Design method and system of multi-hopper siphonic roof drainage system

Abstract

The present invention discloses a design method and system for a multi-hopper siphonic roof drainage system. The method includes: S1. Establishing a three-dimensional model of the overall building roof based on a BIM software platform and establishing a BIM database for each device of the siphonic drainage system; S2. Analyzing the building roof; S3. Combining the analysis results of the building roof with local hydrology and meteorology to perform preliminary parameter calculation and analysis of the drainage system for each water collection area; S4. Selecting each drainage device in the BIM database and establishing a complete BIM model of the drainage system; S5. Converting the complete BIM model of the drainage system into a CFD grid model and performing siphonic numerical simulation analysis; S6. Judging whether the drainage system meets the evaluation index; if so, outputting the result; if not, calling an intelligent optimization algorithm to perform iterative design of the drainage system scheme and repeating steps S4-S5 until the established siphonic drainage system evaluation index is met. The present invention provides new technical support for the performance and optimization analysis of the siphonic drainage system for large-span building roofs.

Description

Technical Field

[0001] The present invention belongs to the fields of the design of building roof rainwater drainage systems and the application of CFD numerical simulation, and particularly relates to a design method and system for a multi-hopper siphonic roof drainage system. Background Art

[0002] With the increasing development of the design and construction technologies of large-span space structures, tall-space buildings with complex roof shapes are widely used in projects such as stadiums, airport stations, and commercial complexes. For large-span buildings, compared with traditional gravity roof rainwater drainage systems, siphonic roof rainwater drainage systems have the advantages of high drainage efficiency and flexible design layout, and have great market potential. The technical principle of the siphonic roof rainwater drainage system is to utilize the water head formed by the height difference between the roof and the ground, rely on special rainwater hoppers to achieve air-water separation, make the pipes filled with rainwater and in a negative pressure state, so as to generate a siphon effect and quickly discharge rainwater.

[0003] However, the existing calculation and design methods for multi-hopper siphonic drainage systems mainly have the following defects or deficiencies: 1) Based on theoretical analysis, it is impossible to reflect in real time the changes in indicators such as the flow velocity and pressure of each cross-section of the pipes in the roof drainage system of large-span buildings; 2) Most of the calculation formulas are obtained through experience or summary, and it is impossible to accurately calculate parameters such as the head loss of the pipes. Design errors may cause operation failure or non-siphon mode, resulting in drainage failures and even overflow phenomena; 3) The full-scale simulation test in the scheme stage is costly, and it is difficult to analyze the flow phenomena of various complex boundaries; 4) Compared with single-hopper systems, the hydraulic conditions between multiple rainwater hoppers in multi-hopper systems will affect each other, and the entire system is more massive and complex. The existing research results of single-hopper systems cannot be fully applied to multi-hopper systems; 5) Although the existing computational fluid dynamics (CFD) numerical simulation can carry out the simulation of the drainage process of multi-hopper drainage systems, the existing public methods and research still fail to combine the CFD technology with the BIM three-dimensional design in a coordinated manner to form an automatic design process for drainage systems that fully exploits the performance analysis advantages of BIM models.

[0004] In recent years, building information modeling (BIM) technology and intelligent design technology have developed rapidly and been widely applied in the field of architectural design: the former can promote the efficient collaboration of various specialties in the design process, combine building technology with information technology, change the traditional management mode, improve the entire construction process from design to construction, reduce resource consumption and improve economic benefits, and realize information sharing throughout the life cycle of the building; the latter can quickly complete the entire design process through defined logics, or automatically iterate and optimize the design results by adding certain rules and limiting conditions to achieve efficient and accurate design.

[0005] Summarizing the current status of the existing technologies in this engineering field, in view of the deficiencies and existing problems in the calculation and design methods of multi-hopper siphonic drainage systems for building roofs, the present invention proposes an intelligent design method for multi-hopper siphonic roof drainage systems based on dynamic rainwater simulation. This method constructs a modular automatic iterative analysis process, collaboratively integrating the dynamic rainwater simulation and the design process of multi-hopper siphonic drainage systems, which can not only provide strong data support for the accuracy of design results, but also greatly improve the digitization and intelligence of the design process. Summary of the Invention

