including surface triangle meshes and tetrahedral volume meshes, as well as mesh data showing node coordinates and element connectivity, the governing fluid dynamics equations are applied to the CFD 3D physical model. These governing equations include the conservation of mass, momentum, and energy, forming the fundamental equations for simulating the flow process within the flow field.

[0078] The mass conservation equation is the fundamental equation governing the distribution of fluid mass within a flow field. It states that the mass of the fluid within any control volume within the flow field calculation domain is conserved. Specifically, the difference between the mass of the fluid flowing into and out of the control volume is equal to the time-varying mass within the control volume. The mass conservation equation is typically expressed as a continuity equation. For example, when a tetrahedral unit within a road construction area is used as the calculation control volume, the difference in the mass flow rates of the air flowing into and out of each unit face must be equal to the rate of change of the gas mass within the unit over time.

[0079] The momentum conservation equation is used to describe the flow characteristics of the airflow within the flow field and to determine the distribution of physical quantities such as velocity and pressure field of the airflow in the construction area, around the emission source, and under terrain conditions. The momentum conservation equation is usually described using Newton's second law, which shows the relationship between the force acting on the fluid control body and the rate of change of the momentum of the fluid in the control body. In the implementation of the CFD model of the road construction area, the momentum conservation equation is used to calculate the velocity field and pressure field of the fluid after being affected by the exhaust airflow of the construction equipment. For example, in an actual embodiment, a road paver emits a high-speed hot air flow, which is set as a momentum source term at the smoke outlet of the paver. The velocity and pressure in the surrounding grid cells are updated with the calculation, reflecting the disturbance effect of the exhaust airflow on the ambient air.

[0080] The energy conservation equation is used to describe the temperature field and energy distribution within the fluid, reflecting the energy exchange between the high-temperature gases emitted during the construction process and the ambient air. The energy conservation equation is often expressed in terms of the first law of thermodynamics during CFD calculations, clarifying the relationship between the energy carried by the fluid when it flows into and out of the control body and the heat change within the control body. For example, the hot gases emitted by asphalt mixing equipment and paving equipment at a road construction site undergo significant heat exchange with the surrounding air, and the energy conservation equation can clearly describe the temperature field distribution at the construction site. For example, when the exhaust air temperature of the mixing plant is set to 130 degrees Celsius, the energy equation ensures that the temperature distribution after heat exchange with the surrounding air is accurately calculated, thereby reflecting the actual heat diffusion process.

[0081] A turbulence model is selected to describe the flow characteristics of the airflow, and the Reynolds-averaged Navier-Stokes equation method is used to close the turbulent momentum term;

[0082] Because construction site airflow exhibits significant turbulent characteristics, an appropriate turbulence model is required to describe the airflow patterns during road construction emissions. The Reynolds-averaged Navier-Stokes equations are used to describe turbulent flow in the flow field. The Reynolds-averaged method decomposes the instantaneous flow variables into a time-averaged component and a pulsating component, allowing complex unsteady turbulent motion to be resolved by computing steady-state or quasi-steady-state equations.

[0083] The Reynolds-averaged Navier-Stokes equations method requires an additional set of model equations to close the turbulent momentum terms. This set of equations is called a turbulence closure model. For example, in specific embodiments, the standard k-ε turbulence model can be used. Two additional transport equations, the turbulent kinetic energy (k) and the turbulent dissipation rate (ε), are introduced to the model to describe the transfer of turbulent fluctuating velocity and energy, making the Reynolds-averaged Navier-Stokes equations completely closed and solvable.

[0084] In the implementation of road construction environmental emission simulation, for example, when pavers and milling machines emit hot air during urban road widening construction, the standard k-ε turbulence model is used as a closed-loop method. By setting the corresponding turbulence model coefficients and boundary conditions, the numerical solution of the turbulent flow field in the construction site area is completed, and the specific characteristics of airflow diffusion, suction and expansion at the construction site are accurately simulated, fully reflecting the actual situation of construction environmental emissions.

[0085] Set up a computational model for gas-solid two-phase flow and define the interaction between the gas and solid phases, including the coupling relationship between the gas and solid phases, particle motion trajectories, and interaction forces;

[0086] Road construction emissions not only include gaseous pollutants but also generate a large amount of solid particulate matter, such as dust. A gas-solid two-phase flow model is required to accurately describe the dynamic behavior between the gas and particles. Specifically, the Lagrangian-Eulerian method can be used to describe the gas-solid two-phase flow model, with the gas phase described using the Euler method and the particle phase using the Lagrangian method.

