Method for calculating low-frequency sound and vibration characteristics of laminated plate structure under turbulence boundary layer excitation

Abstract

The invention belongs to the technical field related to sound and vibration calculation of composite structures, and discloses a low-frequency sound and vibration characteristic calculation method for a laminated plate structure under turbulence boundary layer excitation, and the method comprises the steps: obtaining a three-dimensional model of a to-be-measured target containing the laminated plate structure; performing grid division on the three-dimensional model to obtain a structured grid model; establishing a flow field grid model; importing the grid model into ABAQUS software for finite element analysis, and obtaining a modal result of the to-be-tested target; importing the structured grid model into VAOne software to establish a finite element subsystem, and importing the modal result into the VAOne software; and turbulent load loading is carried out on the finite element subsystem through a turbulent boundary layer in VAOne software, and the acoustic vibration characteristics of the to-be-measured target are obtained. Accurate analysis of the low-frequency sound and vibration characteristics of the laminated plate under turbulence boundary layer excitation can be achieved through ABAQUS and VAone, and the combined research effect is remarkable.

Description

Technical Field

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

[0002] With the rapid development of modern industry, especially in the fields of aerospace, automobile manufacturing, rail transportation and shipbuilding, the performance requirements for structural components are becoming increasingly stringent. Not only are materials required to have an excellent strength-to-weight ratio, but they are also required to be able to effectively resist the influence of various external factors, including noise and vibration, in complex working environments. Composite laminates have become one of the preferred materials for key structures in these industries due to their unique performance advantages. In actual application scenarios, composite laminates are often subject to turbulent boundary layer excitation. For example, when an aircraft is flying at high speed, the carbon fiber laminate structure on the surface of the fuselage will be strongly impacted by the turbulent boundary layer formed by the airflow; when a submarine is sailing at high speed underwater, the special composite laminate on the outside of the hull will also be excited by the turbulent boundary layer of seawater, becoming one of the main noise sources of submarine hydrodynamic noise; when a car is driving at high speed, the carbon fiber laminate components on the outside of the car body will also encounter similar excitation situations. This turbulent boundary layer excitation will induce vibration of the laminate structure and further generate noise radiation, which will have an adverse effect on the stability of the structure and the surrounding acoustic environment.

[0003] However, turbulence itself is a complex and irregular flow phenomenon, and the pulsating pressure is random, with its amplitude and phase varying randomly in time and space. Therefore, the structural vibration excited by turbulence involves fluid-solid coupling and random vibration problems, and the solution process is complex and time-consuming. At the same time, composite laminates have significant anisotropic characteristics and complex multi-layer ply structures, which makes their material behavior extremely complex when excited by turbulent boundary layers, posing great challenges to the accurate analysis of their low-frequency acoustic vibration characteristics. Summary of the invention

[0004] In view of the above defects or improvement needs of the prior art, the present invention provides a method for calculating the low-frequency acoustic vibration characteristics of a laminate structure under turbulent boundary layer excitation, which is used to solve the problem that it is difficult to accurately analyze the low-frequency acoustic vibration characteristics of composite laminate structures.

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

[0006] S1, obtaining a three-dimensional model of a target to be measured including a laminate structure;

[0007] S2, gridding the three-dimensional model to obtain a structural grid model; and establishing a flow field grid model based on the external flow field of the target to be measured;

[0008] S3, importing the structural grid model and the flow field grid model into ABAQUS software to perform finite element analysis to obtain modal results of the target to be measured at a preset analysis frequency;

[0009] S4, importing the structural mesh model generated when the ABAQUS software solves and calculates the modal results into the VAOne software to establish a finite element subsystem, and importing the modal results into the VAOne software;

[0010] S5, in the VAOne software, the finite element subsystem is loaded with turbulent load through the turbulent boundary layer, the vibration response characteristics of the target to be measured are obtained based on the modal superposition method according to the modal results, and the acoustic response characteristics of the target to be measured are solved based on the boundary element method, so as to obtain the acoustic vibration characteristics of the target to be measured.

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

[0012]

[0013] Where λ is the grid size, U c is the velocity of the external flow field, and f is the maximum analysis frequency.

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

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

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

[0017] Establishing a Tie connection between the contact surface of the structural grid model and the flow field grid model to form fluid-solid coupling;

[0018] Defining boundary conditions of the structural grid model and the flow field grid model;

[0019] Setting the preset analysis frequency according to the target research frequency;

[0020] The modal calculation is performed using ABAQUS software to obtain the modal results.

