Method for calculating low-frequency acoustic vibration characteristics of laminated plate structure under turbulent boundary layer excitation

Abstract

The present application belongs to the technical field of composite structure acoustic vibration calculation, and discloses a method for calculating low-frequency acoustic vibration characteristics of a laminated plate structure under turbulent boundary layer excitation, comprising: obtaining a three-dimensional model of a target to be measured containing a laminated plate structure; performing grid division on the three-dimensional model to obtain a structural grid model; and establishing a flow field grid model; importing the grid model into ABAQUS software for finite element analysis to obtain modal results of the target to be measured; importing the structural grid model into VAOne software to establish a finite element subsystem, and importing the modal results into the VAOne software; loading a turbulent load on the finite element subsystem through a turbulent boundary layer in the VAOne software to obtain acoustic vibration characteristics of the target to be measured. The present application proposes that ABAQUS and VAone can realize accurate analysis of low-frequency acoustic vibration characteristics of a laminated plate under turbulent boundary layer excitation, and the combined research effect is remarkable.

Description

Technical Field

[0001] This invention belongs to the technical field of acoustic and vibration calculation of composite structures, and more specifically, relates to a method for calculating the low-frequency acoustic and vibration characteristics of a laminated plate structure under turbulent boundary layer excitation. Background Technology

[0002] In the rapid development of modern industry, especially in aerospace, automotive manufacturing, rail transportation, and shipbuilding, the performance requirements for structural components are becoming increasingly stringent. Materials must not only possess excellent strength-to-weight ratios but also effectively withstand various external factors, including noise and vibration, in complex working environments. Composite laminates, due to their unique performance advantages, have become one of the preferred materials for critical structures in these industries. In practical applications, composite laminates are often subjected to turbulent boundary layer excitation. For example, during high-speed flight of aircraft, the carbon fiber laminate structure on the fuselage surface is subjected to strong impacts from the turbulent boundary layer formed by airflow; during high-speed underwater navigation of submarines, the special composite laminates on the outer side of the hull are also excited by the turbulent boundary layer of seawater, becoming one of the main sources of hydrodynamic noise; similar excitation occurs to the carbon fiber laminate components on the exterior of automobiles during high-speed driving. This turbulent boundary layer excitation induces vibration in the laminate structure and further generates noise radiation, adversely affecting the stability of the structure and the surrounding acoustic environment.

[0003] However, turbulence itself is a complex and irregular flow phenomenon, with fluctuating pressure exhibiting randomness; its amplitude and phase vary randomly in time and space. Therefore, turbulent-excited structural vibrations involve fluid-structure interaction and random vibration problems, making the solution process complex and time-consuming. Furthermore, composite laminates possess significant anisotropy and complex multilayered structures, which makes their material behavior under turbulent boundary layer excitation extremely complex, posing a significant challenge to accurately analyzing their low-frequency acoustic and vibration characteristics. Summary of the Invention

[0004] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a method for calculating the low-frequency acoustic and vibration characteristics of laminated structures under turbulent boundary layer excitation, thereby solving the problem that it is currently difficult to accurately analyze the low-frequency acoustic and vibration characteristics of composite laminated structures.

[0005] To achieve the above objectives, according to one aspect of the present invention, a method for calculating the low-frequency acoustic and vibration characteristics of a laminated plate structure under turbulent boundary layer excitation is provided, comprising:

[0006] S1, Obtain a 3D model of the target object containing the laminated plate structure;

[0007] S2, perform mesh generation on the three-dimensional model to obtain a structural mesh model; and establish a flow field mesh model based on the external flow field of the target to be measured;

[0008] S3. Import the structural mesh model and the flow field mesh model into ABAQUS software for finite element analysis to obtain the modal results of the target under test at the preset analysis frequency.

[0009] S4. Import the structural mesh model generated when solving the modal results in ABAQUS software into VAOne software to establish the finite element subsystem, and import the modal results into VAOne software;

[0010] S5. In VAOne software, turbulent loads are applied to the finite element subsystem through a turbulent boundary layer. Based on the modal results, the vibration response characteristics of the target under test are obtained using the modal superposition method. The acoustic response characteristics of the target under test are solved using the boundary element method, thereby obtaining the acoustic and vibration characteristics of the target under test.

