A calculation method for the drainage performance of long-span roofs considering the coupling effect of wind and rain

Abstract

The present invention discloses a calculation method for the drainage performance of a large-span roof considering the coupling effect of wind and rain, which is realized based on a building parametric BIM model and CFD, and includes: parameterizing the existing roof surface shape and drainage facilities; extracting the overall building model of the building roof, setting the boundary conditions required for CFD simulation analysis, and carrying out the coupled simulation calculation of wind and rain on the overall building roof based on the CFD wind-driven rain algorithm; conducting the visualization analysis of the water accumulation per unit time, and extracting the rainfall data file on the roof; conducting the rainwater runoff analysis, and counting the drainage volume per unit time; checking whether the roof drainage facilities meet the drainage requirements. If not, modify the roof surface shape and drainage facility parameters. If so, end the simulation test. The present invention considers the influence of wind-driven rain and the dynamic runoff of roof rainwater on the roof drainage facilities, and more refined and intuitively visualizes the drainage volume at the drainage outlet position, providing a digital technical basis for the review of the drainage facilities of large-span space buildings.

Description

Technical Field

[0001] The present invention belongs to the technical field of building water supply and drainage and building information modeling (BIM) performance analysis. More specifically, it relates to a method for calculating the drainage performance of large-span roofs considering the coupled action of wind and rain. Background Art

[0002] Under the background of global climate change, extreme rainfall events often pose severe challenges to the roof drainage performance of large-span spatial buildings in cities. For example, during continuous heavy rain weather, the roofs of large-span spatial buildings are prone to problems such as rainwater leakage, ponding on the roof surface, and roof dampness, which affect the building's safety performance and normal use function and reduce the building's durability. Therefore, especially for large-span building roofs with non-linear curved surface modeling features, it is often necessary to fully consider the rationality of the roof drainage form and drainage plan during the scheme design stage. On the other hand, due to the tight construction period and cost control of some projects, it is difficult to conduct rainwater tests to evaluate the runoff and drainage performance of the entire building roof during construction.

[0003] For the existing design of the water supply and drainage plan for the roofs of large-span spatial buildings, usually in combination with local rainwater conditions and water supply and drainage design specification materials, the design rainwater flow under certain return period conditions is determined, and then multiple drainage plans are designed and compared based on the actual experience of existing projects. The catchment area, drainage ditch width, drainage outlet flow, and key joints and other positions of the proposed drainage facility plan are checked and calculated. The problems existing in the existing drainage plan design process are that it is impossible to dynamically analyze the rationality of the overall drainage form of large-span spatial buildings, the rainwater intensity of the building roof calculated by the specification does not consider the coupled action of wind and rain and the influence of rainwater dynamic runoff at the same time, and the theoretical empirical formula may not be applicable to the review calculation of the drainage plan for complex curved roofs. In recent years, computational fluid dynamics (CFD) simulation technology has been applied at home and abroad to carry out rainwater simulation, but how to carry out rainwater simulation-assisted design during the building scheme design stage and construction stage has not yet formed an effective technical method. Summary of the Invention

[0004] In view of the above deficiencies or improvement requirements of the prior art, the present invention proposes a calculation method for the drainage performance of large-span roofs considering the coupled action of wind and rain, which is used to review and calculate the rationality of the curved surface shape of large-span complex non-linear roofs and the parameters of drainage facilities in the building scheme stage and the preliminary design stage. Based on the BIM model platform and computational fluid dynamics (CFD) simulation technology, the calculation method establishes a solution that can count the rainwater volume at the drainage outlet positions of the roof, uses the wind-driven rain coupled solution algorithm developed by open-source CFD software to calculate the accumulated rain distribution of the overall building roof under given rainfall conditions, and then further analyzes the rainwater runoff algorithm in the BIM model platform based on the accumulated rain volume distribution of the roof after considering wind-driven rain, and counts the drainage volume at each drainage position of the roof, providing a new technical means for the drainage analysis and optimized design of the roof curved surface shape.

