Sound field regulation and control calculation method based on bright spot model gradient phase change

Abstract

The invention discloses a bright spot model gradient phase change-based sound field regulation and control calculation method, which relates to the technical field of acoustic metasurfaces and comprises the following steps of: defining frequency parameters for carrying out sound field regulation and control; calculating a target surface bright spot, and determining a main scattering position; after surface bright spots are calculated, an acoustic metasurface is arranged at the position where scattering is strong for regulation and control; finite element software is used for verifying or verifying whether the result of fragment superposition is consistent with the result of directly calculating the fragment bright spot model or not through a theoretical solution, and if yes, the fragment bright spot model method is correct; solving a scattering sound field by using a fragmented bright spot model method and phase change; and quickly calculating scattering characteristics of the acoustic metasurface. According to the sound field regulation and control calculation method based on the gradient phase change of the bright spot model, the bright spot model method is used, the gradient change phase is given, regulation and control of the scattering sound field can be achieved, and rapid calculation of the acoustic metasurface is achieved by setting the appropriate phase.

Description

Technical Field

[0001] The present invention relates to the technical field of acoustic metasurfaces, and particularly to a calculation method for sound field regulation based on gradient phase change of a bright point model. Background Art

[0002] An acoustic metasurface is a novel acoustic metamaterial based on subwavelength dimensions and is composed of an array of metamaterial structural units. It controls the wavefront phase of sound waves through the design of microstructural functional elements, thereby achieving directional regulation of reflected or transmitted sound waves. An actual underwater vehicle is relatively complex, with complex linear structures such as superstructures, sterns, and rudder fins. Currently, it is relatively difficult to model the complex linear structure of convex bodies using acoustic metasurfaces.

[0003] When calculating the scattering characteristics of a simple structure, the bright point model method has advantages such as fast calculation speed and accurate calculation results. The piecewise bright point model method is further developed on the basis of the bright point model method, making the calculation of the scattering characteristics of any convex body structure fast and accurate.

[0004] To calculate the scattering characteristics of an acoustic metasurface, the finite element method or the plate element method is mainly used. However, the calculation speed of these two methods is relatively slow. The calculation speed will be greatly improved using the bright point model method. Through this method, not only can the scattering characteristics of the acoustic metasurface be calculated quickly, but also the regulation phase of the metasurface in actual situations can be determined through calculation. Summary of the Invention

[0005] The purpose of the present invention is to provide a calculation method for sound field regulation based on gradient phase change of a bright point model, to solve the problems raised in the above background art, achieve regulation of the scattering sound field, and realize fast calculation of the acoustic metasurface by setting appropriate phases.

[0006] To achieve the above purpose, the present invention provides a calculation method for sound field regulation based on gradient phase change of a bright point model, including the following steps:

[0007] Step S1: For any underwater vehicle, clarify the frequency parameters for sound field regulation;

[0008] Step S2: Take the structure of any complex underwater vehicle as the target, use the plate element method to calculate the bright points on the target surface, and decompose its surface bright point characteristic components. By observing the distribution of the bright points on the target surface, determine the main positions of scattering;

[0009] Step S3: After calculating the surface bright points, arrange acoustic metasurfaces at the positions with stronger scattering for regulation, thereby changing the scattering sound field on the target surface;

[0010] Step S4: Use finite element software to verify or verify through theoretical solutions whether the results of piecewise superposition are consistent with the results of directly calculating the piecewise highlight model. If they are consistent, the piecewise highlight model method is correct;

[0011] Step S5: Use the piecewise highlight model method plus phase change to solve the scattered sound field;

[0012] Step S6: Calculate the scattered sound field and then assign the corresponding phase to the metasurface or find the phase change of the metasurface to quickly calculate the scattering characteristics of the acoustic metasurface.

[0013] Preferably, in step S1, the frequency parameters include the calculation frequency and the step size. Among them, the calculation frequency is set to 100 Hz to 1000 Hz, and the step size is set to 10 Hz.

[0014] Preferably, in step S2, the plate element method is used to calculate the highlights on the target surface, which specifically includes:

[0015] Divide the target into N surface elements. Each surface element represents a local area in the medium. Use the plate element method to find the scattered sound field of each surface element, use matlab to draw the mesh on the model surface, and assign the calculated scattered sound field values to the mesh, so as to obtain the highlights on the target surface.