[0011] According to the method for calculating the low-frequency acoustic and vibration characteristics of a laminated structure under turbulent boundary layer excitation provided by the present invention, the mesh size of the structural mesh model in S2 is obtained by the following formula:

[0012]

[0013] In the formula, λ is the grid size, and U c denoted as the external flow velocity, and f as the highest analysis frequency.

[0014] According to the method for calculating the low-frequency acoustic and vibration characteristics of a laminated structure under turbulent boundary layer excitation provided by the present invention, the boundary size of the flow field mesh model in S2 is 3-5 times the surface size of the corresponding structural mesh model; the mesh size of the flow field mesh model is divided according to 1 / 6 of the acoustic wavelength.

[0015] According to the method for calculating the low-frequency acoustic and vibration characteristics of a laminated structure under turbulent boundary layer excitation provided by the present invention, S3 specifically includes:

[0016] In ABAQUS software, material properties are set for the structural mesh model by region. For the laminate structure region, the material, thickness, and layup angle information of each layer are set. The flow field mesh model is defined as an acoustic mesh, and acoustic properties are set.

[0017] Tie connections are established between the contact surfaces of the structural mesh model and the flow field mesh model to form fluid-structure coupling;

[0018] Define the boundary conditions for the structural mesh model and the flow field mesh model;

[0019] The preset analysis frequency is set according to the target research frequency;

[0020] Modal calculations were performed using ABAQUS software to obtain the modal results.

[0021] According to the method for calculating the low-frequency acoustic and vibration characteristics of a laminated plate structure under turbulent boundary layer excitation provided by the present invention, the boundary conditions of the structural mesh model are defined as follows: the boundary conditions of the structural mesh model are set as simply supported conditions or free boundary conditions according to the actual situation of the target to be measured.

[0022] The boundary conditions of the flow field mesh model are defined as follows: set non-reflective boundary conditions outside the fluid;

[0023] The preset analysis frequency is set according to the target research frequency as follows: the upper limit of the preset analysis frequency is 1.5-2.0 times the upper limit of the target research frequency.

[0024] The method for calculating the low-frequency acoustic and vibration characteristics of a laminated structure under turbulent boundary layer excitation according to the present invention further includes, in step S3:

[0025] Verify the mesh node numbering of the structural mesh model: Set the mesh node numbering of the structural mesh model in the ABAQUS software to start from 1;

[0026] Export the obtained modal results as *.fil format to successfully import them into VAOne software.

[0027] The method for calculating the low-frequency acoustic and vibration characteristics of a laminated structure under turbulent boundary layer excitation provided by the present invention, S4 specifically includes:

[0028] Import the structured mesh model into VAOne software, and ensure that the mesh node numbers in VAOne software are consistent with those in ABAQUS software;

[0029] A finite element subsystem is established using the imported structural mesh model, and the material properties set in the ABAQUS software are called to set the self-loss factor and coupling loss factor.

[0030] Import the modal results in *.fil format and verify that the import results are consistent with the modal results obtained in ABAQUS software.

[0031] The method for calculating the low-frequency acoustic and vibration characteristics of a laminated structure under turbulent boundary layer excitation according to the present invention further includes, in step S4:

[0032] Boundary elements are established outside the structural mesh model to simulate the external flow field. The boundary elements are connected to the finite element subsystem located on the outer surface by line, and the fluid medium of the boundary elements is set.

[0033] Set the target research frequency range.

[0034] According to the method for calculating the low-frequency acoustic and vibration characteristics of a laminated structure under turbulent boundary layer excitation provided by the present invention, step S5, which involves applying turbulent loads to the finite element subsystem through a turbulent boundary layer in VAOne software, specifically includes:

[0035] For any finite element subsystem in contact with an external flow field, the turbulent boundary layer in VAone software is used to set the turbulent pulsating pressure parameters.

