Compact broadband anti-flow sound absorption structure and preparation method thereof

Abstract

The invention belongs to the technical field of acoustic metamaterials, pipeline noise control and aeroacoustics, and discloses a compact broadband anti-flow sound absorption structure and a preparation method thereof.The broadband anti-flow sound absorption structure comprises a resonance body and a flow resistance control interface layer arranged on the incident plane of the resonance body, the resonance body comprises a sound absorption unit, and the flow resistance control interface layer is arranged on the incident plane of the resonance body; each sound absorption unit comprises a first cavity and a second cavity, a first micro-tube array is arranged in the first cavity, a second micro-tube array is arranged in the second cavity, the first micro-tube array comprises an upper panel and a first embedded micro-tube, the second micro-tube array comprises a partition plate and a second embedded micro-tube, the first embedded micro-tube extends towards the interior of the first cavity, and the second embedded micro-tube extends towards the interior of the second cavity. The second embedded microtube extends into the second cavity, an interface gap is formed between the flow resistance control interface layer and the upper panel, and the interface gap is located between the flow resistance control interface layer and an inlet of the first microtube array. The invention has the advantages of compact structure, broadband low-frequency sound absorption, glancing loss resistance, suitability for additive manufacturing and the like.

Description

Technical Field

[0001] This application belongs to the fields of acoustic metamaterials, pipeline noise control and aeroacoustics, specifically relating to a compact broadband anti-flow sound-absorbing structure and its preparation method. Background Technology

[0002] In ventilation ducts, data center cooling systems, HVAC systems, and vehicle air ducts and exhaust systems, low-to-mid-frequency noise is often generated by the combined effects of rotating machinery and high-speed airflow. While traditional resistive sound-absorbing materials can provide a certain broadband dissipation capability, in the low-frequency range, a structural thickness close to the wavelength of sound is usually required for effective sound absorption, making them difficult to apply in space-constrained fluid transport systems.

[0003] To achieve low-frequency sound absorption within a limited space, existing technologies have proposed structures such as micro-perforated plates, Helmholtz resonators, and multi-layered and multi-cavity couplings. Related research indicates that while micro-perforated sound-absorbing structures offer advantages such as being fiber-free and highly designable, their basic structures often struggle to simultaneously achieve low-frequency and broadband high absorption, requiring multi-layered configurations or parameter optimization to extend the effective frequency band. For Helmholtz resonator structures, although low-frequency sound absorption can be achieved at deep subwavelength scales, their absorption bandwidth is typically narrow due to the resonant absorption mechanism, making it difficult to achieve continuous and efficient broadband sound absorption.

[0004] More importantly, existing resonant sound-absorbing structures often experience performance degradation in actual grazing jet or tangential flow environments. On the one hand, grazing jets alter the acoustic impedance characteristics of the perforated interface or orifice, thus affecting the original acoustic matching state and noise reduction performance. On the other hand, open cavities are prone to shear layer oscillations and acoustic-flow feedback coupling under flow conditions, thereby inducing flow-induced noise or cavity sound problems. To address the acoustic performance degradation caused by fluid grazing, existing technologies have proposed setting a protective layer or grazing jet shielding layer on the acoustic liner surface to reduce the adverse effects of flow on acoustic admittance.

[0005] However, existing technologies still lack a systematic solution that can simultaneously achieve low-frequency broadband sound absorption with limited thickness, stable operation under flow conditions, flow capacity, and engineering manufacturability. Therefore, it is necessary to propose a novel compact flow-resistant and noise-absorbing structure and its design method to meet the broadband low-frequency noise reduction requirements under dynamic flow conditions. Summary of the Invention

[0006] To address the challenge of existing pipeline noise reduction technologies in achieving a balance between low-frequency noise reduction, broadband sound absorption, structural compactness, and stability under flow conditions, this application provides a compact broadband anti-flow sound-absorbing structure and its fabrication method. By setting up a multi-layer, multi-tube embedded coupled resonant structure, broadband low-frequency sound absorption is achieved under limited thickness conditions. Furthermore, by controlling the interface layer and interface gap through flow resistance, a decoupling structure between the sound field and the flow field is constructed to suppress flow-induced self-noise and reduce the adverse effects of flow on acoustic performance, thereby improving the noise reduction capability and operational stability of the device under dynamic conditions.

[0007] To achieve the above objectives, this application employs the following technical solution:

[0008] This application discloses a compact broadband anti-flow sound-absorbing structure, comprising a resonant body and a flow resistance control interface layer disposed on the incident surface of the resonant body, wherein...

[0009] The resonant body includes multiple sound-absorbing units arranged in parallel. Each sound-absorbing unit includes a first cavity and a second cavity arranged sequentially along the direction of sound wave propagation. A first microtube array is arranged in the first cavity, and a second microtube array is arranged in the second cavity. The first cavity and the second cavity are separated by a partition.

[0010] The first microtube array includes a top panel and multiple parallel first embedded microtubes disposed on the top panel. The second microtube array includes a partition and one or more parallel second embedded microtubes disposed on the partition. The first embedded microtubes extend into the first cavity, and the second embedded microtubes extend into the second cavity.

[0011] The flow resistance control interface layer is not directly attached to the resonant body, and a predetermined thickness interface gap is formed between the flow resistance control interface layer and the upper panel. The interface gap is located between the flow resistance control interface layer and the inlet of the first microtube array.

[0012] A further improvement of this application is that the outer contours of the first cavity and the second cavity are aligned, the first cavity is located on the side closer to the incident sound wave, the second cavity is located on the side of the first cavity and away from the incident sound wave, the first cavity and the second cavity are connected in series along the direction of sound wave propagation, and are coupled through the intermediate partition and adjacent sound fields to form a double-layer coupled resonant system.

[0013] A further improvement of this application is that the cross-section of the sound-absorbing unit is square, and the internal geometric parameters of multiple sound-absorbing units are different, so as to form a non-uniform parameter array and obtain a broadband response.

[0014] A further improvement of this application is that the flow resistance control interface layer is made of precision metal mesh, and the precision metal mesh has a specific acoustic impedance of 65Rayl.

[0015] A further improvement of this application is that the interface gap is a double-sided adhesive mesh, a support frame, a gasket, a boss, or a spacer.

[0016] This application provides a method for fabricating a compact broadband anti-flow sound-absorbing structure, comprising the following steps:

[0017] Step 1: Establish a parameterized structural model that includes a first cavity, a second cavity, a first microtube array, a second microtube array, a flow resistance control interface layer, and interface gaps;

[0018] Step 2: Obtain the complex effective density and complex bulk modulus of the air medium inside the first and second embedded microtubes. The characteristic impedance of a single embedded microtube is equivalently converted according to the number of tubes to characterize the boundary layer dissipation enhancement effect brought about by the parallel connection of multiple tubes. A correction term is introduced, and the acoustic transfer matrix of the first microtube array, the first cavity, the second microtube array, and the second cavity are cascaded in sequence to obtain the surface impedance of multiple parallel sound-absorbing units and the total acoustic impedance of the broadband anti-flow sound-absorbing structure.

