Oblique incidence sound propagation numerical simulation method

Abstract

The invention discloses a numerical simulation method for oblique incidence sound propagation. The method comprises the steps of geometric domain construction, physical domain definition, parameter setting, boundary condition setting, grid division and numerical calculation. According to the method, high-precision numerical simulation can be carried out aiming at the oblique incidence condition in the sound wave transmission process, the noise reduction effect of the sound absorber can be predicted, and compared with conventional normal incidence numerical simulation, the method is more suitable for the actual application condition, so that the acoustic performance of the sound absorber is more accurately evaluated.

Description

Technical Field

[0001] The invention relates to the field of acoustic numerical simulation, and in particular to a numerical simulation method for oblique incident sound propagation. Background Art

[0002] Numerical simulation of sound propagation is an important means of modern acoustic research and is widely used in the fields of sound source characteristic analysis, sound propagation characteristics and sound absorption structure design. At present, numerical simulation of sound propagation is usually based on straight pipes, and the incident direction of the sound wave is parallel to the pipe axis. For the sound absorber at the port, the sound source is a normal incidence case. In the real world, the incident direction of the sound source and the incident surface form a certain angle, that is, oblique incidence. Therefore, the existing normal incidence sound propagation simulation technology has limitations. Summary of the invention

[0003] In view of the problems in the prior art, the present invention proposes a numerical simulation method for oblique-incidence sound propagation, which responds to the characteristics of oblique incidence of sound sources in real environments, divides the physical domain and defines boundary conditions, thereby achieving accurate numerical simulation of sound propagation.

[0004] The purpose of the present invention is achieved through the following technical solutions:

[0005] A numerical simulation method for oblique incident sound propagation comprises the following steps:

[0006] Step 1: Construct a 2D or 3D geometric domain;

[0007] Step 2: Divide the geometric domain into a perfect matching layer, a sound source domain, and a sound absorption domain in sequence; the perfect matching layer is used to simulate the infinite distance area, that is, to achieve a non-reflecting boundary; the sound source domain is also the area where the sound wave propagates after reflection; the sound absorption domain is the area corresponding to the sound absorber;

[0008] Step 3: setting the medium parameters of sound propagation in the entire geometric domain and the sound source information of the sound source domain;

[0009] Step 4: setting boundary conditions, including: setting the interface or boundary line between the sound source domain and the sound absorption domain as an acoustic impedance boundary condition, setting other boundaries of the sound absorption domain as acoustic solid wall boundary conditions; setting other boundaries of the sound source domain except the boundary with the perfect matching layer as periodic boundary conditions; the periodic boundary conditions are specifically:

[0010] The direction of the normal of the acoustic impedance boundary pointing to the sound source domain is the positive direction of the z-axis. According to the right-hand rule, the Cartesian coordinate system is set. The angle between the incident direction of the sound wave and the direction of the normal of the acoustic impedance boundary pointing to the sound absorption domain is set as α. The angle between the projection of the incident direction of the sound wave on the acoustic impedance boundary and the y-axis is set as β. The relationship between the wave number and the incident angle in each direction under the three-dimensional coordinates is:

[0011] k x=k*sinα*sinβ

[0012] k y =k*sinα*cosβ

[0013] k z = k*cosα

[0014] Among them, k x , k y , k z are the wave numbers in the x-axis, y-axis and z-axis directions respectively;

[0015] Step 5: Grid division;

[0016] Step 6: Set the iteration step size and the numerical range and initial value of the angles α and β, and perform numerical simulation calculations; when the geometric domain is two-dimensional, β is set to 90°.

[0017] Furthermore, when dividing the grid in step 5, a directional grid is used, and the grid size a satisfies the following conditions:

[0018]

[0019] in,

[0020]

[0021] Among them, δ fmax represents the thickness of the viscous boundary layer, λ fmax Indicates the wavelength of the highest frequency sound wave simulated, c 0 represents the speed of sound propagation in the medium, μ represents the viscosity of the medium, and ρ represents the density of the medium.

[0022] Furthermore, when dividing the grid in step 5, it is also necessary to set the grid growth rate, curvature factor, and narrow domain resolution.

[0023] Furthermore, the angle α has a value range of -90° to 90°.

[0024] Furthermore, the medium parameters of sound propagation in step three include medium density, medium viscosity and medium sound velocity, and the sound source information in the sound source domain includes amplitude, phase, frequency and incident angle.

