A BIM-based hydraulic analysis method for pipelines in hydropower station buildings

Abstract

The present invention discloses a hydraulic analysis method for a hydropower plant building pipeline based on BIM, comprising: S1, creating a BIM three-dimensional model of the pipeline system, obtaining initial attribute information of each model object, and converting the model object into corresponding component objects, wherein the model objects include four categories: straight pipes, pipe fittings, valves, and equipment; S2, selecting some model objects in the pipeline system, constructing a network relationship diagram, and obtaining a hydraulic analysis model of the pipeline network to be calculated; S3, setting initial hydraulic condition information of the hydraulic analysis model of the pipeline network to be calculated, calculating the hydraulic state of the pipeline system at equilibrium, and realizing pipeline hydraulic analysis. The present invention can quickly and accurately calculate the hydraulic state of each pipeline in a real pipeline system, reflect the hydraulic characteristics of the actual pipeline system in the project, effectively avoid the problem of repeated pipeline modification and large deviation from the actual layout, improve design accuracy, reduce material waste, and improve pipeline design efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic design of pipelines in hydropower stations, and in particular to a hydraulic analysis method for pipelines in a hydropower station building based on BIM. The method is suitable for hydraulic calculation of pipelines in a hydropower station building. Background Art

[0002] The three-dimensional design of hydraulic piping in hydropower stations is a technically complex field requiring extremely high precision. The pipeline design process requires comprehensive consideration of the nominal diameter, pressure rating, type, and material of the pipeline objects to ensure the stable operation of the entire hydropower station piping system. Currently, when designing hydraulic analysis for hydropower station pipelines, the main approach is to use pipeline logic diagrams, which fail to display the specific pipeline routes and objects such as pipe fittings, valves, and equipment. Furthermore, during the design process, coordination between the hydraulic engineering department and other disciplines requires design optimization and repeated adjustments to the pipeline routes. These issues cannot be reflected in the logic, affecting design accuracy and reducing design efficiency. This also further increases the deviation between the logic diagram and the actual layout results. To ensure safety, the design tends to be conservative, resulting in material waste. Summary of the Invention

[0003] In order to overcome the shortcomings of the above technologies, the present invention provides a BIM-based hydraulic analysis method for hydropower station plant pipelines. By constructing a BIM three-dimensional model of the hydropower station plant pressure pipeline, the present invention quickly calculates the hydraulic conditions in each section of the pipeline, realizes the integrated design of professional calculation and layout, and improves the efficiency of pipeline design.

[0004] Explanation of terms:

[0005] 1. BIM: Building Information Modeling.

[0006] The technical solution adopted by the present invention to overcome the technical problems is:

[0007] A BIM-based hydraulic analysis method for pipelines in a hydropower station building includes the following steps:

[0008] Step S1: Create a BIM 3D model of the piping system, obtain the initial attribute information of each model object, and convert the model object into a corresponding component object. The model objects include four categories: straight pipes, pipe fittings, valves, and equipment.

[0009] Step S2: Select some model objects in the pipeline system, construct a network relationship diagram, and obtain the hydraulic analysis model of the pipeline network to be calculated, specifically including:

[0010] S21. Select some model objects in the pipeline system, obtain component objects corresponding to the selected model objects according to step S1, set the straight pipe elements as edges, and set the resistance elements and equipment elements as nodes;

[0011] S22, judging whether the component objects are connected based on whether the interface coordinates of the component objects are the same, and determining the connected interfaces;

[0012] S23. Traverse all component objects, obtain the connection relationship between all component objects, and assign the component object information to the corresponding edge or node;

[0013] S24, marking the interfaces in the component object that do not form a connection relationship with other component objects as open interfaces, and determining whether the open interfaces belong to a certain node, and then establishing a connection relationship;

[0014] S25. Repeat step S24 until all open interfaces are determined, thereby constructing a network relationship diagram and obtaining a hydraulic analysis model of the pipe network to be calculated;

[0015] Step S3: setting the initial hydraulic condition information of the hydraulic analysis model of the pipe network to be calculated, calculating the hydraulic state of the pipe system at equilibrium, and realizing the pipe hydraulic analysis.

[0016] Furthermore, in step S1, within the BIM three-dimensional model of the pipeline system, the converted component objects include three categories: straight pipe elements, resistance elements, and equipment elements. Among them, the straight pipe model object is converted into a straight pipe element, the pipe fitting model object and the valve model object are converted into resistance elements, and the equipment model object is converted into an equipment element.