[0036] The method for calculating the low-frequency acoustic and vibration characteristics of a laminated structure under turbulent boundary layer excitation according to the present invention further includes, in step S5:

[0037] In VAOne software, create acoustic cavities and semi-infinite fluids: create acoustic cavities inside the structural mesh model at locations where sound pressure monitoring is required, and establish surface connections between the acoustic cavities and the walls of the structural mesh model to detect internal sound pressure; create semi-infinite fluids outside the structural mesh model at locations where sound pressure monitoring is required, and establish line connections between the semi-infinite fluids and all finite element subsystems located on the outer surface.

[0038] In summary, compared with the prior art, the method for calculating the low-frequency acoustic and vibration characteristics of a laminated plate structure under turbulent boundary layer excitation provided by this invention is as follows:

[0039] 1. A structural mesh model and a flow field mesh model are established based on the actual model of the target under test and the actual flow field distribution. A fluid-structure interaction model is established using ABAQUS software, and wet modal analysis with flow field is performed. This allows for the acquisition of modal results for the target under test that take into account the actual flow field conditions. These modal results are closer to the actual situation and more accurate. Furthermore, turbulent loads are applied to the structural mesh model using VAone software, and the acoustic and vibration characteristics are calculated under these loads. This turbulent load takes into account phase randomness, which is more consistent with the actual turbulent conditions, making the results more accurate and reliable. Thus, by using ABAQUS and VAone, accurate analysis of the low-frequency acoustic and vibration characteristics of laminated plates under turbulent boundary layer excitation can be achieved. The joint research results are significant.

[0040] 2. In structural vibration simulation, ABAQUS can establish fluid-structure interaction models and consider the laminated structure, material parameters and mechanical boundary conditions of laminates, providing an accurate modal basis for subsequent vibration analysis; VAone can consider the randomness of turbulence in the simulation of turbulent excitation, which greatly improves the simulation accuracy of vibration response and acoustic results.

[0041] 3. Setting the material properties of laminated plate structures in ABAQUS software provides a more detailed characterization of the laminate's ply information. Considering the anisotropy of the laminate, the stress and strain distribution of each layer can be accurately calculated when simulating tensile, bending, and torsional loads on the laminate. Modal analysis and static analysis of the structure can be completed in a shorter time with more accurate results.

[0042] 4. By setting the mesh node numbering of the structural mesh model in the ABAQUS software and the specific settings of the modal result export format, the joint research between ABAQUS and VAone was successfully achieved. Attached Figure Description

[0043] Figure 1 This is a flowchart of the method for calculating the low-frequency acoustic and vibration characteristics of a laminated plate structure under turbulent boundary layer excitation provided by the present invention;

[0044] Figure 2 This is a schematic diagram of setting the material properties of laminated plate structures in ABAQUS software, provided by the present invention.

[0045] Figure 3 This is a schematic diagram of the format settings for exporting modal results in ABAQUS software provided by the present invention;

[0046] Figure 4 This is a schematic diagram comparing the modal results in the ABAQUS software and VAone software provided by this invention;

[0047] Figure 5 This is a schematic diagram of the turbulent boundary layer setting in the VAone software provided by this invention. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0049] Please see Figure 1 This embodiment provides a method for calculating the low-frequency acoustic and vibration characteristics of a laminated plate structure under turbulent boundary layer excitation. This calculation method is a simulation calculation method, which includes:

[0050] S1, Obtain a 3D model of the target object containing the laminated plate structure;

[0051] S2, perform mesh generation on the three-dimensional model to obtain a structural mesh model; and establish a flow field mesh model based on the external flow field of the target to be measured;

[0052] S3. Import the structural mesh model and the flow field mesh model into ABAQUS software for finite element analysis to obtain the modal results of the target under test at the preset analysis frequency.