[0019] Step 3: Construct a multi-objective function To calculate the objective function value, the formula is constructed as follows:

[0020]

[0021] in, The objective function value, The matrix of geometric parameters of the microtube to be optimized. The total number of frequency points. For the first Discrete frequency points, For the microtube geometry parameter matrix And the discrete frequency points are The total sound absorption coefficient of the broadband anti-flow sound-absorbing structure was calculated at that time. It is the negative value of the average sound absorption coefficient. This is a one-sided, double-penalty term. The preset penalty weight factor, The preset critical sound absorption performance threshold is defined as follows: when a certain local discrete frequency point... The overall sound absorption coefficient of the broadband anti-flow sound-absorbing structure at the location Fall to The following times, The result is positive;

[0022] Step 4: In the population initialization phase of the global optimization algorithm, the geometric parameter matrix of the microtube to be optimized is... Initialization based on bidirectional physical gradients is performed to ensure that the initial resonant frequencies of each sound-absorbing unit are approximately uniformly distributed within the target frequency band.

[0023] Step 5: Based on the population initialized in Step 4, execute a hybrid optimization strategy based on genetic algorithm (GA) and sequential quadratic programming algorithm (SQP), and introduce physical space and manufacturing accuracy boundary constraints to obtain the globally optimal geometric parameter matrix.

[0024] Step 6: Based on the optimal geometric parameter matrix obtained through optimization, the solid is manufactured and assembled to finally obtain a compact broadband anti-flow sound-absorbing structure.

[0025] A further improvement in this application is that step 2 specifically includes the following steps:

[0026] Step 2.1: To address the dissipation effect of the confined space within the first and second microtube arrays, a hierarchical parameter is introduced. ,in Calculate the first microtube array and the second microtube array respectively. Complex effective density of air medium inside microtubes With complex bulk modulus :

[0027]

[0028]

[0029] in, Angular frequency, This is the static density of air at room temperature. Standard atmospheric pressure The specific heat ratio of air. and These represent the zeroth and first-order Bessel functions of the first kind, respectively. For the first The shear wavenumber of the air medium inside the microtube. For the first The thermal wavenumber of the air medium inside the microtube;

[0030] Step 2.2, the first The characteristic impedance of a single embedded microtube in a layered microtube array divided by the number of parallel tubes in that layer. The equivalent characteristic impedance of the array is obtained by equivalent conversion, so as to characterize the boundary layer dissipation enhancement effect brought about by the parallel connection of multiple tubes;

[0031] Step 2.3: Introduce correction terms for the first and second cavities, and calculate the effective volume of the corresponding cavities after correction:

[0032]

[0033] in, The cross-sectional area of ​​the top panel. This corresponds to the geometric depth of the cavity. This corresponds to the internal radius of the embedded microtube within the cavity. This corresponds to the geometric length of the embedded microtube within the cavity;

[0034] Step 2.4: Using the transfer matrix method, the effective volume of the cavity after the above correction is calculated. The acoustic transfer matrices of the first microtube array, the first cavity, the second microtube array, and the second cavity are sequentially cascaded to obtain the surface impedance of each sound-absorbing unit. The reciprocal of the surface impedance of each sound-absorbing unit is taken and summed in parallel to calculate the total admittance of the array. Then, the surface impedance of the sound-absorbing unit can be obtained. ,in Finally, the surface impedance of the sound-absorbing unit is... The inherent specific acoustic impedance of the flow resistance control interface layer By performing series superposition, the total acoustic impedance of the broadband anti-flow sound-absorbing structure can be finally obtained. .

[0035] A further improvement in this application is that step 4 specifically includes the following steps:

[0036] Step 4.1: Introduce the spatial distribution coefficient , According to the serial number of the sound-absorbing unit It exhibits a gradient distribution;

[0037] Step 4.2: Construct the bidirectional physical gradient matrix: Based on the following linear physical mapping formula, forcibly generate the first... The initial geometric parameter matrices of the first and second microtube arrays within each sound-absorbing unit:

[0038]

[0039]

[0040]

[0041]

[0042] in, and The first The initial internal radius and initial geometric length of the first embedded microtube in each sound-absorbing unit. and The first The initial internal radius and initial geometric length of the second embedded microtube in each sound-absorbing unit. and These are the upper and lower limits of the radius of the embedded microtube, respectively. and These are the upper and lower limits of the length of the first embedded microtube, respectively. and These are the upper and lower limits of the length of the second embedded microtube, respectively. and This is the gradient adjustment factor;

[0043] Step 4.3: Perform initial fitness assessment: Set the radius and length of the first and second embedded microtubules to spatial distribution coefficients. The opposite changes form a bidirectional physical gradient that couples positive and negative features, resulting in the generated microtube geometric parameter matrix. Inject it into the global optimization algorithm and call the multi-objective function. Perform fitness assessment on the initial population.

[0044] A further improvement in this application is that step 5 specifically includes the following steps:

[0045] Step 5.1, Global Optimization and Boundary Constraints: Based on the population initialized in Step 4, a genetic algorithm is used to perform global optimization iterations. During each iteration, the internal radius of the embedded microtube is adjusted. and geometric length Apply hard boundary constraints:

[0046]

[0047]

[0048]

[0049] in, and These are the geometric depths of the first cavity and the second cavity, respectively. The preset acoustic gap threshold, and These are the lower and upper limits of the radius of the embedded microtube;

[0050] Step 5.2: Set the maximum number of generations for the genetic algorithm to be [value missing]. As a hard termination criterion for global search, when the genetic algorithm reaches... Or the optimal fitness of individuals in a population is continuous When there is no promotion, the switching mechanism is automatically triggered. At this time, the currently globally optimal chromosome vector output by the genetic algorithm is extracted. As an initial value, a sequential quadratic programming algorithm (SQP / fmincon) is seamlessly injected to enable gradient-based local refinement mode;

[0051] Step 5.3, Gradient Descent and Convergence Output: The sequential quadratic programming algorithm uses the globally optimal chromosome vector. Starting with a multi-objective function The local gradient information is used for iterative fine-tuning with continuous descent until the preset algorithm convergence tolerance is met, and finally the globally optimal geometric parameter matrix that satisfies the hard boundary constraints is output. .

[0052] A further improvement in this application is that step 6 specifically includes the following steps:

[0053] Step 6.1, Solid Modeling and Additive Manufacturing: Extract the embedded microtube radius and length data from the optimal geometric parameter matrix output in Step 5, generate a three-dimensional parametric solid model containing the first microtube array, the first cavity, the second microtube array, and the second cavity, and use additive manufacturing technology to print a compact broadband anti-flow sound-absorbing structure based on the three-dimensional parametric solid model.