[0017] Furthermore, in step S1, initial attribute information of each model object is obtained, and the model object is converted into a corresponding component object, specifically including:

[0018] First, the initial attribute information of each model object is obtained. The initial attribute information of a straight pipe includes at least the serial number, the coordinates of the interfaces at both ends of the straight pipe, the pipe diameter, the length of the straight pipe, and the material. The initial attribute information of a pipe fitting includes at least the serial number, the coordinates of each interface of the pipe fitting, and the pipe diameter. The initial attribute information of a device includes at least the serial number, the coordinates of each interface of the device, and the pipe diameter.

[0019] Then all model objects are converted into corresponding component objects, and the obtained initial attribute information of each model object is stored in the corresponding component object.

[0020] Furthermore, in step S24, it is determined whether the open interface belongs to a certain node, and then a connection relationship is established, which specifically includes the following:

[0021] If the open interface does not belong to a node, a new node is created based on the open interface, and a connection relationship is established. At the same time, a virtual node and a virtual edge are additionally created at the open interface. The virtual node is connected to the node containing the open interface through the virtual edge, thus forming a connection relationship. The coordinate values ​​of the virtual node are the same as the coordinate values ​​of the open interface connected to it.

[0022] If an open interface belongs to a certain node, a virtual node and a virtual edge are additionally created at the open interface. The virtual node is connected to the node containing the open interface through the virtual edge, forming a connection relationship, wherein the coordinate value of the virtual node is the same as the coordinate value of the open interface connected to it.

[0023] Furthermore, in step S3, the initial hydraulic information of the hydraulic analysis model of the pipe network to be calculated is set, the hydraulic state of the pipe system at equilibrium is calculated, and the pipe hydraulic analysis is completed, which specifically includes the following steps:

[0024] S31. Setting initial hydraulic information for all virtual edges connected to the open interface, including: the pipe diameter of the virtual edge is the same as the pipe diameter of the component object to which the open interface belongs, the length of the virtual edge is 0, and the head loss coefficient along the way is 0;

[0025] S32. Setting initial hydraulic information for all virtual nodes connected to the open interface, with the pipe diameter of the virtual node being the same as the pipe diameter of the component object to which the open interface belongs;

[0026] S33, setting the initial hydraulic information of all model objects selected in step S2, and matching them to the corresponding nodes and edges of the network relationship diagram;

[0027] S34. Based on the mass balance and energy balance relationship of each edge and node, at least the water flow velocity and flow rate at the interfaces at both ends of each edge when balanced are calculated, the hydraulic state calculation of the pipeline system when balanced is completed, and the pipeline hydraulic analysis is realized.

[0028] Furthermore, in step S32, the initial hydraulic information of all virtual nodes connected to the open interface varies due to different calculation conditions, including but not limited to the initial head value, initial flow rate, and local head loss coefficient.

[0029] Furthermore, in step S33, the initial hydraulic information of all selected model objects varies due to different calculation conditions, as follows:

[0030] For straight pipe model objects, set initial hydraulic information including but not limited to head loss coefficient along the pipe and water demand;

[0031] For pipe fittings and valve model objects, set initial hydraulic information including but not limited to local head loss coefficient;

[0032] For the equipment model object, the initial hydraulic information is set including but not limited to the local head loss coefficient, water consumption, and head lift.

[0033] As a preferred embodiment of the present invention, step S3 further includes step S4, which includes the following:

[0034] Calculate the minimum wall thickness of the straight pipe, output the hydraulic calculation results, and complete the calculation.

[0035] Furthermore, in step S4, the minimum wall thickness of the straight pipe is calculated, and the hydraulic calculation result is output to complete the calculation, which specifically includes the following steps:

[0036] Use the following formula to calculate the minimum wall thickness required for straight pipe:

[0037] (1)

[0038] In formula (1), Indicates the density of water; represents the acceleration due to gravity; Indicates the water head value at the straight pipe interface, and the larger water head value at the interfaces at both ends of the straight pipe is taken; Indicates the outer diameter of the straight pipe; Indicates the allowable pressure of straight pipe material; represents the coefficient;

[0039] Output the required hydraulic calculation results according to preset requirements and complete the calculation.

