Method, system and device for acquiring half-shell modal data
By obtaining the modal frequencies and mode shapes of the symmetrical model and combining them with the node information of the symmetrical plane, the modal data of the half-side model is calculated, which solves the problem of inconsistent discretization between the half-side model and the symmetrical model and improves the calculation accuracy and efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CALCULATION AERODYNAMICS INST CHINA AERODYNAMICS RES & DEV CENT
- Filing Date
- 2022-12-27
- Publication Date
- 2026-06-02
AI Technical Summary
In existing technologies, the discretization of half-side models and symmetric models is inconsistent, resulting in inaccurate acquisition of modal data and affecting computational efficiency and accuracy.
By obtaining the first set of modal frequencies and the second set of modal shapes of the symmetrical model, and combining the node information on one side of the symmetrical plane, the modal data of the half-side model are calculated to ensure discrete consistency.
This method achieves consistent acquisition of modal data between the half-side model and the symmetric model, improving computational accuracy and efficiency, and avoiding errors caused by discrepancies.
Smart Images
Figure CN116011099B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of modal analysis, and in particular to a method, system and apparatus for acquiring half-side model modal data. Background Technology
[0002] Modal data, due to its simple structure, is easy to share and transmit between different departments, and is widely used in structural numerical simulation in the aerospace field.
[0003] Aerospace vehicles typically adopt symmetrical shapes and structures. In aeroelastic coupling simulations, most of the analysis states are symmetrical flows. In order to reduce computational costs and improve computational efficiency, half of the symmetrical model is usually used for fluid-structure interaction numerical simulation calculations.
[0004] Currently, there are two methods for obtaining modal data for half-side models. One method is to directly construct a symmetric model of the half-side model from scratch and then perform finite element modal analysis to obtain modal data. The other method is to modify the symmetric model by dividing the symmetric model along the plane of symmetry, applying appropriate boundary conditions, and then performing modal analysis to obtain the modal data of the half-side model. Both of these methods of constructing symmetric models of the half-side model carry the risk of inconsistency with the discretization of the symmetric model.
[0005] Therefore, how to obtain the modal data of the half-side model while ensuring that the half-side model and the symmetric model are discretely consistent has become a technical problem that technicians need to solve. Summary of the Invention
[0006] The purpose of this application is to provide a method, system, and apparatus for acquiring modal data of a half-side model. This method ensures that the modal data of the half-side model is acquired when the half-side model and the symmetric model are discretely consistent. Another purpose of this application is to provide a system and apparatus for acquiring modal data of a half-side model.
[0007] A method for obtaining modal data of a half-model, wherein the half-model is half of a symmetrical model and is located on one side of the symmetrical plane of the symmetrical model, the method comprising: obtaining a first set of modal frequencies of the symmetrical model; obtaining a second set of mode shapes of the symmetrical model based on all nodes on one side of the symmetrical plane of the symmetrical model; and obtaining modal data of the half-model based on the first set of modal frequencies and the second set of mode shapes.
[0008] Preferably, the step of obtaining the first set of modal frequencies of the symmetrical model specifically involves: obtaining the first modal data of the symmetrical model; obtaining the first set of modal frequencies based on the first set of modal shapes in the first set of modal data, wherein the left and right modes of any mode shape in the first set of modal shapes are the same.
[0009] Preferably, the step of taking all nodes on one side of the symmetry plane of the symmetry model as a node set to obtain the second set of modal shapes on one side of the symmetry plane of the symmetry model specifically includes: obtaining the second modal data on one side of the symmetry plane of the symmetry model; and obtaining the second set of modal shapes based on the first set of modal frequencies and the second set of modal data.
[0010] Preferably, both the first modal data and the second modal data include the modal frequency and mode shape for each order.
[0011] Preferably, the step of obtaining the modal data of the half-model based on the first set of modal frequencies and the second set of modal shapes specifically involves: multiplying all the second set of modal shapes by √2 to obtain the third set of modal shapes of the half-model; and obtaining the modal data of the half-model based on the third set of modal shapes and the first set of modal frequencies.