[0087] The model setup requires defining the coupling relationship between the gas and particle phases, including the drag, buoyancy, gravity, and collision and rebound forces generated by these interactions. For example, the particle diameters of particles generated at road construction sites range from 1 to 100 microns. The particle trajectory is tracked in the simulation using a discrete phase model. Specifically, the trajectory, settling rate, and position of each particle within the airflow field are calculated, and the particle's collision, rebound, or adhesion behavior with surfaces such as construction equipment and the ground is accounted for.

[0088] Set the physical property parameters of the fluid during the calculation process;

[0089] Before performing CFD simulations, it is necessary to define the physical properties of the fluid, including density, dynamic viscosity, specific heat capacity, thermal conductivity, and particle density and diameter. These can be determined based on the construction site's ambient temperature, atmospheric pressure, and actual emission characteristics.

[0090] For example, the air density in the simulation area is 1.225 kg / m³ under standard conditions, and the dynamic viscosity is 1.789×10⁻ 5 kg / (m·s), specific heat capacity is 1006 J / (kg·K), and thermal conductivity is 0.0242 W / (m·K). Particle density can be set to the density of quartz sand (2650 kg / m³) based on actual site conditions, with particle diameters ranging from 1 to 100 microns. Precisely setting physical property parameters ensures a rigorous physical foundation for CFD simulations and reliable results.

[0091] During the asphalt discharge process from the road, the mass of asphalt smoke and air flowing in per unit time is equal to the mass flowing out. The CFD simulation model is controlled by the mass conservation principle. The calculation formula is as follows:

[0092]

[0093] in, is the fluid density, For time, 、 、 They are 、 、 The velocity component on the axis, is the mass added to the continuous phase by other terms;

[0094] In the CFD simulation model, the sum of the initial momentum and the sum of the final momentum in the flow field are equal, and Newton's second law of momentum conservation is used to characterize it. The calculation formula is expressed as follows:

[0095]

[0096] in, is the hydrostatic pressure, is the stress tensor, and are gravitational body force and external body force respectively;

[0097] As the asphalt release source continues to dissipate heat, the ambient temperature gradually rises, causing internal heat exchange. The heat exchange process is characterized by the law of energy conservation, and the calculation formula is expressed as follows:

[0098]

[0099] in, is the specific heat capacity, is the temperature, is the heat transfer coefficient of the fluid, It is the part of the fluid's internal heat source and the fluid's mechanical energy that is converted into thermal energy due to the viscosity effect.

[0100] In a natural environment, asphalt smoke moves irregularly in the flow field due to factors such as wind, temperature, and its own gravity, which is a natural turbulence. The standard k-ε turbulence model is used to simulate the movement of asphalt smoke in the flow field. The calculation formula is expressed as follows:

[0101]

[0102]

[0103]

[0104] in, is the turbulent kinetic energy caused by the laminar velocity gradient, is the buoyancy turbulent kinetic energy, is the diffusion effect of compressible flow, 、 and is the model constant, and for and The turbulent Prandtl number of the equation, is a constant, taken as 0.09.

[0105] During asphalt pavement construction, asphalt smoke and air will form a dust-laden airflow composed of solid particles and gas, which will move under the action of the flow field, forming a gas-solid two-phase flow phenomenon. The motion trajectory of solid particles is simulated using gas-solid two-phase flow, and the calculation formula is expressed as follows:

[0106]

[0107] in, is the mass of the particle, is the particle's velocity vector, is the net force acting on the particle.

[0108] S4: Set the boundary conditions of the CFD simulation model to form a calculation model for simulating road system environmental emissions; the boundary conditions include inlet conditions, outlet conditions, and wall conditions, including:

[0109] Based on the grid data structure of the flow field calculation domain and the fluid mechanics control equations, the boundary conditions of the CFD three-dimensional physical model are set, including the boundary conditions of the inlet area, the outlet area and the wall area;

[0110] Boundary condition setting involves defining parameters for the boundary regions of a CFD 3D physical model after constructing the flow field computational domain mesh data structure and applying the governing fluid dynamics equations. Setting boundary conditions is crucial for ensuring the reliability and accuracy of CFD simulation results. Boundary conditions include inlet, outlet, and wall conditions, each corresponding to a different spatial location and physical definition.

