Low-frequency broadband underwater acoustic structure based on rubber column parallel connection technology and design method thereof

Abstract

The invention discloses a low-frequency broadband underwater acoustic structure based on a rubber column parallel connection technology, which comprises a plurality of periodic structures arranged in parallel, and is characterized in that each periodic structure comprises n rubber column parallel connection devices arranged in parallel; each single rubber column parallel connection device comprises a thin rubber layer, a rubber column, a resin matrix and a steel plate backing which are sequentially arranged from the sound wave incidence position to the sound wave transmission position. Wherein the interior of the rubber column sequentially comprises a homogeneous rubber layer, a cylindrical cavity layer and a circular truncated cone cavity layer, the homogeneous rubber layer is connected with the thin rubber layer, the cylindrical cavity layer is communicated with the circular truncated cone cavity layer, and the circular truncated cone cavity layer is connected with the resin matrix; air is filled between the adjacent rubber columns to form an air layer. According to the structure, by means of parallel combination of the multiple layers of rubber columns, low-frequency broadband efficient absorption of sound waves underwater is achieved, and according to the design method, the designed structure has the low-mass, thin-thickness and low-frequency broadband sound absorption effects.

Description

Technical Field

[0001] The present invention relates to the technical field of underwater sound absorbing structures, and in particular to a low-frequency broadband underwater acoustic structure based on a rubber column parallel connection technology and a design method thereof. Background Art

[0002] Acoustic stealth performance is one of the key factors for underwater vehicles to maintain stealth when performing missions. Effective acoustic stealth can reduce the possibility of underwater vehicles being detected by enemy sonar systems, thereby reducing the risk of being discovered and tracked, and ensuring the stealth of combat operations. Laying an acoustic covering on the surface of an underwater vehicle can effectively reduce the reflection of sound waves and improve acoustic stealth performance. Structures embedded with periodically distributed cavities and local resonances have been widely used in acoustic coverings. The strong monopole resonance of the cavity and the multiple scattering of sound waves between cavities lead to broadband attenuation of sound waves, but the low-frequency sound absorption effect mainly depends on the size of the cavity, which is limited by the thickness of the covering. The addition of local resonance can improve the sound absorption performance through strong waveform conversion at the resonant frequency, but the sound absorption bandwidth is narrow, and the resonant sound absorption frequency is mainly related to the mass of the resonant body. Therefore, how to design a lightweight covering structure with low-frequency broadband sound absorption is an urgent problem to be solved for ship acoustic stealth. Summary of the invention

[0003] The main purpose of the present invention is to provide a low-frequency and broadband underwater acoustic structure based on rubber column parallel technology to address the shortcomings of traditional covering layer structures that often require large thickness and large mass local resonance to have good low-frequency and broadband sound absorption effects. The structure utilizes a parallel combination of multiple layers of rubber columns to achieve low-frequency and broadband efficient absorption of sound waves underwater; at the same time, a design method for the structure is proposed, and the designed structure has low mass, thin thickness and low-frequency and broadband sound absorption effects.

[0004] The technical solution adopted by the present invention is:

[0005] A low-frequency broadband underwater acoustic structure based on rubber column parallel technology includes a plurality of periodic structures arranged in parallel, wherein the periodic structure includes n rubber column parallel devices arranged in parallel; a single rubber column parallel device includes a thin rubber layer, a rubber column, a resin matrix, and a steel plate backing arranged in sequence from the incident point of the sound wave to the transmission point; wherein the interior of the rubber column includes a homogeneous rubber layer, a cylindrical cavity layer, and a truncated cone cavity layer in sequence, wherein the homogeneous rubber layer is connected to the thin rubber layer, the cylindrical cavity layer is connected to the truncated cone cavity layer, and the truncated cone cavity layer is connected to the resin matrix; air is filled between adjacent rubber columns to form an air layer.

[0006] In the above scheme, the truncated cone cavity layer includes a plurality of cylindrical cavity layers with linearly increasing diameters.

[0007] In the above solution, the diameter of the cylindrical cavity layer is equal to the diameter of the cylindrical cavity layer connected thereto.

[0008] In the above scheme, the adjacent thin rubber layers, resin matrix and steel plate backing are closely connected to each other.

[0009] In the above scheme, the thickness of the thin rubber layer of each rubber column parallel is equal, the thickness of the steel plate backing is equal, and the total thickness of the rubber column and the resin matrix is ​​equal.