[0016] Preferably, step S4 specifically includes:

[0017] Perform piecewise processing on the surface highlight feature components to obtain multiple piecewise units. Calculate each piecewise unit using the piecewise highlight model, and superimpose the phases of each piecewise unit to form the entire piecewise highlight model. Assume that the transfer function of the tiny piecewise unit is I i , and the transfer function after phase superposition is:

[0018]

[0019] In the formula, δ i is the phase distance of the i-th unit, θ is the incident angle, j represents the imaginary number, k represents the wave number, and N represents the number of piecewise units;

[0020] According to the transfer function, the target strength calculation formula of the entire piecewise highlight model is as follows:

[0021]

[0022] In the formula, TS represents the target strength, N represents the number of piecewise units, and λ represents the wavelength;

[0023] Verify the accuracy of the target strength through simulation calculation or theoretical formula.

[0024] Preferably, the step S5 specifically includes: assigning a phase to each slice unit, where the assigned phase is a phase with a gradient change, such that there is a gradient change between different slice units, thereby regulating the scattering sound field.

[0025] Preferably, the specific steps of the step S6 are as follows:

[0026] Step S61: Find the maximum value of the difference between the original target intensity and the regulated target intensity through the objective function, and optimize the phase parameters in combination with the genetic algorithm;

[0027] Step S62: According to different requirements, change different objective functions and optimization parameter settings, so as to obtain the phase change corresponding to the target sound field.

[0028] Preferably, the expression of the objective function in the step S61 is as follows:

[0029]

[0030] In the formula, TS 原 represents the original target intensity value, TS 新 represents the regulated target intensity value, and f represents the frequency.

[0031] Preferably, the parameters of the genetic algorithm in the step S62 are set, including: the initial population size is 500, the crossover rate is 0.5, the elite rate is 0.3, the maximum number of generations is 400, and other parameters are default values.

[0032] Therefore, the present invention adopts the above-mentioned sound field regulation calculation method based on the gradient phase change of the bright spot model. By using the bright spot model method and assigning a phase with a gradient change, the regulation of the scattering sound field can be realized. By setting an appropriate phase, the rapid calculation of the acoustic metasurface can be achieved; by using the segmented bright spot model method for sound field regulation, not only can the advantages of fast calculation of the bright spot model be utilized, but also the calculation accuracy of the scattering characteristics of complex models can be improved, and the sound field regulation effect is obvious.

[0033] Next, through the drawings and embodiments, the technical solutions of the present invention will be further described in detail. Description of the Drawings

[0034] Figure 1 It is a flowchart of an embodiment of the sound field regulation calculation method based on the gradient phase change of the bright spot model of the present invention;

[0035] Figure 2 It is a surface bright spot distribution diagram of the model when the sound wave is incident at 45° in an embodiment of the sound field regulation calculation method based on the gradient phase change of the bright spot model of the present invention;

[0036] Figure 3The surface bright spot distribution diagram of the model when the sound wave is incident at 90° in the embodiment of the sound field regulation calculation method based on the gradient phase change of the bright spot model of the present invention;

[0037] Figure 4 The surface bright spot distribution diagram of the model when the sound wave is incident at 120° in the embodiment of the sound field regulation calculation method based on the gradient phase change of the bright spot model of the present invention;

[0038] Figure 5 The segmented bright spot model diagram of the present invention, where (a) is the calculation model diagram and (b) is the approximate schematic diagram;

[0039] Figure 6 The comparison result diagram of the target intensity values calculated by the present invention through the segmented bright spot model and the empirical formula;

[0040] Figure 7 The calculation model diagram of the segmented cylindrical shell of the present invention;

[0041] Figure 8 The comparison result diagram of the target intensity values calculated by the segmented bright spot model of the present invention under two conditions of without adding phase and adding phase;

[0042] Figure 9 The comparison result diagram of the target intensity values of the present invention, where (a) is the comparison diagram of without adding phase and the phase changing according to π / 9, (b) is the comparison diagram of without adding phase and the phase changing according to π / 7, (c) is the comparison diagram of without adding phase and the phase changing according to π / 6, (d) is the comparison diagram of without adding phase and the phase changing according to π / 5, (e) is the comparison diagram of without adding phase and the phase changing according to π / 4, and (f) is the comparison diagram of without adding phase and the phase changing according to π / 3;