[0111] The inlet boundary conditions are set at the location within the flow field computational domain where the airflow enters the simulation area, typically corresponding to the airflow input location at the construction site. The outlet boundary conditions are set at the location where the airflow leaves the simulation area, and the wall boundary conditions are set on the surfaces of solid objects within the construction site, including construction equipment, roads, terrain, and building exteriors. The division of the regions is consistent with the geometric closure and boundary division of the flow field computational domain.

[0112] For example, during the simulation of the urban road widening construction environment, the pre-processing software is used to set the upwind boundary of the road construction site in the CFD calculation domain as the inlet area, and the leeward boundary of the construction site as the outlet area. At the same time, the road surface, construction equipment on both sides of the road, and all surfaces of temporary buildings and facilities in the construction area are set as wall areas to accurately reflect the actual airflow characteristics during road construction.

[0113] Inlet condition setting: The flow field inlet includes the wind field velocity inlet and the environmental emission release source inlet. The wind flow from the road construction site is air at room temperature and is connected to the atmosphere, so the velocity inlet is used. The wind speed uses the measured value of 0.53m / s, and the pressure value is atmospheric pressure. The environmental emission release source inlet uses a particulate matter injection source. The initial surface source has a total of 600 injection points, the temperature is 140℃, the boundary conditions of the inlet and outlet are set to Escape, and the remaining wall surfaces are Reflect.

[0114] Outlet condition setting: The outlet condition adopts pressure outlet, and since the flow field outlet is connected to the atmosphere, the static pressure is 0, that is, one atmosphere.

[0115] The setting of the boundary conditions of the inlet area includes determining the velocity magnitude, airflow direction, temperature and particle concentration distribution of the inlet boundary;

[0116] Setting inlet boundary conditions defines the physical parameters of the inlet boundary within the CFD 3D physical model. These parameters, including velocity, airflow direction, temperature, and particle concentration distribution, fully reflect the initial characteristic state of the airflow entering the computational domain. The definition of this initial characteristic state directly impacts the simulation results of airflow, particle diffusion, and energy transfer within the computational domain.

[0117] For example, in the environmental emission simulation of urban road construction, the speed setting at the boundary of the inlet area can be determined based on actual observations or meteorological data. For example, the wind speed at the inlet boundary is set at 3 meters per second, and the airflow direction is clearly specified as an angle of approximately 30 degrees with the longitudinal direction of the road. At the same time, the temperature parameters of the boundary of the inlet area are determined based on local meteorological data. For example, during summer construction, the air temperature in the inlet area is set at 32 degrees Celsius. The particle concentration distribution is defined based on the actual construction process characteristics. For example, the particle concentration at the inlet area is set at 0.1 mg of dust per cubic meter. These particles are mainly smaller particles in the dust at the construction site. They are input into the CFD model through boundary conditions to fully reflect the initial state of the on-site emission airflow.

[0118] The setting of the boundary conditions of the outlet area includes specifying the pressure conditions of the outlet boundary and the distribution of the outflow fluid parameters;

[0119] The outlet boundary conditions describe the flow exit state at the computational domain's exit. Specifically, they include pressure conditions and the distribution of outflow fluid parameters. Pressure conditions can be specified using either fixed static pressure or atmospheric pressure to ensure smooth and continuous flow out of the computational domain at the outlet, avoiding instabilities in the computational domain boundary conditions.

[0120] For example, in urban road construction, the exit area boundary conditions are explicitly specified as atmospheric pressure boundary conditions, with the static pressure in the exit area set to the standard atmospheric pressure of 101,325 Pa. This ensures that the fluid in the flow field within the computational domain can flow smoothly out without generating countercurrents or flow anomalies that are inconsistent with physical reality. Furthermore, the outflow fluid parameter distribution, including the temperature and particle concentration distribution in the exit area, is automatically determined by the model's internal solution results, or initial conditions are set based on actual site conditions, ensuring that the exit area boundary conditions accurately correspond to the entire simulation process.

[0121] The setting of the boundary conditions of the wall region includes the no-slip velocity condition at the wall, the wall temperature condition, and the boundary limiting conditions for the interaction between particles and the wall;

[0122] Wall region boundary conditions are defined for all solid surfaces within the flow domain, including construction equipment, road surfaces, surrounding buildings, ground, and terrain. These include no-slip velocity conditions, wall temperature conditions, and constraints on particle-wall interactions.

[0123] Specifically, the no-slip velocity condition specifies that the velocity of the fluid on the wall is zero. This means that the air velocity on the construction equipment, road, and ground surfaces at the wall is equal to the velocity of the wall itself. This is usually static, reflecting the physical constraints of the fluid on the solid surface. For example, on the surface of the construction site pavement and paving equipment, no-slip boundary conditions are set to ensure that the air velocity in the computational domain is zero at these surfaces.

