Acoustic metamaterial suitable for leading edge slat, design method and slat

Abstract

The invention provides an acoustic metamaterial suitable for a leading edge slat, a design method and the slat, and belongs to the field of aircraft noise reduction. The acoustic metamaterial comprises a plurality of acoustic metamaterial subunits, and each subunit is composed of a micro-perforated plate and a cavity. And at least one of the plurality of subunits is linear and the internal channel of the cavity is linear, and at least one of the plurality of subunits is curved and the internal channel of the cavity is curved. The linear and curved subunits form a conformal unitary structure by an adaptive arrangement including profile adaptation within the airfoil profile and location distribution and combination within a profile perpendicular to the airfoil profile and along the leading and trailing edges. According to the invention, extremely limited space in the slat is utilized to the maximum extent through conformal design, a sound wave propagation path is prolonged at a sub-wavelength scale through linear and curved cavity channels, efficient low-frequency sound absorption is realized, broadband noise is covered through combination of multiple subunits, and the problem of insufficient low-frequency sound absorption in a slat space in a traditional scheme is effectively solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of aircraft noise reduction technology, and particularly relates to an acoustic metamaterial suitable for a leading edge slat, a design method of the acoustic metamaterial, and a leading edge slat applying the acoustic metamaterial. BACKGROUND

[0002] With the rapid development of the aviation transportation industry, aviation noise pollution has become a key factor restricting the sustainable growth of the industry. International authoritative research has confirmed that aviation noise not only significantly reduces the quality of life of residents around the airport, but also induces health risks such as cardiovascular diseases. In response to this challenge, the European Union has successively introduced the Vision 2020 (requiring a 50% reduction in aircraft noise by 2020 compared with the 2000 baseline) and Flightpath 2050 (requiring a further 65% reduction by 2050) mandatory noise reduction targets, posing a severe challenge to the acoustic design of aircraft.

[0003] During the approach and take-off phase of a civil aviation passenger aircraft, the leading edge slat, as the core component of the lift augmentation device, has been identified as one of the main noise sources. Its noise mechanism is complex, showing a wide frequency characteristic dominated by low frequency, and the traditional noise reduction methods face two major bottlenecks: first, the contradiction between aerodynamic performance and noise reduction, by modifying the slat cavity shape such as filling, super-long chord or serrated trailing edge, although the noise can be improved, the flow field structure will be changed, thereby affecting the wing lift; second, space constraints and low-frequency failure, the available space in the slat is extremely limited, for example, in the 30P30N wing, the slat occupies only 2.7% of the entire wing space, and the slat also needs to reserve connection interfaces and control systems, further compressing the noise reduction design space, traditional acoustic solutions such as porous materials and honeycomb acoustic liners require a large thickness for low-frequency sound absorption, which is difficult to achieve effective low-frequency absorption in the small scale space of the slat. SUMMARY

[0004] The purpose of the present application is to solve the problems that the existing aircraft leading edge slat noise reduction scheme affects the wing lift and the low-frequency sound absorption fails due to insufficient space, and to provide an acoustic metamaterial suitable for a leading edge slat, a design method of the acoustic metamaterial, and a leading edge slat applying the acoustic metamaterial, which can achieve efficient suppression of medium and low frequency wideband noise in the highly limited space of the slat while preserving the aerodynamic performance of the slat.

[0005] To achieve the above purpose, the technical solution provided by the present application is:

[0006] On the one hand, an acoustic metamaterial suitable for a leading edge slat is provided, comprising a plurality of acoustic metamaterial subunits.

[0007] Each acoustic metamaterial subunit comprises a micro-perforated plate and a cavity, the micro-perforated plate covers the open end of the cavity, and one or more perforations are formed on the micro-perforated plate as sound wave incidence ports;

[0008] Among the plurality of acoustic metamaterial subunits, at least one subunit is linear, and the internal passage of the cavity is linear; at least one subunit is curved, and the internal passage of the cavity is curved;

[0009] The linear subunits and the curved subunits are adaptively arranged to form an overall structure conforming to the geometric profile of the leading edge slat; the adaptive arrangement includes profile adaptation within the airfoil section, and position distribution and combination within the section perpendicular to the airfoil section and along the leading and trailing edges.

[0010] Further, the perforations on the micro-perforated plate are all arranged away from the central region of the cavity to maximize the propagation path of the sound wave in the cavity.

[0011] Further, among the plurality of acoustic metamaterial subunits, the internal tortuous passage of the cavity of the curved subunit comprises at least one 90° bending segment or at least one 180° bending segment.

[0012] Further, there are two linear subunits, namely a first linear subunit and a second linear subunit; there are three curved subunits, the internal tortuous passage of the cavity of two of which comprises a 90° bending segment, namely a first curved subunit and a second curved subunit, and the internal tortuous passage of the cavity of one of which comprises a 180° bending segment, namely a third curved subunit.

[0013] Further, the plurality of acoustic metamaterial subunits are adaptively arranged within the airfoil section of the leading edge slat; among them, the first curved subunit is located in the front region of the slat, the second linear subunit and the third curved subunit are located in the middle region of the slat, the first linear subunit and the second curved subunit are located in the rear region of the slat, and the subunits partially overlap and stagger in the direction perpendicular to the airfoil section and along the leading and trailing edges, in the spanwise direction and in the direction perpendicular to the spanwise direction.

