Reconfigurable torsional Mohr acoustic metasurface

Abstract

The invention belongs to the field of acoustic metasurfaces, and particularly relates to a reconfigurable torsional Moore acoustic metasurface which is formed by superposing two layers of same metasurface structures, the two layers of metasurface structures can be relatively twisted to set an angle, each metasurface structure is formed by stacking a plurality of unit cell structures, each unit cell structure comprises a central pipeline and a communicating cavity, and the central pipeline is communicated with the communicating cavity. Communicating pipelines are symmetrically arranged in the middle of the central pipeline, communicating cavities are formed in the ends of the communicating pipelines, and the communicating cavities of the multiple unit cell structures are buckled with one another to form a metasurface structure; the central pipeline is formed by combining two pipelines made of different materials, the central pipeline comprises an external pipeline and an internal pipeline, the internal pipeline is attached to the inner wall of the external pipeline, the external pipeline and the internal hollow pipeline are made of different materials, and the acoustic impedance difference of air in the central pipeline is effectively increased through the design; the low-frequency-band and high-frequency-band sound waves can be affected by extreme anisotropy, and directional low-loss propagation of the sound waves can be achieved in a wider frequency range.

Description

Technical Field

[0001] The present invention belongs to the field of acoustic metasurfaces, and particularly relates to a reconfigurable torsional Moore acoustic metasurface. Background Art

[0002] As a new type of artificial structural material, acoustic metasurfaces can precisely control the propagation characteristics of sound waves by designing unit structures at the sub-wavelength scale. Compared with traditional acoustic materials, acoustic metasurfaces can efficiently control the propagation direction, frequency, polarization state, and other wave characteristics of sound waves. With the in-depth research of acoustic metasurfaces, their applications in the fields of sound wave manipulation, super-resolution imaging, acoustic isolation, noise control, acoustic filters, and non-reciprocal acoustic devices have gradually emerged and shown great potential.

[0003] In acoustic metasurfaces, traditional designs mostly use single-material structures. Although they can achieve sound wave control at specific frequencies, they often have high scattering losses in a relatively wide frequency range and it is difficult to ensure low-loss directional propagation. The low-loss directional propagation of sound waves guided by metasurfaces in a relatively wide frequency range is of great significance for applications in underwater acoustic communication and detection, non-destructive testing and structural health monitoring, and sound energy transmission and acoustic wireless power supply. Therefore, how to design a reconfigurable Moore acoustic metasurface that can achieve low-loss sound wave directional propagation in a wider frequency range is an important research direction in the current field of acoustic metamaterials. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention proposes a reconfigurable torsional Moore acoustic metasurface for realizing the directional low-loss channelized propagation of sound waves in a relatively wide frequency range.

[0005] A reconfigurable torsional Moore acoustic metasurface is composed of two identical metasurface structures stacked on top of each other, where the two metasurface structures can be relatively twisted by a set angle. Each metasurface structure is composed of a plurality of unit cell structures stacked together. The unit cell structure includes a central pipe and a communicating cavity. A communicating pipe is symmetrically arranged in the middle of the central pipe, and a communicating cavity is arranged at the end of the communicating pipe. The communicating cavities of a plurality of unit cell structures are buckled with each other to form the metasurface structure; the central pipe is composed of a combination of pipes made of two different materials.

[0006] The central pipe includes an outer pipe and an inner pipe, and the inner pipe is attached to the inner wall of the outer pipe, and the materials of the outer pipe and the inner hollow pipe are different.

[0007] The materials of the outer pipe and the inner pipe are any resin materials with an elastic modulus in the range of 1 GPa to 5 GPa.

[0008] The connected cavity includes a central cavity and cavity pipes. The central cavity is connected to the connecting pipe, and cavity pipes are communicated on two symmetrical end faces of the central cavity. The cavity pipes are of a semi-circular structure.

[0009] A reconfigurable torsional Moore acoustic metasurface further includes a sound source, which is arranged at a distance of 8.5 - 10 mm from the first-layer metasurface structure and is located at the center of the unit cell structure at the exact center of the metasurface.

[0010] The torsional angle between the two layers of metasurfaces is 0 - 44°.

[0011] The sound source is a point sound source or a surface sound source.

[0012] The beneficial effects of the present invention are as follows:

[0013] 1. Compared with the traditional single-material metasurface, in the present application, an internal hollow pipe is attached to the inner wall of the outer pipe of the central pipe of the present invention. At the same time, the materials of the outer pipe and the internal hollow pipe are different. This design effectively increases the acoustic impedance difference of the air inside the central pipe. A greater acoustic impedance difference means stronger anisotropy, enabling sound waves in the low-frequency band and high-frequency band to also be affected by extreme anisotropy and undergo the same resonance in this system, capable of achieving directional low-loss propagation of sound waves within a wider frequency range and optimizing the local propagation characteristics of sound waves. Therefore, by changing the materials inside the structure, the structure can be adjusted according to the need to broaden the magic angle frequency range, thereby achieving a reconfigurable effect.

