Model simplification method for acoustic reflection characteristic calculation of ribbed plate type structure

Abstract

The invention discloses a model simplification method for calculating acoustic reflection characteristics of a ribbed plate type structure, which comprises the following steps of: firstly, constructing a solid plate model and a shell plate model, and comparing acoustic reflection characteristic parameters under the two models to determine whether the two models can be mutually simplified or not; on the basis of mutual simplification, three types of models of'solid plate + rib ', 'shell plate + rib' and'shell plate + beam 'are respectively constructed, then acoustic reflection characteristic parameters under different models are compared and analyzed, and an equivalent relationship between the models is established. According to the method, step-by-step equivalent simplification from a high-dimensional entity model to a low-dimensional structure model is achieved, the calculation efficiency is improved, and the method can be used for underwater acoustic scattering analysis, structural sound reflection characteristic research and large-scale parameter calculation and has good engineering application value.

Description

Technical Field

[0001] This invention belongs to the field of underwater acoustics and structural acoustics numerical simulation technology, and relates to an acoustic-structure coupling modeling method based on the multiphysics finite element software COMSOL, and particularly to a model simplification method for calculating the acoustic reflection characteristics of ribbed structures. Background Technology

[0002] Ribbed plate structures are widely used in ships, marine engineering equipment, and various engineering structures. Their acoustic reflection characteristics have a significant impact on structural noise control and acoustic performance evaluation. Current technologies for calculating the acoustic reflection characteristics of ribbed plate structures often employ three-dimensional solid elements to model the plate and reinforcing ribs as a whole, and then combine this with a pressure acoustic model to construct an acoustic-structure interaction (AS / RS) computational model. While this modeling approach can accurately describe the structure's geometry and mechanical behavior, the model's degrees of freedom increase rapidly with increasing model size and computational frequency, leading to high computational resource consumption and long solution times, making it difficult to meet the computational efficiency requirements of parametric analysis and engineering design. Summary of the Invention

[0003] Purpose of the invention: The purpose of this invention is to provide a simplified model method for calculating the acoustic reflection characteristics of ribbed structures with high computational efficiency.

[0004] Technical solution: The present invention provides a simplified model method for calculating the acoustic reflection characteristics of ribbed structures, comprising:

[0005] S1: Construct an acoustic-structure interaction model that includes a fluid domain and a structural domain, wherein the fluid domain adopts a pressure acoustics module, and the structural domain adopts at least one of the solid mechanics module, shell module, and structural mechanics-beam module;

[0006] S2: Establish a "solid plate" model and a "shell plate" model in a fixed domain, where the "solid plate" model serves as the first reference model and the "shell plate" model serves as the first simplified model; calculate the acoustic reflection characteristic parameters of the two models. When the maximum relative error of the acoustic reflection characteristic parameters of the two models does not exceed the maximum relative error threshold and the average relative error does not exceed the average relative error threshold, the "solid plate" model and the "shell plate" model can be simplified to each other, and proceed to step S3; otherwise, adjust at least one of the equivalent thickness, equivalent material parameters, and boundary conditions of the "shell plate" model to re-establish the "shell plate" model and repeat step S2.

[0007] S3: Establish a "solid plate + rib" model as the second reference model. Apply acoustic excitation to the "solid plate + rib" model and solve for the corresponding acoustic reflection characteristic parameters. Under the premise of maintaining consistent material parameters and boundary conditions, replace the solid plate in the "solid plate + rib" model with shell elements to establish a "shell plate + rib" model as the second simplified model. The shell plate thickness is determined based on the equivalent mechanical properties of the solid plate. The connection between the shell plate and the rib structure is realized through a solid-thin structure coupling method. The corresponding acoustic reflection characteristic parameters are calculated. When the maximum relative error of the acoustic reflection characteristic parameters between the "solid plate + rib" model and the "shell plate + rib" model does not exceed the maximum relative error threshold and the average relative error does not exceed the average relative error threshold, the "solid plate + rib" model and the "shell plate + rib" model can be simplified to each other, and proceed to step S4. Otherwise, adjust at least one of the equivalent thickness, equivalent material parameters, and boundary conditions of the "shell plate + rib" model to re-establish the "shell plate + rib" model and repeat step S3.