[0053] S4. Import the structural mesh model generated when solving the modal results in ABAQUS software into VAOne software to establish the finite element subsystem, and import the modal results into VAOne software;

[0054] S5. In VAOne software, turbulent loads are applied to the finite element subsystem through a turbulent boundary layer. Based on the modal results, the vibration response characteristics of the target under test are obtained using the modal superposition method. The acoustic response characteristics of the target under test are solved using the boundary element method, thereby obtaining the acoustic and vibration characteristics of the target under test.

[0055] This embodiment addresses the simulation calculation of the low-frequency acoustic and vibration characteristics of a test target containing a laminated plate structure under turbulent boundary layer excitation. Considering that the finite element analysis software ABAQUS has powerful functions in structural mechanics simulation and can be applied to simulate the vibration characteristics of laminated plate structures, when simulating the structural vibration analysis caused by turbulent boundary layer excitation, a set of pulsating pressure loads is usually applied to the structural surface for harmonic response analysis. However, the harmonic response analysis is a deterministic sine wave and cannot consider randomness, resulting in a large deviation from the actual situation when simulating the effect of turbulent boundary layer excitation on the laminated plate structure.

[0056] On the other hand, the acoustic simulation software VAone can effectively simulate various acoustic scenarios, and its turbulent boundary layer can be used to account for phase randomness through turbulence statistical theory. However, it also reveals several shortcomings when studying the low-frequency acoustic and vibration characteristics of laminated plate structures. First, in low-frequency conditions involving the interaction between the laminated plate and the surrounding fluid, it cannot perform wet modal analysis with an external fluid domain, thus failing to accurately reflect the true modal characteristics of the structure. Second, VAone lacks the function of setting laminated plate layup information for finite element subsystems. For laminated plates with complex layup structures, it cannot accurately characterize their material properties and structural parameters, and therefore cannot accurately simulate the acoustic and vibration response of laminated plates under turbulent boundary layer excitation.

[0057] Given the limitations of both ABAQUS and VAone, neither software can accurately simulate the low-frequency acoustic and vibration characteristics of laminated structures under turbulent boundary layer excitation. Therefore, this embodiment proposes an innovative method that organically combines the two software programs, leveraging their respective strengths to compensate for their weaknesses, in order to achieve an accurate solution to this complex problem.

[0058] This embodiment aims to provide a simulation calculation method for the low-frequency acoustic and vibration characteristics of a test object containing a laminated plate structure under turbulent boundary layer excitation. By combining ABAQUS and VAOne software, it provides a new and effective solution for studying the acoustic and vibration characteristics of laminated plate structures under turbulent excitation. The laminated plate structure can be a multi-layered composite material structure such as carbon fiber laminate. The test object containing a laminated plate structure is a relevant target object with a laminated plate structure, such as aircraft, ships, submarines, and automobiles. These objects can be used as a whole as the test object for low-frequency acoustic and vibration characteristic calculation, or they can be used as a part of the test object for low-frequency acoustic and vibration characteristic calculation. The specific size and shape of the test object are not limited, as long as it contains a laminated plate structure.

[0059] In some specific embodiments, taking a submarine structure as an example, the specific implementation of the present invention will be described in detail. A method for calculating the low-frequency acoustic and vibration characteristics of a submarine structure under turbulent boundary layer excitation specifically includes the following steps:

[0060] Step 1: Obtain the 3D model of the submarine and simplify it.

[0061] Based on the structural characteristics of the submarine, a comprehensive and in-depth analysis of its 3D model is conducted. This involves considering the submarine model's geometric features (including external shape, size, and internal structural layout), the distribution of laminated plate materials (layout direction, number of layers, and thickness of each layer), and the expected analytical accuracy requirements. Local features with minimal impact on the overall low-frequency acoustic and vibration characteristics, such as minor chamfers and non-critical connection structures, are identified and simplified to streamline the model. Generally, the submarine's hull, reinforcing ribs, and bulkheads are retained to form the 3D model.

[0062] By simplifying the 3D model and ignoring small structures and features, the number of meshes can be effectively reduced, the overall mesh quality can be improved, which is beneficial to improving simulation accuracy and shortening computation time.