[0006] The object of the present invention is to provide a design method and system for a multi-hopper siphonic roof drainage system based on dynamic rainwater simulation, providing new technical support for the performance and optimization analysis of the siphonic drainage system of large-span building roofs in the building scheme design stage and construction stage. The present invention establishes a modular-based automatic analysis and design process method for multi-hopper siphonic roof drainage systems, which can not only collaboratively apply CFD technology in BIM 3D design to dynamically simulate the drainage performance of the drainage system under multiple rainfall conditions with high precision, providing an efficient analysis means for the model size and layout selection of each component part of the multi-hopper drainage system; at the same time, through parametric programming, steps such as roof catchment area analysis, preliminary calculation, scheme generation, simulation, performance evaluation, and design optimization can be built into a set of intelligent design processes in a modular form, greatly improving the digitization and intelligence of the entire design process.

[0007] The object of the present invention can be achieved through the following technical solutions:

[0008] A design system for a multi-hopper siphonic roof drainage system, comprising:

[0009] A model establishment module, used to establish a three-dimensional model of the overall building roof based on the BIM software platform;

[0010] A database module, used to collect and organize the equipment of the siphonic roof rainwater drainage system, and establish a BIM database for each equipment of the siphonic drainage system;

[0011] A runoff analysis module, used to analyze the building roof, including roof rainwater runoff analysis and roof catchment area division;

[0012] A preliminary calculation module, used to combine the analysis results of the building roof and the local hydrometeorology to conduct preliminary parameter calculation and analysis of the drainage system for each catchment area;

[0013] A scheme generation module, used to select each drainage equipment in the BIM database according to the analysis results of the preliminary parameter calculation of the drainage system, and establish a complete BIM model of the drainage system;

[0014] A numerical simulation module for converting a complete drainage system BIM model into a CFD grid model and performing siphon numerical simulation analysis. The analysis content includes the overall performance of the drainage system and the operation process of the drainage system under various working conditions;

[0015] An intelligent optimization module for judging whether the drainage system meets the evaluation index; if so, output the result; if not, call the intelligent optimization algorithm for iterative design of the drainage system scheme, and repeat steps S4 - S5 until the established siphon drainage system evaluation index is met.

[0016] An intelligent design method for a multi - bucket siphon roof drainage system based on dynamic rainwater simulation, which includes the following implementation steps:

[0017] S1. Establish a three - dimensional model of the overall building roof based on the BIM software platform, and collect and organize data on common and frequently used siphon roof rainwater drainage system equipment to establish a BIM database for each device of the siphon drainage system;

[0018] S2. Use the runoff analysis module to perform intelligent analysis on the building roof, mainly including dynamic rainwater catchment simulation and roof catchment area division, etc.;

[0019] S3. Use the preliminary calculation module to combine the results output by the runoff analysis module in step S2 and the local hydrometeorological data of the project site to perform preliminary parameter calculation and analysis of the drainage system for each catchment area;

[0020] S4. Use the scheme generation module to automatically select each drainage device in the BIM model database according to the calculation and analysis results, and establish a complete drainage system BIM model;

[0021] S5. Use the numerical simulation module to automatically convert the BIM model into a CFD grid model and perform siphon numerical simulation. The analysis content mainly includes the overall performance of the drainage system and the operation process of the drainage system under various working conditions;

[0022] S6. Use the intelligent optimization module to perform iterative design of the scheme by calling various intelligent optimization algorithms, continuously repeat steps S4 - S5 until the established siphon drainage system evaluation index is met. During this process, the simulation results can be observed through the visualization module, or the parameters of the design process can be adjusted through the interactive change module.

[0023] Further, the BIM software platform in step S1 includes Revit, Rhino, or CATIA, etc.

[0024] Further, the BIM three - dimensional model of the building roof in step S1 must be consistent with the actual building roof shape and be able to truly reflect geometric features such as the slope of the building roof.

[0025] Furthermore, the main equipment of the siphonic roof rainwater drainage system in step S1 mainly includes: gutter, siphonic rainwater bucket, non-slope rainwater suspension pipe, rainwater riser, buried pipe, discharge pipe, pipe joint, etc. The database established mainly contains information such as: the model, size, design discharge flow, average cost, etc. of components in each part.

[0026] Furthermore, the runoff analysis module in step S2 mainly includes the function of roof rainwater runoff analysis and the function of roof catchment area division.

