A non-standard pressure-containing shell support layout design method for a recirculating wind tunnel

Abstract

A kind of backflow formula wind tunnel with non-standard pressure shell support layout design method belongs to wind tunnel design field, the present application is to solve the repeated iteration and optimization problem involved in the process of existing wind tunnel support support layout design, especially the problem of low design efficiency.Three means of adjusting the number of support, changing the characteristics of support and adjusting the position of support are used to solve the problem of wind tunnel shell support layout design, the support reaction force distribution of different layout is calculated respectively, and the layout is optimized according to the evaluation criteria to form the final optimized support layout.The optimization method is to establish a finite element geometric model to accurately predict the reaction force of each support in different layout.This method is especially suitable for predicting the support reaction force under complex load conditions, and can quickly solve the iteration operation problem of different layout schemes by using parameterization means.

Description

Technical Field

[0001] This invention belongs to the field of wind tunnel design, and particularly relates to a non-standard pressure-bearing shell support layout design method for a recirculation wind tunnel. Background Technology

[0002] One crucial design consideration for large wind tunnels is ensuring their stable support on the ground. The main structure of a recirculating wind tunnel is a large, complex, unconventional pressure-bearing structure, forming a ring-shaped integral loop with strong mechanical connections between its sections. Wind tunnel structures are enormous; for example, the FL-62 wind tunnel is nearly 100 meters long, almost 30 meters wide, and has a maximum diameter of 18 meters. Due to the sheer size and considerable mass of large wind tunnels, careful consideration must be given to the design details of the support system for such massive systems. For the wind tunnel shell structure, the support layout has a critical impact on the force transmission path and is a key factor determining the stress distribution of the wind tunnel structure. Different support layouts imply different support models, types, and numbers, directly affecting the cost of the support layout. For civil engineering, the number of supports and the magnitude of the transmitted load directly influence the design of the wind tunnel foundation and the installation of civil engineering pile foundations. The design of the support layout not only requires balancing cost, accuracy, and safety, but also involves a process of repeated iteration and optimization. Moreover, time is tight, and the optimal solution needs to be selected before the start of civil construction. Therefore, there is an urgent need for an accurate and efficient method to complete the design of the support layout.

[0003] The optimization design of the support system involves many design variables, and its optimization objective is affected by multiple factors, making it highly complex and subject to various constraints, such as the number of supports. For large-scale wind tunnels, if there are too few supports and the distance between them is too far, it will affect the stiffness of the structure and generate a large additional moment due to the long force transmission path, thus putting a burden on the strength of the tunnel structure. If there are too many supports, serious internal force problems may occur under temperature loads. From a cost perspective, too many supports will also increase costs.

[0004] The design of support systems for large wind tunnels involves complex load conditions and numerous operating conditions. Wind tunnels are pressure vessels, and especially for recirculation wind tunnels, pressure loads drastically affect the distribution of support reactions. Temperature and pressure vary significantly under different operating conditions. Supports at different locations exhibit varying sensitivities to different operating conditions, requiring comprehensive consideration during the design process. An inappropriate support layout can severely increase internal forces between supports, complicate civil engineering design, and cause drastic load fluctuations under different operating conditions. This not only makes support selection difficult but also affects the lifespan of both the supports and the foundation. Summary of the Invention

[0005] The purpose of this invention is to provide a design method for a non-standard pressure-bearing shell support layout for a recirculation wind tunnel, thereby solving the problem of low design efficiency caused by repeated iterations and optimizations in the existing wind tunnel support layout design process. The technical solution adopted by this invention is as follows: A method for designing a non-standard pressure-bearing shell support layout for a recirculation wind tunnel, comprising: Step 1: Establish the finite element geometric model of the wind tunnel structure using ANSYS Design Modeler; Step 2: Compensate for the simplified part of the shell structure, apply constraints and loads, and form a finite element analysis model; Step 3: Adjust the number of supports, change the support characteristics, adjust the support positions, and calculate the support reaction force distribution for different layouts; Step 4: Optimize the layout according to the evaluation criteria to form the final support layout.