[0010] Accordingly, the present invention also proposes a design method for the low-frequency broadband underwater acoustic structure based on the rubber column parallel connection technology, comprising the following steps:

[0011] S1. Determine the frequency range [f min ,f max ], the average sound absorption α in this range 0 ; Define efficient sound absorption as α m , reaching α for the first time m The frequency f m ;

[0012] S2. Establish a model of a single periodic structure, each periodic structure includes n rubber column parallel devices arranged in parallel, and a single rubber column parallel device includes a thin rubber layer, a rubber column, a resin matrix, and a steel plate backing arranged in sequence from the incident position to the transmission position of the sound wave;

[0013] S3. Set the geometric parameters of a single periodic structure in the model, including: the thickness of the thin rubber layer h c , the total thickness of the rubber column and the resin matrix h 0 , steel plate backing thickness h s , the side length of a single rubber column parallel is L, the thickness of the air layer between the rubber columns is t, the side length of the rubber column is Lt, the thickness of the i-th rubber column is h ri , i = 1 ~ n; then: In the rubber column, the thickness of the homogeneous rubber layer is h r1i =h ri / 2, the thickness of the cylindrical cavity layer is h r2i =h ri / 3, the inner cylinder diameter is D u =L / 5, the thickness of the truncated cone cavity layer is h r3i =h ri / 6, the bottom diameter of the inner truncated cone is D u =L / 5, the bottom diameter is D d = L / 1.5; then the impedance Z of the i-th rubber column, resin matrix and steel plate backing is calculated by simulation or theory i ;

[0014] S4, design n rubber column parallel devices in parallel, that is, arrange the rubber column parallel devices horizontally, separate the adjacent rubber columns by air layers, and directly connect the thin rubber layer, resin matrix, and steel plate backing; then, simulate or theoretically according to Z i Calculate the parallel impedance Z t , and further calculate the total surface impedance Z in ;

[0015] S5. Calculate the sound absorption coefficient α of n rubber columns connected in parallel by simulation or theory;

[0016] S6. Calculate the sound absorption coefficient after parallel connection through simulation or theory, and calculate the frequency range [f min ,f max The arithmetic mean of the sound absorption coefficients within The sound absorption coefficient α is reached for the first time m The corresponding frequency f is used to determine whether the following conditions are met at the same time:

[0017]

[0018] If all the above conditions are met, then enter S7; otherwise, increase the number of parallel connections and re-enter S2 to design the rubber column;

[0019] S7. Introduce coupling performance parameter ξ and determine coupling performance parameter threshold ξ 0 ; The expression of coupling performance parameter ξ is:

[0020]

[0021] In the formula, ρ w is the density of water, ρ is the average density of the parallel structure without steel plate backing, H = 40mm is the reference value of the cover layer thickness; the relative size of ξ indicates that the structure is in the frequency range [f min ,f max ]’s sound absorption capacity and quality level;

[0022] S8. Comparison of ξ and ξ 0 Size: If ξ<ξ 0 , it means that the coupling performance does not meet expectations, and re-enter S3 to design the parameters; if ξ≥ξ 0 , which shows that the designed low-frequency broadband hydroacoustic structure based on rubber column parallel technology meets the design requirements of low-frequency broadband sound absorption and lightweight.

[0023] In the above method, in step S3, the impedance Z between the i-th rubber column and the resin matrix and the steel plate backing is i The theoretical calculation methods include:

[0024] (1) First calculate the transfer matrix of each part of the i-th rubber column, including the transfer matrix T of the homogeneous rubber layerr1i , cylindrical cavity layer transfer matrix T r2i , the transfer matrix of the truncated cone cavity layer T r3i , and then calculate the transfer matrix T of the i-th rubber column ri :

[0025] T ri =T r1i T r2i T r3i (8)

[0026] (2) Calculate the i-th resin matrix transfer matrix T bi :

[0027]

[0028] In the formula, is the wave number in the resin matrix, Z b =ρ b c b is the resin impedance, ρ b is the resin density, c b is the velocity of longitudinal waves in the resin;

[0029] (3) Calculate the i-th steel plate backing transfer matrix T s :

[0030]

[0031] In the formula, k s is the wave number in the steel plate, Z s =ρ s c s is the steel plate impedance, ρ s is the density of steel plate, c s is the velocity of longitudinal wave in the steel plate;

[0032] (4) Calculate the transfer matrix T of the i-th rubber column, resin matrix and steel plate backing i for

[0033]

[0034] Where, T 11 ,T 12 ,T 21 ,T 22 T i The elements of the matrix are calculated by equations (8)-(9);

[0035] (5) Calculate the impedance Z of the i-th rubber column, resin matrix and steel plate backing i :

[0036]

[0037] In the above method, the transfer matrix T of the homogeneous rubber layer of the i-th rubber column is r1i for:

[0038]