[0027] Furthermore, the specific method of roof rainwater runoff analysis is as follows: Randomly select several points on the three-dimensional model of the building roof to simulate rainwater. The number of points cannot be too small, otherwise it cannot truly reflect the convergence of rainwater on the roof. Too many points will lead to a longer calculation process and cause waste of computing power. Therefore, the selected points should be appropriate to cover all parts of the roof and have an appropriate density. Taking the selected points as the initial positions of rainwater, find the vector of the point along the roof surface downward to simulate the direction of the raindrop moving on the roof under the action of gravity. Then, according to the set rainwater flow velocity, move the point in this direction. Finally, find the nearest point of the moved point on the roof surface. If the z coordinate of the nearest point is less than that of the initial point, it proves that the raindrop is indeed flowing downward, and the nearest point is a valid point, otherwise it is an invalid point. Loop the above steps until convergence or the maximum number of calculation iterations is reached, and connect the initial points and the valid points in the calculation process into curves to obtain the runoff curve and realize the runoff analysis of the roof surface.

[0028] Furthermore, the specific method of roof catchment area division is as follows: According to the results obtained from the roof runoff analysis, it can be found that all rainwater points will eventually gather at certain parts of the roof surface, which are the final catchment positions. Combining the initial positions of the rainwater points, it is easy to know which part of the entire roof surface each catchment position specifically corresponds to. At the same time, according to the regulations in the code, the catchment area served by a siphonic multi-bucket system should not be greater than 2500m 2 , and the roof surface can be divided into multiple catchment areas according to the catchment positions and catchment areas.

[0029] Furthermore, the preliminary calculation module in step S3 is mainly implemented according to the following calculation formula:

[0030] According to the existing code "Design Standard for Building Water Supply and Drainage", the design rainwater flow of the building roof should be calculated by the following formula:

[0031]

[0032] 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 ). The design rainstorm intensity shall be calculated and determined according to the rainstorm intensity formula of the local or adjacent areas. The specific calculation formula is as follows:

[0033]

[0034] In the formula, P is the design return period, t is the rainfall duration, and A, b, c, and n are local rainfall parameters.

[0035] According to the existing specification "Technical Code for Rainwater Drainage System of Building Roofs", the preliminary design of the gutter is calculated according to the following formula:

[0036] Q = Av

[0037]

[0038] In the formula, Q is the designed drainage capacity of the gutter (m 3 / s), A is the effective cross-sectional area of the water flow (m 2 ), v is the water flow velocity (m / s), R is the hydraulic radius (m), I is the gutter slope, and n is the roughness coefficient of the gutter.

[0039] According to the existing specification "Technical Code for Rainwater Drainage System of Building Roofs", the preliminary design of the overflow outlet is calculated according to the following formula:

[0040]

[0041] In the formula, Q is the designed flow rate of the overflow outlet (L / s), b is the width of the overflow outlet (m), h is the height of the overflow outlet (m), and g is the acceleration due to gravity (m / s 2 ).

[0042] Furthermore, the scheme generation module in step S4 specifically includes: referring to the output result of the runoff analysis module, automatically arranging the gutter at the corresponding final catchment position, then determining the number of siphonic rainwater inlets in the gutter and the model layout positioning points according to the calculation and analysis results, automatically generating the pipeline positioning center line through the positioning points and various formulated pipeline connection rules, and finally assembling the corresponding equipment models in the database according to their respective positioning points or positioning lines to obtain the complete BIM model of the roof drainage system.

[0043] Further, the numerical simulation module in step S5 has the following specific implementation process: automatically convert the BIM models of the roof multi-hopper siphonic drainage systems in each catchment area into CFD analysis grid models, conduct simulations of the rainwater siphon process based on the free surface calculation model, conduct refined analysis of the overall performance of the drainage system under various rainfall intensity conditions such as specifications and historical measurements, and visually analyze the pipe flow velocity, head loss, pressure balance process, and the position and value of the maximum negative pressure according to the CFD simulation results, providing a quantitative reference for subsequent quantitative evaluation of the drainage system performance.

[0044] Further, the CFD analysis software mainly includes xflow, fluent, openfoam, etc.