[0040] The beneficial effects of the present invention are:

[0041] The BIM-based hydraulic analysis method for hydropower plant pipelines proposed in this paper directly captures pipeline system information by creating a three-dimensional BIM model of the pipeline system. By selecting only a portion of the model objects, a network diagram can be constructed and converted into a pipeline network hydraulic analysis model. This method avoids the cumbersome steps of first drawing a pipeline system diagram and then inputting additional pipeline system information, as is commonly done in existing technologies. This method can quickly and accurately calculate the hydraulic state of each pipeline in a real-world pipeline system, reflecting the hydraulic characteristics of the actual pipeline system in the project. This method effectively avoids the problem of repeated pipeline modifications and large deviations from the actual layout, improving design accuracy, reducing material waste, and increasing pipeline design efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a flow chart of a BIM-based hydraulic analysis method for pipelines in a hydropower plant building according to an embodiment of the present invention.

[0043] Figure 2 This is an example diagram of the BIM three-dimensional model of the pipeline system described in an embodiment of the present invention.

[0044] Figure 3 This is a schematic diagram of constructing a network relationship diagram according to an embodiment of the present invention.

[0045] Figure 4 This is a schematic diagram of selecting a hydraulic analysis model for a pipe network to be calculated according to an embodiment of the present invention. DETAILED DESCRIPTION

[0046] In order to facilitate those skilled in the art to better understand the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. The following is only exemplary and does not limit the scope of protection of the present invention.

[0047] The present invention discloses a hydraulic analysis method for pipelines in a hydropower station building based on BIM, comprising the following steps:

[0048] Step S1: Create a BIM 3D model of the piping system, obtain the initial attribute information of each model object, and convert the model object into a corresponding component object. The model objects include four categories: straight pipes, pipe fittings, valves, and equipment.

[0049] Step S2: Select some model objects in the pipeline system, construct a network relationship diagram, and obtain a hydraulic analysis model of the pipeline network to be calculated;

[0050] Step S3: setting the initial hydraulic condition information of the hydraulic analysis model of the pipe network to be calculated, calculating the hydraulic state of the pipe system at equilibrium, and realizing the pipe hydraulic analysis.

[0051] To better understand the above technical solutions, exemplary embodiments of the present invention will be described in detail below with reference to the accompanying drawings. These are merely exemplary embodiments of the present invention. However, it should be understood that the present invention can be implemented in various forms and is not limited to the embodiments described herein. These embodiments are intended to enable those skilled in the art to understand the present invention more clearly and thoroughly.

[0052] The BIM-based hydraulic analysis method for a hydropower plant building pipeline described in this embodiment displays the entire process of pipeline modeling, hydraulic analysis, and calculation output based on the MicroStation three-dimensional graphics platform.

[0053] like Figure 1 As shown, the following steps are included:

[0054] Step S1: Create a BIM three-dimensional model of the pipeline system, obtain the initial attribute information of each model object, and convert the model object into a corresponding component object. The model objects include four categories: straight pipes, pipe fittings, valves, and equipment.

[0055] Specifically, straight pipes, pipe fittings, valves, and equipment are all commonly used terms in pipeline engineering. For example, elbows, tees, and crosses are pipe fittings; gate valves, ball valves, and control valves are valves; and equipment includes water-using equipment, pumps, and water filters, which are not further explained here. 3D pipeline modeling technology is already very mature and can be implemented in commercial 3D graphics platforms such as Revit and MicroStation. Therefore, we will not elaborate on the modeling methods here.

[0056] In this embodiment, in the BIM three-dimensional model of the pipeline system, the converted component objects include three categories: straight pipe elements, resistance elements and equipment elements. Among them, the straight pipe model object is converted into a straight pipe element, the pipe fitting model object and the valve model object are converted into resistance elements, and the equipment model object is converted into an equipment element.