[0039] In the formula, j is an imaginary unit, is the wave number in the homogeneous rubber layer, ω is the circular frequency of the sound wave in water, Z r1 =ρ r c r is the rubber impedance, ρ r is the rubber density, c r is the velocity of longitudinal waves in rubber;

[0040] The transfer matrix T of the i-th rubber cylinder cavity layer r2i for:

[0041]

[0042] In the formula, k r2 is the wave number in the cylindrical cavity layer, Z r2 is the impedance of the cylindrical cavity layer; k r2 , Z r2 The expressions are:

[0043]

[0044] Where λ,μ is the Lame constant of rubber, ρ r2 ,c r2 are the density and longitudinal wave velocity of the cylindrical cavity layer, respectively, and their expressions are

[0045]

[0046] In the formula, ρ r is the rubber density, ρ air is the air density, ω is the circular frequency of sound waves in water;

[0047] The i-th rubber cylinder cone cavity layer includes several cylindrical cavity layers with linearly increasing diameters. The number of layers is set to M. Then the diameter of the cylindrical cavity layer in the m-th layer is D um for

[0048] D um =D u +(m-1)(D d -D u ) / M (5)

[0049] Wherein, m = 1 ~ M;

[0050] The layered transfer matrix T of the m-th cylindrical cavity r3im for

[0051]

[0052] In the formula, h r3im =h r3i / M is the thickness of the mth cylindrical cavity layer, k r3m is the wave number in the mth cylindrical cavity layer, Z r3m is the layer impedance of the m-th cylindrical cavity, which can be calculated similarly according to equations (3) and (4);

[0053] Then the transfer matrix T of the i-th rubber cylinder cone cavity layer is r3i for

[0054]

[0055] In the above method, in step S4, the parallel impedance Z t The theoretical calculation method is as follows:

[0056]

[0057] The total surface impedance Z in The calculation method is as follows:

[0058]

[0059] In the formula, j is the imaginary unit, Z r =ρ r c r is the impedance of rubber, is the wave number of rubber.

[0060] In the above method, in step S5, the theoretical calculation method of the sound absorption coefficient α is calculated as follows:

[0061]

[0062] In the formula, Z w =ρ w c w is the impedance of water, ρ w is the density of water, c w is the speed of sound in water.

[0063] The beneficial effects produced by the present invention are:

[0064] The present invention utilizes the parallel combination of multiple layers of rubber columns to design a low-mass, thin-thickness covering layer structure for underwater low-frequency, broadband, and efficient sound absorption. In the structure, a single rubber column parallel device includes a thin rubber layer, a rubber column, a resin matrix, and a steel plate backing arranged in sequence from the sound wave incident point to the transmission point, wherein the interior of the rubber column includes a homogeneous rubber layer, a cylindrical cavity layer, and a truncated cone cavity layer in sequence, and the cavity can generate waveform conversion under the action of sound waves to improve the sound absorption efficiency. The cavity arranged in the present invention is a cylindrical cavity and a truncated cone cavity from the sound wave incident point to the transmission point, and its impedance changes gradually layer by layer, which is conducive to the sound wave entering the deep part of the structure and dissipating.

[0065] The present invention also proposes a design method for the covering layer structure. By designing the structural parameters, size and arrangement of the rubber columns, the low-frequency (500-2000Hz) broadband (high-efficiency sound absorption (sound absorption coefficient is greater than a certain reference value, usually 0.7-0.9) bandwidth) absorption of sound wave energy can be effectively achieved. The method simultaneously considers the average sound absorption coefficient of the covering layer structure, the low-frequency sound absorption effect, lightweight and other design factors. The structure designed by the method of the present invention has low-frequency broadband sound absorption capability while also meeting the requirements of lightweight and thin thickness, and has good application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0067] Figure 1 It is a schematic structural diagram of a single rubber column parallel device in a low-frequency broadband underwater acoustic structure based on the rubber column parallel technology of the present invention;

[0068] Figure 2 It is a schematic diagram of the rubber column frustum cavity layer being equivalent to being layered by multiple cylindrical cavities;

[0069] Figure 3 It is the front view of a single periodic structure formed by connecting multiple rubber column parallels in parallel;

[0070] Figure 4 It is a stereogram of two periodic structures formed by connecting multiple rubber column parallels in parallel;

[0071] Figure 5 It is a flow chart of a design method of a single rubber column parallel in a low-frequency broadband underwater acoustic structure based on the rubber column parallel technology of the present invention;

[0072] Figure 61 is a graph showing the variation of the sound absorption coefficient α with frequency obtained through simulation calculation in an embodiment of the present invention. DETAILED DESCRIPTION

[0073] In order to make the purpose, technical solution 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 used to limit the present invention.