[0045] Further, the automatic conversion of the BIM model into a CFD analysis grid model mainly includes the following contents: grid division strategy, fluid parameter setting, establishment of computational domain boundary conditions, and solution parameter setting.

[0046] Further, the intelligent optimization module in step S6 has the following specific process: taking the best overall performance of the drainage system as the optimization goal, taking the models of each device in the database as design variables, taking the roof design rainwater flow rate obtained in the initial calculation module as the constraint condition, and conducting intelligent optimization using genetic algorithms, particle swarm algorithms, etc.

[0047] Further, the evaluation indexes of the siphonic drainage system in step S6 mainly include the following contents:

[0048] (1) The water flow velocity in each pipe: To ensure that the drainage system has a certain self-cleaning ability, the rainwater flow velocity in the connecting pipe and the suspended pipe must be greater than 1.0 m / s. At the same time, to avoid fatigue damage to the metal surface inside the pipe due to excessive flow velocity, it is necessary to control the rainwater flow velocity in the riser not to exceed 10 m / s. The flow velocity of the pipe downstream of the transition section should not be greater than 2.5 m / s to avoid damaging the rain inspection well.

[0049] (2) The actual head loss of the system: To prevent the water level in front of a certain rainwater hopper from dropping too fast, causing air to enter and thus destroying the siphon effect of the entire system, it is necessary to limit that the difference in the calculated head loss of the upstream branch of each rainwater hopper under full pipe conditions should not be greater than 10 kPa. At the same time, the difference between the total head and the total head loss caused by resistance can be called the maximum siphon discharge. The time when the end of the suspended pipe reaches 60% of the maximum discharge is called the siphon start time, and this value should not be greater than 60 s.

[0050] (3) The maximum negative pressure value of the system: To ensure the suction effect of the entire drainage system on rainwater and avoid the adverse impact on the system caused by the "cavitation" phenomenon due to rainwater vaporization, it is necessary to simulate the operating conditions of all rainwater hoppers in the system running at the maximum flow rate to review the maximum negative pressure value of the system and control it not to be less than -90 kPa.

[0051] Furthermore, the visualization module in step S6 mainly functions to post-process the CFD simulation results and present parameters such as the rainwater flow velocity and pressure in the system pipeline in the form of contour maps or tables. The main tool software includes paraview, CFD-post, tecplot, etc.

[0052] Furthermore, the interactive change module in step S6 mainly functions to intervene in the intelligent design results by manually changing various parameters or data to achieve specific goals.

[0053] Compared with the traditional design method of the siphonic roof rainwater drainage system, the present invention has the following beneficial effects:

[0054] (1) The present invention uses intelligent design technology to establish an automatic selection and design process for the drainage system, sorts out the established logics such as the layout of rainwater inlets and the connection of pipelines, and combines the limiting conditions specified by specifications or practical experience to form reusable design rules and design tools, enabling precise and controllable connections between various devices in the entire drainage system. By simply modifying the input parameters, the original design scheme can be quickly adjusted or multiple new design schemes can be generated, which can greatly improve the design efficiency and design accuracy. At the same time, based on the BIM model information database of the siphonic drainage system, a bill of materials can be directly output from the design results for component procurement, avoiding material waste caused by various factors and facilitating precise control of construction costs.

[0055] (2) The present invention applies rainwater runoff analysis and CFD numerical simulation and simulation technologies, which can accurately simulate the actual operation of the multi-inlet siphonic drainage system of specific building roofs in various actual rainfall conditions, visually display the data such as pressure and flow velocity at each part during the operation process in real time, and can accurately calculate parameters such as the head loss of each pipeline, facilitating more refined design and optimization of the entire drainage system, making the design results have more complete and reliable data support, making up for problems such as design errors caused by relying on empirical formulas in traditional design methods, and enabling the drainage system to operate more efficiently.

[0056] (3) The intelligent design method of the multi-inlet siphonic roof drainage system based on dynamic rainwater simulation proposed by the present invention is no longer limited to the preliminary design based on empirical formulas only for pipeline routes, waterproof sleeves, etc., but gives full play to the advantages of the BIM model and uses simulation technology to conduct detailed and complete in-depth design of each part of the entire drainage system. The results can not only provide data support for full-scale drainage experiments, but also avoid construction difficulties and economic disputes caused by differences from the secondary design results of equipment manufacturers. Description of the Drawings

[0057] Figure 1 It is the specific flow chart of the method in the present invention.