[0057] Furthermore, the initial attribute information of each model object is obtained, and the model object is converted into a corresponding component object, specifically including:

[0058] (1) First, obtain the initial attribute information of each model object. The initial attribute information of the straight pipe includes at least the number, the coordinates of the interfaces at both ends of the straight pipe, the pipe diameter, the length of the straight pipe, and the material. The initial attribute information of the pipe fitting includes at least the number, the coordinates of each interface of the pipe fitting, and the pipe diameter. The initial attribute information of the equipment includes at least the number, the coordinates of each interface of the equipment, and the pipe diameter. Figure 2 As shown in the figure, some straight pipes, pipe fittings (tees, elbows and caps), valves (gate valves, ball valves, stop valves) and equipment (water filters, water pumps) are marked. Figure 2 Take the straight pipe, pipe fitting and a device in the model as an example. For the straight pipe, the number, coordinates of the interfaces at both ends of the straight pipe, pipe diameter, straight pipe length and material can be obtained according to the model object; for the elbow, the number, coordinates of each interface of the elbow and pipe diameter can be obtained; for the tee, the number, coordinates of each interface of the tee and pipe diameter can be obtained; for the pipe cap, only one end is connected to the pipeline, so the pipe cap number, pipe cap interface coordinates and pipe diameter can be obtained; for the equipment, the number of the equipment, coordinates of each interface of the equipment and pipe diameter can be obtained.

[0059] (2) Then attach Figure 2 All model objects in the are converted into corresponding component objects, and the initial attribute information of each model object is stored in the corresponding component object. Figure 2 A total of 25 straight pipe elements can be obtained; a total of 18 resistance elements, including 5 elbows, 5 tees, 1 pipe cap and 7 valves; and 4 equipment elements.

[0060] Step S2: Select some model objects in the pipeline system, construct a network relationship diagram, and obtain a hydraulic analysis model of the pipeline network to be calculated.

[0061] In this embodiment, step S2 specifically includes the following steps:

[0062] S21. Select some model objects in the pipeline system, obtain component objects corresponding to the selected model objects according to step S1, set the straight pipe elements as edges, and set the resistance elements and equipment elements as nodes.

[0063] S22. Determine whether the component objects are connected based on whether the interface coordinates of the component objects are the same, and determine the connected interfaces.

[0064] S23. Traverse all component objects to obtain the connection relationships between all selected model objects and the connection relationships between component objects corresponding to the model objects, and assign the component object information to the corresponding edges or nodes.

[0065] S24: Mark the interfaces in the component object that do not form a connection relationship with other component objects as open interfaces, determine whether the open interfaces belong to a certain node, and then establish a connection relationship; specifically, the process includes the following:

[0066] If the open interface does not belong to a node, a new node is created based on the open interface to establish a connection relationship. At the same time, an additional virtual node and a virtual edge are created at the open interface. The virtual node is connected to the node containing the open interface through the virtual edge, thus forming a connection relationship. The coordinate value of the virtual node is the same as the coordinate value of the open interface connected to it.

[0067] If an open interface belongs to a certain node, a virtual node and a virtual edge are additionally created at the open interface. The virtual node is connected to the node containing the open interface through the virtual edge, forming a connection relationship, wherein the coordinate value of the virtual node is the same as the coordinate value of the open interface connected to it.

[0068] S25. Repeat step S24 until all open interfaces are judged, thereby constructing the network relationship diagram corresponding to the selected model object and obtaining the hydraulic analysis model of the pipe network to be calculated.

[0069] like Figure 3 As shown, Figure 3Subgraph a) in the figure shows the selected model object. The corresponding component types are marked on the figure. There are two straight pipe components and one tee resistance component, numbered P1, P2, and T1. T1's left-end interface (Interface 1) is the same as P1's right-end interface, thus forming a connection between the two. Similarly, T1's upper interface (Interface 2) is the same as P2's lower interface, also forming a connection. The component object information is then assigned to the corresponding edges or nodes. Specifically, the attributes of straight pipe P1 are assigned to edge E1, those of straight pipe P2 are assigned to edge E2, and the attributes of tee T1 are assigned to node N1. Among them, the right-end open interface (interface 3) of T1 belongs to the node N1, so a virtual node VN3 and a virtual edge VE3 are additionally created at the open interface. The virtual node VN3 is connected to the node N1 containing the open interface (interface 3) through the virtual edge VE3, that is, a connection relationship is formed. In order to show the connection relationship between the virtual node and the virtual edge, the virtual node VN3 and the virtual edge VE3 are drawn next to the interface 3. In fact, the coordinate value of the virtual node VN3 is the same as the coordinate value of the open interface (interface 3) connected to it. The open interface (interface A) on the left side of P1 does not belong to an existing node. A new node N2 is created based on the open interface. Node N2 contains interface A and is connected to node N1 through E1. At the same time, an additional virtual node VE1 and virtual edge VN1 are created at the open interface. Virtual node VE1 is connected to node N2 containing the open interface (interface A) through virtual edge VN1. Similarly, the open interface (interface B) at the top of P2 is operated in the same way. Virtual node VE2 is connected to node N3 containing the open interface (interface B) through virtual edge VN2, and the network relationship diagram is finally constructed. Figure 3 As shown in sub-figure b), the hydraulic analysis model of the pipe network to be calculated is obtained.