[0074] It should be noted that the illustrations provided in the embodiments of the present invention are only used to illustrate the basic concept of the present invention in a schematic manner. Therefore, the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout type may also be more complicated.

[0075] In the present invention, it is also necessary to explain that, if the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, if the terms "first" and "second" appear, they are only used for description and distinction purposes, and cannot be understood as indicating or implying relative importance.

[0076] Traditional covering layer structures mainly achieve low-frequency broadband sound absorption by mixing cavities or local resonances in viscoelastic materials, and such covering layer structures often require large thickness and large mass local resonance to have good low-frequency broadband sound absorption effects. In response to this, the present invention proposes a low-frequency broadband underwater acoustic structure based on rubber column parallel technology, including a number of periodic structures arranged in parallel, and the periodic structure includes n rubber column parallels arranged in parallel. Figure 1 As shown, a single rubber column parallel device includes a thin rubber layer, a rubber column, a resin matrix, and a steel plate backing arranged in sequence from the incident point of the sound wave to the transmission point. Among them, the thin rubber layer is located at the incident point of the sound wave, and its main function is to isolate the rubber column from the outer water area and provide a sealing effect. The interior of the rubber column includes a homogeneous rubber layer, a cylindrical cavity layer, and a truncated cone cavity layer in sequence. The cavity can generate waveform conversion under the action of sound waves to improve the sound absorption efficiency. The cavity arranged in the present invention is a cylindrical cavity and a truncated cone cavity from the incident point of the sound wave to the transmission point, and its impedance changes gradually layer by layer, which is conducive to the sound wave entering the deep part of the structure and dissipating.

[0077] The homogeneous rubber layer is connected to the thin rubber layer, the cylindrical cavity layer is connected to the truncated cone cavity layer, and the truncated cone cavity layer is connected to the resin matrix. The resin matrix provides support for the rubber column, and the rubber column is fixed in the whole by connecting to it. The steel plate backing is located at the rear of the resin matrix to enhance the stability and durability of the structure.

[0078] like Figure 2 As shown, the truncated cone cavity layer includes several cylindrical cavity layers with linearly increasing diameters. By converting the truncated cone cavity layer into multiple cylindrical cavity layers, the approximate equivalent wave number of the truncated cone cavity layer can be obtained, which is convenient for solving the impedance. The diameter of the cylindrical cavity layer is equal to the diameter of the cylindrical cavity layer connected to it.

[0079] like Figure 3 As shown, when multiple rubber column parallelers are connected in parallel, air is filled between adjacent rubber columns to form an air layer. Adjacent thin rubber layers, resin matrix, and steel plate backing are closely connected. The thickness of the thin rubber layer of each rubber column paralleler is equal, the thickness of the steel plate backing is equal, and the total thickness of the rubber column and the resin matrix is ​​equal, while the thickness of the rubber column can be unequal to adjust the sound absorption effect of different frequencies.

[0080] The three-dimensional diagram of the periodic structure formed by connecting multiple rubber column parallels in parallel is shown in Figure 4 shown.

[0081] Further optimization, the present invention also proposes a design method for the low-frequency broadband hydroacoustic structure based on the rubber column parallel connection technology, such as Figure 5 As shown, the following steps are included:

[0082] S1. Determine the frequency range to be calculated according to the actual application scenario [f min ,f max ], the average sound absorption α in this range 0 ; Define efficient sound absorption as α m , reaching α for the first time m The frequency f m .

[0083] Among them, the frequency range [f min ,f max ] is the frequency range to be calculated, and the average sound absorption α in this range 0 is the average value of the required sound absorption effect, and the high-efficiency sound absorption α m The sound absorption coefficient with high sound absorption effect in practice has reached α for the first time m The frequency f m , these values ​​are determined by the actual application scenarios.

[0084] S2. Establish a model of a single periodic structure, each periodic structure includes n rubber column parallels arranged in parallel, and a single rubber column parallel includes a thin rubber layer, a rubber column, a resin matrix, and a steel plate backing arranged in sequence from the sound wave incident point to the transmission point.

[0085] S3. Set the geometric parameters of a single periodic structure in the model, including: the thickness of the thin rubber layer h c , the total thickness of the rubber column and the resin matrix h 0 , steel plate backing thickness h s , the side length of a single rubber column parallel is L, the thickness of the air layer between the rubber columns is t, the side length of the rubber column is Lt, the thickness of the i-th rubber column is h ri , i = 1 ~ n; then: In the rubber column, the thickness of the homogeneous rubber layer is h r1i =h ri / 2, the thickness of the cylindrical cavity layer is h r2i =h ri / 3, the inner cylinder diameter is D u =L / 5, the thickness of the truncated cone cavity layer is h r3i =h ri / 6, the bottom diameter of the inner truncated cone is D u =L / 5, the bottom diameter is D d =L / 1.5.