[0058] Figure 2 Schematic diagram of calling the siphonic rainwater bucket database in the embodiment of the present invention.

[0059] Figure 3 Schematic diagram of the runoff analysis tool in the embodiment of the present invention.

[0060] Figure 4 Schematic diagram of the roof surface runoff analysis result in the embodiment of the present invention.

[0061] Figure 5 Schematic diagram of the final water collection position of the roof surface in the embodiment of the present invention.

[0062] Figure 6 Schematic diagram of the result of the division of the water collection area of the roof surface in the embodiment of the present invention.

[0063] Figure 7 Schematic diagram of the preliminary design tool for the siphonic roof rainwater drainage system in the embodiment of the present invention.

[0064] Figure 8 Schematic diagram of the automatic modeling program for the siphonic roof rainwater drainage system in the embodiment of the present invention.

[0065] Figure 9 Schematic diagram of the overall model of the multi-bucket siphonic roof drainage system in the embodiment of the present invention.

[0066] Figure 10 Schematic diagram of the XFlow grid model in the embodiment of the present invention.

[0067] Figure 11 Cloud diagram of the rainwater flow velocity distribution in the whole system obtained by CFD analysis in the embodiment of the present invention.

[0068] Figure 12 Chart of the head loss of each upstream branch of the system obtained by CFD analysis in the embodiment of the present invention.

[0069] Figure 13 Cloud diagram of the total pressure distribution in the pipe of the whole system obtained by CFD analysis in the embodiment of the present invention. Specific embodiments

[0070] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several changes and improvements can still be made. These all belong to the protection scope of the present invention.

[0071] The present invention proposes an intelligent design method for a multi-hopper siphonic roof drainage system based on dynamic rainwater simulation. The specific process is as follows Figure 1 As shown below. Taking the roof of a large-span building as an example, the specific implementation steps of the method of the present invention are introduced:

[0072] (1) Select Rhino software as the BIM platform, and build a three-dimensional roof model in it according to the building's curved surface shape. At the same time, collect information such as the models, sizes, and costs of commonly used components on the market, such as gutters, siphonic rainwater hoppers, drainage pipes, and pipe joints, and establish three-dimensional models of each device. Based on the Grasshopper visual programming tool in Rhino software, build a BIM model database for subsequent direct retrieval and use. For example, call the results of a certain model of rainwater hopper from the siphonic rainwater hopper database as Figure 2 shown.

[0073] (2) Under the Visual Studio environment, use the C# language to combine the API functions of Rhino and Grasshopper to perform secondary development on Grasshopper, and compile a runoff analysis tool according to the logic in the invention content as Figure 3 shown. In this tool, the input end B is connected to the roof surface to be analyzed, the input end P is connected to the initial position point of the raindrop. Here, the PopulateGeometry battery can be used to randomly select several points on the surface to be analyzed. The number of points should be appropriate to cover all parts of the roof and have an appropriate density. The input end Sp is connected to the rainwater flow velocity, and the input end St is connected to the total number of iterative calculations. After a period of calculation, a list of multiple points can be obtained from the output end Pt. Each point list contains the new position points of the raindrop after each iteration, and the runoff curve can be obtained at the output end Crv. Figure 4 is the runoff analysis result of the roof surface of this case, Figure 5 is the final water collection position. Similarly, based on Grasshopper, the analysis results are simply processed, and combined with the roof water collection area and the specification requirement that "the water collection area served by a siphonic multi-hopper system should not be greater than 2500 m 2 ", the water collection area of the entire roof surface is divided, and the result is as Figure 6 shown.

[0074] (3) In Grasshopper, write a set of preliminary calculation tools for a multi-hopper siphonic roof rainwater drainage system according to the formula in the invention content as Figure 7 shown. The main function of this tool is to perform preliminary calculations on the rainwater design flow rate, gutter drainage volume, and overflow port flow rate. Only need to connect the roof model to the corresponding input end, and input the corresponding values at the other parameter ends such as the runoff coefficient and rainstorm recurrence period according to the actual situation, and the calculation results can be obtained.