[0063] Step 2: Simulation model preprocessing and mesh generation;

[0064] The simplified 3D model was imported into HyperMesh software. The mid-surface of the submarine's stiffeners and bulkheads was extracted, and the outer surface of the hull model was extracted. Shell elements were used to create a mesh model of the structure. When simulating the vibration of the structure caused by turbulent pressure, the pressure changes generated by the migrating waves in the fluid on the structural surface need to be represented by an appropriate mesh to accurately calculate the vibration response of the structure and the feedback effect of the structural vibration on the fluid. In other words, an appropriate mesh size is beneficial for better reflecting the influence of the external flow field on the structural mesh. To ensure accurate simulation results, at least 4 to 6 mesh nodes are required within one migrating wave wavelength. Quadrilateral meshes are used, therefore the mesh size follows the principle of 1 / 6 of the migrating wave wavelength.

[0065] Specifically, the mesh size of the structural mesh model described in S2 is obtained using the following formula:

[0066]

[0067] In the formula, λ is the grid size, and U c denoted as the external flow velocity, and f as the highest analysis frequency.

[0068] To account for the influence of external fluids, a flow field mesh needs to be established. The size of the flow field needs to comprehensively consider the dimensions and shape of the structure being analyzed. The boundary of the flow field mesh is 3 to 5 times the surface size of the corresponding structural mesh model to ensure that the influence of the structure on the surrounding fluid during vibration can be taken into account. The flow field mesh size is 1 / 6 of the sound wave wavelength. That is, the boundary size of the flow field mesh model described in S2 is 3-5 times the surface size of the corresponding structural mesh model; the mesh size of the flow field mesh model is divided according to 1 / 6 of the sound wave wavelength.

[0069] In this embodiment, the surface size of the corresponding structural mesh model is the surface size on the side in contact with the flow field. That is, on any side of the structural mesh model where the flow field is located, the boundary size of the flow field mesh model is 3-5 times the surface size of the structural mesh model on that side. The flow field mesh is established according to the actual flow field location of the target. For example, for a submarine, the flow field mesh should wrap around the structural mesh model, and the boundary of the flow field mesh model is proportionally enlarged by 3-5 times compared to the structural mesh model. That is, in the width direction of the structural mesh model, the boundary of the flow field mesh model is 3-5 times the corresponding width; in the length direction of the structural mesh model, the boundary of the flow field mesh model is 3-5 times the corresponding length; and in the height direction of the structural mesh model, the boundary of the flow field mesh model is 3-5 times the corresponding height.

[0070] When the target to be measured is a ship, considering the actual flow field location, the flow field mesh model is built at the bottom of the structure mesh model. In the width direction of the structure mesh model, the boundary of the flow field mesh model is 3-5 times the corresponding width; in the length direction of the structure mesh model, the boundary of the flow field mesh model is 3-5 times the corresponding length.

[0071] Step 3, Model Building and Modal Calculation in ABAQUS, i.e., S3, specifically includes:

[0072] 1) Define Material Properties: After grouping the above finite element mesh model by material and region, import it into ABAQUS software. Define the material properties for each imported component. For the laminate region, select shell→composite type to set the layup information of the laminate, such as... Figure 2 As shown, the material, thickness, and ply angle of each layer are set. The flow field region needs to be defined as an acoustic mesh, and its acoustic properties (sound velocity, bulk modulus) are defined. The structural mesh type is changed from linear elements to quadratic elements to improve the accuracy of structural response calculations. Specifically, in ABAQUS software, material properties are set for the structural mesh model by region; for the laminated plate structure region, the material, thickness, and ply angle information of each layer are set; the flow field mesh model is defined as an acoustic mesh, and its acoustic properties are set.

[0073] 2) Fluid-structure interaction: A tie connection is established between the contact surface of the structural mesh model and the flow field mesh model to form fluid-structure interaction.