[0043] Figure 10 The schematic diagram of the ellipsoid segmentation of the present invention;

[0044] Figure 11 The regulation effect diagram of the segmented bright spot model of the present invention at different angles. Detailed implementation mode

[0045] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0046] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the field to which the present invention pertains. The "first", "second" and similar terms used in the present invention do not denote any order, quantity or importance, but are only used to distinguish different components. Words such as "comprising" or "including" mean that the elements or objects appearing before this word cover the elements or objects listed after this word and their equivalents, without excluding other elements or objects. Words such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Upper", "lower", "left", "right", etc. are only used to represent relative position relationships. When the absolute position of the object being described changes, the relative position relationship may also change accordingly.

[0047] Embodiment

[0048] Please refer to Figures 1-11 , the present invention provides a method for calculating acoustic field regulation based on the gradient phase change of the bright spot model, including the following steps:

[0049] Step S1: For any underwater vehicle, clarify the frequency parameters for acoustic field regulation. The frequency parameters include the calculation frequency and the step size. In this embodiment, the calculation frequency is set to 100 Hz to 1000 Hz, and the step size is set to 10 Hz.

[0050] Step S2: Take any complex underwater vehicle structure as the target, use the panel element method to calculate the bright spots on the target surface, and decompose its surface bright spot characteristic components. By observing the distribution of the bright spots on the target surface, determine the main positions of scattering. Using the panel element method to calculate the bright spots on the target surface specifically includes:

[0051] Divide the target into N surface elements, each surface element representing a local area in the medium. Obtain the scattering sound field of each surface element through the panel element method, use matlab to draw the surface grid of the model, and assign the calculated scattering sound field values to the grid, so as to obtain the bright spots on the target surface.

[0052] Step S3: After calculating the bright spots on the surface, arrange acoustic metasurfaces at the positions with stronger scattering for regulation, so as to change the scattering sound field of the target surface.

[0053] Step S4: Use finite element software to verify or verify through theoretical solutions whether the results of piecewise superposition are consistent with the results of directly calculating the piecewise bright spot model. If they are consistent, the piecewise bright spot model method is correct.

[0054] Step S5: Use the piecewise bright point model method plus phase change to solve the scattering sound field. Assign a phase to each piecewise unit. The assigned phase is a phase with gradient change, so that there is a gradient change between different piecewise units, thereby regulating the scattering sound field. Specifically, it includes:

[0055] Perform piecewise processing on the surface bright point feature components to obtain multiple piecewise units. Calculate each piecewise unit using the piecewise bright point model, and superimpose the phases of each piecewise unit to form the entire piecewise bright point model. Assume that the transfer function of the tiny piecewise unit is I i , and the transfer function after phase superposition is:

[0056]

[0057] In the formula, δ i is the phase distance of the i-th unit, θ is the incident angle, j represents the imaginary number, k represents the wave number, and N represents the number of piecewise units;

[0058] According to the transfer function, obtain the target strength calculation formula of the entire piecewise bright point model as follows:

[0059]

[0060] In the formula, TS represents the target strength, N represents the number of piecewise units, and λ represents the wavelength.

[0061] Verify the accuracy of the target strength through simulation calculation or theoretical formula.

[0062] Step S6: Calculate the scattering sound field and then assign the corresponding phase to the metasurface or obtain the phase change of the metasurface to quickly calculate the scattering characteristics of the acoustic metasurface. The specific steps are as follows:

[0063] Step S61: Find the maximum value of the difference between the original target strength and the regulated target strength through the objective function, and combine the genetic algorithm to optimize the phase parameters.

[0064] Step S62: According to different requirements, change different objective functions and optimization parameter settings to obtain the phase change corresponding to the target sound field.

[0065] The above method will be further described below in conjunction with the accompanying drawings of this application document.

[0066] Please refer to the following Figures 2-4 , Figure 2 , Figure 3 , Figure 4They are the surface bright point distributions of the model when the acoustic wave is incident at 45°, 90°, and 120° respectively. The main scattering bright points are shown within the red frames in the figure. The darker the color, the stronger the echo. Therefore, an acoustic metasurface needs to be arranged at the positions of the bright points in the figure to regulate the scattering sound field of the strong scattering component, which can change the direction or energy of its scattered echo.

