A numerical simulation method for oblique-incidence sound propagation

Abstract

This invention discloses a numerical simulation method for oblique incidence sound propagation, the process of which includes: geometric domain construction, physical domain definition, parameter setting, boundary condition setting, mesh generation, and numerical calculation. This method can perform high-precision numerical simulations of oblique incidence sound propagation, predict the noise reduction effect of sound absorbers, and is more closely aligned with practical applications than conventional normal incidence numerical simulations, thus more accurately evaluating the acoustic performance of sound absorbers.

Description

Technical Field

[0001] This invention relates to the field of acoustic numerical simulation, and more specifically to a numerical simulation method for oblique incidence sound propagation. Background Technology

[0002] Numerical simulation of sound propagation is an important tool in modern acoustics research, widely used in fields such as sound source characteristic analysis, sound propagation features, and sound absorption structure design. Currently, numerical simulations of sound propagation are typically based on straight pipes with the incident sound wave direction parallel to the pipe axis. This means that for the sound absorber at the port, the sound source is in a normal incidence case. However, in the real world, the incident sound source direction is at an angle to the incident surface, i.e., oblique incidence. Therefore, existing normal incidence sound propagation simulation techniques have limitations. Summary of the Invention

[0003] To address the problems in existing technologies, this invention proposes a numerical simulation method for oblique incidence sound propagation. This method responds to the characteristics of oblique incidence of sound sources in real-world environments, divides the physical domain and defines boundary conditions, thereby achieving accurate numerical simulation of sound propagation.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] A numerical simulation method for oblique incidence sound propagation includes the following steps:

[0006] Step 1: Construct a two-dimensional or three-dimensional 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 infinity region, that is, to achieve a reflection-free boundary; the sound source domain is also the region where sound waves propagate after reflection; the sound absorption domain is the region corresponding to the sound absorber.

[0008] Step 3: Set the medium parameters for sound propagation in the entire geometric domain, and the sound source information for the sound source domain;

[0009] Step 4: Set boundary conditions, including: setting the interface or boundary line between the sound source domain and the sound absorption domain as acoustic impedance boundary conditions, and setting other boundaries of the sound absorption domain as acoustic-solid wall boundary conditions; setting other boundaries of the sound source domain that meet the perfectly matched layer as periodic boundary conditions; the periodic boundary conditions are specifically as follows:

[0010] Taking the direction from the normal of the acoustic impedance boundary pointing to the sound source domain as the positive z-axis, and following the right-hand rule, we establish a Cartesian coordinate system. We define the angle between the incident direction of the sound wave and the direction from the normal of the acoustic impedance boundary pointing to the sound absorption domain as α, and the angle β between the projection of the incident direction of the sound wave onto the acoustic impedance boundary and the y-axis. Then, the relationship between the wave number and the incident angle in each direction under three-dimensional coordinates is as follows:

[0011] k x= k*sinα*sinβ

[0012] k y = k*sinα*cosβ

[0013] k z =k*cosα

[0014] Where, k x k y k z These are the wavenumbers in the x, y, and z axes, respectively.

[0015] Step 5: Mesh generation;

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

[0017] Furthermore, in step five, directional meshing is used for mesh generation, and the mesh size a satisfies the following condition:

[0018]

[0019] in,

[0020]

[0021] Where, δ fmax λ represents the thickness of the viscous boundary layer. fmax c represents the wavelength corresponding to the highest frequency sound wave being simulated, c0 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, in step five, when dividing the grid, it is also necessary to set the grid growth rate, curvature factor, and narrow domain resolution.

[0023] Furthermore, the included angle α ranges from -90° to 90°.

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

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

[0026] The numerical simulation method for oblique incidence sound propagation proposed in this invention analyzes real sound wave incidence conditions and sets the geometric domain, physical domain, boundary conditions, mesh, and research parameters, enabling accurate numerical simulation of sound propagation at arbitrary angles. By applying this numerical simulation method, the noise reduction effect of sound absorbers under different sound incidence angles can be accurately and quickly analyzed, which is beneficial for supporting the rapid iterative design of sound absorbers. Furthermore, this invention is unaffected by the intensity of the sound source or the internal structure of the sound absorber, possessing universality. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the physical domain partitioning in Embodiment 1 of the present invention.

[0028] Figure 2 The results are numerical simulations of the sound absorption coefficient under different sound incident angles in Embodiment 1 of the present invention.

[0029] Figure 3 This is a schematic diagram of the three-dimensional geometric domain division and incident angle in Embodiment 2 of the present invention. Detailed Implementation

[0030] The present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. The purpose and effects of the present invention will become clearer. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0031] An embodiment of the present invention provides a numerical simulation method for oblique incidence sound propagation, which includes geometric domain construction, physical domain division, parameter setting, boundary condition setting, mesh generation, and calculation settings.

