Underwater sound-absorbing metamaterial and underwater vehicle

Abstract

The present invention relates to the technical field of sound absorbing materials, and in particular to an underwater sound absorbing metamaterial and an underwater vehicle. An embodiment of the present invention provides an underwater sound absorbing metamaterial, comprising a plurality of periodically arranged basic units, the basic units are cylindrical, and the basic units include a first cover layer, a structural layer, and a second cover layer in sequence along their axis, the structural layer includes a trident-shaped cavity and a cylindrical cavity distributed along its axial direction, the trident-shaped cavity includes a middle column cavity and two side column cavities symmetrically distributed with the axis of the middle column cavity as the symmetry axis, the middle column cavity and the side column cavity are flush with one end close to the cylindrical cavity, and are connected to each other by connecting the column cavities, and the media filled in the trident-shaped cavity and the cylindrical cavity are different. An embodiment of the present invention provides an underwater sound absorbing metamaterial and an underwater vehicle, which can provide a metamaterial with strong low-frequency and broadband sound absorption performance, enhanced water pressure resistance, and simple preparation process.

Description

Technical Field

[0001] The present invention relates to the technical field of sound absorbing materials, and in particular to an underwater sound absorbing metamaterial and an underwater vehicle. Background Art

[0002] With the rapid development of underwater technology, especially in the fields of underwater detection and marine engineering, the demand for underwater sound-absorbing materials is growing. Traditional underwater sound-absorbing materials often have problems such as poor low-frequency sound absorption, limited water pressure resistance, and complex preparation process. In order to solve these problems, researchers have been committed to developing new underwater sound-absorbing metamaterials in recent years to improve low-frequency broadband sound absorption performance, enhance water pressure resistance, and simplify the preparation process. Summary of the invention

[0003] The embodiments of the present invention provide an underwater sound-absorbing metamaterial and an underwater vehicle, which can provide a metamaterial with strong low-frequency and broadband sound absorption performance, enhanced water pressure resistance and simple preparation process.

[0004] In a first aspect, an embodiment of the present invention provides an underwater sound-absorbing metamaterial, comprising a plurality of periodically arranged basic units, wherein the basic units are cylindrical, and the basic units include a first cover layer, a structural layer, and a second cover layer in sequence along their axis, the structural layer includes a trident-shaped cavity and a cylindrical cavity distributed along its axial direction, the trident-shaped cavity includes a middle column cavity and two side column cavities symmetrically distributed with the axis of the middle column cavity as a symmetry axis, the middle column cavity and the side column cavity are flush with one end close to the cylindrical cavity, and are connected to each other through a connecting column cavity, and the media filled in the trident-shaped cavity and the cylindrical cavity are different.

[0005] In a possible design, the length and diameter of the middle column cavity are greater than the length and diameter of the side column cavity.

[0006] In a possible design, the middle column cavity is communicated with the outside of the structural layer and is blocked by the first cover layer, and the columnar cavity is communicated with the outside of the structural layer and is blocked by the second cover layer.

[0007] In one possible design, the trident-shaped cavity contains water, and the cylindrical cavity contains air.

[0008] In a possible design, the material used to prepare the first cover layer includes silicone rubber, and the material used to prepare the structural layer includes a polymer damping material.

[0009] In a possible design, the material used to make the second cover layer includes resin.

[0010] In a possible design, the first cover layer has a thickness of 2-7 mm and a radius of 13-23 mm;

[0011] The thickness of the structural layer is 45-55 mm, the thickness of the middle column cavity is 35-45 mm, the diameter is 1.5-2.5 mm, the thickness of the side column cavity is 20-30 mm, the diameter is 0.5-1.5 mm;

[0012] The thickness of the cylindrical cavity is 3-7 mm and the radius is 10-15 mm;

[0013] The second cover layer has a thickness of 2-7 mm and a radius of 13-23 mm.

[0014] In a possible design, a support tube is sleeved outside the structural layer.

[0015] In a possible design, the support tube is made of aluminum, and the wall thickness of the support tube is 1.5-2.5 mm.