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

[0022] The boundary conditions of the flow field grid model are specifically defined as follows: setting a non-reflecting boundary condition outside the fluid;

[0023] The preset analysis frequency is set according to the target research frequency specifically 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] According to the method for calculating the low-frequency acoustic vibration characteristics of a laminate structure under turbulent boundary layer excitation provided by the present invention, S3 further includes:

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

[0026] The obtained modal results are exported to *.fil format so as to be smoothly imported into VAOne software.

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

[0028] Import the structural mesh model into VAOne software, and make the mesh node number in VAOne software consistent with that 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 the coupling loss factor;

[0030] Import the modal results in *.fil format, and check the imported results to make the modal results imported into VAOne software consistent with the modal results obtained in ABAQUS software.

[0031] According to the method for calculating the low-frequency acoustic vibration characteristics of a laminate structure under turbulent boundary layer excitation provided by the present invention, S4 further includes:

[0032] Establishing a boundary element outside the structural grid model to simulate an external flow field, connecting the boundary element with a finite element subsystem located on the outer surface by line connection, and setting a fluid medium of the boundary element;

[0033] Set the target study frequency range.

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

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

[0036] According to the method for calculating the low-frequency acoustic vibration characteristics of a laminate structure under turbulent boundary layer excitation provided by the present invention, S5 further includes:

[0037] An acoustic cavity and a semi-infinite fluid are established in the VAOne software: an acoustic cavity is established at a position inside the structural grid model where sound pressure monitoring is required, and a surface connection is established between the acoustic cavity and the wall of the structural grid model to detect the internal sound pressure; a semi-infinite fluid is created at a position outside the structural grid model where sound pressure monitoring is required, and a line connection is established between the semi-infinite fluid and all finite element subsystems located on the outer surface.

[0038] In general, compared with the prior art, the above technical solution conceived by the present invention provides a method for calculating the low-frequency acoustic vibration characteristics of a laminate structure under turbulent boundary layer excitation:

[0039] 1. It is proposed to establish a structural grid model and a flow field grid model according to the actual model of the target to be measured and the actual flow field distribution, establish a fluid-solid coupling model based on ABAQUS software, and perform wet modal analysis with flow field, so as to obtain the modal results of the target to be measured that take into account the actual flow field conditions. The modal results are closer to the actual situation and more accurate. Further, the structural grid model is loaded with turbulent loads based on VAone software, and the acoustic vibration characteristics are calculated and obtained under the load. The turbulent load can consider the phase randomness and is more in line with the actual turbulence conditions, making the results more accurate and reliable. Therefore, ABAQUS and VAone can realize the accurate analysis of the low-frequency acoustic vibration characteristics of the laminate under the excitation of the turbulent boundary layer, and the joint research effect is remarkable.

[0040] 2. In structural vibration simulation, ABAQUS can establish a fluid-solid coupling model and consider the ply structure, material parameters and mechanical boundary conditions of the laminate, providing an accurate modal basis for subsequent vibration analysis; VAone can consider the turbulent randomness in the process of simulating turbulent excitation, greatly improving the simulation accuracy of vibration response and acoustic results;

[0041] 3. The material properties of the laminate structure are set in ABAQUS software, which characterizes the ply information of the laminate in more detail. Considering the anisotropy of the laminate, the stress and strain distribution of each layer can be accurately calculated when simulating the tensile, bending and torsional loads of the laminate. The modal analysis and static analysis of the structure can be completed in a shorter time, and the results are more accurate.

[0042] 4. By setting the mesh node numbering of the structural mesh model in ABAQUS software and the specific setting of the modal result export format, the joint research between ABAQUS and VAone can be successfully realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a flow chart of a method for calculating low-frequency acoustic vibration characteristics of a laminate structure under turbulent boundary layer excitation provided by the present invention;

[0044] Figure 2 It is a schematic diagram of setting the material properties of a laminate structure in ABAQUS software provided by the present invention;

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

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

[0047] Figure 5 It is a schematic diagram of setting the turbulent boundary layer in the VAone software provided by the present invention. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0049] See also Figure 1 This embodiment provides a method for calculating the low-frequency acoustic vibration characteristics of a laminate structure under turbulent boundary layer excitation. The calculation method is a simulation calculation method, which includes:

