CN108443631A - A kind of asymmetric acoustic propagation triangle superstructure - Google Patents

Abstract

The invention discloses a kind of asymmetric acoustic propagation triangle superstructures, the regular triangular prism 1 biased including one, 21 equilateral triangle resonant cavities (2 22) are arranged in 1 periphery of regular triangular prism, one equilateral triangle cavity 23 surrounds 21 equilateral triangle resonant cavities (2 22), and three sides of equilateral triangle cavity 23 are connected to rectangular waveguide 24,25 and 26 respectively.It is six identical right angled triangle helmholtz resonance chambers (27 32) inside each equilateral triangle resonant cavity.The asymmetric acoustic propagation triangle superstructure of the present invention, when regular triangular prism biases, which can make original tape gap be divided into two new band gap, and generate a new passband therebetween.Asymmetric acoustic propagation triangle superstructure modal distribution shows that two rectangular waveguides of regular triangular prism biased direction interconnect.Asymmetric acoustic propagation triangle superstructure can change direction and the transmission efficiency of acoustic propagation by adjusting the biasing of center regular triangular prism.

Description

A Triangular Superstructure for Asymmetric Acoustic Propagation

technical field

The invention relates to acoustic Helmholtz resonance, sound propagation control technology, sound scattering block offset structure and acoustic superstructure, in particular to an asymmetrical sound propagation triangular superstructure.

Background technique

Acoustic wave control in pipeline systems is an important challenge in pipeline acoustics. The pipeline itself does not generate noise, but the noise generated by the connected fans, blowers, compressors, water pumps, oil pumps and steam turbines is transmitted through the medium in the pipeline and the pipeline itself. In addition, the fluid in the pipeline produces flow noise due to turbulent flow, and the flow noise will increase with the increase of the flow velocity. Controlling the sound wave of the pipeline can effectively block the transmission of noise and reduce the impact of pipeline noise on the surrounding environment. In addition, the control of the transmission path of the pipeline noise makes the sound wave propagate according to the preset path and reach the predetermined area, which can greatly expand the existing sound propagation control technology. At present, the sound wave of the pipeline can be effectively transmitted along any path by rotating the air, but its stability and inherent noise seriously affect the robustness and reliability of its sound wave control, making it difficult to realize its engineering application.

Contents of the invention

The technical problem to be solved by the present invention is to provide an asymmetric sound propagation triangular superstructure, which can control the sound propagation in the pipeline and realize the directional and fixed-point propagation of the sound.

In order to solve the above technical problems, the present invention provides an asymmetric sound propagation triangular superstructure. Asymmetrical sound propagation triangular superstructure: including an offset regular triangular prism, 21 regular triangular resonant cavities, and a regular triangular cavity with three rectangular waveguides connected to each of its three sides. Each equilateral triangular resonator consists of six identical right-angled triangular Helmholtz resonators. The thin tube of the Helmholtz resonance cavity communicates with the equilateral triangular cavity.

As an improvement of the asymmetric sound propagation triangular superstructure of the present invention: the asymmetric sound propagation triangular superstructure adopts a regular triangular cavity.

As a further improvement of the asymmetric sound propagation triangular superstructure of the present invention: the three sides of the equilateral triangular cavity are respectively connected with a rectangular waveguide.

As a further improvement of the asymmetric sound propagation triangular superstructure of the present invention: there is an offset regular triangular prism inside the regular triangular cavity.

As a further improvement of the asymmetric sound propagation triangular superstructure of the present invention: the periphery of the offset regular triangular prism is twenty-one regular triangular resonant cavities.

As a further improvement of the asymmetric sound propagation triangular superstructure of the present invention: the regular triangular resonant cavity is composed of six identical right-angled triangular Helmholtz resonant cavities.

Compared with the background technology, the present invention has beneficial effects as follows:

The asymmetrical sound propagation triangular superstructure can be processed by materials with high rigidity (such as steel and aluminum alloy, etc.), and the production cost is relatively low. The asymmetric acoustic propagating triangular superstructure of the present invention enables sound waves to squeeze space through the offset of the regular triangular prism in the regular triangular acoustic cavity. The asymmetric acoustic propagating triangular superstructure of the present invention enables acoustic waves to propagate between two rectangular waveguides in the offset direction of the regular triangular prism. The asymmetric sound propagation triangular superstructure of the present invention can be assembled into a two-dimensional sound propagation network, and by adjusting the offset direction of the regular triangular prism inside the asymmetric sound propagation triangular superstructure, the sound propagation direction can be controlled to realize sound propagation along any path.