[0016] In a second aspect, an embodiment of the present invention further provides an underwater vehicle, comprising a shell and an underwater sound absorbing metamaterial covering the surface of the shell, wherein the underwater sound absorbing metamaterial is any of the above-mentioned underwater sound absorbing metamaterials.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects:

[0018] In this embodiment, a plurality of basic units are arranged periodically to obtain a sound-absorbing metamaterial. In this application, when sound is transmitted to the underwater sound-absorbing metamaterial, the sound waves are transmitted to the trident-shaped cavity and the cylindrical cavity in turn. The trident-shaped cavity and the cylindrical cavity are not connected to each other. This design helps the sound waves to undergo complex reflection and scattering inside, thereby enhancing the sound absorption effect. Furthermore, the trident-shaped cavity and the cylindrical cavity are filled with different media respectively. The acoustic impedance difference between the two media is large, which is conducive to the attenuation of sound waves. In addition, the sound-absorbing metamaterial composed of a plurality of cylindrical basic units has a higher mechanical strength, and the structure of the two cavities in the basic unit is relatively simple, the processing difficulty is small, and the process is simpler. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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.

[0020] Figure 1 A schematic cross-sectional view of a basic unit of an underwater sound-absorbing metamaterial provided by an embodiment of the present invention;

[0021] Figure 2A schematic diagram of an overall explosion of a basic unit of an underwater sound-absorbing metamaterial provided by an embodiment of the present invention;

[0022] Figure 3 An exploded schematic diagram of a cross section of a basic unit of an underwater sound-absorbing metamaterial provided by an embodiment of the present invention;

[0023] Figure 4 A schematic diagram of the cross-sectional dimensions of a basic unit of the underwater sound-absorbing metamaterial provided by an embodiment of the present invention;

[0024] Figure 5 The sound absorption coefficient curve generated by the underwater sound absorption metamaterial provided by the present invention;

[0025] FIG6( a ) is a cloud diagram of the effective displacement of the underwater sound-absorbing metamaterial provided by the present invention at a frequency of 1080 Hz;

[0026] FIG6( b ) is a cloud diagram of the effective displacement of the underwater sound-absorbing metamaterial provided by the present invention at a frequency of 1700 Hz;

[0027] FIG6( c ) is a cloud diagram of the effective displacement of the underwater sound-absorbing metamaterial provided by the present invention at a frequency of 5000 Hz;

[0028] FIG. 7( a ) is a schematic diagram of energy conversion of the underwater sound-absorbing metamaterial provided by the present invention at a frequency of 1080 Hz;

[0029] FIG7( b ) is a schematic diagram of energy conversion of the underwater sound-absorbing metamaterial provided by the present invention at a frequency of 1700 Hz;

[0030] FIG7( c ) is a schematic diagram of energy conversion of the underwater sound-absorbing metamaterial provided by the present invention at a frequency of 5000 Hz;

[0031] Figure 8 A schematic diagram of an underwater vehicle provided in an embodiment of the present invention.

[0032] In the figure:

[0033] 100-basic unit;

[0034] 1- first cap layer;

[0035] 2-Structural layer;

[0036] 21-trident-shaped cavity;

[0037] 211-middle column cavity;

[0038] 212-side column cavity;

[0039] 213-connecting column cavity;

[0040] 22- cylindrical cavity;

[0041] 3- second capping layer;

[0042] 4- support tube;

[0043] 5-seawater layer;

[0044] 6-Perfectly matched layer;

[0045] 200 - underwater vehicles;

[0046] 201-basal layer. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0048] In the description of the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance; unless otherwise specified or explained, the term "multiple" refers to two or more; the terms "connected" and "fixed" should be understood in a broad sense, for example, "connected" can be a fixed connection, a detachable connection, an integral connection, or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0049] In the description of this specification, it should be understood that the directional words such as "upper" and "lower" described in the embodiments of the present invention are described at the angles shown in the drawings and should not be understood as limiting the embodiments of the present invention. In addition, in the context, it should also be understood that when it is mentioned that an element is connected to another element "upper" or "lower", it can not only be directly connected to another element "upper" or "lower", but also indirectly connected to another element "upper" or "lower" through an intermediate element.

[0050] like Figures 1 to 3As shown, an embodiment of the present invention provides an underwater sound-absorbing metamaterial, comprising a plurality of periodically arranged basic units 100, the basic unit 100 being cylindrical, and the basic unit 100 including a first cover layer 1, a structural layer 2, and a second cover layer 3 in sequence along its axis, the structural layer 2 including a trident-shaped cavity 21 and a cylindrical cavity 22 distributed along its axial direction, the trident-shaped cavity 21 including a middle cylindrical cavity 211 and two side cylindrical cavities 212 symmetrically distributed with the axis of the middle cylindrical cavity 211 as the symmetry axis, the middle cylindrical cavity 211 and the side cylindrical cavity 212 being flush with one end close to the cylindrical cavity 22, and being interconnected through a connecting column cavity 213, and the media filled in the trident-shaped cavity 21 and the cylindrical cavity 22 are different.