[0050] S1, obtaining a three-dimensional model of a target to be measured including a laminate structure;

[0051] S2, gridding the three-dimensional model to obtain a structural grid model; and establishing a flow field grid model based on the external flow field of the target to be measured;

[0052] S3, importing the structural grid model and the flow field grid model into ABAQUS software to perform finite element analysis to obtain modal results of the target to be measured at a preset analysis frequency;

[0053] S4, importing the structural mesh model generated when the ABAQUS software solves and calculates the modal results into the VAOne software to establish a finite element subsystem, and importing the modal results into the VAOne software;

[0054] S5, in the VAOne software, the finite element subsystem is loaded with turbulent load through the turbulent boundary layer, the vibration response characteristics of the target to be measured are obtained based on the modal superposition method according to the modal results, and the acoustic response characteristics of the target to be measured are solved based on the boundary element method, so as to obtain the acoustic vibration characteristics of the target to be measured.

[0055] This embodiment aims at the problem of simulating and calculating the acoustic and vibration characteristics of the target to be tested containing a laminate structure in the low-frequency band under the excitation of a turbulent boundary layer. Considering that the current finite element analysis software ABAQUS has powerful functions in structural mechanics simulation, it can be used to simulate the vibration characteristics of the laminate structure. However, when simulating the structural vibration analysis caused by the turbulent boundary layer excitation, a set of pulsating pressure loads is usually applied to the structural surface for harmonic response analysis. 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 laminate structure.

[0056] On the other hand, the acoustic simulation software VAone can effectively simulate a variety of acoustic scenarios, among which the turbulent boundary layer (Turbulent boundary Layer) can consider the phase randomness through the turbulence statistical theory. However, when faced with the study of low-frequency acoustic and vibration characteristics of laminate structures, it also exposes many shortcomings. First, under low-frequency conditions involving the interaction between laminates and surrounding fluids, wet modal analysis with external fluid domains cannot be performed, and the true modal characteristics of the structure cannot be accurately reflected. Second, VAone does not have the function of setting the laminate ply information for the finite element subsystem. For laminates with complex ply structures, it is impossible to accurately characterize their material properties and structural parameters, and thus it is impossible to accurately simulate the acoustic and vibration response of the laminate under turbulent boundary layer excitation.

[0057] Given the limitations of ABAQUS and VAone, a single software can no longer meet the requirements for accurate simulation of the low-frequency acoustic vibration characteristics of laminate structures under turbulent boundary layer excitation. Therefore, this embodiment proposes an innovative method to organically combine the two software to complement each other and achieve an accurate solution to this complex problem.

[0058] This embodiment aims to provide a method for simulating and calculating the acoustic and vibration characteristics of a target to be measured containing a laminate structure in the low-frequency band under the excitation of a turbulent boundary layer. By combining ABAQUS and VAOne software, a new and effective solution is provided for the study of the acoustic and vibration characteristics of a laminate structure under turbulent excitation. The laminate structure can be a composite multilayer structure such as a carbon fiber laminate, and the target to be measured containing a laminate structure is a related target object provided with a laminate structure, such as airplanes, ships, submarines, and automobiles, which are all equipped with laminate structures. These objects can be used as a whole as a target to be measured for low-frequency acoustic and vibration characteristics calculation, or they can be used as a part of a target to be measured for low-frequency acoustic and vibration characteristics calculation. The specific size and shape of the target to be measured are not limited, as long as it contains a laminate structure.

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

[0060] Step 1: Obtain a three-dimensional model of a submarine and simplify the three-dimensional model;

[0061] Combined with the structural characteristics of the submarine, its three-dimensional model is comprehensively and deeply analyzed, and the geometric characteristics of the submarine model (including appearance shape, size, internal structure layout, etc.), the distribution of laminate materials (laying direction, number of layers, thickness of each layer, etc.) and the expected analysis accuracy requirements are comprehensively considered to identify and reasonably simplify the local features that have little effect on the overall low-frequency acoustic vibration characteristics, such as small chamfers, connection structures in non-critical parts, etc., and simplify these local features with little effect to simplify the model. Generally, the outer shell, stiffeners, bulkheads and other components of the submarine are retained to form a three-dimensional model.

[0062] By simplifying the three-dimensional model and ignoring small structures and features, the number of grids can be effectively reduced and the overall grid quality can be improved, which is beneficial to improving simulation accuracy and shortening calculation time.