[0070] Step S3: setting the initial hydraulic information of the hydraulic analysis model of the pipe network to be calculated, calculating the hydraulic state of the pipe system at equilibrium, and implementing the pipe hydraulic analysis.

[0071] In this embodiment, step S3 specifically includes the following steps:

[0072] S31. Set the initial hydraulic information of all virtual edges connected to the open interface, including: the pipe diameter of the virtual edge is the same as the pipe diameter of the component object to which the open interface belongs, the length of the virtual edge is 0, and the head loss coefficient along the way is 0.

[0073] S32. Set the initial hydraulic information of all virtual nodes that form a connection relationship with the open interface. The pipe diameter of the virtual node is the same as the pipe diameter of the component object to which the open interface belongs. The initial hydraulic information of all virtual nodes that form a connection relationship with the open interface varies due to different calculation conditions, including but not limited to the initial head value, initial flow rate, and local head loss coefficient.

[0074] S33. Set the initial hydraulic information for all model objects selected in step S2 and match them to the corresponding nodes and edges in the network diagram. The initial hydraulic information for all selected model objects varies depending on the calculation conditions. For straight pipe model objects, the initial hydraulic information includes but is not limited to the head loss coefficient along the pipe and the water demand. For pipe fitting and valve model objects, the initial hydraulic information includes but is not limited to the local head loss coefficient. For equipment model objects, the initial hydraulic information includes but is not limited to the local head loss coefficient, water consumption, and head lift.

[0075] S34. Based on the mass balance and energy balance relationship of each edge and node, at least the water flow velocity and flow rate at the interfaces at both ends of each edge when balanced are calculated, the hydraulic state calculation of the pipeline system when balanced is completed, and the pipeline hydraulic analysis is realized.

[0076] Now combined Figure 4 To explain, Figure 4 Subgraph a) is from Figure 2 A part of the object model selected from the above example contains 6 straight pipe elements, 4 resistance elements, including 2 pipe fittings and 2 valves, and 1 equipment element. The corresponding network relationship diagram is shown in the figure below. Figure 4 Subgraph b). Figure 4 There are three open interfaces in subgraph b) of the example. Three virtual nodes (VN1', VN2', and VN3') and three virtual edges (VE1', VE2', and VE3') are generated near the open interfaces. The corresponding initial hydraulic information is set, and the head value and local head loss coefficient of the virtual nodes VN1' and VN3' are set. The initial flow rate is 0. Figure 4 In subgraph a), there are 4 resistance elements and 1 equipment element, which generate corresponding nodes N1'~N5'. Specifically, the first valve corresponds to node N1', the tee corresponds to node N2', the second valve corresponds to node N3', the water pump corresponds to node N4', and the elbow corresponds to node N5'. Among them, N1', N2', N3' and N5' are corresponding resistance element objects, and their local head loss coefficients are set; N4' corresponds to the equipment element object, and its head lift, local head loss coefficient, and water consumption are set to 0. Figure 4 Subgraph b) in Figure 1 has six edges, corresponding to six straight pipe elements. The head loss coefficient and water demand along the edges are set to zero. Hydraulic parameters such as flow velocity and flow rate at the interfaces at each end of the edge are calculated based on the equilibrium equation. This calculation process is part of the hydraulic network balance calculation and is public knowledge, so it will not be explained in detail here.