[0032] Example 1

[0033] (1) Geometric domain construction

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

[0035] (2) Physical domain partitioning

[0036] The purpose of numerical simulation of sound propagation is to study the sound absorption effect of sound absorbers. Therefore, it is necessary to set up a sound source, a sound propagation path, and the region corresponding to the sound absorber. It is also necessary to simulate the region where sound waves propagate to infinity after reflection. Specifically, such as... Figure 1As shown, rectangle ABCHA is set as the perfect matching layer, simulating the infinity region, i.e., achieving a reflection-free boundary; rectangle CDGHC is set as the sound source domain, which is also the region where sound waves propagate after reflection; rectangle DEFGD is set as the sound absorption domain, i.e., the region 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 regions, i.e., ABEFA, is set to air, and the corresponding air density ρ, air viscosity μ, and sound velocity c0 in the air are determined. For the sound source domain CDGHC, sound source information needs to be defined, including amplitude A, frequency f, and incident angle α, where the incident angle is as follows: Figure 1 As shown.

[0039] (4) Boundary condition settings

[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. Therefore, the boundary DEFG is set as a sound-solid wall boundary condition, that is, the sound wave is totally reflected through this boundary. The boundary between the sound source domain and the sound absorption domain is the boundary line boundary DG. The boundary DG is set as an acoustic impedance boundary condition, that is, an internal perforated boundary, simulating a perforated plate. The boundary ABCHA is within the perfectly matched layer domain and does not need to be defined separately.

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

[0042] In a two-dimensional geometric domain, the three-dimensional coordinates are transformed into two-dimensional coordinates, such as... Figure 1 As shown, the acoustic vector wavenumber also needs to be set on the periodic boundary, specifically:

[0043]

[0044] Where, k x k y These are the wavenumbers in the x, y, and z axes, respectively.

[0045] (5) Grid generation

[0046] According to at least one example of this disclosure, a directional grid is used for mesh division. Specifically, upper and lower limits for the grid size need to be set, where the upper limit is the wavelength λ corresponding to the highest frequency sound wave under study. fmax One-tenth, with the lower limit being the viscous boundary layer thickness δ. fmax One-tenth, 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 this 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 conditions are determined by setting the frequency and angle study ranges. According to at least one example of this disclosure, the frequency range is 200 Hz to 4000 Hz, the step size is 20 Hz, and the angles α are set to 45° and 80°. Numerical simulation calculations then commence.

[0053] Comparison of calculation results and experimental test results, for example Figure 2 As shown, by selecting the sound absorption coefficient as an indicator to evaluate the acoustic performance of a sound absorber, from... Figure 2 As can be seen, the sound absorption coefficient curve decreases with increasing incident angle, and the numerical simulation results correspond well with 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, as follows: Figure 3 As shown, regions ABCDEFGH represent the perfect matching layer; regions EFGHIJKL represent the sound source region; and regions IJKLMNOP represent the sound absorption region.

[0056] The surfaces EFJI, FJKG, GKLH, and EHLI are periodic boundaries.

[0057] The surface IJKL is the acoustic impedance boundary.

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

[0059] When setting periodic boundary conditions, the relationship between wave number and incident angle in each direction 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 remaining settings in this embodiment are the same as in Embodiment 1.

[0064] It will be understood by those skilled in the art that the above descriptions are merely preferred examples of the invention and are not intended to limit the invention. Although the invention has been described in detail with reference to the foregoing examples, those skilled in the art can still modify the technical solutions described in the foregoing examples or make equivalent substitutions for some of the technical features. All modifications and equivalent substitutions made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A numerical simulation method for oblique incidence sound propagation, characterized in that, Includes the following steps: Step 1: Construct a two-dimensional or three-dimensional 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 infinity region, that is, to achieve a reflection-free boundary; the sound source domain is also the region where sound waves propagate after reflection; the sound absorption domain is the region corresponding to the sound absorber. Step 3: Set the medium parameters for sound propagation in the entire geometric domain, and the sound source information for the sound source domain; Step 4: Set boundary conditions, including: setting the interface or boundary line between the sound source domain and the sound absorption domain as acoustic impedance boundary conditions, and setting other boundaries of the sound absorption domain as acoustic-solid wall boundary conditions; setting other boundaries of the sound source domain that meet the perfectly matched layer as periodic boundary conditions; the periodic boundary conditions are specifically as follows: Taking the direction from the normal of the acoustic impedance boundary pointing to the sound source domain as the positive z-axis, and following the right-hand rule, we establish a Cartesian coordinate system. We define the angle between the incident direction of the sound wave and the direction from the normal of the acoustic impedance boundary pointing to the sound absorption domain as α, and the angle β between the projection of the incident direction of the sound wave onto the acoustic impedance boundary and the y-axis. Then, the relationship between the wave number and the incident angle in each direction under three-dimensional coordinates is as follows: k x =k*sinα*sinβ k y =k*sinα*cosβ to z =k*cosα Where, k x k y k z These are the wavenumbers in the x, y, and z axes, respectively. Step 5: Mesh generation; Step 6: Set the iteration step size and the numerical range and initial values ​​of the included 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 incidence sound propagation according to claim 1, characterized in that, In step five, when dividing the grid, a directional grid is used, and the grid size a satisfies the following condition: in, Where, δ fmax λ represents the thickness of the viscous boundary layer. fmax c represents the wavelength corresponding to the highest frequency sound wave being simulated, c0 represents the speed of sound propagation 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 incidence sound propagation according to claim 1, characterized in that, When performing mesh generation in step five, it is also necessary to set the mesh growth rate, curvature factor, and narrow domain resolution.

4. The numerical simulation method for oblique incidence sound propagation according to claim 1, characterized in that, The included angle α ranges from -90° to 90°.

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

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