[0006] In the above technical solution, the specific steps of step one are as follows: Step 11: Create the initial geometric shell in ANSYS Design Modeler: First, convert the solid wind tunnel structure into a shell structure composed of geometric surfaces. For structures with symmetrical mid-surfaces, extract their geometric mid-surfaces to form the shell structure; for structures without symmetrical mid-surfaces, select one surface of the structure as the shell structure to form the initial geometric shell. Step 12: Shared shell structure geometry topology: Since there are gaps between the initial geometric shells, the initial geometric shells need to be extended to an intersecting state, and the continuity of the subsequently generated mesh is ensured by sharing the topology; Step 13: Assign shell thickness: Based on the actual thickness value of the shell structure, assign a corresponding thickness value to the geometric shell. For a geometric shell formed by a symmetrical mid-plane, the mesh is of equal thickness and symmetrical about the mid-plane. For a geometric shell formed by a surface, when assigning thickness, the surface is used as the bottom surface of the mesh, and a variable thickness mesh is assigned according to the actual shell structure thickness.

[0007] In the above technical solution, the specific steps of step two are as follows: Step 21: Simplified Shell Structure Compensation: For structures with low stiffness and high mass that were ignored during modeling, convert them into mass points to compensate for their mass properties, and connect them to the force transmission points using the MPC method. Step 22: Apply constraints and loads: Support constraints are applied at the corresponding support locations by restricting displacement degrees of freedom; pressure loads are applied to the pressure-bearing inner surface of the shell; gravity loads are applied to the overall shell structure; impact loads are applied to the supports; and temperature loads are applied to the diffuser section. Step 23: Forming the finite element analysis model: Generate the mesh while ensuring the continuity of the multibody mesh. For structures that cannot share topology, connect them together by establishing binding contact. For the connection at the large tie rod, connect them by establishing beam elements. Divide the mesh and perform mesh independence test.

[0008] In the above technical solution, the specific steps of step three are as follows: Step 31: First, verify the effect of the number of supports on the support reaction force. By adjusting the number of supports under each section, observe the changes in support reaction force before and after the support adjustment under different working conditions. Step 32: When the number of supports is initially determined, adjust the support positions using ANSYS Design Modeler and observe the changes in support reaction force with working conditions by parameterizing the support positions. Step 33: Change the constraint behavior of the selected support and observe how the support reaction force changes with the working conditions.

[0009] In the above technical solution, the evaluation criteria are specifically as follows: a: Multi-directional sliding supports must not be subjected to negative forces; b: Under both temperature and pressure conditions, the support with the smallest sum of absolute values ​​of reaction forces is preferred. c: The support with lower degree of drastic change under different working conditions is superior; d: Minimize the number of supports; e: The theoretical axis deviation of the wind tunnel test area shall not exceed 0.01 degrees.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows: Wind tunnel support layout analysis involves numerous factors and complex calculations. Support layout design requires multiple iterations, and is time-sensitive and demanding. Traditional methods can only estimate support reactions under relatively simple load conditions, lacking a fast and accurate solution for the complex load conditions of recirculating wind tunnels. This method effectively overcomes the shortcomings of traditional methods. Thanks to a high-fidelity finite element model, it can accurately predict the reactions of each support under different layouts, making it particularly suitable for predicting support reactions under complex load conditions. Utilizing parametric techniques, it can quickly solve the iterative calculation problem for different layout schemes. Attached Figure Description

[0011] Figure 1 It is a schematic diagram of a model with a geometrically symmetrical mid-plane; Figure 2 yes Figure 1 A schematic diagram of a model with the middle surface removed and the gaps filled; Figure 3 yes Figure 2 A schematic diagram of the model forming the surface; Figure 4 It is a schematic diagram of a model that does not have a geometrically symmetric mid-plane; Figure 5 yes Figure 4 Choose one surface as the shell structure; Figure 6 yes Figure 5 A schematic diagram of a model that reconstructs geometric features by assigning thickness attributes; Figure 7 This is the front view of the actual wind tunnel; Figure 8 This is a side view of a physical wind tunnel.