[0074] The boundary conditions of the structural mesh model and the flow field mesh model are defined, specifically including: 3) The boundary conditions of the structural mesh model are defined as follows: the boundary conditions of the structural mesh model are set as simply supported conditions or free boundary conditions according to the actual situation of the target to be measured; that is, the boundary conditions of the structural model are set according to the actual situation of the model, generally simply supported conditions, and if it is a free boundary condition, it is not necessary to set it.

[0075] 4) Define the boundary conditions of the flow field mesh model as follows: Set non-reflective boundary conditions outside the fluid; since the fluid region model is finite in size, but the external flow field is actually an approximately infinitely large region, it is necessary to define non-reflective conditions on the outer surface of the fluid domain.

[0076] 5) Renumbering Nodes: S3 also includes: verifying the mesh node numbers of the structural mesh model: setting the mesh node numbers in the ABAQUS software to start from 1; to ensure correct node mapping after importing the modal results and structural mesh into VAOne, the node numbers in the ABAQUS structural mesh must start from 1. For example, if the structure has 300,000 nodes, the node numbers must start from 1 and end at 300,000. This can be set in the EditMesh module of the ABAQUS software, or it can be renumbered during the HyperMesh software mesh generation in step one.

[0077] 6) Set the modal preset analysis frequency according to the target research frequency: Specifically, the upper limit of the preset analysis frequency is 1.5-2.0 times the upper limit of the target research frequency. The upper limit of the solution analysis step frequency is set to 1.5 to 2.0 times the research frequency. For example, if the upper limit of the target research frequency is 1000Hz, then in the ABAQUS software, the upper limit of the preset analysis frequency, i.e., the frequency range of modal analysis, should be extended to 1500Hz or 2000Hz.

[0078] 7) Perform modal calculations using ABAQUS software to obtain the modal results. S3 also includes: The modal result file obtained from the ABAQUS solution needs to be exported in *.fil format before it can be imported into VAOne. To export this format file, the keyword for `model` needs to be modified by adding the following two lines of code, such as... Figure 3 As shown:

[0079] *node file,global=yes

[0080] U,

[0081] The obtained modal results are exported as *.fil format for successful import into VAOne software. This embodiment mainly focuses on the low-frequency acoustic and vibration characteristics of laminated plate structures, with low frequency referring to an upper limit of the target research frequency of 1000Hz.

[0082] Step 4, Model Import and System Building in VAOne, i.e., S4, specifically includes:

[0083] 1) Import the structural mesh model into VAOne software, ensuring that the mesh node numbers in VAOne are consistent with those in ABAQUS software: The structural mesh model generated by ABAQUS software when solving the modal results is the structural mesh model with material properties set in ABAQUS software. This structural mesh model with material properties set is a *.inp format file. Import the *.inp format file of the structural mesh model in ABAQUS into VAOne, and check whether the node numbers in VAOne are consistent with those in ABAQUS. After ensuring complete consistency, the finite element subsystem (FE subsystem) can be constructed.

[0084] 2) Establish a finite element subsystem using the imported structural mesh model and call the material properties set in the ABAQUS software, setting the self-loss factor and coupling loss factor: The FE subsystem can be established by region, material, or component. The material properties of the FE subsystem can be selected using FEproperty, which calls the material properties set in the ABAQUS software; there is no need to redefine the material properties in VAone. The self-loss factor and coupling loss factor can be set based on experience or experimental measurement results; typically, they are set to 0.001 or 0.01 for steel structures.

[0085] 3) Import the modal results in *.fil format and verify the import results to ensure consistency between the modal results imported into VAOne software and those obtained in ABAQUS software: After the FE subsystem is established, the *.fil file of the modal results can be imported. The import success can be verified in the FE Modes module of Solve→Options. The modal shape contour plots can be viewed under the FE / BEM Animation controls command in the toolbar. Figure 4 The image shows a comparison of the modal shape contour plots in ABAQUS and VAOne, with the two modes shown. Figure 1 If the frequencies are consistent, it indicates that the modal results were successfully imported.