[0008] S4: Using the "shell plate + rib" model as the third reference model, the rib structure is further replaced with beam elements to establish a "shell plate + beam" model as the third simplified model. The cross-sectional parameters of the beam elements are set equivalently according to the geometric dimensions of the original rib structure. The connection between the shell plate and the beam structure is realized through shell-beam coupling. The corresponding acoustic reflection characteristic parameters are calculated. When the maximum relative error of the acoustic reflection characteristic parameters between the "shell plate + rib" model and the "shell plate + beam" model does not exceed the maximum relative error threshold and the average relative error does not exceed the average relative error threshold, the "shell plate + beam" model replaces the "solid plate + rib" model for subsequent acoustic calculations. Otherwise, at least one of the equivalent thickness, equivalent material parameters, and boundary conditions of the "shell plate + beam" model is adjusted to re-establish the "shell plate + beam" model and step S4 is repeated.

[0009] Furthermore, in step S1, the calculation frequency range is set to 100~1500Hz.

[0010] Furthermore, in step S3, the shell plate thickness is determined by making the shell plate equivalent to the corresponding solid plate in terms of bending stiffness and in-plane stiffness.

[0011] Furthermore, in step S4, the cross-sectional form and dimensions of the beam element are set equivalently based on the height, thickness and cross-sectional area of ​​the original rib structure.

[0012] Furthermore, the shell plate is connected to the ribs or beams through a multiphysics coupling interface in COMSOL, which includes solid-thin structure connection and shell-beam connection.

[0013] Furthermore, the acoustic reflection characteristic parameters can be the reflection coefficient, transmission coefficient, or scattering intensity, or any parameter used to characterize the reflection behavior in the acoustic response characteristics.

[0014] Furthermore, the reflection coefficient is obtained by setting up the incident sound field and the received sound field in the fluid domain and calculating the ratio of the reflected sound pressure to the incident sound pressure.

[0015] Furthermore, the average relative error threshold is less than the maximum relative error threshold, and the two are determined according to a preset proportional relationship.

[0016] Furthermore, in step S3, the acoustic excitation is a plane wave excitation.

[0017] Furthermore, in step S4, the subsequent acoustic calculations include the calculation of the reflection coefficient, transmission coefficient, scattering intensity, or acoustic response characteristics of the ribbed structure.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0019] (1) By establishing an equivalent relationship between the three-dimensional solid model and the low-dimensional structural model, the present invention achieves a reasonable simplification of the ribbed plate type structural model. Under the premise of ensuring the consistency of the calculation results, the model's degree of freedom is reduced and the calculation efficiency is improved.

[0020] (2) By introducing acoustic reflection characteristic parameters as model equivalence criteria, the model simplification process has a clear physical basis and verifiability.

[0021] (3) The model simplification method proposed in this invention provides an effective modeling idea and technical path for the rapid evaluation of the acoustic reflection characteristics of ribbed structures under acoustic-solid coupling conditions. It can provide reference and guidance for model equivalence and computational optimization in the acoustic characteristic analysis of complex structures. Attached Figure Description

[0022] Figure 1 This is a flowchart of a simplified model method for calculating the acoustic reflection characteristics of ribbed structures provided in an embodiment of the present invention;

[0023] Figure 2 This is a comparison chart of the reflection coefficients of the solid plate and the shell plate in an embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram of the "solid plate + rib" model structure in an embodiment of the present invention;

[0025] Figure 4 This is the reflection coefficient curve of the "solid plate + rib" model in the embodiment of the present invention;

[0026] Figure 5This is a comparison chart of the reflection coefficient results between the "solid plate + rib" model and the "shell plate + rib" model in the embodiments of the present invention;

[0027] Figure 6 This is a comparison chart of the reflection coefficient results between the "solid plate + rib" model and the "shell plate + beam" model in the embodiments of the present invention. Detailed Implementation

[0028] The invention will now be further described with reference to the accompanying drawings.