[0077] Let's use a specific operating condition as an example. Assuming the hydraulic head of the equipment model is A, calculate the flow direction and flow velocity within the pipe segment of the pipe network model to be calculated. Set the local head loss coefficients and head values ​​for virtual nodes VN1' and VN3'. Set the local head loss coefficient for virtual node VN2' to infinite, with a head value of 0, meaning no flow. Set the head loss coefficient along the straight pipe to 0, and the water demand to 0. Set the local head loss coefficients for pipe fittings and valves, and the local head loss coefficient for the equipment, with the hydraulic head A and water demand set to 0. In this case, the difference in elevation (z-coordinate value) between virtual nodes VN1' and VN3' is denoted as h1. As water flows from virtual node VN1' to virtual node VN3', it incurs a head loss Δh as it passes through each edge and node. If the head lift A of the equipment is greater than h1+Δh, the water flows from the virtual node VN1' to the virtual node VN3'. Conversely, the water flows from the virtual node VN3' to the virtual node VN1'. If they are equal, the water flow in the pipeline remains stationary. The hydraulic parameters such as the flow velocity in each straight pipe, the head loss when the water flows through each model object, and the head value at each interface of the component are calculated to complete the hydraulic calculation of the pipeline network and realize the hydraulic analysis of the pipeline in the hydropower station plant.

[0078] As a preferred solution of this embodiment, to facilitate output of the calculation result table, step S3 is followed by step S4, which includes the following:

[0079] Calculate the minimum wall thickness of the straight pipe, output the hydraulic calculation results, and complete the calculation.

[0080] Specifically, step S4 includes the following steps:

[0081] Use the following formula to calculate the minimum wall thickness required for straight pipe:

[0082] (1)

[0083] In formula (1), Indicates the density of water; represents the acceleration due to gravity; Indicates the head value at the straight pipe interface. and The water head at the two ends of the straight pipe is proportional to the water head, so the larger value is taken. The water head value comes from the hydraulic analysis result in step S3. This calculation result is safer. Indicates the outer diameter of the straight pipe; Indicates the allowable pressure of straight pipe material; Represents the coefficient, its value ≤1, which can be regarded as the allowable pressure A reduction, the pipe is thicker, and the calculated result is more secure.

[0084] Output the required hydraulic calculation results according to the preset requirements to complete the calculation. The hydraulic calculation results include the hydraulic parameters of straight pipes, pipe fittings, valves and equipment, specifically the head value of each end node of each pipe, pipe fitting, valve and equipment, the flow rate, flow velocity, head loss and other hydraulic parameters passing through the pipeline. The calculation results of specific model objects need to be output according to preset requirements such as design requirements or format requirements, generally including but not limited to the form of calculation tables or calculation books.

[0085] The above only describes the basic principles and preferred embodiments of the present invention. Those skilled in the art may make many changes and improvements based on the above description, and these changes and improvements should fall within the scope of protection of the present invention.

Claims

1. A hydraulic analysis method for pipelines in a hydropower station building based on BIM, characterized in that: The steps include: Step S1: Create a BIM 3D model of the piping system, obtain the initial attribute information of each model object, and convert the model object into a corresponding component object. The model objects include four categories: straight pipes, pipe fittings, valves, and equipment. Step S2: Select some model objects in the pipeline system, construct a network relationship diagram, and obtain the hydraulic analysis model of the pipeline network to be calculated, which specifically includes: S21. Select some model objects in the pipeline system, obtain component objects corresponding to the selected model objects according to step S1, set the straight pipe elements as edges, and set the resistance elements and equipment elements as nodes; S22, judging whether the component objects are connected based on whether the interface coordinates of the component objects are the same, and determining the connected interfaces; S23. Traverse all component objects, obtain the connection relationship between all component objects, and assign the component object information to the corresponding edge or node; S24: Mark the interfaces in the component object that do not form a connection relationship with other component objects as open interfaces, determine whether the open interfaces belong to a certain node, and then establish a connection relationship, which specifically includes the following: If the open interface does not belong to a node, a new node is created based on the open interface, and a connection relationship is established. At the same time, a virtual node and a virtual edge are additionally created at the open interface. The virtual node is connected to the node containing the open interface through the virtual edge, thus forming a connection relationship. The coordinate values ​​of the virtual node are the same as the coordinate values ​​of the open interface connected to it. If an open interface belongs to a node, a virtual node and a virtual edge are created at the open interface. The virtual node is connected to the node containing the open interface through the virtual edge, forming a connection relationship. The coordinate value of the virtual node is the same as the coordinate value of the open interface connected to it. S25. Repeat step S24 until all open interfaces are determined, thereby constructing a network relationship diagram and obtaining a hydraulic analysis model of the pipe network to be calculated; Step S3: setting the initial hydraulic condition information of the hydraulic analysis model of the pipe network to be calculated, calculating the hydraulic state of the pipe system at equilibrium, and realizing the pipe hydraulic analysis.