[0086] Then, the impedance Z of the i-th rubber column, resin matrix and steel plate backing is calculated by simulation or theory. i , the calculation methods include:

[0087] (1) First calculate the transfer matrix of each part of the i-th rubber column, including the transfer matrix T of the homogeneous rubber layer r1i , cylindrical cavity layer transfer matrix T r2i , the transfer matrix of the truncated cone cavity layer T r3i , and then calculate the transfer matrix T of the i-th rubber column ri .

[0088] Transfer matrix T of the i-th rubber column homogeneous rubber layer r1i for:

[0089]

[0090] In the formula, j is an imaginary unit, is the wave number in the homogeneous rubber layer, ω is the circular frequency of the sound wave in water, Z r1 =ρ r c r is the rubber impedance, ρ r is the rubber density, c r is the velocity of longitudinal waves in rubber;

[0091] The transfer matrix T of the i-th rubber cylinder cavity layer r2i for:

[0092]

[0093] In the formula, k r2 is the wave number in the cylindrical cavity layer, Z r2 is the impedance of the cylindrical cavity layer; k r2 , Z r2 The expressions are:

[0094]

[0095] Where λ,μ is the Lame constant of rubber, ρ r2 ,c r2 are the density and longitudinal wave velocity of the cylindrical cavity layer, respectively, and their expressions are

[0096]

[0097] In the formula, ρ r is the rubber density, ρ air is the air density, ω is the circular frequency of sound waves in water;

[0098] The i-th rubber cylinder cone cavity layer includes several cylindrical cavity layers with linearly increasing diameters. The number of layers is set to M. Then the diameter of the cylindrical cavity layer in the m-th layer is D um for

[0099] D um =D u +(m-1)(D d -D u ) / M (5)

[0100] Wherein, m = 1 ~ M;

[0101] The layered transfer matrix T of the m-th cylindrical cavity r3im for

[0102]

[0103] In the formula, h r3im =h r3i / M is the thickness of the mth cylindrical cavity layer, k r3m is the wave number in the mth cylindrical cavity layer, Z r3m is the layer impedance of the m-th cylindrical cavity, which can be calculated according to equations (3) and (4);

[0104] Then the transfer matrix T of the i-th rubber cylinder cone cavity layer is r3i for

[0105]

[0106] Then, the transfer matrix T of the i-th rubber column is ri for:

[0107] T ri =T r1i T r2i T r3i (8)

[0108] (2) Calculate the i-th resin matrix transfer matrix T bi :

[0109]

[0110] In the formula, is the wave number in the resin matrix, Z b =ρ b c b is the resin impedance, ρ b is the resin density, c b is the velocity of longitudinal waves in the resin;

[0111] (3) Calculate the i-th steel plate backing transfer matrix T s :

[0112]

[0113] In the formula, k s is the wave number in the steel plate, Z s =ρ s c s is the steel plate impedance, ρ s is the density of steel plate, c s is the velocity of longitudinal wave in the steel plate;

[0114] (4) Calculate the total transfer matrix T i for

[0115]

[0116] Where, T 11 ,T 12 ,T 21 ,T 22 T i The elements of the matrix are calculated by equations (8)-(9);

[0117] (5) Calculate the impedance Z of the i-th rubber column, resin matrix and steel plate backing i :

[0118]

[0119] S4, design n rubber column parallels in parallel, that is, arrange the rubber column parallels horizontally, separate the adjacent rubber columns by air layers, and directly connect the thin rubber layer, resin matrix, and steel plate backing. Then, according to Z i Calculate the parallel impedance Z t , and further calculate the total surface impedance Z in .

[0120] The boundary conditions of the parallel model specifically include free boundary conditions on the side of the rubber column and Floquet periodic boundary conditions on the thin rubber layer, the resin matrix and the steel plate backing.

[0121] Parallel impedance Z t The calculation method is as follows:

[0122]

[0123] The total surface impedance Z in The calculation method is as follows:

[0124]

[0125] In the formula, j is the imaginary unit, Z r =ρ r c r is the impedance of rubber, is the wave number of rubber.

[0126] S5. Calculate the sound absorption coefficient α after n rubber columns are connected in parallel. The sound absorption coefficient α is calculated according to the following formula:

[0127]

[0128] In the formula, Z w =ρ w c w is the impedance of water, ρ w is the density of water, c w is the speed of sound.