[0054] Step 6.2, Interface Layer Decoupling Assembly: Provide a flow resistance control interface layer, assemble the flow resistance control interface layer on the acoustic wave incident surface side of the resonant body, and ensure that the flow resistance control interface layer and the upper panel maintain an interface gap of a predetermined thickness to obtain a compact broadband anti-flow sound absorption structure.

[0055] The beneficial effects of this application are: through the coupling effect of the double-layer cascaded cavity and the embedded microtube, this application achieves the downward shift of low-frequency resonance and the widening of the sound absorption frequency band within a limited structural thickness, which is conducive to solving the problems of large thickness and narrow bandwidth of traditional low-frequency sound absorption structures.

[0056] This application increases the tube wall perimeter length per unit flow cross-sectional area by using a structure of multiple microtubes connected in parallel within the first cavity, thereby enhancing the thermal viscous dissipation capacity and achieving high sound absorption performance without the need for filling with fiber materials.

[0057] This application constructs a physical decoupling structure between the external flow field and the internal sound field by setting a flow resistance control interface layer on the incident side of the resonant body and forming an interface gap between the interface layer and the microtube inlet. This helps to suppress shear layer feedback, reduce flow-induced self-noise, and reduce the disturbance of high-speed airflow on the acoustic impedance of the resonant structure. At the same time, this application uses a non-uniform parameter unit array and combines it with optimization design methods to disperse the resonant response of different sound-absorbing units within the target frequency band, thereby obtaining a continuous and stable broadband sound absorption effect.

[0058] The structure of this application is clearly defined and suitable for integral processing and forming using additive manufacturing or other methods, facilitating modular design, parameter customization, and engineering applications. Preferred embodiments show that the device exhibits a high average sound absorption coefficient in the 250 Hz to 900 Hz range and maintains good dynamic noise reduction performance even under grazing jet conditions, demonstrating that it possesses both excellent acoustic performance and aeroacoustic stability. Attached Figure Description

[0059] Figure 1 This is a schematic diagram of the sound-absorbing unit of this application. Figure 2 This is a schematic diagram of the physical field setup and finite element model of the sound-absorbing unit in this application.

[0060] Figure 3 This is a comparison chart of the verification results of the TMM analytical method and the finite element model used in this application.

[0061] Figure 4 This is a comparison diagram of the sound absorption mechanisms of the double-layer cavity and the single-layer cavity in this application. Figure 5 This is a flowchart of the sound-absorbing structure preparation method of this application. Figure 6 The optimized first and second microtube arrays and their impedance and sound absorption characteristics are shown in the diagram. Figure 7 This is a schematic diagram illustrating the manufacturing and assembly of the prototype of this application. Figure 8 This is a diagram showing the static sound absorption test results of the prototype in the impedance tube. Figure 9 This is a schematic diagram of the dynamic testing platform in the wind tunnel pipeline of this application. Figure 10 This is a verification diagram showing the effect of the flow resistance control interface on suppressing flow-induced additional noise. Figure 11 This is a comparison chart showing the difference in flow-induced self-noise with and without a flow resistance control interface layer. Figure 12 The figure shows the dynamic pipe insertion loss test results of the device in this application under different flow rates.

[0062] Figure 13 This is a schematic diagram of an embodiment of the present application where the interface gap is an acrylic strip. Detailed Implementation

[0063] The embodiments of the present invention will be disclosed below with reference to the drawings. For clarity, many practical details will be described in the following description. However, it should be understood that these practical details are not intended to limit the present invention. That is, in some embodiments of the present invention, these practical details are not essential. In addition, for the sake of simplicity, some conventional structures and components will be shown in the drawings in a simple schematic manner.

[0064] like Figure 1As shown, this application discloses a compact broadband anti-flow sound-absorbing structure suitable for ventilation ducts, heat dissipation ducts, exhaust channels, and fluid transport pipelines. The broadband anti-flow sound-absorbing structure includes a resonant body and a flow resistance control interface layer disposed on the incident surface of the resonant body. The resonant body includes multiple parallel-arranged sound-absorbing units. Each sound-absorbing unit includes a first cavity and a second cavity arranged sequentially along the sound wave propagation direction. The first cavity is located on the side closer to the sound wave incident point, and the second cavity is located on the side of the first cavity and away from the sound wave incident point. The first and second cavities are connected in series along the sound wave propagation direction and are coupled through a partition and adjacent sound fields, thus forming a double-layer coupled resonant structure. A first microtube array is disposed within the first cavity, and a second microtube array is disposed within the second cavity. The first and second cavities are separated by a partition.

[0065] The first microtube array includes a top panel and multiple parallel first embedded microtubes disposed on the top panel. The second microtube array includes a partition and one or more parallel second embedded microtubes disposed on the partition, forming a double-layer resonant channel while maintaining a compact overall structure. Compared with the traditional single-neck resonant structure, this embodiment, through the combination of a double-layer cavity and multiple embedded channels, is beneficial to improving low-frequency sound absorption performance and widening the effective operating frequency band. The first embedded microtube extends into the first cavity, and the second embedded microtube extends into the second cavity to increase the equivalent acoustic neck length within a limited thickness and form a folded sound channel. Through the above arrangement, the sound propagation path can be extended under limited structural thickness conditions, and coupling between the front and rear cavities can be achieved.

[0066] In this embodiment, the sound-absorbing unit has a square cross-section with a side length of 37.5 mm; the first cavity has a depth of 60 mm, and the second cavity has a depth of 36 mm. The first microtube array includes 12 first embedded microtubes, each with a radius of 2.03 mm and a length of 26.61 mm; the second microtube array includes 4 second embedded microtubes, each with a radius of 2.90 mm and a length of 27.49 mm. The outer contours of the first and second cavities are aligned to facilitate the arrayed arrangement and modular splicing of multiple sound-absorbing units. The depths of the first and second cavities, as well as the number, radius, and length of the first and second microtube arrays, can be adjusted according to the target frequency band and installation space requirements, while maintaining the structure of double-layer cavity series coupling and multi-tube embedded extension. The internal geometric parameters of the multiple sound-absorbing units are different to form a non-uniform parameter array and obtain a broadband response.

[0067] like Figure 1 , Figure 7 , Figure 10 and Figure 11As shown, a flow resistance control interface layer is provided on the incident surface of the resonant body. This flow resistance control interface layer is located in front of the first microtube array and covers the incident surface area of ​​the sound-absorbing unit, and is used to adjust the interface between the incident sound wave and the grazing airflow.

[0068] Preferably, the flow resistance control interface layer of this application is a precision metal mesh made using an anti-Dutch weave process, wherein the precision metal mesh has a specific acoustic impedance of 65 Rayl. Unlike conventional industrial porous meshes or micro-perforated plates, the anti-Dutch weave metal mesh has an extremely complex microscopic topology. This special microstructure can introduce extremely high fluid resistance on the surface of the structure, thereby effectively disrupting and suppressing the shedding of convective vortices generated by the grazing airflow; at the same time, the structure can maintain precise and moderate acoustic impedance characteristics, ensuring efficient transmission of incident sound waves. Through this asymmetric design in physical properties, the flow resistance control interface layer of this application not only acts as a physical protective layer, but also as a core aeroacoustic stabilizer, successfully shielding the shear layer feedback at the inlet of the microtube array and achieving decoupling between the acoustic resonant field and the external convective disturbance field.