[0051] In this embodiment, a plurality of basic units 100 are arranged periodically to obtain a sound-absorbing metamaterial. In this application, when sound is transmitted to the underwater sound-absorbing metamaterial, the sound waves are transmitted to the trident-shaped cavity 21 and the cylindrical cavity 22 in turn. The trident-shaped cavity 21 and the cylindrical cavity 22 are not interconnected and are at least separated by a preset distance. This design helps the sound waves to undergo complex reflection and scattering inside, thereby enhancing the sound absorption effect. Furthermore, the trident-shaped cavity 21 and the cylindrical cavity 22 are filled with different media respectively. The acoustic impedance difference between the two media is large, which is conducive to the attenuation of sound waves. In addition, the sound-absorbing metamaterial composed of a plurality of cylindrical basic units 100 has a higher mechanical strength, and the structure of the two cavities in the basic unit 100 is relatively simple, the processing difficulty is small, and the process is simpler.

[0052] It should be noted that the trident-shaped cavity 21 increases the complexity of the cavity and introduces more resonance modes during the sound wave propagation process, which is beneficial to increasing the sound absorption effect.

[0053] It should be noted that the first cover layer 1, the structural layer 2 and the second cover layer 3 may be an integrally formed structure or a separately connected structure.

[0054] In some embodiments of the present invention, the length and diameter of the middle column cavity 211 are greater than the length and diameter of the side column cavity 212. With such an arrangement, the sound absorption effect of the structure is better.

[0055] In some embodiments of the present invention, the middle column cavity 211 is connected to the outside of the structural layer 2 and is blocked by the first cover layer 1 , and the columnar cavity 22 is connected to the outside of the structural layer 2 and is blocked by the second cover layer 3 .

[0056] In this embodiment, the basic unit 100 may be a split structure, and the middle column cavity 211 and the columnar cavity 22 are both connected to the outside of the structural layer 2, which is more conducive to process preparation.

[0057] In some embodiments of the present invention, the trident-shaped cavity 21 contains water, and the cylindrical cavity 22 contains air. The acoustic impedance of water and air is greatly different, so the attenuation effect of the sound wave is more obvious.

[0058] In some embodiments of the present invention, the material used to prepare the first cover layer 1 includes silicone rubber, and the material used to prepare the structure layer 2 includes a polymer damping material.

[0059] In this embodiment, the first cover layer 1 made of silicone rubber functions as impedance matching. The acoustic impedance of silicone rubber is close to that of water. The first cover layer 1 made of silicone rubber, as the first layer in contact with sound waves, can achieve partial impedance matching, reduce the reflection of sound waves when incident on the first cover layer 1, and make most of the sound waves enter the structural layer 2 to be absorbed and attenuated. The structural layer 2 is made of a polymer damping material, which has a good sound absorption effect itself, and has a better sound absorption effect in combination with its two cavity structures.

[0060] In this embodiment, the structural layer 2 may be filled with silicon material, and such a configuration may further enhance its damping performance.

[0061] In some embodiments of the present invention, the second cover layer 3 is made of resin. The resin material can more conveniently bond the basic unit 100 to the steel body of the ship's hull.

[0062] In some embodiments of the present invention, the first cover layer 1 has a thickness of 2 to 7 mm and a radius of 13 to 23 mm;

[0063] The thickness of the structural layer 2 is 45-55 mm, the thickness of the middle column cavity 211 is 35-45 mm, the diameter is 1.5-2.5 mm, the thickness of the side column cavity 212 is 20-30 mm, the diameter is 0.5-1.5 mm;

[0064] The thickness of the cylindrical cavity 22 is 3-7 mm and the radius is 10-15 mm;

[0065] The second cover layer 3 has a thickness of 2-7 mm and a radius of 13-23 mm.

[0066] In some embodiments of the present invention, a support tube 4 is sleeved on the outside of the structural layer 2 .

[0067] In some embodiments of the present invention, the support tube 4 is made of aluminum, and the wall thickness of the support tube 4 is 1.5-2.5 mm.

[0068] In this embodiment, the introduction of the aluminum support tube 4 can enhance the rigidity and stability of the structure, and may also affect the propagation path of the sound waves, working together with the two cavities in the structural layer 2 to further enhance the sound absorption effect.

[0069] The embodiment of the present invention further provides an underwater vehicle 200, comprising a shell and an underwater sound absorbing metamaterial covering the surface of the shell, wherein the underwater sound absorbing metamaterial is any of the above-mentioned underwater sound absorbing metamaterials.