[0086] Furthermore, S4 also includes:

[0087] 4) Establish boundary elements outside the structural mesh model to simulate the external flow field. Connect the boundary elements to the finite element subsystems located on the outer surface using lines, and set the fluid medium for the boundary elements: that is, create boundary elements and connect them to all the finite element subsystems located on the outer surface established in step 2), and set the fluid medium, such as water or air. All the finite element subsystems located on the outer surface are the finite element subsystems located on the outer surface of the structural mesh model, that is, the finite element subsystems established based on the shell part.

[0088] 5) Set the target research frequency range: Set according to the target analysis frequency and frequency interval. For example, the target research frequency range can be 1 to 1000 Hz.

[0089] Step 5: Load application and acoustic-vibration characteristic calculation;

[0090] 1) In S5, applying turbulent loads to the finite element subsystem using a turbulent boundary layer in VAOne software specifically includes:

[0091] For any finite element subsystem in contact with an external flow field, such as Figure 5 As shown, the turbulent boundary layer (TBL) in VAone software is used to set the turbulent fluctuation pressure parameters. These parameters include at least one of the following: pressure spectrum, fluid medium, fluid flow velocity, boundary layer thickness, fluid direction, and correlation coefficient. For finite element subsystems in contact with the external flow field, the actual flow field conditions must be considered. For submarines, the flow field is encompassed by the entire external surface of the submarine; therefore, all finite element subsystems located on the outer surface are in contact with the flow field and their turbulent fluctuation pressure parameters should be set using the Turbulent Boundary Layer (TBL).

[0092] For different finite element subsystems in contact with the external flow field, the turbulent pulsating pressure parameters can be set individually. The parameters set for different finite element subsystems, such as pressure spectrum, boundary layer thickness, and fluid direction, can be different. The specific settings of each parameter can be based on existing turbulent excitation research data of the target under test, or the load parameters can be set using data from existing turbulence models. The specific parameter values ​​are not limited.

[0093] 2) S5 also includes: creating acoustic cavities and semi-infinite fluids in VAOne software: creating acoustic cavities at locations where sound pressure monitoring is required inside the structural mesh model, and establishing surface connections between the acoustic cavities and the walls of the structural mesh model to detect internal sound pressure; creating semi-infinite fluids at locations where sound pressure monitoring is required outside the structural mesh model, and establishing line connections between the semi-infinite fluids and all finite element subsystems located on the outer surface.

[0094] In VAOne software, acoustic cavities are created between the internal bulkheads of the submarine, and surface connections are established between the acoustic cavities and the structural walls to detect the internal sound pressure. Semi-infinite fluids are created at the external locations where sound pressure monitoring is required, and these semi-infinite fluids must be connected linearly to all subsystems on the outer surface of the structure.

[0095] 3) Create sensors: For structural mesh models, insert sensors on the mesh nodes near the locations where the vibration response needs to be studied.

[0096] After the above settings are completed, the vibration response of the low-frequency structure can be solved based on the modal superposition method, and the sound pressure can be solved based on the boundary element method, thus realizing the calculation of the acoustic and vibration characteristics of the structure.

[0097] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for calculating the low-frequency acoustic and vibration characteristics of a laminated plate structure under turbulent boundary layer excitation, characterized in that, include: S1, Obtain a 3D model of the target object containing the laminated plate structure; S2, perform mesh generation on the three-dimensional model to obtain a structural mesh model; and establish a flow field mesh model based on the external flow field of the target to be measured; S3. Import the structural mesh model and the flow field mesh model into ABAQUS software for finite element analysis to obtain the modal results of the target under test at the preset analysis frequency. S4. Import the structural mesh model generated when solving the modal results in ABAQUS software into VAOne software to establish the finite element subsystem, and import the modal results into VAOne software; S5. In VAOne software, turbulent loads are applied to the finite element subsystem through a turbulent boundary layer. Based on the modal results, the vibration response characteristics of the target under test are obtained using the modal superposition method. The acoustic response characteristics of the target under test are solved using the boundary element method, thereby obtaining the acoustic and vibration characteristics of the target under test. S3 specifically includes: In ABAQUS software, material properties are set for the structural mesh model by region. For the laminate structure region, the material, thickness, and layup angle information of each layer are set. The flow field mesh model is defined as an acoustic mesh, and acoustic properties are set. Tie connections are established between the contact surfaces of the structural mesh model and the flow field mesh model to form fluid-structure coupling; Define the boundary conditions for the structural mesh model and the flow field mesh model; The preset analysis frequency is set according to the target research frequency; Modal calculations were performed using ABAQUS software to obtain the modal results; S3 also includes: Verify the mesh node numbering of the structural mesh model: Set the mesh node numbering of the structural mesh model in the ABAQUS software to start from 1; Export the obtained modal results as *.fil format for successful import into VAOne software; The structural mesh model generated by the ABAQUS software in S4 when solving the modal results is a *.inp format file.