[0067] After calculating the surface bright points, the arrangement position of the acoustic metasurface is determined, which is the red frame area in the figure.

[0068] Verify the accuracy of the calculation of the cylindrical shell structure by the segmented bright point model. The total length of the cylinder is 42m and the radius is 3.75m. Take the cross-section of the cylinder, which can be approximately composed of N micro-element cylinders. Let the bright point transfer function of the small elliptical frustum be Taking the origin O as the calculation reference for the phase distance, then the bright point transfer function considering the phase is:

[0069]

[0070] In the formula, j represents the imaginary part, k represents the wave number, L i represents the phase distance, and N represents the number of segmented units.

[0071] Finally, coherently superimpose the bright point transfer function considering the phase, and approximately calculate the scattering sound field or target strength of the variable cross-section oblique convex structure with the superimposed bright point transfer function. The target strength calculation formula is:

[0072]

[0073] Among them, the bright point transfer function is which can be calculated by the following formula:

[0074]

[0075] In order to verify the accuracy of the calculation method of the segmented bright point model, when the acoustic wave is incident beam-on, the following empirical formula is used:

[0076]

[0077] Among them, a is the radius and L is the length.

[0078] From Figure 6 the results, it can be seen that the segmented bright point model is in good agreement with the empirical formula and the panel element results, which proves the reliability of the segmented bright point model for calculating the cylindrical shell.

[0079] When performing phase regulation on the cylindrical shell structure, when using the segmented bright point model, a specific phase can be assigned to each segment, so that the cylindrical shell has a gradient change, and the structure is as Figure 7As shown, the calculated frequency ranges from 100 Hz to 1000 Hz with a step size of 10 Hz. First, calculate the target strength contrast when the phase of the sound wave changes by π / 8 under normal incidence.

[0080] From Figure 8 the calculation results, it can be seen that when the sound wave is incident normally, adding a phase to each micro-cylindrical element has an obvious effect of reducing the target strength, with an average reduction of about 18.7 dB.

[0081] The objective function can be defined as finding the maximum value of the difference between the original target strength and the regulated target strength. Since the target strength in the normal direction is the largest within the circumferential angle range, only the normal direction is optimized in this example.

[0082] The objective function is:

[0083]

[0084] In the formula, TS 原 represents the original target strength value, TS 新 represents the regulated target strength value, and f is the frequency. The parameter settings of the genetic algorithm have an impact on the accuracy and speed of the reflection coefficient parameter inversion. Among them, the initial population size is 500, the crossover rate is 0.5, the elite rate is 0.3, the maximum number of generations is 400, and other parameters are default values.

[0085] Figure 9 shows the results after rounding the parameters in the optimization process of the genetic algorithm. Different phase parameters are selected according to different required reduction amounts. From Figure 9 the calculation results, it can be seen that as the phase regulation range increases, the effect of adding a phase to the cylinder is better. When the phase changes by π / 9, the target strength is reduced by an average of 17.39 dB; when the phase changes by π / 7, the target strength is reduced by an average of 20.40 dB; when the phase changes by π / 6, the target strength is reduced by an average of 21.75 dB; when the phase changes by π / 5, the target strength is reduced by an average of 23.46 dB; when the phase changes by π / 4, the target strength is reduced by an average of 25.62 dB; when the phase changes by π / 3, the target strength is reduced by an average of 28.31 dB.

[0086] When the sound wave is incident at a low angle, the bow ellipsoid is the main scatterer. Using the above method to regulate its scattering sound field, the ellipsoid is segmented as Figure 10 shown. After calculation at an incident frequency of 2000 Hz, the regulation effect of the scattering sound field at a low incident angle is as Figure 11 shown.

[0087] As can be seen from the above results, by using the bright point model method and endowing a phase with gradient variation, the regulation of the scattering sound field can be achieved. By setting an appropriate phase, the rapid calculation of the acoustic metasurface can be realized. By using the piecewise bright point model method for sound field regulation, not only can the advantage of fast calculation of the bright point model be utilized, but also the calculation accuracy of the scattering characteristics of complex models can be improved, and the sound field regulation effect is obvious.