[0069] like Figure 1 and Figure 7 As shown, the flow resistance control interface layer is not directly attached to the resonant body, and a 2.5 mm double-sided adhesive mesh is formed between the flow resistance control interface layer and the upper panel, fixing it to the front side of the sound-absorbing unit, thus creating a stable interface gap between the flow resistance control interface layer and the sound-absorbing unit body. This spaced support method separates the metal mesh from the rigid main frame, effectively avoiding parasitic vibration-acoustic contact resonance that may be induced by direct physical contact, while forming a relatively independent transition space on the incident side, balancing the flow capacity and acoustic adjustment capability.

[0070] like Figure 10 and Figure 11 As shown, in actual high-speed grazing jet flow environments, such as a flow velocity of 9.8 m / s, unprotected open cavities and microtube arrays are highly susceptible to strong aeroacoustic feedback loops induced by shear layer instability, generating narrowband flow-induced cavity noise and severe pseudo-acoustic pressure fluctuations caused by the turbulent boundary layer. However, by deploying the flow resistance control interface layer and interface gap of this embodiment, the direct disturbance of the airflow to the microtube inlet region is effectively shielded, completely cutting off the shear layer feedback loop. Dynamic flow field tests demonstrate that flow-induced self-noise is completely suppressed, and the pressure spectrum exhibits a smooth broadband response, resulting in a significant improvement in the signal-to-noise ratio (SNR). This mechanism eliminates spontaneous noise phenomena in dynamic flow field environments, ensuring that the device maintains stable inherent impedance under high-speed grazing jet conditions, combining excellent broadband noise reduction performance with aeroacoustic stability. The flow resistance control interface layer of this application participates in overall acoustic impedance regulation as a resistive component, while simultaneously weakening the direct coupling between the external flow field and the internal resonant sound field, thereby suppressing flow-induced self-noise and resonant frequency shift.

[0071] The first cavity and the second cavity of this application are connected in series along the direction of sound wave propagation and are coupled through the intermediate partition and adjacent sound fields to form a double-layer coupled resonant system.

[0072] When sound waves are incident, the incident sound energy first enters the first cavity through the first microtube array, forming a coupling effect between the acoustic mass and the cavity elasticity in the first layer. Subsequently, the sound field is further transmitted to the second microtube array and the second cavity through the rear structure, forming an additional resonant response in the second layer. Since the two resonant units are not independent but are structurally connected in series and acoustically coupled, the overall structure can form a more complex resonant response compared to a single-layer single-cavity resonant structure, and exhibits a wider sound absorption range within the target frequency band. Both the first and second layers use multiple parallel microtubes to form the sound channel. Compared to a single large channel, multiple parallel microtubes can provide a larger tube wall contact area under the condition of similar total flow area, thereby increasing the interaction between the sound wave and the tube wall boundary layer when the sound wave propagates inside the microtube. Since heat dissipation and viscous dissipation are mainly concentrated in the region near the microtube wall, the above-mentioned multi-tube parallel structure is beneficial to enhance the boundary layer dissipation effect, improve the resistive characteristics of the structure, and reduce the sharp peak response caused by a single strong resonance.

[0073] like Figure 4 As shown, in this embodiment, the two cavities, the first microtube array, and the second microtube array enable the sound-absorbing unit to simultaneously possess both low-frequency response and wide-bandwidth operation capabilities within a limited structural thickness. The volumes of the two-stage cavities, the number of microtube arrays, and their dimensional parameters are coordinated to ensure that the double-layer coupling effect and the multi-tube dissipation effect are synergistically utilized within the target frequency band. The specific dimensional ratios and microtube arrangements of the two-stage structures can be adjusted according to the target sound-absorbing frequency band, but all remain within the basic concept of this invention.

[0074] In order to design and predict the performance of the sound-absorbing structure of this application, this embodiment establishes a corresponding acoustic finite element simulation model, such as... Figure 2 As shown.

[0075] like Figure 3 As shown, this embodiment uses the three-dimensional finite element method COMSOL software to verify the established TMM theoretical analytical model. During the simulation, acoustic modeling is performed on the cavity region and the microtube region respectively, and the thermoviscous boundary layer effect inside the microtube is considered. By comparing the theoretical model and the finite element model, the response characteristics of the structure of this application at different frequencies can be analyzed.

[0076] The verification results show that the theoretical model and numerical simulation results have good consistency within the target frequency band, and both can reflect the bimodal response and coupling characteristics of the structure of this invention. This indicates that the theoretical model established in this embodiment can accurately characterize the acoustic behavior of the double-layer multi-tube embedded sound-absorbing unit and can serve as the basis for subsequent parameter design and structural optimization.

[0077] Figure 5 A flowchart of the sound-absorbing structure preparation method of this application is provided. Figure 6 The optimized structures of the first and second microtube arrays, along with their impedance and sound absorption characteristics, are presented. This method combines thermoviscous acoustic theory, hybrid heuristic optimization algorithms, and physical fabrication processes to form a closed-loop design process from theoretical modeling and parameter solving to prototype output.

[0078] like Figure 5 As shown, this application provides a method for fabricating a compact broadband anti-flow sound-absorbing structure, comprising the following steps:

[0079] Step 1: Establish a parameterized structural model that includes a first cavity, a second cavity, a first microtube array, a second microtube array, a flow resistance control interface layer, and interface gaps;

[0080] Step 2: For the first and second embedded microtubes, a cylindrical tube thermoviscous propagation model based on Bessel functions is used to obtain the complex effective density and complex bulk modulus of the air medium inside the first and second embedded microtubes. For the parallel connection of multiple microtubes, the characteristic impedance of a single embedded microtube is equivalently converted according to the number of tubes to characterize the boundary layer dissipation enhancement effect brought about by the parallel connection of multiple tubes. For the first and second cavities, a correction term for the effective acoustic volume occupation of the cavity by the embedded microtubes is introduced. Based on this, the acoustic transfer matrices of the first microtube array, the first cavity, the second microtube array, and the second cavity are cascaded sequentially to obtain the surface impedance of multiple parallel sound-absorbing units and the total acoustic impedance of the broadband anti-flow sound-absorbing structure. Specifically, the steps include the following:

[0081] Step 2.1: To address the dissipation effect of the confined space within the first and second microtube arrays, a hierarchical parameter is introduced. ,in Calculate the first microtube array and the second microtube array respectively. Complex effective density of air medium inside microtubes With complex bulk modulus :

[0082]

[0083]

[0084] in, Angular frequency, This is the static density of air at room temperature. Standard atmospheric pressure The specific heat ratio of air. and These represent the zeroth and first-order Bessel functions of the first kind, respectively. For the first The shear wavenumber of the air medium inside the microtube. For the first The thermal wavenumber of the air medium inside the microtube;

[0085] Step 2.2, the first The characteristic impedance of a single embedded microtube in a layered microtube array divided by the number of parallel tubes in that layer. The equivalent characteristic impedance of the array is obtained by equivalent conversion, so as to characterize the boundary layer dissipation enhancement effect brought about by the parallel connection of multiple tubes;

[0086] Step 2.3: For the first and second cavities, a correction term is introduced to address the impact of the embedded microtubes on the effective acoustic volume of the cavities. The corrected effective volumes of the corresponding cavities are then calculated.