[0129] S6. Calculate the average value of the sound absorption coefficient after parallel connection, and reach α for the first time m The frequency f is used to determine whether the following conditions are met at the same time:

[0130]

[0131] in, Determine whether the overall average sound absorption coefficient of the parallel structure within a given frequency range meets the expected standard. m ≤0 to judge whether the low-frequency sound absorption capacity of the parallel structure meets the expected standard.

[0132] If the average value of the sound absorption coefficient after parallel connection First reached alpha m If the frequencies f meet the standards at the same time, it means that the overall average sound absorption coefficient of the parallel structure and the low-frequency sound absorption capacity meet the expected standards respectively, then enter S7; otherwise, increase the number of parallel connections, that is, n=n+1, and re-enter S2 to design the rubber column.

[0133] S7. Introduce coupling performance parameter ξ and determine coupling performance parameter threshold ξ 0 ; The expression of coupling performance parameter ξ is:

[0134]

[0135] In the formula, ρ w =1000kg / m 3 is the density of water, ρ is the average density of the parallel structure without steel plate, and H=40mm is the reference value of the covering layer thickness.

[0136] The meaning of the coupling performance parameter ξ is: the higher the coupling performance parameter ξ, the better the overall sound absorption performance and the lighter the overall mass of the structure. 0 You can set it according to the actual application scenario.

[0137] S8. Comparison of ξ and ξ 0 Size: If ξ<ξ 0 , it means that the coupling performance does not meet expectations, and re-enter S3 to design the parameters; if ξ≥ξ 0 , which shows that the designed low-frequency broadband hydroacoustic structure based on rubber column parallel technology meets the design requirements of low-frequency broadband sound absorption and lightweight.

[0138] The following is a calculation example to specifically illustrate the design method of the low-frequency broadband underwater acoustic structure based on the rubber column parallel connection technology of the present invention:

[0139] S1. Determine the frequency range [500, 10000] to be calculated according to the actual application scenario, in Hz, and the average sound absorption α within this range. 0 =0.7; define efficient sound absorption as α m =0.8, reaching α for the first time m The frequency f m =1500Hz;

[0140] S2. Establish a model of a single periodic structure, each periodic structure includes n=4 rubber column parallel devices arranged in parallel, and a single rubber column parallel device includes a thin rubber layer, a rubber column, a resin matrix, and a steel plate backing arranged in sequence from the incident position to the transmission position of the sound wave;

[0141] S3. Set the geometric parameters of a single periodic structure in the model, including: the thickness of the thin rubber layer h c=1mm, the total thickness of the rubber column and the resin matrix h 0 =30mm, steel plate backing thickness h s =15mm, the side length of a single rubber column parallel is L=8mm, the thickness of the air layer between the rubber columns is t=0.5mm, the side length of the rubber column is Lt=7.5mm, the thickness of the i-th rubber column is h ri , i = 1 to 4, including h r1 =25mm,h r2 =5mm,h r3 =5mm,h r4 =15mm, then: In the rubber column, the thickness of the homogeneous rubber layer is h r1i =h ri / 2, including h r11 =12.5mm,h r12 =2.5mm,h r13 =2.5mm,h r14 =7.5mm. The thickness of the cylindrical cavity layer is h r2i =h ri / 3, including h r21 =8.33mm,h r22 =1.67mm,h r23 =1.67mm,h r24 =5mm. Its inner cylindrical diameter is D u =L / 5=1.6mm, the thickness of the truncated cone cavity layer is h r3i =h ri / 6, including, h r31 =4.17mm,h r32 =0.83mm,h r33 =0.83mm,h r34 =2.5mm, the diameter of the inner truncated cone is D u =L / 5=1.6mm, the bottom diameter is D d = L / 1.5 = 5.33 mm; then the impedance Z of the i-th rubber column, resin matrix and steel plate backing is calculated by simulation or theory i ;

[0142] S4, design the four rubber column parallel devices in parallel, that is, arrange the rubber columns horizontally, and separate the adjacent rubber columns by air layers, and then simulate or theoretically according to Z i Calculate the parallel impedance Z t , and further calculate the total surface impedance Z in ;

[0143] S5. Calculate the sound absorption coefficient α of n rubber columns connected in parallel by simulation or theory;

[0144] In this embodiment, the sound absorption coefficient α obtained by simulation calculation is as follows: Figure 6 shown.

[0145] S6. Calculate the average value of the sound absorption coefficient after parallel connection through simulation or theoretical calculation First reached alpha m =0.8 frequency f=980Hz, and at the same time satisfies equation (16):

[0146]

[0147] Enter S7.