[0063] Step 2: Simulation model pre-processing and meshing;

[0064] The simplified three-dimensional model is imported into the HyperMesh software, and the mid-surface of the submarine's reinforcement ribs, bulkheads and other models is extracted, and the outer surface is extracted from the shell model, and the mesh model of the structure is established using shell elements. When simulating the vibration of the structure caused by turbulent pressure, the pressure changes caused by the migration waves in the fluid on the surface of the structure need to be reflected by a suitable mesh in order to correctly calculate the vibration response of the structure and the feedback effect of the structural vibration on the fluid, that is, the appropriate mesh size is conducive to better reflecting the influence of the external flow field on the structural mesh. In order to ensure the accuracy of the simulation results, it is necessary to meet at least 4 to 6 mesh nodes within a migration wave wavelength, and quadrilateral meshes are used for division. Therefore, the mesh size is based on the principle of 1 / 6 of the wavelength of the migration wave.

[0065] Specifically, the grid size of the structure grid model described in S2 is obtained by the following formula:

[0066]

[0067] Where λ is the grid size, U c is the velocity of the external flow field, and f is the maximum analysis frequency.

[0068] In order to consider the influence of external fluid, it is also necessary to establish a flow field grid. The size of the flow field needs to comprehensively consider the size and shape of the analysis structure. The boundary of the flow field grid is 3 to 5 times the surface size of the corresponding structural grid model to ensure that the impact of the structure on the surrounding fluid during vibration can be considered. The flow field grid size is 1 / 6 of the acoustic wavelength. That is, the boundary size of the flow field grid model in S2 is 3-5 times the surface size of the corresponding structural grid model; the grid size of the flow field grid model is divided according to 1 / 6 of the acoustic wavelength.

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

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

[0071] Step 3: Model construction and modal calculation in ABAQUS, namely S3, specifically includes:

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

[0073] 2) Fluid-solid coupling: A Tie connection is established between the contact surfaces of the structural grid model and the flow field grid model to form fluid-solid coupling.

[0074] Defining the boundary conditions of the structural grid model and the flow field grid model specifically includes: 3) Defining the boundary conditions of the structural grid model specifically: setting the boundary conditions of the structural grid model to four-sided simply supported conditions or free boundary conditions according to the actual situation of the target to be measured; that is, setting the boundary conditions for the structural model according to the actual situation of the model, generally four-sided simply supported conditions, if it is a free boundary condition, it does not need to be set.

[0075] 4) The boundary conditions of the flow field grid model are defined as follows: setting a non-reflection boundary condition outside the fluid; since the size of the fluid region model is limited, but the external flow field is an approximately infinite region in actual conditions, it is necessary to define a non-reflection condition for the outer surface of the fluid domain.

[0076] 5) Renumbering nodes: S3 also includes: Verifying the mesh node numbering of the structural mesh model: Setting the mesh node numbering of the structural mesh model in the ABAQUS software to start from 1; To ensure that the nodes can be correctly mapped after the modal results and the structural mesh are imported into VAOne, it is necessary to ensure that the node numbering of the structural mesh in ABAQUS starts from 1. For example, if the structure has 300,000 nodes, the node numbering needs to 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 meshing of the HyperMesh software in step 1.

[0077] 6) Set the modal preset analysis frequency according to the target research frequency: The preset analysis frequency is set 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. Set the upper frequency limit of the solution analysis step to 1.5 to 2.0 times the studied frequency. For example, if the upper limit of the target research frequency is 1000Hz, the preset analysis frequency in the ABAQUS software, that is, the upper limit of the frequency range of the 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 solved by ABAQUS needs to be exported in *.fil format before it can be imported into VAOne. To export this format file, the keyword model needs to be modified, and the following two lines of statements need to be added, such as Figure 3 As shown:

[0079] *node file,global=yes

[0080] U,

[0081] The modal results to be obtained are exported to *.fil format to be smoothly imported into VAOne software. This embodiment mainly studies the low-frequency acoustic vibration characteristics of the laminate structure, and the low frequency mainly refers to the upper limit of the target research frequency of 1000Hz.

[0082] Step 4: Model import and system construction in VAOne, namely S4, specifically includes:

[0083] 1) Import the structural mesh model into VAOne software, and make the mesh node number in VAOne software consistent with that in ABAQUS software: the structural mesh model generated when ABAQUS software solves and calculates the modal results is the structural mesh model with material properties set in ABAQUS software, and the 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, check in VAOne whether the node number is consistent with that in ABAQUS, and after ensuring complete consistency, the finite element subsystem (FE subsystem) can be constructed.