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Description of drawings

Fig. 1 is a kind of asymmetric sound propagation triangular superstructure of the present invention;

Fig. 2 is a kind of asymmetrical acoustic propagating triangular superstructure Bravais square lattice of the present invention and the positive grid and inverted lattice figure;

Fig. 3 is the energy band structure of a kind of asymmetric sound propagation triangular superstructure of the present invention;

Fig. 4 is the sound pressure modal diagram of a kind of asymmetric sound propagation triangular superstructure of the present invention;

Fig. 5 is a transfer function and sound pressure field distribution diagram of an asymmetric sound propagation triangular superstructure of the present invention.

Fig. 6 is a two-dimensional sound propagation network assembled by the asymmetric sound propagation triangular superstructure of the present invention, and one of the sound propagation paths is marked.

Detailed ways

Figure 1 shows an asymmetric acoustic propagation triangular superstructure. The asymmetric sound propagation triangular superstructure is a regular triangle. 1 is an offset regular triangular prism. Twenty-one equilateral triangular resonant cavities (2-22) are arranged on the periphery of the cylinder. The outside of the twenty-one equilateral triangular resonance cavities (2-22) is an equilateral triangular cavity 23. The three sides of an equilateral triangle cavity 23 are respectively connected with rectangular waveguides 24 , 25 and 26 . Each equilateral triangle resonator contains six identical right triangle Helmholtz resonators (27-32).

The working principle of the fractal sound-absorbing superstructure of the present invention is as follows:

(1) The geometric parameters of the asymmetric sound propagation triangular superstructure are L ₁ =43.301mm, L ₂ =214.77mm, L ₃ =77.942mm, X=43.301mm, a=34.641mm, b=1mm, c=1mm , t=1mm.

(2) As shown in Fig. 2, two asymmetric acoustic propagation triangular superstructures are taken as a unit cell, and the unit cell is placed in a Bravais hexagonal lattice with a lattice constant of 664.77 mm. The basis of the Bravais hexagonal lattice is e=(e ₁ , e ₂ ). Any other primitive cell can be defined as a set of integer pairs (n ₁ ,n ₂ ). When n ₁ =0 and n ₂ =0, it represents the initial primitive cell. Any other primitive cell can be obtained by translating n ₁ steps along e ₁ direction and n ₂ steps along e ₂ direction.

The response of the lattice point r in the initial primitive cell can be expressed as u(r). Since the Bravais hexagonal lattice is periodic, the sound pressure of the primitive cell (n ₁ ,n ₂ ) is also periodic:

u(r)=u(r+R _n ) (1)

Wherein R _n =n ₁ e ₁ +n ₂ e ₂ is positive lattice loss.

The Fourier series form of the periodic function u(r) can be expressed as:

Substitute formula (2) into formula (1) to get:

G _j R _n =2πk (3)

where G _j is the reciprocal lattice loss, and its base loss can be expressed as

(3) Calculate the band structure diagram of the structure by using the finite element method. The elastic wave equation with linear elasticity, anisotropy and inhomogeneous media can be expressed as:

Where r=(x, y, z) represents the position loss; u=(u _x , u _y , u _z ) represents the displacement vector; Represents the gradient operator; C(r) represents the elasticity tensor; ρ(r) represents the density tensor.

When the elastic wave is a simple harmonic, the displacement vector u(r,t) can be expressed as:

u(r,t)=u(r)e ^iωt (5)

in ω represents the angular frequency. Substituting formula (5) into formula (4), the elastic wave equation can be simplified as:

▽[C(r):▽·u(r,t)]+ω ² ρ(r)u(r)＝0 (6)

Since there are only longitudinal waves in the fluid, the simple harmonic acoustic wave equation of the fluid can be expressed as:

Where c _l (r) is the wave speed of longitudinal wave; p (r) is the flow field pressure.

The fluid-solid coupling interface needs to meet the normal particle acceleration and normal pressure continuity conditions:

where n _f and n _s represent the normal vectors of the fluid and solid on the fluid-solid coupling surface; v represents the particle vibration velocity; p _f represents the flow field pressure; σ _ij represents the stress component of the solid.

In space, the Bravais lattice is infinitely periodic. Using Bloch theory, the displacement vector u(r) and flow field pressure p(r) can be expressed as

Where k=(k _x , _ky , k _z ) represents the wave loss; u _k (r) and p _k (r) represent the periodic displacement vector and the periodic flow field vector of the lattice lattice. Applying the Bloch-Floquet condition on the periodic boundary, the band structure diagram of the periodic structure can be calculated in the initial primitive cell by using the finite element method. The discrete finite element eigenvalue equation of the initial primitive cell is:

Among them, K _s and K _f are the stiffness matrix of solid and fluid; M _s and M _f are mass matrix of solid and fluid; Q is the fluid-solid coupling matrix.

