A metasurface model that enables asymmetric propagation of sound waves

Abstract

A metasurface model that can realize asymmetric propagation of sound waves belongs to the field of acoustic metasurface technology, and solves the shortcomings of the existing structure principle being complex, difficult to manufacture, and large volume. The model includes: a plurality of uniform dielectric units and a partition; the uniform dielectric units have the same structure, and the cross-section of the uniform dielectric unit is the same as that of the partition; every two uniform media are separated by a partition, and every three uniform dielectric units with different impedances are arranged periodically on the horizontal plane, and every three uniform dielectric units with different impedances form a group, and the impedances are arranged in order from small to large; the metasurface model includes multiple groups of uniform dielectric unit columns. The present invention designs a metasurface by changing the sound velocity of the uniform dielectric unit, and has a simple structure; it realizes asymmetric propagation of sound waves within a wider period width range; it can conduct forward when the sound wave is transmitted in the forward direction, and it is reversely suppressed and cannot conduct when the sound wave is transmitted in the reverse direction.

Description

Technical Field

[0001] The present invention belongs to the technical field of acoustic metasurfaces, and in particular relates to a metasurface model capable of realizing asymmetric propagation of sound waves. Background Art

[0002] Acoustic metasurface is a two-dimensional planar structure composed of subwavelength-sized structural units arranged on a plane. The phenomenon of asymmetric propagation of sound waves refers to the phenomenon that sound waves can be transmitted along a specific direction, but cannot be transmitted when the direction of the sound waves changes, or the phenomenon that the sound waves are not transmitted equally in two directions. It essentially changes the concept of reciprocal propagation of energy in the medium, and has the characteristics of concealment, high security and uniqueness. Among the traditional methods for realizing acoustic asymmetric transmission, on the one hand, nonlinear mechanisms can be used to break the time reversal symmetry, but this method has the disadvantages of low nonlinear conversion efficiency and complex experimental implementation; on the other hand, asymmetric geometric structures can also be used to destroy spatial inversion symmetry, but this method has problems such as complex device manufacturing and large volume, which hinder the further practical application of acoustic asymmetric transmission. In recent years, the emergence of acoustic metasurfaces has provided an effective new way to realize acoustic asymmetric transmission.

[0003] At present, the more common asymmetric transmission structures include: (1) the acoustic diode model composed of phononic crystals and nonlinear acoustic media. This structure breaks through the constraints of the reciprocity principle in the acoustic field by introducing nonlinear destruction of the time reversal symmetry of the system, and relies on the bandgap characteristics of the phononic crystal to produce an asymmetric frequency selection mechanism, achieving unidirectional conduction and reverse cutoff. (2) Asymmetric propagation of Lamb waves using mode conversion and mode selection. This method uses a periodic Lamb wave type phononic crystal structure. Based on the decoupling characteristics of the symmetric mode and the antisymmetric mode in the symmetric structure unit, the symmetric mode or the antisymmetric mode can pass. In the antisymmetric structure unit, the situation is just the opposite. The strong coupling between the two modes can transform the two modes into each other, and finally produce the characteristics of unidirectional propagation of sound waves. (3) A unidirectional acoustic waveguide model based on phononic crystals. (4) A square acoustic wave rectifier structure composed of two phononic crystals. This structure mainly uses two phononic crystals with different grid constants and cylindrical radii, arranges them into a triangular structure and then combines them into a square phononic crystal. When the sound wave is incident vertically from the side with the smaller grid constant and cylindrical radius, most of the sound waves can pass through, while the sound waves incident in the opposite direction can hardly pass through.

[0004] At present, relevant research on the realization of asymmetric transmission of sound waves has achieved certain results. However, the existing structure still has disadvantages such as complex principles, difficulty in production, and large size. In addition, since its inception, the asymmetric transmission model of sound waves has been mostly used in the air, and there is a lack of research on water as the background medium. Therefore, it is extremely necessary to make a relatively light and simple asymmetric sound wave model for underwater asymmetric sound wave propagation. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a metasurface model that can realize asymmetric propagation of sound waves, which solves the shortcomings of the prior art such as complex structural principles, great difficulty in manufacturing, and large size.