[0075] (4) Automatically select the models or sizes of each device in the BIM database according to the preliminary calculation results or CFD analysis results. Using the parametric modeling function of Grasshopper, build an automatic modeling program for the drainage system as shown in Figure 8 . The program mainly includes the following logic: the connection relationship between the roof surface and the gutter, the dimensions and connection relationship between the gutter and the siphonic rainwater hopper, the position and connection relationship between the connecting pipe, the suspension pipe and the riser, etc. Combining the 3D models of each device in the database, generate the overall model of the multi-hopper siphonic roof drainage system as shown in Figure 9 .

[0076] (5) Select XFlow as the CFD analysis software. Export the geometric attribute information data of the BIM model of the multi-hopper siphonic roof drainage system, establish a CFD model for the multi-hopper siphonic drainage system for the gutter drainage volume and the overflow port flow position, and sequentially perform model mesh generation, fluid parameter setting, calculation domain, boundary condition, and solution parameter setting.

[0077] In terms of model mesh generation, import XFlow for dynamic simulation analysis of the drainage process. Since the gap at the deflector of the siphonic drainage hopper is small, it is necessary to refine the mesh near this position when establishing the XFlow mesh model to arrange more particles to solve the flow state change process at this place. It is recommended that there be at least two grids at the smallest gap of the deflector to ensure that the water body can flow out freely. It is recommended that the grid size of the pipeline be less than one-fifth of the pipeline diameter. The XFlow mesh model is as shown in Figure 10 .

[0078] In terms of boundary condition setting, set the top of the gutter of the roof drainage system as a pressure outlet, and its pressure is consistent with the atmospheric pressure; set the side wall of the gutter connected to the roof end as an inlet condition, and according to the specifications and historical measurement conditions, this side wall boundary condition is set as a mass inlet or a velocity inlet to simulate the rainwater collection under various rainfall conditions; for the bottom of the gutter, it can be set as a wall condition, and set as an enhanced wall boundary condition in the XFlow software; for the siphonic pipeline, the side wall of the pipeline can be set as a wall condition, and the end of the vertical pipe is set as a pressure outlet. Simulate the head loss along the way during the siphonic drainage process by setting the wall roughness.

[0079] In terms of the parameter settings for calculation and solution, it is recommended to use the efficient XFlow fluid calculation based on the free surface flow model. Turn on the volume correction function in the advanced options of XFlow to ensure the conservation of rainwater mass during the calculation; consider the effect of gravitational acceleration. The initial conditions for the calculation can be set according to different research focuses. Generally, the initial conditions of the pipes and catch basins are set to air, that is, the siphon drainage is carried out under the condition of no accumulated water. According to the "Design Standard for Building Water Supply and Drainage", the total simulation duration in XFlow calculation is set to 300 s (5 min), and when setting the single time integration step, the Courant number range is considered to be set to 1 - 3.

[0080] After completing the XFlow free surface calculation, post - processing analysis can be carried out in XFlow or the open - source software Paraview. The post - processing visualization results include: 1) The cloud map of the water velocity distribution of rainwater in the pipes of the entire system, as shown in Figure 11 ; 2) The calculated head loss of the upstream branches of each rainwater hopper, as shown in Figure 12 ; 3) The cloud map of the total pressure distribution in the pipes of the entire system, as shown in Figure 13 . The intuitive siphon dynamic process can be processed in the Paraview software.

[0081] (6) Build a complete optimization process based on the Galapagos battery in Grasshopper. Statistically analyze the data obtained from the CFD analysis, mainly analyze the water flow velocity, head loss, pressure balance in the connecting pipes, the maximum negative pressure value of the system, etc. in each pipe, and judge the rationality of each parameter and whether it meets the specification requirements. If not, automatically change the equipment model or size in the BIM database, and then repeat steps 4 - 5. If the requirements are met, end the entire design process to obtain the final design result.