[0148] S7. Introduce coupling performance parameter ξ and determine coupling performance parameter threshold ξ 0 =50%; the coupling performance parameter ξ is expressed as:

[0149]

[0150] In the formula, ρ w =1000kg / m 3 is the density of water, ρ is the average density of the parallel structure without steel plate, and H=40mm is the reference value of the cover thickness;

[0151] S8. Comparison of ξ and ξ 0 Size: ξ=70.0%≥ξ 0 =50%, indicating that the designed low-frequency broadband hydroacoustic structure based on rubber column parallel technology meets the design requirements of low-frequency broadband sound absorption and lightweight.

[0152] It should be pointed out that, according to the needs of implementation, the various steps / components described in this application can be split into more steps / components, and two or more steps / components or partial operations of steps / components can be combined into new steps / components to achieve the purpose of the present invention.

[0153] The order of execution of each step in the above embodiment does not mean the order of execution. The order of execution of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present application.

[0154] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A low-frequency broadband underwater acoustic structure based on rubber column parallel technology, comprising a plurality of periodic structures arranged in parallel, characterized in that: The periodic structure includes n rubber column parallelizers arranged in parallel; a single rubber column parallelizer includes a thin rubber layer, a rubber column, a resin matrix, and a steel plate backing arranged in sequence from the sound wave incident point to the transmission point; wherein the interior of the rubber column includes a homogeneous rubber layer, a cylindrical cavity layer, and a truncated cone cavity layer in sequence, the homogeneous rubber layer is connected to the thin rubber layer, the cylindrical cavity layer is connected to the truncated cone cavity layer, and the truncated cone cavity layer is connected to the resin matrix; air is filled between adjacent rubber columns to form an air layer.

2. The low-frequency broadband underwater acoustic structure based on the rubber column parallel connection technology according to claim 1 is characterized in that: The truncated cone cavity layer includes a plurality of cylindrical cavity layers with linearly increasing diameters.

3. The low-frequency broadband underwater acoustic structure based on the rubber column parallel connection technology according to claim 2 is characterized in that: The diameter of the cylindrical cavity layer is equal to the diameter of the cylindrical cavity layer connected thereto.

4. The low-frequency broadband underwater acoustic structure based on the rubber column parallel connection technology according to claim 1 is characterized in that: The adjacent thin rubber layers, resin matrix and steel plate backing are closely connected to each other.

5. The low-frequency broadband underwater acoustic structure based on the rubber column parallel connection technology according to claim 1 is characterized in that: The thickness of the thin rubber layer of each rubber column parallel is equal, the thickness of the steel plate backing is equal, and the total thickness of the rubber column and the resin matrix is ​​equal.

6. The design method of a low-frequency broadband underwater acoustic structure based on rubber column parallel connection technology according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Determine the frequency range [f min ,f max ], the average sound absorption in this range is α0; efficient sound absorption is defined as α m , reaching α for the first time m The frequency f m ; S2. Establish a model of a single periodic structure, each periodic structure includes n rubber column parallel devices arranged in parallel, and a single rubber column parallel device includes a thin rubber layer, a rubber column, a resin matrix, and a steel plate backing arranged in sequence from the incident position to the transmission position of the sound wave; S3. Set the geometric parameters of a single periodic structure in the model, including: the thickness of the thin rubber layer h c , the total thickness of the rubber column and the resin matrix h0, the thickness of the steel plate backing h s , the side length of a single rubber column parallel is L, the thickness of the air layer between the rubber columns is t, the side length of the rubber column is Lt, the thickness of the i-th rubber column is h ri , i = 1 ~ n; then: In the rubber column, the thickness of the homogeneous rubber layer is h r1i =h ri / 2, the thickness of the cylindrical cavity layer is h r2i =h ri / 3, the inner cylinder diameter is D u =L / 5, the thickness of the truncated cone cavity layer is h r3i =h ri / 6, the bottom diameter of the inner truncated cone is D u =L / 5, the bottom diameter is D d = L / 1.5; then the impedance Z of the i-th rubber column, resin matrix and steel plate backing is calculated by simulation or theory i ; S4, design n rubber column parallel devices in parallel, that is, arrange the rubber column parallel devices horizontally, separate the adjacent rubber columns by air layers, and directly connect the thin rubber layer, resin matrix, and steel plate backing; then, simulate or theoretically according to Z i Calculate the parallel impedance Z t , and further calculate the total surface impedance Z in ; S5. Calculate the sound absorption coefficient α of n rubber columns connected in parallel by simulation or theory; S6. Calculate the sound absorption coefficient after parallel connection through simulation or theory, and calculate the frequency range [f min ,f max The arithmetic mean of the sound absorption coefficient within The sound absorption coefficient α is reached for the first time m The corresponding frequency f is used to determine whether the following conditions are met at the same time: If all the above conditions are met, then enter S7; otherwise, increase the number of parallel connections and re-enter S2 to design the rubber column; S7, introduce the coupling performance parameter ξ, and determine the coupling performance parameter threshold ξ0; the coupling performance parameter ξ expression is: In the formula, ρ w is the density of water, ρ is the average density of the parallel structure without steel plate backing, H = 40mm is the reference value of the cover layer thickness; the relative size of ξ indicates that the structure is in the frequency range [f min ,f max ]’s sound absorption capacity and quality level; S8. Compare the sizes of ξ and ξ0: If ξ<ξ0, it means that the coupling performance does not meet expectations, and re-enter S3 to design the parameters; if ξ≥ξ0, it means that the designed low-frequency broadband hydroacoustic structure based on rubber column parallel technology meets the design requirements of low-frequency broadband sound absorption and lightweight.