[0029] like Figure 1 As shown, this embodiment of the invention provides a model simplification method for calculating the acoustic reflection characteristics of ribbed structures, including the following steps:

[0030] S1: Construct an acoustic-structure interaction model that includes a fluid domain and a structural domain. The fluid domain uses the pressure acoustics module, and the structural domain uses at least one of the solid mechanics module, shell module, and structural mechanics-beam module. The calculation frequency range is set to 100~1500Hz.

[0031] S2: Establish a "solid plate" model and a "shell plate" model in a fixed domain, where the "solid plate" model serves as the first reference model and the "shell plate" model serves as the first simplified model; calculate the acoustic reflection characteristic parameters of the two models. When the maximum relative error of the acoustic reflection characteristic parameters of the two models does not exceed the maximum relative error threshold and the average relative error does not exceed the average relative error threshold, the "solid plate" model and the "shell plate" model can be simplified to each other, and proceed to step S3; otherwise, adjust at least one of the equivalent thickness, equivalent material parameters, and boundary conditions of the "shell plate" model to re-establish the "shell plate" model and repeat step S2.

[0032] S3: Establish a "solid plate + rib" model as the second reference model. Apply acoustic excitation to the "solid plate + rib" model and solve for the corresponding acoustic reflection characteristic parameters. Under the premise of keeping the material parameters and boundary conditions consistent, replace the solid plate in the "solid plate + rib" model with shell elements and establish a "shell plate + rib" model as the second simplified model. The shell plate thickness is determined according to the mechanical properties equivalent to the solid plate. The connection between the shell plate and the rib structure is realized through solid-thin structure coupling. The corresponding acoustic reflection characteristic parameters are calculated. When the maximum relative error of the acoustic reflection characteristic parameters of the "solid plate + rib" model and the "shell plate + rib" model does not exceed the maximum relative error threshold and the average relative error does not exceed the average relative error threshold, the "solid plate + rib" model and the "shell plate + rib" model can simplify each other and proceed to step S4. Otherwise, adjust at least one of the equivalent thickness, equivalent material parameters and boundary conditions of the "shell plate + rib" model to re-establish the "shell plate + rib" model and repeat step S3.

[0033] In step S3, the acoustic excitation is a plane wave excitation. The shell thickness is determined by making the shell equivalent to the corresponding solid plate in terms of bending stiffness and in-plane stiffness.

[0034] S4: Using the "shell plate + rib" model as the third reference model, the rib structure is further replaced with beam elements to establish a "shell plate + beam" model as the third simplified model. The cross-sectional parameters of the beam elements are set equivalently according to the geometric dimensions of the original rib structure. The connection between the shell plate and the beam structure is realized through shell-beam coupling. The corresponding acoustic reflection characteristic parameters are calculated. When the maximum relative error of the acoustic reflection characteristic parameters between the "shell plate + rib" model and the "shell plate + beam" model does not exceed the maximum relative error threshold and the average relative error does not exceed the average relative error threshold, the "shell plate + beam" model replaces the "solid plate + rib" model for subsequent acoustic calculations. Otherwise, at least one of the equivalent thickness, equivalent material parameters, and boundary conditions of the "shell plate + beam" model is adjusted to re-establish the "shell plate + beam" model and step S4 is repeated.

[0035] In step S4, the cross-sectional shape and dimensions of the beam element are equivalently set based on the height, thickness, and cross-sectional area of ​​the original rib structure. Subsequent acoustic calculations include the calculation of the reflection coefficient, transmission coefficient, scattering intensity, or acoustic response characteristics of the ribbed structure.

[0036] In steps S3 and S4, the shell plate is connected to the ribs or beams through the multiphysics coupling interface in COMSOL. The coupling interface includes solid-thin structure connection and shell-beam connection.

[0037] The acoustic reflection characteristic parameters can be the reflection coefficient, transmission coefficient, or scattering intensity, or any parameter used to characterize the reflection behavior in the acoustic response characteristics.

[0038] The average relative error threshold is less than the maximum relative error threshold, and the two are determined according to a preset proportional relationship. Taking the acoustic reflection characteristic parameter using the reflection coefficient as an example, in the frequency range of 100Hz to 1500Hz, when the maximum relative error of the reflection coefficient between the simplified model and the reference model does not exceed 2%, and the average relative error does not exceed 1%, the simplified model is determined to be equivalent to the reference model in the frequency range.