[0070] In a specific implementation, the basic unit 100 can be regarded as an independent acoustic unit, and its internal structure and material composition can be customized and optimized as needed. At the same time, the arrangement and combination of the basic units 100 can also be flexibly adjusted to adapt to different application scenarios and needs.

[0071] In order to more clearly illustrate the effect of the underwater sound-absorbing metamaterial provided by the present application, the present application provides some specific embodiments.

[0072] like Figure 4 As shown, the total thickness of the structure of the basic unit 100 is 60 mm, and the height of the first cover layer 1 (Si Rubber) is 5mm, radius The thickness of the two side column cavities 212 is 17 mm. Both are 25mm in diameter The thickness of the middle column cavity 211 is 1 mm. 40mm, diameter 4mm (radius The axial length of the aluminum support tube 4 is 50mm, cylinder wall thickness The thickness of the cylindrical cavity 22 (Air) is 2 mm. 5mm, radius 12mm. Height of the second cover layer 3 (resin) 5mm, radius It is 17mm.

[0073] The parameters of the first cover layer 1 are: density 1100kg / m^3, Poisson's ratio 0.49, and the frequency-variable parameters are as follows:

[0074]

[0075] Where, Er: represents the Young's modulus of the material (usually in Pascals, Pa). It is the stiffness characteristic of the material under dynamic load and is frequency-dependent. ηr: describes the loss factor of the material. It is a dimensionless parameter that describes the energy dissipation ability of the material during dynamic load (such as vibration or sound wave propagation) and is frequency-dependent. Frequency f (unit: Hz) is the independent variable that characterizes the dynamic loading conditions of the sound wave.

[0076] In a specific implementation, the underwater sound-absorbing metamaterial of the present application is designed in a simulation environment, and the outer layer of the first cover layer 1 made of silicone rubber in the basic unit 100 is simulated and designed with a seawater layer 5, and the thickness of the seawater layer 5 is 40 mm. In addition, the open radiation condition is modeled using a perfect matching layer 6 (PML), which is used to absorb sound waves emitted from the edge of the calculation area, simulate the open radiation conditions of an infinite space, and reduce the impact of reflection on the simulation results. The thickness of the perfect matching layer 6 is 10 mm. It also includes a base layer 201 (Steel), which generally refers to a structural layer 2 made of steel. In a variety of application scenarios, such as underwater construction or structural acoustics research, the base layer 201 may serve as the basic structure of the sound-absorbing cover layer, and the thickness of the base layer 201 is 10 mm.

[0077] It should be noted that, in a specific implementation, the size of each structure in the basic unit 100 in the present application can be flexibly set according to actual needs.

[0078] refer to Figure 5 , which is the sound absorption coefficient curve produced by the underwater sound absorption metamaterial provided by the present invention.

[0079] In the embodiments of the present application, the acoustic performance of underwater sound-absorbing metamaterials under the condition of vertical incidence of sound waves under the condition of steel backing is analyzed by finite element method.

[0080] Figure 5 : is the sound absorption coefficient curve of the underwater sound absorbing metamaterial in the embodiment at 1Hz-10000Hz. It can be seen from the sound absorption coefficient curve that the sound absorption coefficient of the underwater sound absorbing metamaterial in the range of 863.167Hz-10000Hz is greater than 0.8, and the sound absorption coefficient in the range of 5000Hz-10000Hz is almost close to 1, which has excellent underwater sound absorption effect. At 1080Hz, the synergistic effect of global vibration, cavity plate resonance, viscous loss, and shear dissipation leads to the appearance of the first sound absorption peak.

[0081] Depend on Figure 5 As shown in Figure 6 (a), at the sound absorption peak of 1080 Hz, the synergistic effect of global vibration, cavity-plate resonance, viscous loss, and shear dissipation leads to the appearance of the first sound absorption peak. The maximum displacement appears on the elastic plate in the water cavity and the cavity. Since the density of water is heavier than that of air, the lateral vibration of the plate along the direction of the incident wave is more intense, and the first rubber layer also undergoes a large bending vibration. Figure 5 As can be seen from Figure 6(b), at the sound absorption valley of 1700Hz, the vibration is weakened as a whole, and the elastic plate undergoes reverse resonance, which leads to an enhanced reflection effect of the sound wave. Figure 5 As shown in Figure 6 (c), at a frequency of 5000 Hz, the vibration is no longer severe and the sound absorption coefficient tends to be stable.