[0025] The beneficial effects of the present invention are as follows:

[0026] The numerical simulation method for oblique incident sound propagation proposed in the present invention can accurately perform numerical simulation of sound propagation at any angle by analyzing the actual sound wave incident situation and setting the geometric domain, physical domain, boundary conditions, grid, and research parameters. By applying the numerical simulation method of the present invention, the noise reduction effect of the sound absorber at different sound incident angles can be accurately and quickly analyzed, which is beneficial to support the rapid iterative design of the sound absorber. Moreover, the present invention is not affected by the strength of the sound source and the internal structure of the sound absorber, and has universal applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of physical domain division according to Embodiment 1 of the present invention.

[0028] Figure 2 These are numerical simulation results of the sound absorption coefficient at different sound incident angles of Example 1 of the present invention.

[0029] Figure 3 Schematic diagram of three-dimensional geometric domain division and incident angle according to embodiment 2 of the present invention. DETAILED DESCRIPTION

[0030] The present invention will be described in detail below based on the accompanying drawings and preferred embodiments, and the purpose and effects of the present invention will become more clear. 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.

[0031] A numerical simulation method for oblique-incident sound propagation according to an embodiment of the present invention includes geometric domain construction, physical domain division, parameter setting, boundary condition setting, grid division, and calculation setting.

[0032] Example 1

[0033] (1) Geometric domain construction

[0034] In order to facilitate subsequent numerical simulation calculations, the principle of geometric domain setting is to capture key geometric features. In this embodiment, connected rectangles are used to construct the geometric domain. In this embodiment, for ease of description, a two-dimensional geometric model is used for display, such as Figure 1 As shown, the area under investigation is the rectangle enclosed by ABEFA, which is divided into three rectangles by line segments CH and DG.

[0035] (2) Physical domain division

[0036] The purpose of numerical simulation of sound propagation is to study the sound absorption effect of the sound absorber. Therefore, it is necessary to set the sound source, the sound propagation path, and the area corresponding to the sound absorber. At the same time, it is also necessary to simulate the area where the sound wave propagates to infinity after reflection. Specifically, Figure 1As shown, rectangle ABCHA is set as a perfect matching layer to simulate the infinite distance area, that is, to achieve a non-reflecting boundary; rectangle CDGHC is set as the sound source domain, and this area is also the area where the sound wave propagates after reflection; rectangle DEFGD is set as the sound absorption domain, that is, the area corresponding to the sound absorber.

[0037] (3) Parameter settings

[0038] To set the parameters, first import the medium information. In this case, the medium in all areas, i.e. ABEFA, is set to air, and the corresponding air density ρ, air viscosity μ, and sound speed in air c 0 For the sound source domain CDGHC, the sound source information needs to be defined, including amplitude A, frequency f, and incident angle α, where the incident angle is Figure 1 shown.

[0039] (4) Boundary condition setting

[0040] The boundary conditions of the sound absorber are determined according to the actual situation and are not unique. In this embodiment, the sound absorber is a resonant sound absorbing structure, so the boundary DEFG is set to the acoustic solid wall boundary condition, that is, the sound wave is fully reflected through this boundary; the boundary between the sound source domain and the sound absorption domain is the boundary line boundary DG, and the boundary DG is set to the acoustic impedance boundary condition, that is, a built-in perforated boundary to simulate the perforated plate; the boundary ABCHA is in the perfect matching layer domain and does not need to be defined separately.

[0041] The boundary HG and CD are set as periodic boundary conditions, that is, the sound propagation in a wide area of ​​the real environment is simulated through a limited geometric domain.

[0042] In a two-dimensional geometry domain, the three-dimensional coordinates are converted to two-dimensional coordinates, such as Figure 1 As shown, the acoustic vector wave number also needs to be set on the periodic boundary, specifically:

[0043]

[0044] Among them, k x , k y are the wave numbers in the x-axis, y-axis and z-axis directions respectively;

[0045] (5) Grid division

[0046] According to at least one example of the present disclosure, directional grids are used for division. Specifically, it is necessary to set upper and lower limits of the grid size, where the upper limit is the wavelength λ corresponding to the highest frequency sound wave under study. fmax The lower limit is the thickness of the viscous boundary layer δ fmax One tenth of, that is:

[0047]

[0048] in:

[0049]

[0050] In addition, the grid growth rate, curvature factor, and narrow domain resolution need to be set. According to at least one example of the present disclosure, the grid growth rate is set to 1.13, the curvature factor is set to 0.3, and the narrow domain resolution is set to 1.

[0051] (6) Calculation settings

[0052] In this section, the numerical simulation working conditions are determined by setting the frequency research range and the angle research range. According to at least one example of the present disclosure, the frequency range is 200 Hz to 4000 Hz, the step size is 20 Hz, and the angle α is set to 45° and 80°. Then the numerical simulation calculation is started.