[0012] A system for acquiring modal data of a half-model, wherein the half-model is half of a symmetrical model and is located on one side of the symmetry plane of the symmetrical model, the acquisition system comprising: a first set of modal frequency solving modules for acquiring a first set of modal frequencies of the symmetrical model; a second set of modal shape solving modules for acquiring a second set of modal shapes of the symmetrical model based on all nodes on one side of the symmetry plane of the symmetrical model; and a calculation module for obtaining the modal data of the half-model based on the first set of modal frequencies and the second set of modal shapes.
[0013] An apparatus for acquiring half-side model modal data includes: a memory for storing a computer program; and a processor connected to the memory, wherein the processor is used to execute the computer program to implement the steps of the above-described method for acquiring half-side model modal data.
[0014] This application discloses a method for obtaining modal data of a half-model. This method fully considers the risk of discrepancy between the half-model finite element model and the symmetrical model finite element model if modal data is obtained by directly establishing the half-model finite element model. Therefore, it obtains the modal data of the half-model based on the symmetrical model finite element model. Specifically, the method involves obtaining the first set of modal frequencies of the symmetrical model and obtaining the second set of mode shapes of the symmetrical model based on all nodes on one side of the symmetry plane. Then, the modal data of the half-model is obtained based on the first set of modal frequencies and the second set of mode shapes. This avoids the risk of discrepancy between the half-model and the symmetrical model finite element model.
[0015] This application also provides a system and device for acquiring half-side model modal data, which has the above-mentioned beneficial effects, and will not be elaborated here. Attached Figure Description
[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0017] Figure 1 A finite element model diagram of a symmetric model;
[0018] Figure 2 This is a diagram of the mode shape of a certain order of a symmetric model;
[0019] Figure 3 The antisymmetric mode shape diagram of a certain order of the symmetric model;
[0020] Figure 4 This is a mode shape diagram of a certain order of the half-model;
[0021] Figure 5 A flowchart illustrating a method for acquiring half-side model modal data provided in this application embodiment;
[0022] Figure 6 This is a structural block diagram of a system for acquiring modal data of a half-side model, provided in an embodiment of this application.
[0023] in:
[0024] 1 is a symmetrical model, and 2 is a half-sided model. Detailed Implementation
[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0026] To enable those skilled in the art to better understand the present application, the following description is provided in conjunction with the appendix. Figure 1 To be continued Figure 6 The present application will be further described in detail with reference to specific embodiments.
[0027] A method for obtaining modal data of a half-model is disclosed, where half-model 2 is half of a symmetric model 1 cut along a plane of symmetry, meaning half-model 2 is located on one side of the plane of symmetry of symmetric model 1. In some fields, such as numerical simulation, half-model 2 is often used for simulation to reduce costs and improve computational efficiency. Therefore, this application proposes a method for obtaining modal data of half-model 2 by performing modal analysis based on a finite element model of symmetric model 1.
[0028] Modal analysis refers to the process of determining the mode shapes and modal frequencies of a multi-degree-of-freedom system. Modes are the inherent vibrational characteristics of a structural system, while mode shapes are the shapes of the system's displacements at its natural frequencies. Modal analysis helps designers determine the frequencies and mode shapes of a structure, effectively avoiding resonance in the design process.
[0029] For detailed methods and steps on obtaining modal data for half-side model 2, please refer to the appendix. Figure 5 , Figure 5 A flowchart illustrating a method for acquiring half-side model 2 modal data provided in an embodiment of this application.
[0030] S001: Obtain the first set of modal frequencies of symmetric model 1.
[0031] In practice, the general procedure for obtaining the first set of modal frequencies of symmetric model 1 is as follows: First, import symmetric model 1 into the finite element software. In the preprocessing module of the finite element software, select an appropriate element type for mesh generation, determine its material properties, and set relevant material properties to establish the corresponding finite element model. Finally, determine the initial boundary conditions and set the solution method to modal solution. Based on the finite element model, calculation requirements, and calculation experience, set the modal order and obtain the first-order modal frequency and its corresponding mode shape, the second-order modal frequency and its corresponding mode shape, the third-order modal frequency and its corresponding mode shape, and so on.
[0032] In the embodiments of this application, as shown in the appendix Figure 1 As shown: Based on the finite element model, modal analysis of symmetric model 1 is carried out.