[0014] 2. The metasurface of the present application not only provides flexible reconfigurability, can be dynamically adjusted under different working frequencies and application scenarios, but also can optimize the impedance matching of sound waves and improve the overall propagation effect. This technology provides a more efficient solution for fields such as acoustic communication, noise control, and ultrasonic sensing. Description of the Drawings

[0015] Figure 1 It is a schematic diagram of a reconfigurable torsional Moore acoustic metasurface of the present invention;

[0016] Figure 2 It is a three-dimensional view of a unit cell of a reconfigurable torsional Moore acoustic metasurface of the present invention;

[0017] Figure 3 It is a top view of a unit cell of a reconfigurable torsional Moore acoustic metasurface of the present invention;

[0018] Figure 4 It is a time-domain characteristic diagram of the transmission rate of the traditional metasurface structure generating the magic angle under the excitation of a sound source;

[0019] Figure 5It is the time-domain characteristic diagram of the transmission rate of the twisted Moiré acoustic metasurface of the present invention when excited by a sound source to generate a magic angle;

[0020] Figure 6 It is the sound pressure distribution diagram generated by the twisted Moiré acoustic metasurface of the present invention when excited by a sound source;

[0021] Explanation of reference numerals:

[0022] 1. Central pipeline; 101. Inner pipeline; 102. Outer pipeline; 2. Connecting pipeline; 3. Connecting cavity; 301. Central cavity; 302. Cavity pipeline. Detailed implementation manners

[0023] The following will make a detailed description of the specific implementation manners of the present invention with reference to the accompanying drawings.

[0024] As Figures 1 to 3 shown, a reconfigurable twisted Moiré acoustic metasurface is formed by stacking two identical metasurface structures, and the two metasurface structures can be twisted relative to each other by a set angle. Each metasurface structure is stacked by a plurality of unit cell structures. The unit cell structure includes a central pipeline 1 and a connecting cavity 3. A connecting pipeline 2 is symmetrically arranged in the middle of the central pipeline 1. A connecting cavity 3 is arranged at the end of the connecting pipeline 2. The connecting cavities 3 of multiple unit cell structures are buckled with each other to form a metasurface structure; the central pipeline 1 is composed of pipelines of two different materials; the central pipeline 1 includes an outer pipeline 102 and an inner pipeline 101. The inner pipeline 101 is attached to the inner wall of the outer pipeline 102. The inner pipeline 101 is a hollow structure, and the materials of the outer pipeline 102 and the inner pipeline 101 are different; the outer pipeline 102 and the inner pipeline 101 are cylindrical structures, and the materials of the outer pipeline 102 and the inner pipeline 101 are any resin materials with an elastic modulus in the range of 1 to 5 GPa.

[0025] Among them, the central pipeline 1, the connecting pipeline 2 and the connecting cavity 3 are all connected to allow the propagation of sound waves; the outer pipeline 102 of the central pipeline 1 constitutes the outer frame of the unit cell structure to provide structural stability, and the inner pipeline 101 is attached to the inner wall of the outer pipeline 102 to optimize the frequency range of the directional propagation of sound waves.

[0026] The metasurface structure of the present application is square, the number of arrays of the metasurface structure is greater than 15*15, the unit cell structure is composed of a central pipeline 1, a connecting pipeline 2 and a connecting cavity 3, and at the same time the central pipeline 1 is composed of pipelines of two different materials, which changes the local impedance matching characteristics of sound waves and realizes that the metasurface can form a low-loss directional sound wave propagation path in a wider frequency range.

[0027] The connected cavity 3 includes a central cavity 301 and cavity pipes 302. The central cavity 301 is connected to the connecting pipe 2. Cavity pipes 302 are connected to two symmetrical end faces of the central cavity 301. The cavity pipes 302 are of semi-circular structure. Through the design of the connected cavity 3, the propagation of sound waves in multiple directions can be achieved. The central cavity 301 can achieve the propagation of sound waves in the left and right directions, and the cavity pipes 302 can achieve the propagation of sound waves in the up and down directions.

[0028] The wall thickness of the inner pipe 101 of the unit cell structure is 1 mm or 2 mm.

[0029] A reconfigurable twisted Moiré acoustic metasurface further includes a sound source, which is arranged 8.5 - 10 mm away from the first-layer metasurface structure and at the center of the unit cell structure located at the exact center of the metasurface. The sound source is a point sound source or a plane sound source.

[0030] The relative twist angle between the two layers of metasurfaces is 0 - 44°.

[0031] The present invention provides a reconfigurable twisted Moiré acoustic metasurface, which realizes the directional low-loss channelized propagation of sound waves through the superposition of two identical metasurface layers and the adjustment of the relative twist angle. The unit cell structure of each metasurface includes a central pipe 1, a connecting pipe 2, and a connected cavity 3. The central pipe 1 is doped with two different materials. The first material is used to construct the external structure of the unit cell, and the second material is designed in the inner pipe of the unit cell. Compared with the traditional single-material structure, the design of doping different materials can effectively optimize the transmission characteristics of sound waves, especially reducing the scattering loss in sound wave propagation in a wider frequency range. By adjusting the structures of the unit cells of the two layers of metasurfaces, the present invention enhances the adaptability and reconfigurability of the metasurface. The metasurface can be widely applied in the fields of acoustic communication, ultrasonic sensing, noise control, etc.