[0087]

[0088] in, The cross-sectional area of ​​the top panel. This corresponds to the geometric depth of the cavity. This corresponds to the internal radius of the embedded microtube within the cavity. This corresponds to the geometric length of the embedded microtube within the cavity;

[0089] Step 2.4: Using the transfer matrix method, the effective volume of the cavity after the above correction is calculated. The acoustic transfer matrix of the first microtube array, the first cavity, the second microtube array, and the second cavity are sequentially cascaded, and the surface impedance of each sound-absorbing unit is obtained by solving the equation.

[0090] For the first microtube array j=1 or the second microtube array j=2, the transfer matrix The calculation formula is:

[0091]

[0092] in, and These are the complex wavenumber and characteristic acoustic impedance within a single microtube, taking into account thermoviscous losses. It is the effective acoustic length of the microtube (including end correction). This represents the number of microtubules in that layer.

[0093] The transfer matrix of the cavity is:

[0094] in, , .

[0095] For this two-layer structure, the sound waves pass sequentially through the first microtube array, the first cavity, the second microtube array, and the second cavity. By concatenating the transfer matrices of these four parts using matrix multiplication, the total transfer matrix of the unit is obtained:

[0096]

[0097] Assuming the bottommost second cavity has a rigid wall, this means the particle velocity (or volume velocity) at that end is zero. Substituting this into the overall transfer matrix equation: Therefore, the input acoustic impedance of this unit can be derived: .

[0098] Finally, to evaluate the sound absorption performance, the input acoustic impedance (based on volume velocity) mentioned above needs to be multiplied by the cross-sectional area of ​​the unit to obtain the surface impedance of the unit. The total admittance of the array is calculated by taking the reciprocal of the surface impedance of each sound-absorbing unit and summing them in parallel. :

[0099]

[0100] in, The number of units is 16 in this embodiment; It is the specific surface impedance calculated for each independent unit using the transfer matrix method (TMM).

[0101] Then the surface impedance of the sound-absorbing unit can be obtained. ,in Finally, the surface impedance of the sound-absorbing unit is... The inherent specific acoustic impedance of the flow resistance control interface layer By performing series superposition, the total acoustic impedance of the broadband anti-flow sound-absorbing structure can be finally obtained. .

[0102] Step 3: Construct a multi-objective function To calculate the objective function value, the multi-objective function At least the objectives include maximizing the average sound absorption coefficient within the target frequency band and flatness constraints. Within the target frequency band of 250 Hz to 900 Hz, the fitness function is constructed with maximizing the array's average sound absorption coefficient as the primary objective. To reduce potential local sound absorption dips during multimodal coupling, a one-sided quadratic penalty term is added to the cost function. Multi-objective function The optimization not only aims to maximize the average sound absorption coefficient within the target frequency band, but also introduces flatness constraints to suppress local sound absorption dips during multimodal coupling. Preferably, the sound absorption coefficient penalty threshold can be set to 0.8, and the penalty weight can be set to 50, to constrain geometric parameter combinations that cause significant local decreases in sound absorption performance during the optimization process. The specific construction formula is as follows:

[0103]

[0104] in, To evaluate the quality of the current solution, the objective function value is... The matrix of geometric parameters of the microtube to be optimized. This refers to the total number of frequency points discretely extracted within a set target frequency band (e.g., 250 Hz to 900 Hz). For the first Discrete frequency points, For the microtube geometry parameter matrix And the discrete frequency points are At that time, the total sound absorption coefficient of the broadband anti-flow sound-absorbing structure is calculated through step 2; The negative value of the average sound absorption coefficient is used for minimizing the main objective function; This is a one-sided, double-penalty term. The preset penalty weight factor, The preset critical sound absorption performance threshold is defined as follows: when a certain local discrete frequency point... The overall sound absorption coefficient of the broadband anti-flow sound-absorbing structure at the location Fall to The following times, The result is positive, the penalty term is activated and significantly increases the cost function value, thereby forcing the optimization algorithm to avoid suboptimal solutions with local troughs;

[0105] Step 4: In the population initialization phase of the global optimization algorithm (such as a genetic algorithm), the microtube geometric parameter matrix to be optimized is... Initialization based on bidirectional physical gradients is performed to ensure that the initial resonant frequencies of each sound-absorbing unit are approximately uniformly distributed within the target frequency band. This method reduces modal redundancy and guides the optimization process towards a smoother broadband response. Specifically, the steps include:

[0106] Step 4.1: Introduce the spatial distribution coefficient , According to the serial number of the sound-absorbing unit It exhibits a gradient distribution;

[0107] Step 4.2: Construct the bidirectional physical gradient matrix: Based on the following linear physical mapping formula, forcibly generate the first... The initial geometric parameter matrices of the first and second microtube arrays within each sound-absorbing unit:

[0108]

[0109]

[0110]

[0111]

[0112] in, and The first The initial internal radius and initial geometric length of the first embedded microtube in each sound-absorbing unit. and The first The initial internal radius and initial geometric length of the second embedded microtube in each sound-absorbing unit. and These represent the upper and lower limits of the radius of embedded microtubes, which are limited by additive manufacturing precision and acoustic requirements. and These are the upper and lower limits of the length of the first embedded microtube, respectively. and These are the upper and lower limits of the length of the second embedded microtube, respectively. and This is the gradient adjustment factor;

[0113] Step 4.3, Perform initial fitness assessment: The above formula sets the radius and length of the first and second embedded microtubules as spatial distribution coefficients. The opposite changes—decreasing radius and increasing length—create a bidirectional physical gradient that couples positive and negative features, resulting in the generated microtube geometric parameter matrix. Inject it into the global optimization algorithm and call the multi-objective function. Perform fitness assessment on the initial population.