[0053] Comparison of calculation results and experimental test results Figure 2 As shown in the figure, by selecting the sound absorption coefficient as an indicator to judge the acoustic performance of the sound absorber, Figure 2 It can be seen that with the increase of the incident angle, the sound absorption coefficient curve shows a decreasing trend, and the numerical simulation results correspond well to the experimental values.

[0054] Example 2

[0055] This embodiment constructs a three-dimensional geometric domain. The three-dimensional geometric domain is divided into a perfect matching layer, a sound source domain, and a sound absorption domain. Figure 3 As shown, area ABCDEFGH is the perfect matching layer; area EFGHIJKL is the sound source domain; and area IJKLMNOP is the sound absorption domain.

[0056] Surface EFJI, surface FJKG, surface GKLH, and surface EHLI are periodic boundaries.

[0057] Surface IJKL is the acoustic impedance boundary.

[0058] Except for surface IJKL, the other surfaces in the sound absorption domain are sound solid wall boundaries.

[0059] When setting periodic boundary conditions, the relationship between the wave number in each direction and the incident angle in three-dimensional coordinates is given:

[0060] k x =k*sinα*sinβ

[0061] k y =k*sinα*cosβ

[0062] k z= k*cosα

[0063] The rest of the configuration in this embodiment is the same as that in Embodiment 1.

[0064] Those skilled in the art can understand that the above are only preferred examples of the invention and are not intended to limit the invention. Although the invention is described in detail with reference to the above examples, those skilled in the art can still modify the technical solutions recorded in the above examples or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, etc. made within the spirit and principle of the invention shall be included in the protection scope of the invention.

Claims

1. A numerical simulation method for oblique-incidence sound propagation, characterized in that: The steps include: Step 1: Construct a 2D or 3D geometric domain; Step 2: Divide the geometric domain into a perfect matching layer, a sound source domain, and a sound absorption domain in sequence; the perfect matching layer is used to simulate the infinite distance area, that is, to achieve a non-reflecting boundary; the sound source domain is also the area where the sound wave propagates after reflection; the sound absorption domain is the area corresponding to the sound absorber; Step 3: setting the medium parameters of sound propagation in the entire geometric domain and the sound source information of the sound source domain; Step 4: setting boundary conditions, including: setting the interface or boundary line between the sound source domain and the sound absorption domain as an acoustic impedance boundary condition, setting other boundaries of the sound absorption domain as acoustic solid wall boundary conditions; setting other boundaries of the sound source domain except the boundary with the perfect matching layer as periodic boundary conditions; the periodic boundary conditions are specifically: The direction of the normal of the acoustic impedance boundary pointing to the sound source domain is the positive direction of the z-axis. According to the right-hand rule, the Cartesian coordinate system is set. The angle between the incident direction of the sound wave and the direction of the normal of the acoustic impedance boundary pointing to the sound absorption domain is set as α. The angle between the projection of the incident direction of the sound wave on the acoustic impedance boundary and the y-axis is set as β. The relationship between the wave number and the incident angle in each direction under the three-dimensional coordinates is: k x =k*sinα*sinβ k y =k*sinα*cosβ to z =k*cosα Among them, k x , k y , k z are the wave numbers in the x-axis, y-axis and z-axis directions respectively; Step 5: Grid division; Step 6: Set the iteration step size and the numerical range and initial value of the angles α and β, and perform numerical simulation calculations; when the geometric domain is two-dimensional, β is set to 90°.

2. The numerical simulation method for oblique incident sound propagation according to claim 1, characterized in that: When dividing the grid in step 5, a directional grid is used, and the grid size a satisfies the following conditions: in, Among them, δ fmax represents the thickness of the viscous boundary layer, λ fmax represents the wavelength corresponding to the highest frequency sound wave simulated, c0 represents the propagation speed of sound in the medium, μ represents the viscosity of the medium, and ρ represents the density of the medium.

3. The numerical simulation method for oblique incident sound propagation according to claim 1, characterized in that: When dividing the grid in step 5, it is also necessary to set the grid growth rate, curvature factor, and narrow domain resolution.

4. The numerical simulation method for oblique incident sound propagation according to claim 1, characterized in that: The value range of the angle α is -90° to 90°.

5. The numerical simulation method for oblique incident sound propagation according to claim 1, characterized in that: The medium parameters of sound propagation in step three include medium density, medium viscosity and medium sound velocity, and the sound source information in the sound source domain includes amplitude, phase, frequency and incident angle.

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