[0005] To achieve the above object, the present invention provides a calculation method for the drainage performance of large-span roofs considering the coupled action of wind and rain, including:

[0006] S1: Carry out the curved surface shape design of the large-span complex building roof and determine the drainage facility scheme based on building BIM software, and establish a BIM model for statistical analysis of the drainage volume.

[0007] S2: Use the geometric model of the large-span roof building created by the information platform of BIM software and the collected historical meteorological climate of the building site and the rainfall information data given by the specifications to carry out the coupled simulation calculation of wind and rain on the external facade of the roof building based on the CFD wind-driven rain algorithm.

[0008] S3: Use CFD post-processing software to conduct a visual analysis of the accumulated rain volume of the large-span roof building during a given rainfall event, and batch extract the accumulated rain data files to the BIM model platform.

[0009] S4: Conduct a dynamic analysis of the rainwater runoff on the overall or partial building roof in the BIM model platform, and count the drainage volume at the drainage outlet positions during a given rainfall event based on the BIM model.

[0010] S5: Parametrically modify the curved surface shape of the roof and the parameters of the drainage facilities according to the calculation results, continue to perform the iterative calculation of steps S1 to S4, finally determine whether the drainage facilities at the reviewed drainage outlet positions meet the drainage requirements, and associate and collaborate with the BIM model for collaborative modification.

[0011] In some optional implementation schemes, step S1 includes: using BIM software in the building scheme stage of the large-span roof building to carry out the curved surface shape design of the roof and the preliminary determination of the drainage scheme, parametrically describe the roof shape and the drainage facility model, and establish simulation monitoring points for statistical collection of the drainage volume in order to conduct a visual analysis of the rainwater at the drainage facility positions on the roof.

[0012] Furthermore, a three-dimensional BIM building information model can be established using Revit, CATIA, or Rhino.

[0013] Furthermore, the BIM information model of the long-span roof building is applicable to data sharing in different stages of the whole life cycle of design, construction, operation and maintenance, and demolition projects, and thus includes detailed attribute information such as detailed building geometric attributes, drainage facilities and drainage design parameters.

[0014] Furthermore, the long-span roof building includes common public buildings with large spans such as high-speed railway station houses, exhibition halls, cultural centers, and stadiums.

[0015] In some alternative embodiments, step S2 includes: collaboratively extracting or offline exporting the geometric information model of the long-span roof from the BIM building information platform. The building information geometric model should at least meet the LOD200 fineness and must include geometric characteristic parameters that can reflect the actual building roof slope, drainage structure measures, curved surface modeling, etc., which affect rainwater runoff.

[0016] Furthermore, according to the geographical location information of the BIM model site, historical meteorological and climatic observation data of the meteorological station closest to the site location on the international meteorological data network or the Chinese meteorological data network are obtained, including conventional data such as hourly-precision rainfall, wind speed, humidity, and temperature. At the same time, combined with the meteorological and climatic data given by the green building code, the average wind speed of the hourly rainfall (unit: mm), humidity, temperature, and dominant wind direction under the conditions of the 50-year return period, 100-year return period, and historical extreme rainfall events are comprehensively determined.

[0017] Furthermore, the steady-state numerical wind tunnel calculation of wind-driven rain on the long-span roof mainly includes the following specific calculation processes: First, without considering the raindrop size, considering the atmospheric boundary layer wind speed profile and turbulent kinetic energy boundary conditions, the k-epsilon turbulence model is used to carry out the wind field calculation of the long-span roof model; then the calculated flow field information is used as the boundary condition for the wind-driven rain calculation condition; then, according to the raindrop characteristic wind speed, rainfall intensity, environmental temperature, and humidity information determined by the design conditions, the atmospheric boundary layer raindrop boundary condition is determined, and the coupled CFD calculation of wind and rain multiphase flow is carried out based on the Euler-Euler multiphase flow method.

[0018] Furthermore, when using the Euler-Euler multiphase flow method to carry out the coupled CFD calculation of wind and rain multiphase flow, the raindrops in the actual atmospheric boundary layer are assumed to be a continuous medium. In the CFD calculation domain, raindrop phases and wind phases with different particle sizes occupy a certain geometric space and have their own volume fractions. The advantage of this method is that it simplifies the boundary conditions of raindrops in the building numerical wind tunnel, and only needs to specify the characteristic wind speed, spatial volume fraction, and velocity components of raindrops with different particle sizes falling near the ground at the inlet boundary position.