[0114] Step 5: Based on the population initialized in Step 4, execute a hybrid optimization strategy based on genetic algorithm (GA) and sequential quadratic programming algorithm (SQP), and introduce strict physical space and manufacturing accuracy boundary constraints to obtain the optimal geometric parameter matrix. Step 5 specifically includes the following steps:

[0115] Step 5.1, Global Optimization and Boundary Constraints: Based on the population initialized in Step 4, a genetic algorithm is used to perform global optimization iterations. During each iteration and fitness evaluation, the internal radius of the embedded microtube is adjusted. and geometric length Apply hard boundary constraints:

[0116]

[0117]

[0118]

[0119] in, and These are the geometric depths of the first cavity and the second cavity, respectively. The preset acoustic gap threshold is used to force the end of the embedded microtube to maintain a minimum distance from the bottom backplate of the cavity, so as to prevent acoustic short circuit. and The lower and upper limits of the radius of embedded microtubes are limited by the precision of additive manufacturing;

[0120] Step 5.2: Set the maximum number of generations for the genetic algorithm to be [value missing]. (e.g., 100 generations) serves as a hard termination criterion for the global search; when the genetic algorithm reaches... Or the optimal fitness of individuals in a population is continuous No significant improvement after 50 generations (the change is less than the preset threshold) When the time condition is met, the switching mechanism is automatically triggered. At this time, the current globally optimal chromosome vector output by the genetic algorithm is extracted. As an initial value, a sequential quadratic programming algorithm (SQP / fmincon) is seamlessly injected to enable gradient-based local refinement mode;

[0121] Step 5.3, Gradient Descent and Convergence Output: The sequential quadratic programming algorithm uses the globally optimal chromosome vector. Starting with a multi-objective function The local gradient information is iteratively fine-tuned continuously until the preset algorithm convergence tolerance is met, such as when the gradient or step size change is lower than a set threshold. Finally, the globally optimal geometric parameter matrix that satisfies the hard boundary constraints is output. .

[0122] Step 6: Based on the optimized geometric parameter matrix obtained through optimization, perform solid fabrication and assembly to ultimately obtain a compact, broadband, flow-resistant, and sound-absorbing structure. This specifically includes the following steps:

[0123] Step 6.1, Solid Modeling and Additive Manufacturing: Extract the embedded microtube radius and length data from the optimal geometric parameter matrix output in Step 5, generate a three-dimensional parametric solid model containing the first microtube array, the first cavity, the second microtube array, and the second cavity, and use additive manufacturing technology to print a compact broadband anti-flow sound-absorbing structure based on the three-dimensional parametric solid model.

[0124] Step 6.2, Interface Layer Decoupling Assembly: A precision acoustic metal mesh with a predetermined specific acoustic impedance is provided as a flow resistance control interface layer. The flow resistance control interface layer is assembled on the acoustic wave incident surface side of the resonant body, and the interface gap between the flow resistance control interface layer and the upper panel is maintained at a predetermined thickness to obtain a compact broadband anti-flow sound absorption structure.

[0125] like Figure 6 As shown in (a), the optimized array consists of multiple sound-absorbing units with identical outer contours but different internal parameters; as Figure 6 As shown in (b), the optimized structure forms a relatively high and continuous sound absorption plateau in the range of 250 Hz to 900 Hz; Figure 6 (c) and Figure 6 As shown in (d) in the figure, its impedance response and characteristic distribution further demonstrate that this non-uniform parameter array is advantageous for achieving broadband sound absorption.

[0126] like Figure 7 As shown, the optimized 3D solid model output in this embodiment is used for prototype manufacturing and physical assembly. Based on the optimized geometric parameters, the main body is preferably prepared using fused deposition modeling (FDM) 3D printing, and the preferred printing material is PLA (polylactic acid). Figure 7 Image (a) shows a front view of the 3D printed structure. Figure 7 (b) shows a side view of the 3D printed structure. Figure 7 (c) in the figure shows the flow resistance control interface layer used. Figure 7 (d) shows the assembled prototype. Figure 7 (a) and Figure 7 As can be seen from (b), the main structure is composed of multiple sound-absorbing units arranged in parallel. Each unit has the same external contour, but the size and arrangement of the internal microtube openings are different.

[0127] To construct the acoustic-flow decoupling interface structure, after the main body is printed, a 2.5 mm thick double-sided adhesive mesh is set on its front acoustic wave incident surface, such as... Figure 13 As shown, this is used to form an interfacial gap and provide support for the flow resistance control interface layer. Subsequently, tension is applied to the flow resistance control interface layer and it is fixed to the surface of the double-sided adhesive mesh. Preferably, the flow resistance control interface layer is made of a reverse Dutch mesh with a specific acoustic impedance of 65 Rayl, such as... Figure 7 As shown in (c).

[0128] like Figure 7As shown in (d) of the assembled prototype, the flow resistance control interface layer maintains a predetermined interval with the rigid body, thereby forming a stable interface gap. This assembly method not only facilitates the reliable fixing of the interface layer, but also helps to avoid the additional vibration effects caused by direct contact between the flexible metal mesh and the rigid body, thus improving the structural stability and operational stability of the device under dynamic conditions.

[0129] like Figure 8 As shown, this embodiment performs static sound absorption verification on the obtained full-size solid sample. Figure 8 Image (a) shows an impedance tube testing platform, which includes the impedance tube body, a sound source, a microphone, and a signal acquisition and analysis system. This platform allows for the measurement of the normal incident sound absorption performance of a sample under controlled conditions. Figure 8 Figure (b) shows a comparison curve between the measured sound absorption results and the numerical prediction results of the prototype. Within the test frequency band of 250 Hz-900 Hz, the prototype maintains a continuous and high sound absorption level without obvious deep valleys, and the measured average sound absorption coefficient reaches 0.938. This result shows that the combination of the double-layer multi-tube embedded structure and the flow resistance control interface layer proposed in this application can achieve broadband and efficient sound absorption under limited thickness conditions, indicating that the method and manufacturing assembly method of this application can well realize the theoretical structure. During the test, the sample is placed in a special acoustic impedance tube for normal incident sound absorption testing. The test system preferably conforms to the ISO10534-2 standard, with an inner cross-sectional dimension of 160mm×160mm in the impedance tube. The sound pressure signal is obtained using the dual-microphone transfer function method, and the sound absorption coefficient of the sample in the target frequency band is calculated.

[0130] Dynamic flow field verification:

[0131] like Figure 9 As shown, a wind tunnel test platform was constructed in a transparent plexiglass duct with a cross-sectional size of 200 mm × 200 mm. The inlet was connected to a low-noise wind tunnel, and six optimized double-layer multi-tube embedded units were installed in the test section. Figure 9 Image (a) in the image is a physical photograph of the test platform. Figure 9 (b) in the diagram is a schematic diagram of the test platform structure. This platform can simulate the actual working state under the action of grazing jet.

[0132] Before conducting the dynamic insertion loss test, it is preferable to first conduct a background noise test under conditions without an external sound source. Figure 10 As shown in (a). At a flow velocity of 9.8 m / s, Figure 10Figure (b) shows a comparison between the cases with and without a flow resistance control interface layer. The results show that the additional peak value and pseudo-sound level in the background pressure spectrum are reduced after the interface layer is set, indicating that the interface layer helps to reduce the direct impact of flow disturbance on the inlet region of the test section.