[0033] Please refer to the attached document. Figure 2The finite element model has 20 nodes distributed along the spanwise direction and 5 nodes distributed along the chord direction, for a total of 100 nodes. Five nodes are distributed on the symmetry plane. The initial boundary conditions are simplified to full constraints at the center of the symmetry plane, and the solution method is set to modal analysis. Based on the computational requirements and experience, the modal order is set to 8. The coordinates of all nodes in the finite element model are obtained, thus obtaining the modal frequencies of the entire symmetric model and the mode shapes corresponding to each modal frequency. Then, the mode shapes that are consistent across the left and right sides of the symmetry plane are selected to obtain the first set of modal frequencies. That is, all modal frequencies in the first set of modal frequencies correspond to mode shapes that are consistent across the left and right sides of the symmetry plane.
[0034] S002' obtains the second set of modal shapes of symmetric model 1 based on all nodes on one side of the symmetry plane of symmetric model 1.
[0035] Similarly, based on the above simplification of the initial boundary conditions to full constraint at the center of the symmetry plane, setting the solution method to modal solution, and setting the modal order to 8 according to the calculation requirements and experience, all nodes on one side of the symmetry plane of symmetry model 1 are used as a node set to obtain the modal frequencies and mode shapes corresponding to each modal frequency of the modal solution on one side of the symmetry plane of symmetry model 1, and then the second set of mode shapes is obtained, that is, the mode shapes of the modal solution include the second set of mode shapes.
[0036] S003: Obtain the modal data of half-model 2 based on the first set of modal frequencies and the second set of modal shapes.
[0037] In other words, the modal data of half-model 2 can be solved by performing a simple conversion process between the first set of modal frequencies and the second set of modal shapes.
[0038] In this embodiment, the step of obtaining the first set of modal frequencies of the symmetrical model 1 is as follows: obtaining the first modal data of the symmetrical model 1; obtaining the first set of modal frequencies based on the first set of modal shapes in the first modal data, wherein the left and right modes of any mode shape in the first set of modal shapes are the same.
[0039] The first modal data specifically includes eight modal frequencies and their corresponding mode shapes. Based on the eight mode shapes obtained from the first modal data, the properties of each mode are determined by observing the mode shapes on the left and right sides of the symmetry plane. Mode shapes that are identical on both sides of the symmetry plane are symmetrical mode shapes; those that are opposite are antisymmetric mode shapes. Figure 2 For a certain order symmetric mode shape diagram and Figure 3 This is a diagram of a certain antisymmetric mode shape. The set of all its symmetric mode shapes is the first set of mode shapes, and the set of modal frequencies corresponding to the first set of mode shapes is the first set of modal frequencies.
[0040] In this embodiment, the step of obtaining the second set of modal shapes of the symmetrical model 1 based on all nodes on one side of the symmetry plane of the symmetrical model 1 is as follows: obtaining the second modal data on one side of the symmetry plane of the symmetrical model 1; and obtaining the second set of modal shapes based on the first set of modal frequencies and the second modal data.
[0041] First, all nodes on the right side of the symmetry plane of symmetry model 1 are taken as a node set. Then, the coordinates of the nodes in this node set and the second modal data corresponding to the nodes in the node set are output. Since the modal frequencies in the second modal data are the same as those in the first modal data, the second set of mode shapes corresponding to the first set of modal frequencies can be determined by comparing the first set of modal frequencies with the modal frequencies in the second modal data.
[0042] Both the first and second modal data include the modal frequencies and mode shapes for each order.
[0043] In this embodiment, the step of obtaining the modal data of half-model 2 based on the first set of modal frequencies and the second set of modal shapes specifically involves: multiplying all the second set of modal shapes by √2 to obtain the third set of modal shapes of half-model 2; obtaining the modal data of half-model 2 based on the third set of modal shapes and the first set of modal frequencies; simultaneously sorting the third set of modal frequencies from smallest to largest; integrating the third set of modal frequencies and the third set of modal shapes; and finally outputting the modal data of half-model 2.
[0044] Since the modal frequencies of symmetric model 1 are equal to those of half-model 2, meaning the first set of modal frequencies is the third set of modal frequencies of half-model 2, and the modal data includes the third set of modal frequencies and the third set of mode shapes, sorting the third set of modal frequencies yields the modal order order of half-model 2. This order, combined with the determined third set of mode shapes, is then stored and output to obtain the complete finite metadata of half-model 2.