[0019] Furthermore, the volume fractions and velocity components of raindrops with different particle sizes can be determined from the rainfall intensity and raindrop size distribution function under different design conditions. Based on a large number of field measurements and theoretical studies in the field of hydrometeorology, there are already recognized and reliable raindrop size distribution functions and calculation formulas for the volume occupancy rate of different raindrop sizes. Considering the computational cost, only a limited range of raindrop sizes and types are considered, and the probability density function values of raindrops of each size category in the horizontal plane are determined according to the raindrop size distribution function calculation formula. The volume occupancy rate α of raindrops of each size category d can be calculated by the following formula:

[0020]

[0021] where R h is the rainfall intensity under different climate design conditions, f h is the probability distribution function of raindrop size d under a given rainfall intensity, and V t is the characteristic velocity of raindrops with different sizes.

[0022] Furthermore, the characteristic wind speeds of raindrops with different sizes at the inlet and top positions of the numerical wind tunnel of large-span roof buildings mainly include horizontal wind speed and vertical wind speed, which are both obtained by considering the balance calculation of the gravity and wind resistance of raindrop particles in the wind-driven rain algorithm.

[0023] In some alternative embodiments, step S3 includes: after the convergence of the coupled CFD calculation of wind and rain multiphase flow, extracting the rainfall distribution on the roof of the large-span building under the design conditions. It should be noted that the wind-driven rain calculation results in step S2 do not consider the flow of rainwater on the ground. The final CFD algorithm calculates the capture rate of raindrops with different sizes on the building surface to reflect the wind-driven rain intensity. The wind-driven rain intensity (unit: mm / h) at different surface positions of the building per unit time is calculated using the following formula:

[0024] R w (x, y, z) = R h × η(x, y, z)

[0025] where R w is the wind-driven rain intensity at different positions on the building roof, and η is the raindrop capture rate on the building surface obtained from the CFD wind-driven rain calculation.

[0026] Furthermore, the wind-driven rain intensity data of the large-span building roof is extracted and imported into the BIM information model platform for visualization analysis of roof waterlogging. The severely waterlogged areas on the large-span building roof can be intuitively displayed through cloud maps and contour maps.

[0027] In some alternative embodiments, step S4 includes: exporting the spatial coordinate positions of the measuring points on the large-span building roof and the raindrop capture rate data obtained from the CFD wind-driven rain calculation into a text in a specific format, reading the data in this text in the BIM model platform, and generating 3D models of several measuring points in a code modeling manner, and each measuring point carries its own raindrop capture rate data.

[0028] Further, perform rainwater runoff analysis and calculation on the real roof surface. The above-mentioned measuring points can be regarded as rainwater points on the roof. For each rainwater point, the following operations are performed: Denote the initial rainwater point as Pt1, find the nearest rainwater point Pt2 of Pt1 on the roof surface S and the normal vector N of Pt2 on the surface S. Establish a plane P1 with Pt2 as the origin and N as the Z-axis. Calculate the angle between the X-axis direction of the P1 plane and the negative Z-axis direction of the world coordinate on the P1 plane, and then rotate the P1 plane by the obtained angle to get a new plane P2. At this time, the X-axis direction of the P2 plane is along the surface S downward, that is, it can simulate the moving direction of Pt1 on the surface S under the action of gravity only. Then move Pt2 in this direction, and set the moving length as a variable Sp. The moved rainwater point is Pt3. Regard the above operation as one cycle. Compare the Z coordinates of Pt3 and Pt2. If the former is smaller, it proves that this rainwater point is indeed moving downward under the action of gravity, then Pt2 is the effective result of this cycle, otherwise this cycle is invalid. Finally, assign the effective result Pt2 to Pt1 and perform the next cycle calculation.

[0029] Further, package the above calculation process into a separate calculation method, use this device to perform runoff analysis on all rainwater measuring points, respectively apply the variables Sp and St to control the rainwater flow rate and the number of cycle calculations, and connect all the effective calculation result points into a curve, then the runoff analysis can be completed to obtain the runoff curve.