7. The design method of low-frequency broadband underwater acoustic structure based on rubber column parallel connection technology according to claim 6 is characterized in that: In step S3, the impedance Z between the i-th rubber column and the resin matrix and the steel plate backing is i The theoretical calculation methods include: (1) First calculate the transfer matrix of each part of the i-th rubber column, including the transfer matrix T of the homogeneous rubber layer r1i , cylindrical cavity layer transfer matrix T r2i , the transfer matrix of the truncated cone cavity layer T r3i , and then calculate the transfer matrix T of the i-th rubber column ri : T ri =T r1i T r2i T r3i (8) (2) Calculate the i-th resin matrix transfer matrix T bi : In the formula, is the wave number in the resin matrix, Z b =ρ b c b is the resin impedance, ρ b is the resin density, c b is the velocity of longitudinal waves in the resin; (3) Calculate the i-th steel plate backing transfer matrix T s : In the formula, k s is the wave number in the steel plate, Z s =ρ s c s is the steel plate impedance, ρ s is the density of steel plate, c s is the velocity of longitudinal wave in the steel plate; (4) Calculate the transfer matrix T of the i-th rubber column, resin matrix and steel plate backing i for Where, T 11 ,T 12 ,T 21 ,T 22 T i The elements of the matrix are calculated by equations (8)-(9); (5) Calculate the impedance Z of the i-th rubber column, resin matrix and steel plate backing i :

8. The design method of low-frequency broadband underwater acoustic structure based on rubber column parallel connection technology according to claim 7 is characterized in that: Transfer matrix T of the i-th rubber column homogeneous rubber layer r1i for: In the formula, j is an imaginary unit, is the wave number in the homogeneous rubber layer, ω is the circular frequency of the sound wave in water, Z r1 =ρ r c r is the rubber impedance, ρ r is the rubber density, c r is the velocity of longitudinal waves in rubber; The transfer matrix T of the i-th rubber cylinder cavity layer r2i for: In the formula, k r2 is the wave number in the cylindrical cavity layer, Z r2 is the impedance of the cylindrical cavity layer; k r2 , Z r2 The expressions are: Where λ,μ is the Lame constant of rubber, ρ r2 ,c r2 are the density and longitudinal wave velocity of the cylindrical cavity layer, respectively, and their expressions are In the formula, ρ r is the rubber density, ρ air is the air density, ω is the circular frequency of sound waves in water; The i-th rubber cylinder cone cavity layer includes several cylindrical cavity layers with linearly increasing diameters. The number of layers is set to M. Then the diameter of the cylindrical cavity layer in the m-th layer is D um for D um =D u +(m-1)(D d -D u ) / M (5) Wherein, m = 1 ~ M; The layered transfer matrix T of the m-th cylindrical cavity r3im for In the formula, h r3im =h r3i / M is the thickness of the mth cylindrical cavity layer, k r3m is the wave number in the mth cylindrical cavity layer, Z r3m is the layer impedance of the m-th cylindrical cavity, which can be calculated similarly according to equations (3) and (4); Then the transfer matrix T of the i-th rubber cylinder cone cavity layer is r3i for 9. The design method of low-frequency broadband underwater acoustic structure based on rubber column parallel connection technology according to claim 6 is characterized in that: In step S4, the parallel impedance Z t The theoretical calculation method is as follows: The total surface impedance Z in The calculation method is as follows: In the formula, j is the imaginary unit, Z r =ρ r c r is the impedance of rubber, is the wave number of rubber.

10. The design method of low-frequency broadband underwater acoustic structure based on rubber column parallel connection technology according to claim 6 is characterized in that: In step S5, the theoretical calculation method of the sound absorption coefficient α is calculated as follows: In the formula, Z w =ρ w c w is the impedance of water, ρ w is the density of water, c w is the speed of sound in water.

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