[0006] The technical solution adopted by the present invention to solve the technical problem is as follows:

[0007] A metasurface model capable of realizing asymmetric propagation of sound waves, the model comprising: a plurality of uniform dielectric units and a partition; the uniform dielectric units have the same structure, and the cross-sections of the uniform dielectric units and the partition are the same; every two uniform media are separated by a partition, and every three uniform dielectric units with different impedances are arranged periodically on a horizontal plane, and every three uniform dielectric units with different impedances form a group, and the impedances are arranged in order from small to large; the metasurface model comprises a plurality of groups of uniform dielectric unit columns.

[0008] Preferably, each group of uniform dielectric units includes a first uniform dielectric unit, a second uniform dielectric unit and a third uniform dielectric unit; the first uniform dielectric unit, the second uniform dielectric unit and the third uniform dielectric unit are arranged in sequence from left to right; the impedance of the first uniform dielectric unit is Z1=1.5×10 6 Pa·s / m, the impedance of the second uniform dielectric unit is Z2=1.56×10 6 Pa·s / m, the impedance of the third uniform dielectric unit is Z3=1.55×10 6 Pa·s / m.

[0009] Preferably, the widths of the first uniform dielectric unit, the second uniform dielectric unit and the third uniform dielectric unit are w, the range of w is 0.07 m to 0.2 m, and the dielectric heights h are all 0.15 m.

[0010] Preferably, the width of the partition is p, the range of p is 0.005m to 0.025m, and the height h1 is 0.15m.

[0011] Preferably, the partition material is steel, and the impedance of steel is 46.8×10 6 Pa·s / m.

[0012] Preferably, the cross-sectional areas of the partition, the first uniform dielectric unit, the second uniform dielectric unit and the third uniform dielectric unit are rectangular.

[0013] Preferably, the metasurface model includes at least two groups of uniform medium units.

[0014] Preferably, the partition is bonded to each uniform medium unit.

[0015] The beneficial effects of the present invention are:

[0016] 1. This device designs the metasurface by changing the sound velocity of a uniform medium unit, and has a simple structure.

[0017] 2. This device can realize asymmetric propagation of sound waves within a wider range of period width.

[0018] 3. This device can conduct forward when the sound wave is transmitted in the forward direction, but when the sound wave is transmitted in the reverse direction, the sound wave is reversely suppressed and cannot conduct. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of a supersurface model capable of realizing asymmetric propagation of sound waves according to the present invention.

[0020] Figure 2 A schematic diagram of the structure of a supersurface model capable of realizing asymmetric propagation of sound waves according to the present invention.

[0021] Figure 3 A geometrical schematic diagram of a supersurface model capable of realizing asymmetric propagation of sound waves according to the present invention.

[0022] Figure 4 is the total sound pressure field of forward transmission in Example 1.

[0023] Figure 5 This is the simulation result of the refraction direction corresponding to the forward transmission in Example 1.

[0024] Figure 6 is the total sound pressure field of reverse transmission in Example 1. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0026] See also Figure 1-3 As shown, a metasurface capable of realizing asymmetric propagation of sound waves invented in this article comprises a plurality of first uniform dielectric units 1, a plurality of second uniform dielectric units 2, a plurality of third uniform dielectric units 3 and a plurality of partitions 4. The first uniform dielectric units 1, the second uniform dielectric units 2 and the third uniform dielectric units 3 are arranged periodically and horizontally, and each two media are separated by a partition 4.

[0027] The first uniform dielectric unit 1, the second uniform dielectric unit 2 and the third uniform dielectric unit 3 have the same size, the dielectric width is w, the range of w is 0.07m to 0.2m, the dielectric height h is 0.15m, and the impedance of the first uniform dielectric unit 1 is Z1=1.5×10 6 Pa·s / m, the impedance of the second uniform dielectric unit 2 is Z2=1.56×10 6 Pa·s / m, the impedance of the third uniform dielectric unit 3 is Z3=1.55×10 6 Pa·s / m. The width of the partition 4 is p, the range of p is 0.005m to 0.025m, the height h1 is 0.15m, and the partition material is steel, the impedance of steel is 46.8×10 6 Pa·s / m.

[0028] The first uniform medium unit 1 to the third uniform medium 3 and the partition 4 are bonded by an adhesive to form a period, and the period width d is 3(w+p). Each periodic structure is bonded to each other by an adhesive to form an acoustic metasurface, and the acoustic metasurface structure contains at least 2 periods.