[0082] In summary, the present invention discloses an intelligent design method and system for a multi - hopper siphon roof drainage system based on dynamic rainwater simulation, mainly based on the BIM design platform and the CFD numerical simulation platform. The key points of its technical solution are: 1) Database module: including the BIM database of each device in the siphon drainage system; 2) Runoff analysis module: conduct dynamic water collection simulation and water collection area division for the roof; 3) Preliminary calculation module: calculate the initial design parameters of the drainage system; 4) Scheme generation module: automatically establish the BIM model of the drainage system; 5) Numerical simulation module: conduct CFD numerical simulation on the drainage system; 6) Intelligent optimization module: use intelligent optimization algorithms to iteratively optimize the design scheme; 7) Visualization module: conduct post - processing on the CFD analysis results;

[0083] 8) Interactive Change Module: Human intervention in the intelligent design process. This paper addresses the current multi-bucket siphonic drainage system on the roofs of large-span buildings and proposes an efficient, iterative, intelligent design method for rainwater drainage performance analysis based on the BIM model. Two different-scale computational models, rainwater runoff and CFD drainage analysis, are applied during the design process. This method can simulate and predict the actual operating conditions of the roof drainage system under varying rainfall intensities. It also implements a modularized, intelligent design and optimization process for the multi-bucket siphonic roof drainage system, providing a new digital technology solution for the BIM-based performance-based design of roof rainwater drainage systems for large-span buildings such as stadiums, airports, and commercial complexes.

[0084] It should be pointed out that, according to the needs of implementation, the various steps described in this application can be split into more steps, or two or more steps or partial operations of the steps can be combined into new steps to achieve the purpose of the present invention.

[0085] It will be easily understood by those skilled in the art that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements 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 design method for a multi-hopper siphonic roof drainage system, characterized in that, It includes the following steps: S1. Based on the BIM software platform, establish a three-dimensional model of the overall building roof, collect and organize the equipment of the siphonic roof rainwater drainage system, and establish a BIM database for each equipment of the siphonic drainage system. Among them, the equipment of the siphonic roof rainwater drainage system includes: gutter, siphonic rainwater bucket, non-slope rainwater suspension pipe, rainwater riser, buried pipe, discharge pipe and pipe joint. The established database includes: the three-dimensional model of each equipment and its model, size, designed discharge flow and average cost; S2. Analyze the building roof, including roof rainwater runoff analysis and roof catchment area division; S3. Combine the analysis results of the building roof and the local hydrology and meteorology, and conduct preliminary parameter calculation and analysis of the drainage system for each catchment area. Among them, the preliminary parameters of the drainage system include the designed rainwater flow of the building roof; S4. According to the results of the preliminary parameter calculation and analysis of the drainage system, select each drainage equipment in the BIM database and establish a complete BIM model of the drainage system. Specifically, referring to the analysis results of the building roof, automatically arrange the gutter at the corresponding final catchment position, and then determine the number of siphonic rainwater buckets in the gutter and the model layout positioning points according to the results of the preliminary parameter calculation and analysis of the drainage system; S5. Convert the complete BIM model of the drainage system into a CFD grid model and conduct siphonic numerical simulation analysis. The analysis content includes the overall performance of the drainage system and the operation process of the drainage system under various working conditions; S6. Judge whether the drainage system meets the evaluation index. If so, output the result; if not, call the intelligent optimization algorithm to conduct iterative design of the drainage system scheme. Take the best overall performance of the drainage system as the optimization goal, take the model of each equipment in the database as the design variable, take the designed rainwater flow of the roof as the constraint condition, use the genetic algorithm or particle swarm algorithm for intelligent optimization, and repeat steps S4 - S5 until the established evaluation index of the siphonic drainage system is met.

2. The design method of the multi-hopper siphonic roof drainage system according to claim 1, characterized in that, The BIM software platform includes Revit, Rhino and CATIA, and the CFD analysis software includes xflow, fluent and openfoam.

3. The design method of the multi-hopper siphonic roof drainage system according to claim 1, characterized in that, The specific roof rainwater runoff analysis is as follows: Randomly select several points on the three-dimensional model of the building roof to simulate rainwater. The selected points cover all parts of the roof and have an appropriate density. Take the selected points as the initial positions of the rainwater, find the vector of the point along the roof surface downward, simulate the direction of the raindrop moving on the roof under the action of gravity, and then move the point in this direction according to the set rainwater flow velocity. Finally, find the nearest point of the moved point on the roof surface. If the height coordinate of the nearest point is less than the initial point, it proves that the raindrop is indeed flowing downward, then the nearest point is a valid point, otherwise it is an invalid point. Loop the above steps until convergence or the maximum calculation iteration times are reached, and connect each initial point and the valid points in the calculation process into a curve to obtain the runoff curve and realize the runoff analysis of the roof surface.