[0124] The wall temperature conditions are set based on the specific conditions on site. For example, during road construction, the outer surface temperature of the paver exhaust stack is set to approximately 90°C, the surface temperature of the asphalt pavement after construction is 120°C, and the surface temperature of ordinary pavement is set to approximately 30°C based on actual measurement results.

[0125] The constraints for particle-wall interactions determine the physical behavior of particles in the wall region, such as rebound, deposition, or adhesion after collision. For example, in an urban road construction site simulation, the interaction between particles and construction equipment and the road surface can be explicitly set to a rebound coefficient of 0.6, meaning that particles will bounce off the wall at 60% of their initial velocity after colliding with the wall. Alternatively, the adhesion probability can be set to 10%, meaning that 10% of particles will adhere to the wall after collision, thus reflecting the true interaction between particles and solid walls.

[0126] Wall condition setting: At the asphalt road construction site, the road surface and the paver surface are set to a constant temperature and non-slip wall surface.

[0127] S5: Collect actual construction site data, perform simulation solutions based on the CFD simulation model, and verify the accuracy of the CFD simulation model using the relative error method, including:

[0128] Obtain actual emission data at road construction sites, including the location of construction equipment emission sources, emission air velocity, emission gas temperature, and particulate matter concentration;

[0129] Actual emissions data is collected through on-site measurements and recording at road construction sites, serving as a foundation for CFD environmental emissions simulations. This data includes the location of construction equipment emission sources, exhaust air velocity, exhaust gas temperature, and particulate matter concentration. This data is obtained through real-time on-site measurements using specialized measuring instruments and equipment, ensuring a reliable and authentic data foundation for CFD three-dimensional physical model simulations.

[0130] Specifically, the location of construction equipment emission sources refers to the precise spatial coordinates of construction equipment generating pollutants within a road construction site. This includes the precise coordinates of the emission outlets of construction machinery such as pavers, mixing plants, milling machines, and rollers. These locations are located using a total station or GPS measuring device. For example, at an urban road widening construction site, a total station could be used to locate the spatial locations of paver exhaust outlets and mixing plant chimney outlets within the construction site and record these locations as three-dimensional coordinates.

[0131] Exhaust air velocity is the real-time velocity at the exhaust outlet of construction equipment, measured using an anemometer or pitot tube flowmeter. For example, at an urban road widening construction site, the exhaust air velocity at the paver exhaust pipe outlet is measured and recorded as a real-time value of 3.5 meters per second, with the specific time and environmental conditions of the measurement noted.

[0132] Exhaust gas temperature refers to the real-time temperature of exhaust gases from construction equipment exhaust outlets, measured using high-precision thermocouples or infrared thermometers. For example, at a construction site, the airflow temperature from the outlet of a paver or mixing plant is measured and recorded as 140 degrees Celsius to clarify the initial temperature conditions of the emission source during simulation calculations.

[0133] Particulate matter concentration refers to the mass concentration of solid particulate matter generated during construction in the air near the emission source, and is measured in real time using a particulate matter monitor. For example, on-site measurements of the particulate matter concentration in the air near the paver exhaust port can yield a real-time value, such as 0.8 mg / m³, reflecting the actual dust or exhaust emissions generated during road construction.

[0134] The actual emission data is used as the boundary condition data of the import area to input into the CFD three-dimensional physical model to perform environmental emission simulation calculations;

[0135] For example, during the construction of urban road widening, the actual measured exhaust air velocity of the paver was 3.5 meters per second, the temperature was 140 degrees Celsius, and the particulate matter concentration was 0.8 mg per cubic meter. These were input into the inlet area boundary condition parameters of the CFD three-dimensional physical model as the model's initial calculation conditions, reflecting the initial state of the actual emissions during the construction process and ensuring that the simulation calculation can truly reflect the characteristics of on-site emissions and the environmental impact.

[0136] Specifically, the grid data structure of the CFD three-dimensional physical model has been established, and the boundary conditions have been divided and defined. The on-site measurement data is entered into the CFD calculation software in digital form and set at the entrance position of the boundary conditions. The emission data set in the software is accurately mapped to each grid cell in the inlet area to ensure that the initial input of the calculation process is accurate, meet the requirements of CFD simulation calculations, and ensure that the simulation calculation process fully and accurately reflects the characteristics of the actual road construction emission process.