[0012] In the diagram: 1-Second corner section, 2-First corner section, 3-First diffuser section, 4-Stationary chamber, 5-Stabilizing section, 6-Fourth corner section, 7-Third corner section, 8-Heat exchanger, 9-Second diffuser section, 10-Stationary chamber door, 11-Stationary chamber door, 12-Bearing wall, 13-Corner guide vane. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below with reference to specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0014] The connections mentioned in this invention are divided into fixed connections and detachable connections. Fixed connections, also known as non-detachable connections, include but are not limited to conventional fixed connection methods such as folded connections, riveted connections, adhesive connections, and welded connections. Detachable connections include but are not limited to conventional disassembly methods such as bolted connections, snap-fit ​​connections, pin connections, and hinged connections. When a specific connection method is not explicitly defined, it is assumed that at least one existing connection method can be found to achieve this function, and those skilled in the art can choose according to their needs. For example, a welded connection can be chosen for fixed connections, and a bolted connection can be chosen for detachable connections.

[0015] The present invention will be further described in detail below with reference to the accompanying drawings. The following embodiments are explanations of the present invention, but the present invention is not limited to the following embodiments.

[0016] Example: Figure 1-8 As shown, a method for designing a non-standard pressure-bearing shell support layout for a recirculation wind tunnel includes: Step 1: Create the initial geometric shell in ANSYS Design Modeler: First, convert the solid wind tunnel structure into a shell structure composed of geometric surfaces. For structures with symmetrical midplanes (most structures in a wind tunnel have symmetrical midplanes), extract their geometric midplanes to form the shell structure; for structures without symmetrical midplanes (such as guide vanes in the four corner sections, etc.), extract the geometric midplanes to form the shell structure. Figure 4 As shown in the figure, which is an asymmetric structure, one surface of the structure is selected as the shell structure to form the initial geometric shell; Step 2: Shared shell structure geometry topology: Since there are gaps between the initial geometric shells, the initial geometric shells need to be extended to an intersecting state, and the continuity of the subsequently generated mesh is ensured by sharing the topology; Step 3: Assign shell thickness: Based on the actual thickness value of the shell structure, assign a corresponding thickness value to the geometric shell. For a geometric shell formed by a symmetrical mid-plane, the mesh is of equal thickness and symmetrical about the mid-plane. For a geometric shell formed by a surface, when assigning thickness, the surface is used as the bottom surface of the mesh, and a variable thickness mesh is assigned according to the actual shell structure thickness. The ribs and stiffeners of the wind tunnel are all reproduced using a planar structure. The complex structures at typical abrupt cross-section locations such as the main door, guide vanes, hooks, supports, main doors, small doors, isolation doors, and load-bearing walls are modeled to form a shell structure based on the actual structural dimensions. Step 4: Simplified Shell Structure Compensation: For structures with low stiffness and high mass that were ignored during modeling in the wind tunnel structure, convert them into mass points (with mass and inertia) to compensate for their mass properties, and connect them to the force transmission points through the MPC (Multi-Point Constraint) method; Step 5: Apply constraints and loads: Support constraints are applied at the corresponding support locations by restricting displacement degrees of freedom; pressure loads are applied to the bearing inner surface of the shell (direction parallel to the local normal of the surface); gravity loads are applied to the overall shell structure; impact loads are applied at the supports; and temperature loads are applied to the diffuser section 9. Step 6: Forming the finite element analysis model: Generate the mesh while ensuring the continuity of the multi-body mesh. For structures that cannot share topology, connect them together by establishing binding contacts. For the connection at the large tie rod, connect them by establishing beam elements. Mesh the structure and perform mesh independence tests. Step 7: Extract the support reaction force and support reaction moment at the support location where the constraint is applied; Step 8: First, verify the effect of the number of supports on the support reaction force. By adjusting the number of supports under each section, observe the changes in support reaction force before and after the support adjustment under different working conditions. Changing the number of supports: During the finite element model establishment phase, supports are established at equal intervals according to the segments. At the start of the analysis, the initial number of