[0084] 2) Use the imported structural mesh model to establish a finite element subsystem, call the material properties set in the ABAQUS software, and set the self-loss factor and coupling loss factor: Use the imported structural mesh model to establish a FE subsystem. The structural mesh model can be established by region, material, or component. The material properties of the FE subsystem can be selected by FEproperty to call 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 according to experience or test measurement results, usually 0.001 or 0.01 for steel structures.

[0085] 3) Import the modal results in *.fil format and check the imported results to make the modal results imported into VAOne consistent with the modal results obtained in ABAQUS: After the FE subsystem is established, you can import the *.fil file of the modal results and check whether the modal results are successfully imported in the FE Modes module of Solve→Options. You can view the modal vibration shape cloud diagram under the FE / BEM Animation controls command in the toolbar, such as Figure 4 The following is a comparison between the modal shape cloud diagram in ABAQUS and that in VAOne. Figure 1 The frequencies are consistent, indicating that the modal results were imported successfully.

[0086] Furthermore, S4 also includes:

[0087] 4) Establishing boundary elements outside the structural grid model to simulate the external flow field, connecting the boundary elements with the finite element subsystem located on the outer surface by lines, and setting the fluid medium of the boundary elements: that is, creating boundary elements, connecting the boundary elements with all the finite element subsystems located on the outer surface established in step 2), and setting the fluid medium, such as water or air. All finite element subsystems located on the outer surface are the finite element subsystems located on the outer surface of the structural grid model, that is, the finite element subsystems established according to the outer 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 characteristics calculation;

[0090] 1) In S5, the turbulent load is applied to the finite element subsystem through the turbulent boundary layer in the VAOne software, specifically including:

[0091] For any finite element subsystem in contact with the external flow field, such as Figure 5 As shown, the turbulent boundary layer (TBL) in the VAone software is used to set the turbulent pulsation pressure parameters; wherein the turbulent pulsation pressure parameters include at least one of the pressure spectrum, fluid medium, fluid flow velocity, boundary layer thickness, fluid direction, and correlation coefficient. The finite element subsystem in contact with the external flow field is determined according to the actual flow field conditions. For submarines, the flow field is included outside the entire submarine, so all finite element subsystems located on the outer surface are in contact with the flow field and the turbulent pulsation pressure parameters should be set through the turbulent boundary layer (TBL).

[0092] For different finite element subsystems in contact with the external flow field, the turbulent pulsation pressure parameters can be set separately; the setting parameters of 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 made according to the existing turbulence excitation related research data of the target to be measured, or the load parameters can be set using the data in the existing turbulence model, and the specific parameter values ​​are not limited.

[0093] 2) S5 also includes: establishing an acoustic cavity and a semi-infinite fluid in the VAOne software: establishing an acoustic cavity at a location inside the structural grid model where sound pressure monitoring is required, and establishing a surface connection between the acoustic cavity and the wall of the structural grid model to detect the internal sound pressure; creating a semi-infinite fluid at a location outside the structural grid model where sound pressure monitoring is required, and establishing a line connection between the semi-infinite fluid and all finite element subsystems located on the outer surface.

[0094] That is, in the VAOne software, an acoustic cavity is established between the bulkheads inside the submarine, and a surface connection is established between the acoustic cavity and the structural wall to detect the sound pressure inside the cabin; a semi-infinite fluid is created at the location where sound pressure monitoring is required outside, and a line connection is established between the semi-infinite fluid and all subsystems on the outer surface of the structure.

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

[0096] After the above settings are completed, the vibration response of the low-frequency structure is solved based on the mode superposition method, and the sound pressure is solved based on the boundary element method, so that the acoustic vibration characteristics of the structure can be calculated.

[0097] It will be easily understood by those skilled in the art that the above description is only 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 in the protection scope of the present invention.