[0030] In some alternative embodiments, step S5 includes: when performing runoff calculation and analysis, adjust the number of cycle calculations to be large enough so that all cycle iterations can converge, and then group the final path points of these rainwater runoff curves according to the aggregation parts, and the aggregation parts are the best positions for arranging drainage outlets.

[0031] Further, for the calculation method of the drainage flow rate at each drainage outlet: take the average value of the raindrop capture rate data carried by the rainwater measuring points at each aggregation part, multiply it by the rainfall intensity under different design conditions to obtain the actually calculated rainfall intensity, and then multiply it by the catchment area covered by each drainage outlet, then the flow rate at each drainage outlet per unit time can be obtained. This data can be used to assist in the design of drainage systems such as rainwater funnels and rainwater pipes.

[0032] Furthermore, for the calculation method of the rainwater flow of the entire building roof: take the average value of the raindrop capture rate data carried by all rain gauges and multiply it by the design rainfall intensity to obtain the calculated rainfall intensity, then multiply it by the total catchment area of the entire roof, and after unit conversion, obtain the calculated rainwater flow (unit: L / s). At the same time, according to the requirements in the "Code for Design of Building Water Supply and Drainage" GB 50015-2019, the design rainwater flow of the building roof should be calculated according to the following formula:

[0033]

[0034] In the formula, q y is the design rainwater flow (L / s), q j is the design rainstorm intensity [L / (s·hm 2 )], Ψ is the runoff coefficient, and F w is the catchment area (m 2 ). Compare the calculated rainwater flow with the design rainwater flow, and take the envelope value between the two, which can supplement and improve the specification to a certain extent, or review the design results of the drainage system.

[0035] Generally speaking, compared with the prior art through the above technical solutions conceived by the present invention, the following beneficial effects can be achieved:

[0036] (1) The method for reviewing and calculating the drainage facilities of the large-span building roof provided by the present invention can consider the drainage volume of the roof drainage outlet positions under different rainfall design conditions in the scheme stage and before construction, more precisely consider various meteorological change parameters and the analysis of the drainage dynamic process, make up for the deficiencies of the existing empirical calculation formulas based on specifications, provide a new technical means for the review and calculation of the drainage facilities of large-span roof buildings, save the costs of on-site rainwater tests during and after construction, and facilitate the early detection of possible drainage problems.

[0037] (2) The present invention uses the BIM information model platform, the CFD wind-rain multiphase flow coupling algorithm, and the parametric analysis of rainwater dynamic runoff to establish a set of collaborative and linked digital solutions for the dynamic analysis of the large-span building roof drainage, giving full play to the advantages of the performance analysis of the BIM model. The method for reviewing and calculating the drainage facilities proposed based on this calculation process can provide a reference for drainage optimization in the building scheme stage and the preliminary design stage, especially for large-span roof buildings with complex curved surface modeling features. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is the schematic diagram of the calculation method principle of the large-span roof drainage performance considering the wind-rain coupling effect in the implementation of the present invention;

[0039] Figure 2 is the schematic diagram of the BIM geometric model of the stadium in the embodiment of the present invention;

[0040] Figure 3 It is a schematic diagram of the CFD grid model of the stadium roof in the embodiment of the present invention;

[0041] Figure 4 It is the case file structure of the open-source CFD program OPENFOAM in the embodiment of the present invention;

[0042] Figure 5 It is the CFD cloud chart of the wind field calculation of the stadium roof in the embodiment of the present invention;

[0043] Figure 6 It is the CFD cloud chart of the rainwater capture rate and the raindrop velocity slice of the stadium roof and the ground surface in the embodiment of the present invention;

[0044] Figure 7 It is the flow chart of the dynamic runoff analysis of the rainwater on the roof of the large-span space building in the embodiment of the present invention;

[0045] Figure 8 It is the raindrop distribution diagram at the initial moment on the surface of the stadium roof in the embodiment of the present invention;

[0046] Figure 9 It is the cloud chart of the final water collection position on the surface of the stadium roof in the embodiment of the present invention;