2. The method for calculating the low-frequency acoustic and vibration characteristics of a laminated plate structure under turbulent boundary layer excitation as described in claim 1, characterized in that, The mesh size of the structural mesh model described in S2 is obtained using the following formula: ； In the formula, λ is the grid size. U c The external flow field velocity, f This represents the highest analysis frequency.

3. The method for calculating the low-frequency acoustic and vibration characteristics of a laminated structure under turbulent boundary layer excitation as described in claim 1, characterized in that, The boundary size of the flow field mesh model in S2 is 3-5 times the surface size of the corresponding structural mesh model; the mesh size of the flow field mesh model is divided according to 1 / 6 of the sound wave wavelength.

4. The method for calculating the low-frequency acoustic and vibration characteristics of a laminated structure under turbulent boundary layer excitation as described in claim 1, characterized in that, The boundary conditions of the structural mesh model are defined as follows: the boundary conditions of the structural mesh model are set as simply supported conditions or free boundary conditions according to the actual situation of the target to be measured. The boundary conditions of the flow field mesh model are defined as follows: set non-reflective boundary conditions outside the fluid; The preset analysis frequency is set according to the target research frequency as follows: the upper limit of the preset analysis frequency is 1.5-2.0 times the upper limit of the target research frequency.

5. The method for calculating the low-frequency acoustic and vibration characteristics of a laminated structure under turbulent boundary layer excitation as described in claim 1, characterized in that, S4 specifically includes: Import the structured mesh model into VAOne software, and ensure that the mesh node numbers in VAOne software are consistent with those in ABAQUS software; A finite element subsystem is established using the imported structural mesh model, and the material properties set in the ABAQUS software are called to set the self-loss factor and coupling loss factor. Import the modal results in *.fil format and verify that the import results are consistent with the modal results obtained in ABAQUS software.

6. The method for calculating the low-frequency acoustic and vibration characteristics of a laminated structure under turbulent boundary layer excitation as described in claim 1, characterized in that, S4 also includes: Boundary elements are established outside the structural mesh model to simulate the external flow field. The boundary elements are connected to the finite element subsystem located on the outer surface by line, and the fluid medium of the boundary elements is set. Set the target research frequency range.

7. The method for calculating the low-frequency acoustic and vibration characteristics of a laminated plate structure under turbulent boundary layer excitation as described in claim 1, characterized in that, In S5, applying turbulent loads to the finite element subsystem using a turbulent boundary layer in VAOne software specifically includes: For any finite element subsystem in contact with an external flow field, the turbulent boundary layer in VAone software is used to set the turbulent pulsating pressure parameters.

8. The method for calculating the low-frequency acoustic and vibration characteristics of a laminated plate structure under turbulent boundary layer excitation as described in claim 1, characterized in that, S5 also includes: In VAOne software, create acoustic cavities and semi-infinite fluids: create acoustic cavities inside the structural mesh model at locations where sound pressure monitoring is required, and establish surface connections between the acoustic cavities and the walls of the structural mesh model to detect internal sound pressure; create semi-infinite fluids outside the structural mesh model at locations where sound pressure monitoring is required, and establish line connections between the semi-infinite fluids and all finite element subsystems located on the outer surface.

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