[0082] Referring to Figures 7(a) to 7(c), it can be seen from Figure 7(a) that at a frequency of 1080 Hz, there is a maximum energy dissipation at the starting point and the end point of the water cavity. The flow of water causes the rubber to vibrate, and the sound energy is converted into vibration energy. It can be seen from Figure 7(b) that at a frequency of 1700 Hz, the overall power consumption density becomes smaller, and the anti-resonance of the elastic plate consumes more sound energy. It can be seen from Figure 7(c) that at a frequency of 5000 Hz, the vibration is no longer violent. At this time, the sound absorption mechanism mainly depends on the damping dissipation of the rubber and the wave mode conversion.

[0083] refer to Figure 8 , which is a schematic diagram of an underwater vehicle 200 provided in an embodiment of the present invention.

[0084] The underwater vehicle 200 provided by the present invention comprises a shell and a metamaterial composed of periodically arranged basic units 100 covering the surface of the shell, wherein the metamaterial is the underwater sound-absorbing metamaterial described above.

[0085] When sound waves encounter underwater sound-absorbing metamaterials, part of the sound waves will enter the material and propagate inside it. Due to the viscoelasticity and impedance matching characteristics of the material, the sound waves will gradually be dissipated and converted into other forms of energy (such as heat energy) during the propagation process. At the same time, the reflected sound waves on the surface of the material will also be reduced due to impedance matching. At a specific frequency, the resonant unit in the underwater sound-absorbing metamaterial will resonate and produce strong vibrations. This vibration will further promote the dissipation and conversion of sound energy. At the same time, the damping effect inside the material will also cause the vibration to gradually decay and convert into heat energy.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An underwater sound-absorbing metamaterial, characterized in that: The invention comprises a plurality of periodically arranged basic units (100), wherein the basic units (100) are cylindrical, and the basic units (100) sequentially comprise a first cover layer (1), a structural layer (2), and a second cover layer (3) along the axis thereof, wherein the structural layer (2) comprises a trident-shaped cavity (21) and a columnar cavity (22) distributed along the axis thereof, wherein the trident-shaped cavity (21) comprises a middle columnar cavity (211) and two side columnar cavities (212) symmetrically distributed with the axis of the middle columnar cavity (211) as a symmetry axis, wherein the middle columnar cavity (211) and the side columnar cavity (212) are flush at one end close to the columnar cavity (22) and are interconnected via a connecting column cavity (213), and different media are filled in the trident-shaped cavity (21) and the columnar cavity (22); The middle column cavity (211) is in communication with the outside of the structural layer (2) and is blocked by the first cover layer (1); the columnar cavity (22) is in communication with the outside of the structural layer (2) and is blocked by the second cover layer (3); The structural layer (2) is externally sleeved with a support tube (4).

2. The underwater sound absorbing metamaterial according to claim 1, characterized in that: The length and diameter of the middle column cavity (211) are both greater than the length and diameter of the side column cavity (212).

3. The underwater sound absorbing metamaterial according to claim 1, characterized in that: The trident-shaped cavity (21) contains water, and the columnar cavity (22) contains air.

4. The underwater sound absorbing metamaterial according to claim 1, characterized in that: The material used to prepare the first cover layer (1) includes silicone rubber, and the material used to prepare the structural layer (2) includes a polymer damping material.

5. The underwater sound absorbing metamaterial according to claim 1, characterized in that: The material used to prepare the second cover layer (3) includes resin.

6. The underwater sound absorbing metamaterial according to claim 1, characterized in that: The first cover layer (1) has a thickness of 2-7 mm and a radius of 13-23 mm; The thickness of the structural layer (2) is 45-55 mm, the thickness of the middle column cavity (211) is 35-45 mm, and the diameter is 1.5-2.5 mm, and the thickness of the side column cavity (212) is 20-30 mm, and the diameter is 0.5-1.5 mm; The cylindrical cavity (22) has a thickness of 3 to 7 mm and a radius of 10 to 15 mm; The second cover layer (3) has a thickness of 2 to 7 mm and a radius of 13 to 23 mm.

7. The underwater sound absorbing metamaterial according to claim 1, characterized in that: The support tube (4) is made of a material comprising aluminum, and the wall thickness of the support tube (4) is 1.5 to 2.5 mm.

8. An underwater vehicle, characterized in that: It comprises a shell and an underwater sound absorbing metamaterial covering the surface of the shell, wherein the underwater sound absorbing metamaterial is the underwater sound absorbing metamaterial according to any one of claims 1 to 7.

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