[0047] Figure 10 It is the rainwater runoff path diagram on the surface of the stadium roof in the embodiment of the present invention. Detailed implementation manners

[0048] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0049] With the development and maturity of digital building application technologies such as BIM information model (Building Information Modeling, BIM) and CFD simulation in the field of construction engineering, the green building performance analysis throughout the whole life cycle based on the BIM engineering model has gradually attracted the attention of technicians. By carrying out parametric collaborative design, construction and operation of complex large-span space buildings on the BIM collaborative platform, and through simulation calculation technology to consider various adverse working conditions in the scheme design and construction stages for virtual calculation of the digital twin model, a comprehensive performance analysis of the physical environments such as indoor and outdoor sound, light, heat and water in the building can be carried out, significantly improving the green building qualities such as the health, comfort, ecological livability, energy conservation and environmental protection of the building. Therefore, aiming at the drainage performance of the facade of large-span roof buildings, combining the BIM parametric model and the CFD wind-driven rain simulation algorithm, this invention improves the deficiencies and defects existing in the existing complex roof drainage analysis methods for large-span space buildings, and proposes a calculation method for the drainage performance of large-span roofs considering the coupling effect of wind and rain. Based on the parametric advantages of the BIM model and the CFD dynamic analysis technology, the wind-driven rain intensity, rain shielding performance on the building facade and the dynamic analysis process of the rainwater runoff on the roof surface under various adverse rainfall conditions can be considered in the building scheme design and construction stages, quantitatively counting the drainage volume at the drainage positions on the building roof surface, facilitating the review of the building drainage scheme, realizing the performance-based design of drainage facilities based on the BIM model, and providing a new digital solution for the review calculation analysis of the roof drainage facilities of large-span complex space buildings.

[0050] The present invention provides a calculation method for the drainage performance of large-span roofs considering the coupling effect of wind and rain. This method is mainly implemented based on a parametric building BIM software and a CFD numerical simulation platform, and specifically includes: 1) Parametrize the existing roof surface shape and drainage facilities based on the Rhino architectural design software, and set simulation monitoring points convenient for statistical drainage volume at the drainage outlet positions of the roof building model; 2) Extract the overall building model of the building roof for CFD mesh generation. At the same time, combine the local historical meteorological data and specification materials to set boundary conditions such as rainfall intensity, wind speed and direction, humidity, and temperature required for CFD simulation analysis, and carry out the coupled simulation calculation of wind and rain on the overall building roof based on the CFD wind-driven rain algorithm; 3) Conduct a visualization analysis of the water accumulation volume per unit time of the overall building and the site, extract the roof rainfall data file and import it into the Rhino software; 4) Conduct a dynamic analysis of rainwater runoff for the overall or partial building roof model, and statistically calculate the drainage volume per unit time based on the simulation monitoring points at the drainage outlet positions of the roof; 5) Check whether the roof drainage facilities meet the drainage requirements. If not, modify the roof surface shape and drainage facility parameters based on the GH visualization programming tool. If so, end the simulation test. Compared with the existing roof drainage volume statistical technology, the present invention based on BIM-CFD technology considers the influence of wind-driven rain and dynamic roof rainwater runoff on the roof drainage facilities, and more refined and intuitively visualizes the drainage volume at the drainage outlet position, providing a digital technical basis for the review calculation of drainage facilities in large-span space buildings such as existing stadiums, high-speed railway station houses, and exhibition halls.

[0051] The calculation method for the drainage performance of large-span roofs considering the coupling effect of wind and rain in the present invention has the principle steps as Figure 1 shown below. The following uses a specific embodiment to illustrate the method of the present invention.

[0052] Taking the drainage dynamic analysis of a BIM model of an open stadium as an example, the specific implementation steps of the present invention are introduced as follows:

[0053] (1) Use the Rhino software and the Grasshopper visualization programming tool to establish on a local desktop computer or import the large-span stadium building model and the BIM model drainage facility parameter data from other BIM software platforms. The BIM roof geometric model of the stadium is as Figure 2 shown. For the BIM roof model and the existing drainage facility scheme. According to the slope analysis of the building roof model, initially determine that the drainage ditch is located at the lower elevation overhanging ring section, and use the Grasshopper parametric modeling tool to establish simulation monitoring points for collecting drainage volume at the drainage outlet positions. The stadium roof building in the embodiment of the present invention is as Figure 2 shown.