[0032] Embodiment 1

[0033] A reconfigurable twisted Moiré acoustic metasurface is formed by superposing two identical metasurface structures. The relative twist angle between the two identical metasurface structures is 23°. Each layer of metasurface structure consists of a 15*15 array of unit cell structures. The unit cell structure includes a central pipe 1, a connecting pipe 2, and a connected cavity 3. The length of the central pipe 1 is 80 mm. The central pipe 1 includes an outer pipe 102 and an inner pipe 101. The wall thickness of the outer pipe 102 is 1 mm, and the wall thickness of the inner pipe 101 is 2 mm. The inner diameter of the inner pipe 101 is 12 mm. The length of the connecting pipe 2 is 20 mm, and the diameter is 3 mm. The connected cavity 3 includes a central cavity 301 and cavity pipes 302. The length of the central cavity 301 is 15 mm, the width is 13 mm, the cavity thickness is 5 mm, and the length of the cavity pipes 302 is 6.5 mm, and the diameter is 3.5 mm.

[0034] The material of the external pipe 102 is R4600 resin, and the material of the internal pipe 101 is R5200 resin. The manufacturing process of this embodiment adopts additive manufacturing (3D printing) technology, which can quickly prepare metasurface units with complex internal structures.

[0035] A sound source is placed at a distance of 8.5 mm from the center of the unit cell structure of the first-layer metasurface structure. By analyzing the time-domain characteristic diagram of the transmission rate of the magic angle, it can be obtained that, as Figure 4 、 5 shown, for the time-domain characteristic diagrams of the transmission rate when the traditional metasurface structure and the metasurface of this application generate the magic angle under the excitation of sound sources with different frequencies, the frequency range of the sound waves that can be propagated by the metasurface structure of this application is between 2620 Hz and 2670 Hz, and the frequency range of the sound waves propagated by the traditional metasurface structure is between 2640 Hz and 2650 Hz. The metasurface structure of this application realizes low-loss propagation of sound waves in a wide frequency range.

[0036] Figure 6 This is the sound pressure distribution diagram of the metasurface structure of this application at an excitation frequency of 2670 Hz and when the thicknesses of both materials are 1 mm. Through Figure 6 it can be seen that the sound waves with a frequency of 2670 Hz are constrained on a straight line, achieving the effect of low-loss channelized propagation of sound waves, and it can be applied to fields such as acoustic communication, noise control, and ultrasonic sensing.

[0037] The specific implementation manners and embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above implementation manners and embodiments. Within the scope of knowledge possessed by those skilled in the art, corresponding changes can also be made without departing from the concept of the present invention.

Claims

1. A reconfigurable torsional moiré acoustic metasurface, characterized in that: It is composed of two layers of identical supersurface structures stacked together, wherein the two layers of supersurface structures can be twisted relative to each other at a set angle, and each supersurface structure is composed of multiple unit cell structures stacked together, and the unit cell structure includes a central pipe and a connecting cavity, and connecting pipes are symmetrically arranged in the middle of the central pipe, and connecting cavities are arranged at the ends of the connecting pipes, and the connecting cavities of multiple unit cell structures are interlocked to form a supersurface structure; the central pipe is composed of a combination of pipes made of two different materials.

2. A reconfigurable torsional moiré acoustic metasurface according to claim 1, characterized in that: The central pipe comprises an outer pipe and an inner pipe. The inner pipe is attached to the inner wall of the outer pipe. The outer pipe and the inner hollow pipe are made of different materials.

3. A reconfigurable torsional moiré acoustic metasurface according to claim 2, characterized in that: The material of the outer pipe and the inner pipe is any resin material with an elastic modulus in the range of 1 GPa to 5 GPa.

4. The reconfigurable torsional moiré acoustic metasurface according to claim 1, characterized in that: The connecting cavity comprises a central cavity, a connecting pipe and a cavity pipe. The central cavity is connected to the connecting pipe. Two symmetrical end faces of the central cavity are connected with the cavity pipe. The cavity pipe is a semicircular structure.

5. The reconfigurable torsional moiré acoustic metasurface according to claim 1, characterized in that: It also includes a sound source, which is set at a distance of 8.5 to 10 mm from the first layer of the metasurface structure and located at the center of the unit cell structure at the center of the metasurface.

6. The reconfigurable torsional moiré acoustic metasurface according to claim 1, characterized in that: The twisting angle between the two super surfaces is 0 to 44 degrees.

7. The reconfigurable torsional moiré acoustic metasurface according to claim 5, characterized in that: The sound source is a point sound source or a surface sound source.

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