supports should be significantly more than the number required by the actual layout. The purpose is to facilitate the reduction of the number of supports in subsequent analyses. This is achieved by suppressing the body (without actually deleting) in the geometric model to exclude unselected supports from the subsequent analysis process. The advantage of this is that unselected supports can return to the analysis process in special circumstances. During the analysis of gradually reducing the number of supports, the impact of the reduction is examined using support evaluation criteria. When the number of supports is reduced to a certain level and cannot fully meet the support evaluation criteria, the analysis of changing the number of supports is stopped, and the analysis of adjusting the position of supports begins. Adjusting the support type: There are three types of supports: unidirectional sliding, multidirectional sliding, and fixed supports. First, determine the location of the fixed supports. Fixed supports are generally located near areas with significant mass in the wind tunnel. For recirculation wind tunnels, they are typically located at the sump chamber and heat exchanger. If there is a significant concentration of mass in the wind tunnel, it is preferable to place the fixed supports near these sections. The second step is to adjust the location of the unidirectional sliding supports. Unidirectional sliding supports can only slide freely in one direction. They are an important means of ensuring the wind tunnel axis, but a side effect is that they significantly affect the distribution of support reactions, and under certain high-temperature conditions, they can significantly increase the internal forces between supports. To avoid excessive temperature stress, the number of unidirectional sliding supports should be minimized. For recirculation wind tunnels, high axis accuracy is generally required at the two major axes, so unidirectional sliding supports need to be positioned appropriately on both axes. By continuously adjusting the combination of various positions, the optimal layout scheme is selected. Step 9: Once the number of supports is initially determined, adjust the support positions using ANSYS Design Modeler. By parameterizing the support positions, observe how the support reaction force changes with the working conditions. Support position adjustment: Using the center of gravity of each section as the origin of the support position adjustment parameters, the support distance is adjusted along the axial direction, and this distance is set as a parameterized analysis. In ANSYS Design Modeler, the support layout with the best comprehensive effect under different working conditions is selected through response surface optimization analysis. Step 10: Change the constraint behavior of the selected support and observe how the support reaction force changes with the working conditions; The evaluation criteria are as follows: a: Multi-directional sliding supports must not be subjected to negative forces; For multi-directional sliding bearings, prefabricated bridge bearings are generally selected. These bearings can only withstand compression but not tension. If the calculation results show negative force, the bearing needs to have tensile strength, which will significantly increase the bearing cost. It also indicates that the bearing position is not set properly. This situation can definitely be improved and eliminated by adjusting the bearing position. b: Under both temperature and pressure conditions, the support with the smallest sum of absolute values ​​of reaction forces is preferred. Temperature and pressure are typical internal forces. For working conditions where the net external force is zero, the greater the sum of the absolute values ​​of the support reaction forces, the more obvious the mutual interference between the supports. On the one hand, this will increase the pressure on the support structure, and on the other hand, it will increase the stress level of the structure. Of course, it is inevitable that this situation will occur if the axis accuracy requirements are met, but the position and form of the supports can be adjusted appropriately to minimize the impact. c: The support with lower degree of drastic change under different working conditions is superior; The reaction force of the support varies drastically under different working conditions. Since the recirculation wind tunnel may switch between various working conditions, the frequent changes in the support reaction force will cause fatigue of the support and foundation. The greater the change, the lower the theoretical life. Therefore, a layout with a higher theoretical life should be selected during the design. d: Minimize the number of supports; e: The theoretical axis deviation of the wind tunnel test area shall not exceed 0.01 degrees; Axis deviation is used to maintain the airflow angle deviation in the wind tunnel within a reasonable range and ensure the flow field quality in the test area. The calculation method is to take multiple sections along the wind tunnel, extract the center coordinates of the deformed sections, connect the center coordinates of multiple sections, calculate the slope and convert it into an angle.