[0054] (2) Since the BIM of stadiums includes various systems such as structure, equipment, and maintenance, the present invention only extracts the building model of the stadium roof and uses the open-source CFD software OpenFOAM based on the finite volume method for building wind-driven rain calculation. First, a CFD model of the stadium building roof model is created, using structured and unstructured mesh division methods. First, a structured orthogonal mesh is created for the overall calculation domain of the building numerical wind tunnel, and then an unstructured encrypted mesh is created for the complex stadium building. The mesh type is preferably a hexahedron mesh to ensure calculation accuracy. The geometric surface mesh model of the stadium roof is as Figure 3 shown. Then, the boundary conditions of the CFD model are set. It is necessary to combine the specifications, historical observations, or the general engineering situation data provided by the existing design documents to statistically obtain the meteorological and climatic design conditions such as local rainfall intensity, dominant wind speed and direction, temperature, and humidity.

[0055] Before carrying out the steady-state numerical wind tunnel calculation of wind-driven rain for the large-span roof, it is necessary to first carry out the wind environment calculation of the building numerical wind tunnel. As Figure 4 shown, each CFD example file of the open-source OPENFOAM software must include three folders: 0, system, and constant, including the initial and boundary conditions of the building numerical wind tunnel (0 folder), mesh division files (blockMeshDict, snappyHexMeshDict, and surfaceFeatureExtractDict), and solution control files (controlDict, fvSchemes, and fvSolution). After setting the inlet wind speed boundary conditions, this example uses the standard k-epsilon turbulence model to carry out the building numerical wind tunnel calculation to obtain the average wind speed information at the calculation domain and boundary positions. The calculation cloud map of the average wind field near the stadium roof awning building is as Figure 5 shown.

[0056] Set the wind-driven rain CFD example file of the stadium, which is similar to the building numerical wind tunnel example file. However, the initial conditions of the wind-driven rain CFD example file need to include the volume fraction and velocity of the rain phase with different raindrop diameters; in the constant folder, the physical properties of the raindrops need to be specified, including the diameter size and probability density function value of each raindrop diameter, the humidity of the wind field, and the temperature parameters, etc.; the mesh file in the wind-driven rain example is directly copied from the building numerical wind tunnel example file, and the initial wind field at the basin and boundary positions is interpolated from the calculation results of the building numerical wind tunnel example file. Finally, by setting the solution control file, the Euler-Euler multiphase flow method is used to carry out the coupled CFD calculation of wind and rain multiphase flow.

[0057] (3) After the wind-driven rain CFD calculation converges, calculate and statistically analyze the movement trajectories of raindrops with different diameters and the distribution of raindrops on the building surface. The raindrop diameter wind speed cloud map and the wind-driven rain intensity cloud map of the roof awning are asFigure 6 As shown in Figure 6 It can be seen that under the given rainfall design conditions, considering the wind-rain coupling, the rainfall distribution on the building surface shows obvious non-uniform characteristics, and at the same time, the rain-blocking performance of the roof canopy can be intuitively analyzed. Multiplying the calculated raindrop capture rate by the design rainfall intensity, the height data of the rainfall amount on the building surface considering wind-driven rain can be calculated.

[0058] (4) Through the secondary development of Grasshopper, in the Visual Studio environment, based on the logic described in the content of the present invention, a set of runoff analysis battery plug-in is compiled using the API functions of Rhino and Grasshopper in C# language. This plug-in mainly includes three parts: the function of the first part is data introduction, the input end is the data file obtained from CFD calculation, and after the internal parsing and reorganization of the data text by this battery, the three-dimensional models of all rain gauging points and the raindrop capture rates of each gauging point are respectively output at the output end; the main function of the second part is runoff analysis, which has four input ends, respectively inputting the roof surface to be analyzed, the rain gauging points output in the first part, the approximate rainwater flow velocity, and the number of cyclic iterations of each gauging point. After a period of internal calculation, the runoff curve and the final positions of each rain gauging point are output; the third part is rainfall calculation, and the main function is to group the rain gauging points output in the second part, and combine parameters such as the newly input catchment area, calculation time, and the raindrop capture rates of each gauging point output in the first part to complete the calculation and analysis of various indicators. The complete flowchart of using this plug-in for runoff analysis is as shown in Figure 7 shown, the initial raindrop distribution is shown in Figure 8 , the final water catchment position is shown in Figure 9 , and the runoff curve on the roof surface is shown in Figure 10 .