[0039] Maximum relative error The calculation formula is:

[0040]

[0041] Mean relative error The calculation formula is:

[0042]

[0043] in, For the first Discrete frequency points, ; This represents the number of discrete frequency points within the specified frequency range. For the baseline model at frequency Reflectance coefficient at that location; To simplify the model at frequency The reflection coefficient at that location.

[0044] The following is a specific example in which the acoustic reflection characteristic parameter is selected as the reflection coefficient.

[0045] First, a solid-plate acoustic-structure interaction (AS / S) model without reinforcing members is established. The plate is modeled using three-dimensional solid elements, and its reflection coefficient is calculated under acoustic excitation, serving as a baseline result. While maintaining consistent material parameters, acoustic excitation conditions, and boundary conditions, the solid plate is replaced with shell elements to establish a shell-plate AS / S model. The shell thickness is set based on the equivalent mechanical properties of the solid plate. The shell model is solved, and its reflection coefficient is calculated. When the maximum relative error between the shell model and the baseline reflection coefficient does not exceed 2% and the average relative error does not exceed 1%, the solid plate is deemed equivalent to a shell plate in the reflection characteristic calculation. Comparison results are shown below. Figure 2 As shown, this verifies that a solid plate can be equivalently simplified to a shell plate in the calculation of its reflection characteristics.

[0046] The reflection coefficient is obtained by setting up the incident and received sound fields in the fluid domain and calculating the ratio of the reflected sound pressure to the incident sound pressure. The calculation formula is as follows:

[0047]

[0048] in, The reflection coefficient, To reflect sound pressure, This is the incident sound pressure.

[0049] Then, based on confirming the equivalence of the plates, reinforcing members are introduced to establish a coupled model of "solid plate + rib" consisting of a solid plate and reinforcing ribs. The calculation model is as follows: Figure 3 As shown, the reflection coefficient, including the influence of the reinforcing members, was calculated and used as the benchmark result for the ribbed structure. The calculation results are as follows: Figure 4 As shown.

[0050] Next, the solid plate was replaced with shell elements to construct a "shell plate + rib" coupled model. The shell plate and the solid ribs were coupled through a solid-thin structure connection. When the maximum relative error between the reflection coefficient calculated by the "shell plate + rib" coupled model and the baseline result of the ribbed structure does not exceed 2% and the average relative error does not exceed 1%, it is determined that the solid plate in the ribbed structure can be equivalently replaced by the shell plate. The comparison results are as follows: Figure 5 As shown, this verifies that the solid plate in the ribbed structure can be equivalently replaced by the shell plate.

[0051] Finally, the stiffening ribs were replaced with beam elements to construct a coupled "shell plate + beam" model, where the cross-sectional parameters of the beam elements were equivalently set based on the geometric characteristics of the original stiffening ribs. By comparing the reflection coefficients calculated from the "shell plate + beam" model and the "solid plate + rib" model, when the maximum relative error between the two did not exceed 2% and the average relative error did not exceed 1%, the "shell plate + beam" model was used to replace the solid model for subsequent acoustic calculations. The comparison results are as follows: Figure 6 As shown, it is verified that the "solid plate + rib" model can be equivalently replaced by the "shell plate + beam" model.