2. The BIM-based hydraulic analysis method for pipelines in a hydropower plant building according to claim 1 is characterized in that: In step S1, in the BIM three-dimensional model of the pipeline system, the converted component objects include three categories: straight pipe components, resistance components and equipment components. Among them, the straight pipe model objects are converted into straight pipe components, the pipe fitting model objects and valve model objects are converted into resistance components, and the equipment model objects are converted into equipment components.

3. The BIM-based hydraulic analysis method for pipelines in a hydropower plant building according to claim 1 or 2, characterized in that: In step S1, the initial attribute information of each model object is obtained and the model object is converted into a corresponding component object, which specifically includes: First, the initial attribute information of each model object is obtained. The initial attribute information of a straight pipe includes at least the serial number, the coordinates of the interfaces at both ends of the straight pipe, the pipe diameter, the length of the straight pipe, and the material. The initial attribute information of a pipe fitting includes at least the serial number, the coordinates of each interface of the pipe fitting, and the pipe diameter. The initial attribute information of a device includes at least the serial number, the coordinates of each interface of the device, and the pipe diameter. Then all model objects are converted into corresponding component objects, and the obtained initial attribute information of each model object is stored in the corresponding component object.

4. The BIM-based hydraulic analysis method for pipelines in a hydropower plant building according to claim 1 is characterized in that: In step S3, the initial hydraulic information of the hydraulic analysis model of the pipe network to be calculated is set, the hydraulic state of the pipe system at equilibrium is calculated, and the pipe hydraulic analysis is implemented, which specifically includes the following steps: S31. Setting initial hydraulic information for all virtual edges connected to the open interface, including: the pipe diameter of the virtual edge is the same as the pipe diameter of the component object to which the open interface belongs, the length of the virtual edge is 0, and the head loss coefficient along the way is 0; S32. Setting initial hydraulic information for all virtual nodes connected to the open interface, with the pipe diameter of the virtual node being the same as the pipe diameter of the component object to which the open interface belongs; S33, setting the initial hydraulic information of all model objects selected in step S2, and matching them to the corresponding nodes and edges of the network relationship diagram; S34. Based on the mass balance and energy balance relationship of each edge and node, at least the water flow velocity and flow rate at the interfaces at both ends of each edge when balanced are calculated, the hydraulic state calculation of the pipeline system when balanced is completed, and the pipeline hydraulic analysis is realized.

5. The BIM-based hydraulic analysis method for pipelines in a hydropower plant building according to claim 4 is characterized in that: In step S32, the initial hydraulic information of all virtual nodes connected to the open interface varies due to different calculation conditions, including but not limited to the initial head value, initial flow rate, and local head loss coefficient.

6. The BIM-based hydraulic analysis method for pipelines in a hydropower plant building according to claim 4 is characterized in that: In step S33, the initial hydraulic information of all selected model objects varies due to different calculation conditions, as follows: For straight pipe model objects, set initial hydraulic information including but not limited to head loss coefficient along the pipe and water demand; For pipe fittings and valve model objects, set initial hydraulic information including but not limited to local head loss coefficient; For the equipment model object, the initial hydraulic information is set including but not limited to the local head loss coefficient, water consumption, and head lift.

7. The BIM-based hydraulic analysis method for pipelines in a hydropower station building according to any one of claims 1 or 2 or 4-6, characterized in that: Step S3 is followed by step S4, which includes the following: Calculate the minimum wall thickness of the straight pipe, output the hydraulic calculation results, and complete the calculation.

8. The BIM-based hydraulic analysis method for pipelines in a hydropower plant building according to claim 7 is characterized in that: In step S4, the minimum wall thickness of the straight pipe is calculated, and the hydraulic calculation results are output to complete the calculation, which specifically includes the following steps: Use the following formula to calculate the minimum wall thickness required for straight pipe: （1） In formula (1), Indicates the density of water; represents the acceleration due to gravity; Indicates the water head value at the straight pipe interface, and the larger water head value at the interfaces at both ends of the straight pipe is taken; Indicates the outer diameter of the straight pipe; Indicates the allowable pressure of straight pipe material; represents the coefficient; Output the required hydraulic calculation results according to preset requirements and complete the calculation.

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