[0137] Compare the airflow velocity, temperature, pressure and particulate matter concentration results obtained from the environmental emission simulation with the actual emission data;

[0138] Specifically, after the CFD simulation is complete, the calculated data for each location within the flow field is output, including the velocity distribution, temperature field distribution, pressure field distribution, and particle concentration distribution of the airflow at each location within the construction area. The calculated data results are displayed in the CFD calculation software in the form of numerical values ​​and graphics.

[0139] Emission data obtained from measurements at the road construction site, such as an air velocity of 3.5 meters per second, a temperature of 140 degrees Celsius, and a particulate matter concentration of 0.8 milligrams per cubic meter measured at the paver exhaust outlet, were compared with the numerical results of CFD simulation calculations at the corresponding spatial locations to evaluate the accuracy and precision of the CFD model in simulating road construction environmental emissions.

[0140] For example, in actual implementation, multiple monitoring points can be selected within the construction area, such as the spatial positions 1 meter, 3 meters, and 5 meters above the paver exhaust port to extract the model simulation results, and compare and analyze them item by item with the actual data measured at the same location on site, record the differences in the comparison process, and form a comparative analysis table or diagram.

[0141] By calculating the relative error between the simulation results and the actual measurement results, we can verify whether the calculation accuracy of the CFD three-dimensional physical model meets the requirements for environmental emission measurement;

[0142] Specifically, the relative error is calculated as follows: each specific parameter obtained from the simulation calculation, such as airflow velocity, temperature, and particulate matter concentration, is subtracted from the corresponding value actually measured on site, the absolute value of the difference is calculated, and then divided by the actual measured value to obtain the relative error percentage for each position and each parameter.

[0143] For example, during road construction, if the simulated airflow velocity at the paver exhaust outlet is calculated to be 3.4 meters per second, but the actual measurement is 3.5 meters per second, the relative error is (3.5-3.4) / 3.5×100%=2.86%. If the calculated temperature is 138 degrees Celsius, but the actual measurement is 140 degrees Celsius, the relative error is (140-138) / 140×100%=1.43%. Using a similar method, the relative error of each parameter is calculated one by one and then comprehensively analyzed.

[0144] Finally, a calculation accuracy evaluation standard is set. For example, if the relative error is less than 10%, the model calculation accuracy is considered to meet the actual environmental emission measurement requirements of the project, thereby completing the verification of the overall calculation accuracy of the CFD three-dimensional physical model.

[0145] Taking into account the impact of temperature, wind speed and wind temperature on the trajectory of environmental emissions, key data from the actual construction site were collected to verify the CFD simulation model, taking asphalt smoke as an example. An infrared thermometer (RNO), an aerosol detector (SDL511), and a wind speed-temperature-humidity measuring instrument (CIMER MC AR856) were used to measure the on-site asphalt smoke concentration, wind speed and wind temperature at the construction site. The locations of environmental emission monitoring points include: 0.5m, 1.0m, 1.5m, 2.0m, and 2.5m from the tail of the emission equipment.

[0146] The relative error method is used to compare the actual monitored environmental emission concentration on site with the environmental emission concentration at the corresponding location in the simulation. The calculation formula is as follows:

[0147]

[0148] in, is the ambient emission concentration obtained by the simulation model, It is the environmental emission concentration obtained from construction site environmental monitoring.

[0149] The above formulas are all dimensionless and numerical calculations. The formulas are obtained by collecting a large amount of data and performing software simulation to obtain the most recent real situation. The preset parameters and thresholds in the formulas are set by technicians in this field according to actual conditions.

[0150] The above embodiments can be implemented in whole or in part via software, hardware, firmware, or any other combination. When implemented using software, the above embodiments can be implemented in whole or in part in the form of a computer program product. The computer program product comprises one or more computer instructions or computer programs. When loaded or executed on a computer, the processes or functions described in the embodiments of this application are fully or partially performed. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired means (e.g., infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium accessible by a computer or a data storage device such as a server or data center that contains a collection of one or more available media. The available medium can be magnetic media (e.g., floppy disks, hard disks, tapes), optical media (e.g., DVDs), or semiconductor media. The semiconductor media can be a solid-state drive.

[0151] Those skilled in the art will appreciate that the modules and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0152] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and modules described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0153] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the modules is only a logical function division. In actual implementation, there may be other division methods, such as multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or modules, which can be electrical, mechanical or other forms.