[0133] like Figure 11 As shown in (a) and (b), with the sound source closed at a higher flow rate, a comparison is made between the case with and without an interface layer, where the sound-absorbing unit is installed. Without an interface layer, a more obvious narrow-band peak appears in the spectrum, indicating a strong coupling between the open cavity and the grazing jet. After the interface layer is installed, the aforementioned narrow-band peak is significantly reduced, and the pressure spectrum tends to be smoother, indicating that the flow resistance control interface layer helps to reduce shear layer feedback and flow-induced cavity sound phenomena.

[0134] like Figure 12 As shown, the dynamic insertion loss was tested under white noise excitation in the range of 250 Hz to 900 Hz. Figure 12 (a) in the figure corresponds to the test results at a flow rate of 3.1 m / s, with a peak noise reduction of 28.63 dB and an average attenuation of 8.94 dB; Figure 12 (b) shows the test results at a flow velocity of 9.8 m / s, with a peak noise reduction of 24.63 dB and an average attenuation of 8.28 dB. These results demonstrate that this application still possesses relatively stable broadband noise reduction capabilities and good aeroacoustic stability under dynamic flow field conditions.

[0135] The above results demonstrate that the present invention still possesses stable broadband noise reduction capability and good aeroacoustic stability in dynamic flow fields.

[0136] This embodiment takes the design of a 4×4 sound-absorbing unit array with a target frequency band of 250 Hz-900 Hz as an example to illustrate the execution process of the method of this application.

[0137] 1. Initialization of physical parameters and constraints

[0138] First, set the acoustic environment parameters: air density speed of sound Set the specific acoustic impedance of the flow resistance control interface layer (acoustic mesh). .

[0139] Define geometric constraints:

[0140] Total number of sound-absorbing units ;

[0141] First cavity depth Second cavity depth ;

[0142] Microtubule radius constraint ;

[0143] upper limit of microtubule length Set as cavity depth minus Acoustic gap threshold .

[0144] 2. Perform bidirectional physics gradient initialization.

[0145] To accelerate convergence and ensure that the sound absorption peaks are uniformly distributed within the target frequency band, the program calls the initialization function to generate the initial population.

[0146] Spatial distribution coefficient : according to the serial number of the sound-absorbing unit (1 to 16) Linear distribution from 0 to 1.

[0147] Bidirectional mapping: Set the first set of seeds (direction coefficients) ) to increase the microtubule radius Follow Decreasing, while length Follow Increment; Set the second seed group ( ) Perform the opposite logic.

[0148] The physical gradient logic generates 200 initial individuals, ensuring that the initial solution space has initially covered the resonance characteristics of 250 Hz - 900 Hz.

[0149] 3. Execution of the hybrid optimization algorithm

[0150] The algorithm employs a smooth switching strategy between genetic algorithm (GA) and sequential quadratic programming algorithm (SQP):

[0151] Global Optimization (GA) Phase:

[0152] Population size: 200; Maximum number of generations: 100.

[0153] Fitness function: The objective is to maximize the average sound absorption coefficient within the target frequency band, while also introducing a penalty term. This penalty clause mandates that the sound absorption coefficient at any frequency point within the 250-900 Hz range must not be lower than 0.82 to ensure spectral flatness.

[0154] Algorithm switching criteria: This embodiment sets a dual switching threshold: when the number of generations reaches 100, or the change in the fitness function value of the best individual in the population within 50 consecutive generations is less than 100. When the time comes, the GA operation is terminated.

[0155] Local Qualification Phase (SQP): The globally optimal geometric parameter matrix output by the GA is extracted as initial values, and the fmincon solver in MATLAB is automatically invoked. Utilizing the local gradient information of the cost function, and while satisfying the physical space boundary constraints, the 16 elements are refined. A total of 64 variables were continuously decreased iteratively.

[0156] 4. Optimization Results and Physical Verification

[0157] After the above hybrid optimization process, the optimal geometric parameter matrix is ​​finally output. The optimized structure achieves an average sound absorption coefficient of over 0.90 in the 250 Hz - 900 Hz range, and the minimum sound absorption coefficient is maintained above 0.82 due to the penalty function constraint, achieving excellent broadband flat sound absorption effect.

[0158] This application has the advantages of compact structure, broadband low-frequency sound absorption, anti-grazing radiation loss stability and suitability for additive manufacturing.

[0159] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A compact, broadband, flow-resistant, sound-absorbing structure, characterized in that: The broadband anti-flow sound-absorbing structure includes a resonant body and a flow resistance control interface layer disposed on the incident surface of the resonant body, wherein, The resonant body includes multiple sound-absorbing units arranged in parallel. Each sound-absorbing unit includes a first cavity and a second cavity arranged sequentially along the direction of sound wave propagation. A first microtube array is arranged in the first cavity, and a second microtube array is arranged in the second cavity. The first cavity and the second cavity are separated by a partition. The first microtube array includes a top panel and multiple parallel first embedded microtubes disposed on the top panel. The second microtube array includes a partition and one or more parallel second embedded microtubes disposed on the partition. The first embedded microtubes extend into the first cavity, and the second embedded microtubes extend into the second cavity. The flow resistance control interface layer is not directly attached to the resonant body, and a predetermined thickness interface gap is formed between the flow resistance control interface layer and the upper panel. The interface gap is located between the flow resistance control interface layer and the inlet of the first microtube array.

2. The compact broadband anti-flow sound-absorbing structure according to claim 1, characterized in that: The outer contours of the first cavity and the second cavity are aligned. The first cavity is located on the side closer to the incident sound wave, and the second cavity is located on the side of the first cavity and away from the incident sound wave. The first cavity and the second cavity are connected in series along the direction of sound wave propagation and are coupled through a middle partition and adjacent sound fields to form a double-layer coupled resonant system.

3. The compact broadband anti-flow sound-absorbing structure according to claim 1, characterized in that: The sound-absorbing unit has a square cross-section, and the internal geometric parameters of multiple sound-absorbing units are different to form a non-uniform parameter array and obtain a broadband response.

4. The compact broadband anti-flow sound-absorbing structure according to claim 1, characterized in that: The flow resistance control interface layer is made of precision metal mesh, and the specific acoustic resistance of the precision metal mesh is 65Rayl.

5. A compact broadband anti-flow sound-absorbing structure according to claim 1, characterized in that: The interface gap consists of double-sided adhesive mesh, support frame, gasket, boss, and spacer.