Claims

1. A simplified model method for calculating the acoustic reflection characteristics of ribbed structures, characterized in that, include: S1: Construct an acoustic-structure interaction model that includes a fluid domain and a structural domain, wherein the fluid domain adopts a pressure acoustics module, and the structural domain adopts at least one of the solid mechanics module, shell module, and structural mechanics-beam module; S2: Establish a "solid plate" model and a "shell plate" model in a fixed domain, where the "solid plate" model serves as the first reference model and the "shell plate" model serves as the first simplified model; calculate the acoustic reflection characteristic parameters of the two models. When the maximum relative error of the acoustic reflection characteristic parameters of the two models does not exceed the maximum relative error threshold and the average relative error does not exceed the average relative error threshold, the "solid plate" model and the "shell plate" model can be simplified to each other, and proceed to step S3; otherwise, adjust at least one of the equivalent thickness, equivalent material parameters, and boundary conditions of the "shell plate" model to re-establish the "shell plate" model and repeat step S2. S3: Establish a "solid plate + rib" model as the second reference model. Apply acoustic excitation to the "solid plate + rib" model and solve for the corresponding acoustic reflection characteristic parameters. While maintaining consistent material parameters and boundary conditions, replace the solid plate in the "solid plate + rib" model with shell elements to establish a "shell plate + rib" model as the second simplified model. The shell plate thickness is determined based on the equivalent mechanical properties of the solid plate. The connection between the shell plate and the rib structure is achieved through a solid-thin structure coupling method. Calculate the corresponding acoustic reflection characteristic parameters. When the maximum relative error of the acoustic reflection characteristic parameters between the "solid plate + rib" model and the "shell plate + rib" model does not exceed the maximum relative error threshold and the average relative error does not exceed the average relative error threshold, the "solid plate + rib" model and the "shell plate + rib" model can be mutually simplified, and proceed to step S4. Otherwise, adjust at least one of the equivalent thickness, equivalent material parameters, and boundary conditions of the "shell plate + rib" model to re-establish the "shell plate + rib" model and repeat step S3. S4: Using the "shell plate + rib" model as the third reference model, the rib structure is further replaced with beam elements to establish a "shell plate + beam" model as the third simplified model. The cross-sectional parameters of the beam elements are set equivalently according to the geometric dimensions of the original rib structure. The connection between the shell plate and the beam structure is realized through shell-beam coupling. The corresponding acoustic reflection characteristic parameters are calculated. When the maximum relative error of the acoustic reflection characteristic parameters between the "shell plate + rib" model and the "shell plate + beam" model does not exceed the maximum relative error threshold and the average relative error does not exceed the average relative error threshold, the "shell plate + beam" model replaces the "solid plate + rib" model for subsequent acoustic calculations. Otherwise, at least one of the equivalent thickness, equivalent material parameters, and boundary conditions of the "shell plate + beam" model is adjusted to re-establish the "shell plate + beam" model and step S4 is repeated.

2. The model simplification method for calculating the acoustic reflection characteristics of ribbed structures according to claim 1, characterized in that, In step S1, the calculation frequency range is set to 100~1500Hz.

3. The model simplification method for calculating the acoustic reflection characteristics of ribbed structures according to claim 1, characterized in that, In step S3, the shell plate thickness is determined by making the shell plate equivalent to the corresponding solid plate in terms of bending stiffness and in-plane stiffness.

4. The model simplification method for calculating the acoustic reflection characteristics of ribbed structures according to claim 1, characterized in that, In step S4, the cross-sectional form and dimensions of the beam element are set equivalently based on the height, thickness and cross-sectional area of ​​the original rib structure.

5. The model simplification method for calculating the acoustic reflection characteristics of ribbed structures according to claim 1, characterized in that, The shell plate is connected to the ribs or beams through a multiphysics coupling interface in COMSOL. The coupling interface includes solid-thin structure connection and shell-beam connection.

6. The model simplification method for calculating the acoustic reflection characteristics of ribbed structures according to claim 1, characterized in that, The acoustic reflection characteristic parameters can be the reflection coefficient, transmission coefficient, or scattering intensity, or any parameter used to characterize the reflection behavior in the acoustic response characteristics.

7. The model simplification method for calculating the acoustic reflection characteristics of ribbed structures according to claim 6, characterized in that, The reflection coefficient is obtained by setting up the incident sound field and the received sound field in the fluid domain and calculating the ratio of the reflected sound pressure to the incident sound pressure.

8. The model simplification method for calculating the acoustic reflection characteristics of ribbed structures according to claim 1, characterized in that, The average relative error threshold is less than the maximum relative error threshold, and the two are determined according to a preset ratio.

9. The model simplification method for calculating the acoustic reflection characteristics of ribbed structures according to claim 1, characterized in that, In step S3, the acoustic excitation is a plane wave excitation.

10. The model simplification method for calculating the acoustic reflection characteristics of ribbed structures according to claim 1, characterized in that, In step S4, the subsequent acoustic calculations include the calculation of the reflection coefficient, transmission coefficient, scattering intensity, or acoustic response characteristics of the ribbed structure.

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