4. The design method of the multi-hopper siphonic roof drainage system according to claim 3, characterized in that, The specific roof catchment area division is as follows: Based on the results obtained from the roof runoff analysis, it is found that all rainwater points ultimately gather at certain parts of the roof surface, which are the final water collection positions. By combining the initial positions of the rainwater points, the specific parts of the entire roof surface corresponding to each water collection position are obtained. Finally, the roof surface is divided into multiple water collection areas according to the water collection positions and water collection areas.

5. The design method of the multi-hopper siphonic roof drainage system according to claim 1, characterized in that, The preliminary parameter calculation and analysis of the drainage system include: The designed rainwater flow rate of the building roof is calculated according to the following formula: In the formula, q y is the designed rainwater flow rate, q j is the designed rainstorm intensity, Ψ is the runoff coefficient, F w is the catchment area; the designed rainstorm intensity is calculated and determined according to the rainstorm intensity formula of the local or adjacent areas, and the calculation formula is: In the formula, P is the design recurrence interval, t is the rainfall duration, A , b , c and n are local rainfall parameters; The preliminary design of the gutter is calculated according to the following formula: In the formula, is the designed drainage capacity of the gutter, is the effective cross-sectional area of the water flow, v is the water flow velocity, R is the hydraulic radius, and I is the slope of the gutter, is the roughness coefficient of the gutter; The preliminary design of the overflow opening is calculated according to the following formula: In the formula, is the designed flow rate of the overflow port, is the width of the overflow port, h is the height of the overflow port, g is the acceleration due to gravity.

6. The design method of the multi-hopper siphonic roof drainage system according to claim 1, characterized in that, Step S4 includes: Referring to the analysis results of the building roof, gutters are automatically arranged at the corresponding final water collection positions. Then, based on the results of the preliminary parameter calculation and analysis of the drainage system, the number of siphonic rainwater inlets in the gutter and the model layout positioning points are determined. The pipeline positioning center line is automatically generated through the positioning points and various pipeline connection rules formulated. Finally, the corresponding equipment models are assembled according to their respective positioning points or positioning lines to obtain a complete BIM model of the roof drainage system.

7. The design method of the multi-hopper siphonic roof drainage system according to claim 1, characterized in that, The siphon numerical simulation analysis includes: Convert the BIM model of the multi-inlet siphonic drainage system for each water collection area of the roof into a CFD analysis grid model, and conduct a simulation of the rainwater siphon process based on the free surface calculation model. Refined analysis of the overall performance of the drainage system under various rainfall intensity conditions. Visualize and analyze the pipeline flow velocity, head loss, pressure balance process, and the position and value of the maximum negative pressure according to the CFD simulation results, providing a quantitative reference for the subsequent quantitative evaluation of the drainage system performance indicators; The evaluation indicators of the drainage system include: the water flow velocity in each pipeline, the actual head loss of the system, and the maximum negative pressure value of the system.

8. A design system for a multi-hopper siphonic roof drainage system for implementing the design method of the multi-hopper siphonic roof drainage system according to any one of claims 1 to 7, characterized in that, Include: A model establishment module for establishing a three-dimensional model of the overall building roof based on the BIM software platform; A database module for collecting and organizing the equipment of the siphonic roof rainwater drainage system and establishing a BIM database for each equipment of the siphonic drainage system; A runoff analysis module for analyzing the building roof, including roof rainwater runoff analysis and roof water collection area division; A preliminary calculation module for combining the analysis results of the building roof and the local hydrology and meteorology to conduct preliminary parameter calculation and analysis of the drainage system for each water collection area; A scheme generation module for selecting each drainage equipment from the BIM database according to the results of the preliminary parameter calculation and analysis of the drainage system and establishing a complete BIM model of the drainage system; A numerical simulation module for converting the complete BIM model of the drainage system into a CFD grid model and conducting siphon numerical simulation analysis. The analysis content includes the overall performance of the drainage system and the operation process of the drainage system under various working conditions; An intelligent optimization module for judging whether the drainage system meets the evaluation indicators; if so, output the results; if not, call the intelligent optimization algorithm for iterative design of the drainage system scheme, and repeat steps S4 - S5 until the established evaluation indicators of the siphonic drainage system are met.

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