6. The compact broadband anti-flow sound-absorbing structure according to claim 1, characterized in that: The method for preparing the broadband anti-flow sound-absorbing structure includes the following steps: Step 1: Establish a parameterized structural model that includes a first cavity, a second cavity, a first microtube array, a second microtube array, a flow resistance control interface layer, and interface gaps; Step 2: Obtain the complex effective density and complex bulk modulus of the air medium inside the first and second embedded microtubes. The characteristic impedance of a single embedded microtube is equivalently converted according to the number of tubes to characterize the boundary layer dissipation enhancement effect brought about by the parallel connection of multiple tubes. A correction term is introduced, and the acoustic transfer matrix of the first microtube array, the first cavity, the second microtube array, and the second cavity are cascaded in sequence to obtain the surface impedance of multiple parallel sound-absorbing units and the total acoustic impedance of the broadband anti-flow sound-absorbing structure. Step 3: Construct a multi-objective function To calculate the objective function value, the formula is constructed as follows: in, The objective function value, The matrix of geometric parameters of the microtube to be optimized. The total number of frequency points. For the first Discrete frequency points, For the microtube geometry parameter matrix And the discrete frequency points are The total sound absorption coefficient of the broadband anti-flow sound-absorbing structure was calculated at that time. It is the negative value of the average sound absorption coefficient. This is a one-sided, double-penalty term. The preset penalty weight factor, The preset critical sound absorption performance threshold is defined as follows: when a certain local discrete frequency point... The overall sound absorption coefficient of the broadband anti-flow sound-absorbing structure at the location Fall to The following times, The result is positive; Step 4: In the population initialization phase of the global optimization algorithm, the geometric parameter matrix of the microtube to be optimized is... Initialization based on bidirectional physical gradients is performed to ensure that the initial resonant frequencies of each sound-absorbing unit are approximately uniformly distributed within the target frequency band. Step 5: Based on the population initialized in Step 4, execute a hybrid optimization strategy based on genetic algorithm (GA) and sequential quadratic programming algorithm (SQP), and introduce physical space and manufacturing accuracy boundary constraints to obtain the globally optimal geometric parameter matrix. Step 6: Based on the optimal geometric parameter matrix obtained through optimization, the solid is manufactured and assembled to finally obtain a compact broadband anti-flow sound-absorbing structure.

7. The compact broadband anti-flow sound-absorbing structure and its preparation method according to claim 6, characterized in that: Step 2 specifically includes the following steps: Step 2.1: To address the dissipation effect of the confined space within the first and second microtube arrays, a hierarchical parameter is introduced. ,in , respectively corresponding to the first microtube array and the second microtube array, calculate the first Complex effective density of air medium inside microtubes With complex bulk modulus : in, Angular frequency, This is the static density of air at room temperature. Standard atmospheric pressure The specific heat ratio of air. and These represent the zeroth and first-order Bessel functions of the first kind, respectively. For the first The shear wavenumber of the air medium inside the microtube. For the first The thermal wavenumber of the air medium inside the microtube; Step 2.2, the first The characteristic impedance of a single embedded microtube in a layered microtube array divided by the number of parallel tubes in that layer. The equivalent characteristic impedance of the array is obtained by equivalent conversion, so as to characterize the boundary layer dissipation enhancement effect brought about by the parallel connection of multiple tubes; Step 2.3: Introduce correction terms for the first and second cavities, and calculate the effective volume of the corresponding cavities after correction: in, The cross-sectional area of ​​the top panel. This corresponds to the geometric depth of the cavity. This corresponds to the internal radius of the embedded microtube within the cavity. This corresponds to the geometric length of the embedded microtube within the cavity; Step 2.4: Using the transfer matrix method, based on the above-corrected effective cavity volume... The acoustic transfer matrices of the first microtube array, the first cavity, the second microtube array, and the second cavity are sequentially cascaded to obtain the surface impedance of each sound-absorbing unit. The reciprocal of the surface impedance of each sound-absorbing unit is taken and summed in parallel to calculate the total admittance of the array. Then, the surface impedance of the sound-absorbing unit can be obtained. ,in Finally, the surface impedance of the sound-absorbing unit is... The inherent specific acoustic impedance of the flow resistance control interface layer By performing series superposition, the total acoustic impedance of the broadband anti-flow sound-absorbing structure can be finally obtained. .

8. A compact broadband anti-flow sound-absorbing structure according to claim 6, characterized in that: Step 4 specifically includes the following steps: Step 4.1: Introduce the spatial distribution coefficient , According to the serial number of the sound-absorbing unit It exhibits a gradient distribution; Step 4.2: Construct the bidirectional physical gradient matrix: Based on the following linear physical mapping formula, forcibly generate the first... The initial geometric parameter matrices of the first and second microtube arrays within each sound-absorbing unit: in, and The first The initial internal radius and initial geometric length of the first embedded microtube in each sound-absorbing unit. and The first The initial internal radius and initial geometric length of the second embedded microtube in each sound-absorbing unit. and These are the upper and lower limits of the radius of the embedded microtube, respectively. and These are the upper and lower limits of the length of the first embedded microtube, respectively. and These are the upper and lower limits of the length of the second embedded microtube, respectively. and This is the gradient adjustment factor; Step 4.3: Perform initial fitness assessment: Set the radius and length of the first and second embedded microtubules to spatial distribution coefficients. The opposite changes form a bidirectional physical gradient that couples positive and negative features, resulting in the generated microtube geometric parameter matrix. Inject it into the global optimization algorithm and call the multi-objective function. Perform fitness assessment on the initial population.

9. A compact broadband anti-flow sound-absorbing structure according to claim 6, characterized in that: Step 5 specifically includes the following steps: Step 5.1, Global Optimization and Boundary Constraints: Based on the population initialized in Step 4, a genetic algorithm is used to perform global optimization iterations. During each iteration, the internal radius of the embedded microtube is adjusted. and geometric length Apply hard boundary constraints: in, and These are the geometric depths of the first cavity and the second cavity, respectively. The preset acoustic gap threshold, and These are the lower and upper limits of the radius of the embedded microtube; Step 5.2: Set the maximum number of generations for the genetic algorithm to be [value missing]. As a hard termination criterion for global search, when the genetic algorithm reaches... Or the optimal fitness of individuals in a population is continuous When there is no promotion, the switching mechanism is automatically triggered. At this time, the currently globally optimal chromosome vector output by the genetic algorithm is extracted. As an initial value, it is seamlessly injected into the sequential quadratic programming algorithm to enable gradient-based local refinement mode; Step 5.3, Gradient Descent and Convergence Output: The sequential quadratic programming algorithm uses the globally optimal chromosome vector. Starting with a multi-objective function The local gradient information is used for iterative fine-tuning with continuous descent until the preset algorithm convergence tolerance is met, and finally the globally optimal geometric parameter matrix that satisfies the hard boundary constraints is output. .

10. A compact broadband anti-flow sound-absorbing structure according to claim 6, characterized in that: Step 6 specifically includes the following steps: Step 6.1, Solid Modeling and Additive Manufacturing: Extract the embedded microtube radius and length data from the optimal geometric parameter matrix output in Step 5, generate a three-dimensional parametric solid model containing the first microtube array, the first cavity, the second microtube array, and the second cavity, and use additive manufacturing technology to print a compact broadband anti-flow sound-absorbing structure based on the three-dimensional parametric solid model. Step 6.2, Interface Layer Decoupling Assembly: Provide a flow resistance control interface layer, assemble the flow resistance control interface layer on the acoustic wave incident surface side of the resonant body, and ensure that the flow resistance control interface layer and the upper panel maintain an interface gap of a predetermined thickness to obtain a compact broadband anti-flow sound absorption structure.

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