In order to obtain a complete band structure, if the structural unit cell has sufficient symmetry, the modal frequencies corresponding to all wave losses k should be calculated theoretically. In Bloch's theory, the wave loss k in reciprocal lattice loss is symmetrical and periodic. Therefore, the wave loss k can be limited to the first irreducible Brillouin region of the reciprocal lattice loss. In addition, since the extremum of the band gap always appears at the boundary of the first irreducible Brillouin region, the wave loss k can be further restricted to the boundaries X→Γ, Γ→M and M→X of the first irreducible Brillouin region.

(4) As shown in Figure 3, Figure a is the energy band structure diagram when the central regular triangular prism of the asymmetric sound propagation triangular superstructure is not biased, and Figure b is when the central regular triangular prism of the asymmetric sound propagation triangular superstructure is biased energy band structure diagram. By comparison, it can be clearly observed that when the regular triangular prism is not biased, the structure has a band gap in the frequency range of [2310Hz, 2390Hz]. In this frequency band, the acoustic wave cannot propagate between the rectangular waveguides through the acoustic cavity. When the regular triangular prism cylinders are biased, the bandgap of the structure changes. The original band gap [2310Hz, 2390Hz] is split into two new band gaps [2310Hz, 2370Hz] and [2373Hz, 2393Hz]. Between the two new bandgaps, a new passband [2370Hz, 2373Hz] is created. In the passband [2370Hz, 2373Hz], the sound can propagate between the rectangular waveguides through the acoustic cavity.

(5) The sound pressure distribution mode of the triangular superstructure with asymmetric sound propagation is shown in Fig. 4. The modal distribution of the asymmetric sound propagation triangular superstructure shows that the two rectangular waveguides in the bias direction of the regular triangular prism are connected to each other, and the sound propagation can be realized.

(6) The transfer function of the asymmetric sound propagation triangular superstructure is shown in Fig. 5. When the frequency is 2371Hz, the sound wave enters from the upper rectangular waveguide of the superstructure, passes through the cavity squeezed by the regular triangular prism, and enters the right rectangular waveguide. The transmission efficiency of sound waves from the upper rectangular waveguide to the right rectangular waveguide is 99.6%, while the transmission efficiency to the left rectangular waveguide is close to zero. Figure (5b) shows that when the sound wave is incident from the left rectangular waveguide, the sound wave cannot propagate to the other two acoustic rectangular waveguides, that is, the sound propagation is cut off. The asymmetric sound propagation triangular superstructure can change the direction of sound propagation and transfer efficiency by adjusting the offset of the central regular triangular column.

(6) Using the grid composed of asymmetric sound propagation triangular superstructure (Figure 6), adjusting the offset direction of the central equilateral triangular column can realize the sound wave propagating along the preset path and reaching the predetermined target area.

Finally, it should also be noted that what is listed above is only a specific embodiment of the present invention. Apparently, the present invention is not limited to the above embodiments, and many variations are possible, such as square, equilateral hexagon, and the like. All deformations that can be directly derived or associated by those skilled in the art from the content disclosed in the present invention should be considered as the protection scope of the present invention.

Claims (7)

1. a kind of asymmetric acoustic propagation triangle superstructure, including 1,21 equilateral triangles of regular triangular prism of a biasing are total The chamber (2-22) that shakes is arranged in the periphery of regular triangular prism 1, and an equilateral triangle cavity 23 is by 21 equilateral triangle resonant cavity (2- 22) it surrounds, three sides of equilateral triangle cavity 23 are connected to rectangular waveguide 24,25 and 26 respectively.In each equilateral triangle resonant cavity Portion is six identical right angled triangle helmholtz resonance chambers (27-32).

2. a kind of asymmetric acoustic propagation triangle superstructure according to claim 1, it is characterised in that：Asymmetric acoustic propagation Triangle superstructure is equilateral triangle cavity.

3. a kind of asymmetric acoustic propagation triangle superstructure according to claim 1, it is characterised in that：Asymmetric acoustic propagation The equilateral triangle cavity center of triangle superstructure is the regular triangular prism 1 of biasing.

4. a kind of asymmetric acoustic propagation triangle superstructure according to claim 1, it is characterised in that：Asymmetric acoustic propagation The equilateral triangle cavity of triangle superstructure has 21 equilateral triangle resonant cavities (2-22).

5. a kind of asymmetric acoustic propagation triangle superstructure according to claim 1 and 4, it is characterised in that：21 Equilateral triangle resonant cavity (2-22) is evenly distributed in 1 periphery of biasing regular triangular prism.

6. a kind of asymmetric acoustic propagation triangle superstructure according to claim 1, it is characterised in that：Asymmetric acoustic propagation Three sides of the equilateral triangle cavity 23 of triangle superstructure are connected to rectangular waveguide 24,25 and 26 respectively.

7. a kind of asymmetric acoustic propagation triangle superstructure according to claim 1 and 4, it is characterised in that：Each is just It is six identical right angled triangle helmholtz resonance chambers (27-32) inside triangle resonant cavity.