[0059] (5) Statistically obtain the drainage volume and the drainage parameters of the drainage facilities, analyze the drainage form, rain-blocking performance of the stadium curved roof, and the rationality of the drainage facilities, and judge whether parameters such as the curved surface form of the stadium roof canopy and the size of the drainage facilities need to be modified and adjusted. If modification is required, use the Grasshopper parametric programming tool to modify the stadium BIM model and repeat steps (1) to (4), otherwise stop the calculation. Through the iterative optimization calculation of the idea of the present invention, the drainage situation of each roof form scheme can be quickly calculated based on the BIM model, and the optimized design scheme of the drainage facilities can be determined, and finally the geometric parameters of the BIM model are modified.

[0060] It should be noted that according to the needs of implementation, each step / component described in this application can be split into more steps / components, or two or more steps / components or partial operations of steps / components can be combined into new steps / components to achieve the purpose of the present invention.

[0061] Those skilled in the art can easily understand that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A calculation method for the drainage performance of a long-span roof considering the coupling effect of wind and rain, characterized in that, Including: S1: Based on building BIM software, carry out the design of the roof surface shape of large-span complex buildings and determine the drainage facility plan, and establish a BIM model for statistical analysis of the drainage volume; S2: Using the geometric model of the large-span roof building created by the BIM software information platform and the collected historical meteorological climate of the building site and the rainfall information data given by the specifications, carry out the wind-driven rain coupling simulation calculation of the exterior facade of the roof building based on the CFD wind-driven rain algorithm; S3: Use CFD post-processing software to conduct a visual analysis of the water accumulation volume of the large-span roof building during a given rainfall event, and batch extract the rain accumulation data files to the BIM model platform; S4: Conduct a dynamic analysis of the rainwater runoff on the overall or partial building roof in the BIM model platform, and statistically analyze the drainage volume at the drainage outlet position during a given rainfall event based on the BIM model; S5: Parametrically modify the roof surface shape and drainage facility parameters according to the drainage volume parameters at the drainage outlet position during a given rainfall event, and continue to perform the iterative calculations of steps S1 to S4. Finally, determine whether the drainage facilities at the drainage outlet position after the review calculation meet the drainage requirements, and perform collaborative modification with the associated BIM model; Step S4 includes: Export the spatial coordinate positions of the measuring points on the roof of the large-span building and the raindrop size capture rate data obtained from the CFD wind-driven rain calculation in a specific format as text. Read the data in this text in the BIM model platform, and use the method of code modeling to generate 3D models of several measuring points, and each measuring point carries its own raindrop capture rate data; Conduct a rainwater runoff analysis calculation on the real roof surface. Regard each measuring point as a rainwater point on the roof, conduct a runoff analysis on each rainwater point, and connect all the rainwater points with valid calculation results into a curve to complete the runoff analysis and obtain a runoff curve; Conduct a runoff analysis on each rainwater point, and connect all the rainwater points with valid calculation results into a curve to complete the runoff analysis and obtain a runoff curve, including: Record the initial rainwater point as Pt1, find the nearest rainwater point Pt2 of Pt1 on the roof surface S and the normal vector N of Pt2 on the surface S. Establish a plane P1 with Pt2 as the origin and N as the Z axis. Calculate the angle between the X-axis direction of the P1 plane and the negative direction of the Z axis of the world coordinate on the P1 plane, and then rotate the P1 plane by the obtained angle to get a new plane P2. At this time, the X-axis direction of the P2 plane is along the surface S downward, which is used to simulate the moving direction of Pt1 on the surface S under the action of gravity only. Then move Pt2 in this moving direction, and set the moving length as a variable Sp. The moved rainwater point is Pt3. Regard the above operation as one cycle; Compare the Z coordinates of Pt3 and Pt2. If Pt3 is smaller, it proves that the Pt3 rainwater point is indeed moving downward under the action of gravity, then Pt2 is the valid result of this cycle, otherwise this cycle is invalid. Finally, assign the valid result Pt2 to Pt1 and perform the next cycle calculation; After performing runoff analysis at all rain points, variables Sp and St are respectively applied to control the rainwater flow velocity and the number of loop calculations, and the rain points of all valid calculation results are connected into a curve to complete the runoff analysis and obtain a runoff curve.