[0029] The cross-sectional shapes of all the uniform dielectric units and the partitions 4 are rectangular.

[0030] The present invention has a critical angle θ i ≤|arc sin(λ / d-1)| obeys Snell's law; when θ i >|arcsin(λ / d-1)|, the generalized Snell's law is obeyed. The generalized Snell's law can be used to theoretically calculate the angle of refracted sound waves generated by the metasurface in the forward direction. The theoretical calculation formula for the refraction angle under any angle of incidence is θ t =arcsin(sinθ i +λ / d), λ / d is the ratio of the wavelength of the sound wave to the period width, θ i is the angle of incidence.

[0031] Embodiment 1:

[0032] When the sound wave frequency f = 10000 Hz, the background medium is water, the sound wave is incident on the acoustic metasurface in the forward horizontal direction, and the sound wave is incident on the acoustic metasurface at a 30° angle in the reverse direction. When the metasurface structural parameters are w = 0.0425m, p = 0.0045m, and d = 0.141m, the simulation calculation is performed using COMSOL Multiphysics software. Figure 4 As a result of the total sound pressure field transmitted in the forward direction, the left boundary of the acoustic metasurface is located at x=h, the sound wave is incident on the acoustic metasurface from the left boundary and exits from the right boundary x=0. Figure 5 is the simulation result of the refraction direction corresponding to the forward transmission, Figure 6is the result of the total acoustic pressure field transmitted in the reverse direction. The left boundary of the acoustic metasurface is located at x = h. The sound wave is incident on the acoustic metasurface from the right boundary x = 0 and exits from the left boundary at x = h. Figure 4 As shown in the figure, it can be seen that for a plane wave incident horizontally in the forward direction, the sound wave emerges horizontally. Figure 6 As shown in FIG. 1 , when the sound wave is incident at 30° in the opposite direction to the plane wave, the sound wave is suppressed and no sound wave passes through. Therefore, the metasurface model can realize asymmetric propagation of sound waves through a simple structure.

Claims

1. A metasurface model capable of realizing asymmetric propagation of sound waves, characterized in that: The model includes: a plurality of uniform dielectric units and a partition; the uniform dielectric units have the same structure, and the cross-section of the uniform dielectric unit is the same as that of the partition; every two uniform dielectrics are separated by a partition, and every three uniform dielectric units with different impedances are arranged periodically on a horizontal plane, and every three uniform dielectric units with different impedances form a group; the metasurface model includes a plurality of groups of uniform dielectric units, and each group of uniform dielectric units includes a first uniform dielectric unit, a second uniform dielectric unit and a third uniform dielectric unit; the first uniform dielectric unit, the second uniform dielectric unit and the third uniform dielectric unit are arranged in sequence from left to right; the impedance of the first uniform dielectric unit is Z1=1.5×10 6 Pa·s / m, the impedance of the second uniform dielectric unit is Z2=1.56×10 6 Pa·s / m, the impedance of the third uniform dielectric unit is Z3=1.55×10 6 Pa·s / m.

2. A supersurface model capable of realizing asymmetric propagation of sound waves according to claim 1, characterized in that: The widths of the first uniform dielectric unit, the second uniform dielectric unit and the third uniform dielectric unit are w, the range of w is 0.07 m to 0.2 m, and the dielectric heights h are all 0.15 m.

3. The metasurface model capable of realizing asymmetric propagation of sound waves according to claim 1, characterized in that: The partition has a width of p ranging from 0.005 m to 0.025 m, and a height h1 of 0.15 m.

4. The metasurface model capable of realizing asymmetric propagation of sound waves according to claim 1, characterized in that: The partition material is steel, and the impedance of steel is 46.8×10 6 Pa·s / m.

5. The metasurface model capable of realizing asymmetric propagation of sound waves according to claim 1, characterized in that: The cross-sectional areas of the partition, the first uniform dielectric unit, the second uniform dielectric unit and the third uniform dielectric unit are rectangular.

6. The metasurface model capable of realizing asymmetric propagation of sound waves according to claim 1, characterized in that: The supersurface model includes at least two groups of uniform medium units.

7. The metasurface model capable of realizing asymmetric propagation of sound waves according to claim 1, characterized in that: The partition is glued to each uniform medium unit.

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