[0017] Wind tunnel support layout analysis involves numerous factors and complex calculations. Support layout design requires multiple iterations, and is time-sensitive and demanding. Traditional methods can only estimate support reactions under relatively simple load conditions, lacking a fast and accurate solution for the complex load conditions of recirculating wind tunnels. This method effectively overcomes the shortcomings of traditional methods. Thanks to a high-fidelity finite element model, it can accurately predict the reactions of each support under different layouts, making it particularly suitable for predicting support reactions under complex load conditions. Utilizing parametric techniques, it can quickly solve the iterative calculation problem for different layout schemes.

[0018] The above embodiments are merely illustrative examples of the present invention and do not limit its scope of protection. Those skilled in the art can make partial changes to them, as long as they do not exceed the spirit and essence of the present invention, they are all within the scope of protection of the present invention.

Claims

1. A method for designing a non-standard pressure-bearing shell support layout for a recirculation wind tunnel, characterized in that, include: Step 1: Establish the finite element geometric model of the wind tunnel structure using ANSYS Design Modeler; Step 2: Compensate for the simplified part of the shell structure, apply constraints and loads, and form a finite element analysis model; Step 3: Adjust the number of supports, change the support characteristics, adjust the support positions, and calculate the support reaction force distribution for different layouts; Step 4: Optimize the layout according to the evaluation criteria to form the final support layout; The specific steps of step two are as follows: Step 21: Simplified Shell Structure Compensation: For structures with low stiffness and high mass that were ignored during modeling, convert them into mass points to compensate for their mass properties, and connect them to the force transmission points using the MPC method. Step 22: Apply constraints and loads: Support constraints are applied at the corresponding support locations by restricting displacement degrees of freedom; pressure loads are applied to the pressure-bearing inner surface of the shell; gravity loads are applied to the overall shell structure; impact loads are applied to the supports; and temperature loads are applied to the diffuser section. Step 23: Forming the finite element analysis model: Generate the mesh while ensuring the continuity of the multibody mesh. For structures that cannot share topology, connect them together by establishing binding contacts. For the connection at the large tie rod, connect them by establishing beam elements. Mesh the structure and perform mesh independence tests. The specific steps of step three are as follows: Step 31: First, verify the effect of the number of supports on the support reaction force. By adjusting the number of supports under each section, observe the changes in support reaction force before and after the support adjustment under different working conditions. Step 32: When the number of supports is initially determined, adjust the support positions using ANSYS Design Modeler and observe the changes in support reaction force with working conditions by parameterizing the support positions. Step 33: Change the constraint behavior of the selected support and observe how the support reaction force changes with the working conditions; The evaluation criteria are as follows: a: Multi-directional sliding supports must not be subjected to negative forces; b: Under both temperature and pressure conditions, the support with the smallest sum of absolute values ​​of reaction forces is preferred. c: The support with lower degree of drastic change under different working conditions is superior; d: Reduce the number of supports; e: The theoretical axis deviation of the wind tunnel test area shall not exceed 0.01 degrees.

2. The method for designing a non-standard pressure-bearing shell support layout for a recirculation wind tunnel according to claim 1, characterized in that, The specific steps of step one are as follows: Step 11: Create the initial geometric shell in ANSYS Design Modeler: First, convert the solid wind tunnel structure into a shell structure composed of geometric surfaces. For structures with symmetrical mid-surfaces, extract their geometric mid-surfaces to form the shell structure; for structures without symmetrical mid-surfaces, select one surface of the structure as the shell structure to form the initial geometric shell. Step 12: Shared shell structure geometry topology: Since there are gaps between the initial geometric shells, the initial geometric shells need to be extended to an intersecting state, and the continuity of the subsequently generated mesh is ensured by sharing the topology; Step 13: Assign shell thickness: Based on the actual thickness value of the shell structure, assign a corresponding thickness value to the geometric shell. For a geometric shell formed by a symmetrical mid-plane, the mesh is of equal thickness and symmetrical about the mid-plane. For a geometric shell formed by a surface, when assigning thickness, the surface is used as the bottom surface of the mesh, and a variable thickness mesh is assigned according to the actual shell structure thickness.

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