[0154] The modules described as separate components may or may not be physically separate, and the components shown as modules may or may not be physical modules, and may be located in one place or distributed across multiple network modules. Some or all of the modules may be selected to achieve the purpose of this embodiment according to actual needs.

[0155] In addition, each functional module in each embodiment of the present application may be integrated into one processing module, or each module may exist physically separately, or two or more modules may be integrated into one module.

[0156] If the functions are implemented in the form of software function modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0157] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

[0158] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for calculating environmental emissions from road construction based on CFD simulation, characterized in that: The steps include: S1: Establish a CFD three-dimensional physical model of the road construction environmental emission system and determine the flow field calculation domain; S2: Grid the established CFD simulation model according to the flow field calculation domain and establish internal connections; S3: Assign fluid dynamics constraints to the CFD simulation model, including conservation of mass, momentum, energy, turbulence model, and gas-solid two-phase flow; S4: Setting the boundary conditions of the CFD simulation model to form a calculation model for simulating environmental emissions of the road system; the boundary conditions include inlet conditions, outlet conditions, and wall conditions; S5: Collect actual data from the construction site, perform simulation solutions based on the CFD simulation model, and verify the accuracy of the CFD simulation model using the relative error method.

2. A method for calculating road construction environmental emissions based on CFD simulation according to claim 1, characterized in that: S1, including: Collect 3D geometric information of the road construction environmental emission system, including road pavement shape, construction area boundaries, and locations of major emission sources; A CFD three-dimensional physical model of the road construction environmental emission system is established based on road geometry information, construction equipment layout information, and surrounding terrain elevation information, including road structure, emission source geometry, and surrounding terrain; Set the flow field calculation domain in the CFD three-dimensional physical model; The flow field calculation domain is geometrically closed, and the inlet area, outlet area and wall area are divided on the boundary.

3. The method for calculating road construction environmental emissions based on CFD simulation according to claim 2, characterized in that: S2, including: Meshing the CFD three-dimensional physical model within the flow field calculation domain. The meshes include surface triangle meshes for representing the road structure and surrounding terrain, and tetrahedral meshes for representing the flow field volume information. Apply localized mesh refinement at locations of major emission sources; Apply a coarse mesh in the far-field boundary region; Perform smoothing on the generated mesh to verify that the distortion and aspect ratio of the mesh elements meet the requirements of CFD simulation calculations; A topological connection relationship between grid nodes and grid cells is established to form a grid data structure containing node coordinates and cell connection information.

4. The method for calculating road construction environmental emissions based on CFD simulation according to claim 3 is characterized in that: S3, including: Based on the established grid data structure, the fluid dynamics control equations, including the mass conservation equation, momentum conservation equation and energy conservation equation, are applied to the CFD three-dimensional physical model; A turbulence model is selected to describe the flow characteristics of the airflow, and the Reynolds-averaged Navier-Stokes equation method is used to close the turbulent momentum term; Set up a computational model for gas-solid two-phase flow and define the interaction between the gas and solid phases, including the coupling relationship between the gas and solid phases, particle motion trajectories, and interaction forces; Set the physical property parameters of the fluid during the calculation process.

5. The method for calculating road construction environmental emissions based on CFD simulation according to claim 4 is characterized in that: S4, specifically: Based on the grid data structure of the flow field calculation domain and the fluid mechanics control equations, the boundary conditions of the CFD three-dimensional physical model are set, including the boundary conditions of the inlet area, the outlet area and the wall area; The setting of the boundary conditions of the inlet area includes determining the velocity magnitude, airflow direction, temperature and particle concentration distribution of the inlet boundary; The setting of the boundary conditions of the outlet area includes specifying the pressure conditions of the outlet boundary and the distribution of the outflow fluid parameters; The setting of the boundary conditions in the wall area includes the no-slip velocity condition at the wall, the wall temperature condition, and the boundary limitation conditions for the interaction between particles and the wall.

6. A method for calculating road construction environmental emissions based on CFD simulation according to claim 5, characterized in that: S5, specifically: Obtain actual emission data at road construction sites, including the location of construction equipment emission sources, emission air velocity, emission gas temperature, and particulate matter concentration; The actual emission data is used as the boundary condition data of the import area to input into the CFD three-dimensional physical model to perform environmental emission simulation calculations; Compare the airflow velocity, temperature, pressure and particulate matter concentration results obtained from the environmental emission simulation with the actual emission data; By calculating the relative error between the simulation results and the actual measurement results, it is verified whether the calculation accuracy of the CFD three-dimensional physical model meets the requirements for environmental emission measurement.

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