Claims

1. A method for calculating the low-frequency acoustic vibration characteristics of a laminate structure under turbulent boundary layer excitation, characterized in that: include: S1, obtaining a three-dimensional model of a target to be measured including a laminate structure; S2, gridding the three-dimensional model to obtain a structural grid model; and establishing a flow field grid model based on the external flow field of the target to be measured; S3, importing the structural grid model and the flow field grid model into ABAQUS software to perform finite element analysis to obtain modal results of the target to be measured at a preset analysis frequency; S4, importing the structural mesh model generated when the ABAQUS software solves and calculates the modal results into the VAOne software to establish a finite element subsystem, and importing the modal results into the VAOne software; S5, in the VAOne software, the finite element subsystem is loaded with turbulent load through the turbulent boundary layer, the vibration response characteristics of the target to be measured are obtained based on the modal superposition method according to the modal results, and the acoustic response characteristics of the target to be measured are solved based on the boundary element method, so as to obtain the acoustic vibration characteristics of the target to be measured.

2. The method for calculating the low-frequency acoustic vibration characteristics of a laminate structure under turbulent boundary layer excitation according to claim 1, characterized in that: The mesh size of the structured mesh model described in S2 is obtained by the following formula: Where λ is the grid size, U c is the velocity of the external flow field, and f is the maximum analysis frequency.

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

4. The method for calculating the low-frequency acoustic vibration characteristics of a laminate structure under turbulent boundary layer excitation according to claim 1, characterized in that: S3 specifically includes: In ABAQUS software, material properties of the structural grid model are set by region. For the laminate structure region, the material, thickness and ply angle information of each layer are set; the flow field grid model is defined as an acoustic grid, and acoustic properties are set; Establishing a Tie connection between the contact surface of the structural grid model and the flow field grid model to form fluid-solid coupling; Defining boundary conditions of the structural grid model and the flow field grid model; Setting the preset analysis frequency according to the target research frequency; The modal calculation is performed using ABAQUS software to obtain the modal results.

5. The method for calculating the low-frequency acoustic vibration characteristics of a laminate structure under turbulent boundary layer excitation according to claim 4, characterized in that: Defining the boundary conditions of the structured grid model specifically includes: setting the boundary conditions of the structured grid model to four-side simply supported conditions or free boundary conditions according to the actual conditions of the target to be measured; The boundary conditions of the flow field grid model are specifically defined as follows: setting a non-reflecting boundary condition outside the fluid; The preset analysis frequency is set according to the target research frequency specifically as follows: the upper limit of the preset analysis frequency is 1.5-2.0 times the upper limit of the target research frequency.

6. The method for calculating the low-frequency acoustic vibration characteristics of a laminate structure under turbulent boundary layer excitation according to claim 4, characterized in that: S3 also includes: Verify the grid node number of the structural grid model: set the grid node number of the structural grid model in ABAQUS software to start from 1; The obtained modal results are exported to *.fil format so as to be smoothly imported into VAOne software.

7. The method for calculating the low-frequency acoustic vibration characteristics of a laminate structure under turbulent boundary layer excitation according to claim 6, characterized in that: S4 specifically includes: Import the structural mesh model into VAOne software, and make the mesh node number in VAOne software consistent with that 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 the coupling loss factor; Import the modal results in *.fil format, and check the imported results to make the modal results imported into VAOne software consistent with the modal results obtained in ABAQUS software.

8. The method for calculating the low-frequency acoustic vibration characteristics of a laminate structure under turbulent boundary layer excitation according to claim 1, characterized in that: S4 also includes: Establishing a boundary element outside the structural grid model to simulate an external flow field, connecting the boundary element with a finite element subsystem located on the outer surface by line connection, and setting a fluid medium of the boundary element; Set the target study frequency range.

9. The method for calculating the low-frequency acoustic vibration characteristics of a laminate structure under turbulent boundary layer excitation according to claim 1, characterized in that: In S5, the turbulence load is applied to the finite element subsystem through the turbulent boundary layer in the VAOne software, specifically including: For any finite element subsystem in contact with the external flow field, the turbulent boundary layer in the VAone software is used to set the turbulent pulsation pressure parameters.

10. The method for calculating the low-frequency acoustic vibration characteristics of a laminate structure under turbulent boundary layer excitation according to claim 1, characterized in that: The S5 also includes: An acoustic cavity and a semi-infinite fluid are established in the VAOne software: an acoustic cavity is established at a position inside the structural grid model where sound pressure monitoring is required, and a surface connection is established between the acoustic cavity and the wall of the structural grid model to detect the internal sound pressure; a semi-infinite fluid is created at a position outside the structural grid model where sound pressure monitoring is required, and a line connection is established between the semi-infinite fluid and all finite element subsystems located on the outer surface.

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