[0088] Therefore, the present invention adopts the above-mentioned sound field regulation calculation method based on the gradient phase change of the bright point model. By using the bright point model method and endowing a phase with gradient variation, the regulation of the scattering sound field can be achieved. By setting an appropriate phase, the rapid calculation of the acoustic metasurface can be realized. By using the piecewise bright point model method for sound field regulation, not only can the advantage of fast calculation of the bright point model be utilized, but also the calculation accuracy of the scattering characteristics of complex models can be improved, and the sound field regulation effect is obvious.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements do not make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A sound field regulation calculation method based on the gradient phase change of the bright spot model, characterized in that It includes the following steps: Step S1: For any underwater vehicle, clarify the frequency parameters for acoustic field regulation; Step S2: Take any complex underwater vehicle structure as the target, use the panel element method to calculate the bright spots on the target surface, decompose the surface bright spot characteristic components from it, and determine the main scattering positions by observing the distribution of the bright spots on the target surface; Step S3: After calculating the surface bright spots, arrange acoustic metasurfaces at the positions with strong scattering for regulation, so as to change the scattering acoustic field on the target surface; Step S4: Use finite element software to verify or verify through theoretical solutions whether the results of piecewise superposition are consistent with the results of directly calculating the piecewise bright spot model. If they are consistent, the piecewise bright spot model method is correct; Step S5: Use the piecewise bright spot model method plus phase change to solve the scattering acoustic field; Step S6: Calculate the scattering acoustic field and then assign the corresponding phase to the metasurface or find the phase change of the metasurface to quickly calculate the scattering characteristics of the acoustic metasurface.

2. The acoustic field regulation calculation method based on the gradient phase change of the highlight model according to claim 1, wherein: In the said step S1, the frequency parameters include the calculation frequency and the step size. Among them, the calculation frequency is set to 100 Hz - 1000 Hz, and the step size is set to 10 Hz.

3. The acoustic field regulation calculation method based on the gradient phase change of the highlight model according to claim 2, wherein, The calculation of the bright spots on the target surface using the panel element method in the said step S2 specifically includes: Divide the target into N surface elements. Each surface element represents a local area in the medium. Obtain the scattering acoustic field of each surface element through the panel element method. Use matlab to draw the mesh on the model surface, and assign the calculated scattering acoustic field values to the mesh, so as to obtain the bright spots on the target surface.

4. A sound field regulation calculation method based on the gradient phase change of the highlight model according to claim 3, characterized in that, The said step S4 specifically includes: The surface highlight feature component is segmented to obtain multiple segmented units. By calculating each segmented unit using the segmented highlight model and superimposing the phases of each segmented unit, the entire segmented highlight model is superimposed. Assume the transfer function of the tiny segmented unit is I i , the transfer function after phase superposition is as follows: where δ i is the phase distance of the i-th unit, θ is the incident angle, j represents the imaginary number, k represents the wave number, and N represents the number of segmented units; Obtain the target strength calculation formula of the entire piecewise bright spot model according to the transfer function, as shown below: In the formula, TS represents the target strength, N represents the number of piecewise units, and λ represents the wavelength; Verify the accuracy of the target strength through simulation calculation or theoretical formula.

5. A method for calculating sound field regulation based on the gradient phase change of a highlight model according to claim 4, characterized in that, The said step S5 specifically includes: Assign a phase to each piecewise unit. The assigned phase is a phase with gradient change, so that there is a gradient change between different piecewise units, thereby regulating the scattering acoustic field.

6. The acoustic field regulation calculation method based on the gradient phase change of the highlight model according to claim 5, characterized in that The specific steps of the said step S6 are as follows: Step S61: Find the maximum value of the difference between the original target strength and the regulated target strength through the objective function, and optimize the parameters of the phase in combination with the genetic algorithm; Step S62: According to different requirements, change different objective functions and optimization parameter settings, so as to obtain the phase change corresponding to the target acoustic field.

7. A method for calculating sound field regulation based on the gradient phase change of the highlight model according to claim 6, characterized in that The expression of the objective function in the said step S61 is as follows: where, TS 原 represents the original target strength value, and TS 新 represents the target strength value after regulation, and f represents the frequency.

8. A sound field regulation calculation method based on the gradient phase change of the highlight model according to claim 7, characterized in that In the said step S62, set the parameters of the genetic algorithm, including: the initial population size is 500, the crossover rate is 0.5, the elitist rate is 0.3, the maximum number of generations is 400, and other parameters are default values.

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