2. The method according to claim 1, wherein Step S1 includes: In the large-span roof building design stage, use BIM software to carry out the roof surface modeling design and preliminarily determine the drainage plan, parametrically describe the roof modeling and drainage facility models, and establish simulation monitoring points for statistically collecting the drainage volume.

3. The method according to claim 2, wherein Step S2 includes: Collaboratively extract or offline export the geometric model of the large-span roof building from the BIM building information platform. According to the geographical location information of the BIM model site, obtain the historical meteorological and climatic observation data of the meteorological station closest to the site location. At the same time, combine the meteorological and climatic data given in the green building code to comprehensively determine the average hourly rainfall, humidity, temperature, and average wind speed of the prevailing wind direction under the given conditions. Without considering the raindrop size, considering the atmospheric boundary layer wind speed profile and turbulent kinetic energy boundary conditions, use the k-epsilon turbulence model to carry out the wind field calculation of the large-span roof model. Then, use the calculated flow field information as the boundary condition for the wind-driven rain calculation condition. Next, according to the characteristic wind speed, rainfall intensity, ambient temperature, and humidity information of raindrops determined by the design conditions, determine the atmospheric boundary layer raindrop boundary conditions, and perform the coupled CFD calculation of wind and rain multiphase flow based on the Euler-Euler multiphase flow method. Assume the raindrops in the actual atmospheric boundary layer as a continuous medium, and specify the characteristic wind speed, spatial volume fraction, and velocity components of raindrops with different particle sizes falling to the ground at the inlet boundary position.

4. The method according to claim 3, wherein Step S3 includes: After the coupled CFD calculation of wind and rain multiphase flow converges, extract the rainfall distribution on the large-span building roof under the design conditions. Extract the wind-driven rain intensity data of the large-span building roof and import it into the BIM information model platform for visual analysis of roof water accumulation. Intuitively display the severely waterlogged areas on the large-span building roof through cloud maps and contour maps. Among them, the capture rate of different raindrop particle sizes on the building surface calculated in the CFD algorithm is used to reflect the wind-driven rain intensity.

5. The method according to claim 4, characterized in that, Step S5 includes: When performing runoff calculation and analysis, adjust the number of loop calculations to a preset value to ensure that all loop iterations can converge. Then, group the final path points of these rainwater runoff curves according to the aggregation parts, and use the aggregation parts as the best positions for arranging drainage outlets to obtain the drainage flow rate at each drainage outlet and the rainwater flow rate of the entire building roof.

6. The method according to claim 5, wherein Obtaining the drainage flow rate at each drainage outlet includes: Take the average value of the raindrop capture rate data carried by the rain points in each aggregation part, multiply it by the rainfall intensity under different design conditions to obtain the actual calculated rainfall intensity, and then multiply it by the catchment area covered by each drainage outlet to obtain the flow rate at each drainage outlet per unit time.

7. The method according to claim 6, wherein Obtaining the rainwater flow rate of the entire building roof includes: Take the average value of the raindrop capture rate data carried by all rain points and multiply it by the design rainfall intensity to obtain the calculated rainfall intensity. Then, multiply it by the total catchment area of the entire roof and perform unit conversion to obtain the calculated rainwater flow rate. At the same time, obtain the design rainwater flow rate of the building roof according to the requirements of the design code. Compare the calculated rainwater flow with the designed rainwater flow, and take the envelope value between the calculated rainwater flow and the designed rainwater flow to supplement and improve the design specifications or review the design results of the drainage system.

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