[0045] Please refer to Figure 6 , Figure 6 This is a structural block diagram of a half-model modal data acquisition system provided in an embodiment of this application. Half-model 2 is half of symmetrical model 1, and half-model 2 is located on one side of the symmetry plane of symmetrical model 1. The half-model 2 modal data acquisition system provided in this embodiment is used to acquire the half-model 2 modal data described in the above embodiment.
[0046] The acquisition system includes a first set of modal frequency solving modules 001, a second set of modal shape solving modules 002, and a calculation module 003. The first set of modal frequency solving modules 001 is used to acquire the first set of modal frequencies of the symmetrical model 1; the second set of modal shape solving modules 002 is used to obtain the modal data of half-model 2 based on the first set of modal frequencies and the second set of modal shapes; and the calculation module 003 is used to obtain the second set of modal shapes based on the first set of modal frequencies and the second set of modal shapes.
[0047] A device for acquiring half-side model modal data includes a memory and a processor. The memory is used to store a computer program; the processor is connected to the memory and is used to execute the computer program to implement the steps of the above-described method for acquiring half-side model 2 modal data.
[0048] It should be noted that in this specification, relational terms such as first and second are used only to distinguish one entity from several other entities, and do not necessarily require or imply any such actual relationship or order between these entities.
[0049] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this application. It should be noted that those skilled in the art can make several improvements and modifications to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.
Claims
1. A method for acquiring modal data of a half-side model, characterized in that, The half-model is half of the symmetrical model, and the half-model is located on one side of the symmetrical plane of the symmetrical model. The method for obtaining the half-model includes: Obtain the first modal data of the symmetric model; The first set of modal frequencies are obtained from the first set of modal shapes in the first set of modal data, and the left and right modes of any mode in the first set of modal shapes are the same on the plane of symmetry. The second set of mode shapes of the symmetrical model is obtained based on all nodes on one side of the symmetry plane of the symmetrical model. The modal data of the half-model are obtained based on the first set of modal frequencies and the second set of modal shapes; The step of obtaining the modal data of the half-model based on the first set of modal frequencies and the second set of modal shapes specifically includes: Expand the second group of modal vibration modes The third set of mode shapes of the half-model is obtained by multiplying the original model. The modal data of the half-model is obtained based on the third set of modal shapes and the first set of modal frequencies; wherein, the first set of modal frequencies is the third set of modal frequencies of the half-model; the modal data of the half-model includes the third set of modal frequencies and the third set of modal shapes.
2. The method for obtaining half-side model modal data according to claim 1, characterized in that, The steps for obtaining the second set of modal shapes of the symmetrical model based on all nodes on one side of the symmetry plane of the symmetrical model are as follows: Obtain the second modal data of one side of the symmetry plane of the symmetry model; The second set of mode shapes is obtained based on the first set of modal frequencies and the second set of modal data.
3. The method for obtaining half-side model modal data according to claim 2, characterized in that, Both the first modal data and the second modal data include the modal frequency and mode shape for each order.
4. A system for acquiring modal data of a half-side model, characterized in that, The half-model is half of the symmetrical model, and the half-model is located on one side of the symmetry plane of the symmetrical model. The acquisition system includes: The first modal frequency solving module is used to obtain the first modal data of the symmetrical model; and to obtain the first modal frequencies based on the first modal shapes in the first modal data, wherein the left and right modes of any mode in the first modal shape are the same on the plane of symmetry. The second set of mode shape solving modules is used to obtain the second set of mode shapes of the symmetrical model based on all nodes on one side of the symmetry plane of the symmetrical model; The calculation module is used to obtain the modal data of the half-model based on the first set of modal frequencies and the second set of mode shapes; The calculation module is used to enlarge all of the second set of modal shapes. The third set of mode shapes of the half-model is obtained by multiplying the frequency of the first set of mode shapes; the modal data of the half-model is obtained based on the third set of mode shapes and the first set of modal frequencies; wherein, the first set of modal frequencies is the third set of modal frequencies of the half-model; the modal data of the half-model includes the third set of modal frequencies and the third set of mode shapes.
5. A device for acquiring modal data of a half-side model, characterized in that, include: Memory, used to store computer programs; A processor, connected to the memory, wherein the processor is configured to execute the computer program to implement the steps of the method for acquiring half-side model modal data as described in any one of claims 1 to 3.