[0014] Further, the aperture of the perforations on the micro-perforated plate is not more than 1.5 mm.

[0015] Another aspect provides a design method of the above acoustic metamaterial, comprising the following steps:

[0016] Step 1: According to the noise spectrum characteristics of the leading edge slat, determine the target noise reduction frequency band; and according to the geometric space of the slat interface, set the number of acoustic metamaterial subunits, and divide the target noise reduction frequency band into a plurality of target sound absorption frequencies corresponding to the number of subunits;

[0017] Step 2: Distribute multiple target sound absorption frequencies to each acoustic metamaterial subunit;

[0018] Step 3: For each acoustic metamaterial subunit, based on its assigned target sound absorption frequency, adjust its structural parameters to match the target acoustic impedance at that frequency; the structural parameters include at least the perforation diameter and number of holes in the micro-perforated plate, and the effective length of the internal channel of the cavity.

[0019] Step 4: Combine multiple acoustic metamaterial sub-units with completed structural parameter design to form an acoustic metamaterial unit;

[0020] Step 5: Calculate the overall sound absorption coefficient of the acoustic metamaterial unit based on the following formula. And by iteratively optimizing the structural parameters in step 3, the sound absorption coefficient is improved. Within the target noise reduction frequency band, the preset requirements are met, including the sound absorption coefficient. Calculated using the following formula:

[0021]

[0022]

[0023] In the formula, The total acoustic impedance of the acoustic metamaterial unit. The number of acoustic metamaterial subunits. For the first The acoustic impedance of each acoustic metamaterial subunit is calculated as follows:

[0024]

[0025] In the formula, and The first Acoustic impedance of the micro-perforated plate and cavity in each acoustic metamaterial subunit and These are the density of air and the speed of sound, respectively. Let be the area of ​​the incident sound wave.

[0026] Furthermore, the acoustic impedances of the micro-perforated plate and the cavity are calculated as follows:

[0027] Z p i = j ω p 0 n i S h i { t [ 1 − 2 B 1 ( x − j ) x − j B 0 ( x − j ) ] − 1 + 0 . 8 5 d i } + 2 m x n i S h i d i

[0028]

[0029] In the formula, The imaginary unit, This represents the cross-sectional area of ​​a single perforation. For the number of holes, The diameter of the perforation hole. and These are the 0th and 1st order Bessel functions of the first kind, respectively. For the thickness of the micro-perforated plate, The dynamic viscosity of air. Angular frequency, The perforation constant; The effective length of the internal channel of the cavity. This represents the cross-sectional area of ​​the internal channel of the cavity; and These are the effective characteristic impedance and effective wavenumber of the air inside the cavity, respectively. and The expressions are as follows:

[0030]

[0031]

[0032] In the formula, and These are the length and width of the internal channel of the cavity, respectively. and For the number of iterations, , , , , and These are the thermal conductivity and specific heat at constant volume of air, respectively. Atmospheric pressure Specific heat ratio.

[0033] Another aspect provides a leading-edge slat using the aforementioned acoustic metamaterial, including a slat skeleton and multiple acoustic metamaterial units composed of multiple acoustic metamaterial subunits, with the multiple acoustic metamaterial units arranged along the spanwise direction in the slat interface of the slat skeleton.

[0034] The advantages of this invention are:

[0035] 1. The sound-absorbing structure for leading-edge slats provided by this invention employs acoustic metamaterial design techniques, adaptively and conformally arranging linear and curved acoustic metamaterial sub-units within the airfoil section and sections perpendicular to the airfoil section and along the leading and trailing edges. This allows the structure to closely conform to the complex geometric contours of the leading-edge slat, achieving the integration of structural conformity and acoustic function under extremely limited spatial constraints. This structure utilizes a combination of linear cavities and internal tortuous channels to effectively extend the sound wave propagation path on the subwavelength scale, significantly enhancing the sound absorption performance of mid-to-low frequency noise (especially in the 400-3000Hz range). Experiments show that its average noise reduction can reach 1.7dB in the 1500-2200 Hz range, effectively solving the problem of insufficient low-frequency sound absorption of traditional porous materials and honeycomb acoustic liners in the narrow space of slats.

[0036] 2. The acoustic metamaterial design method provided by this invention, based on the noise spectrum characteristics of the slat and the interface geometric constraints, decomposes the broadband noise reduction target into multiple single-frequency sound absorption sub-targets. By establishing a theoretical model of the acoustic impedance of the micro-perforated plate and the cavity, the structural parameters of each sub-unit are systematically derived. Iterative optimization is then performed using the sound absorption coefficient formula and the impedance parallel model, achieving precise and controllable acoustic metamaterial design for broadband noise of the leading edge slat. This method can achieve broadband and efficient sound absorption with an average sound absorption coefficient of 0.80 in the frequency range of 1030-2000 Hz.

[0037] 3. The leading-edge slat provided by this invention, which utilizes the aforementioned acoustic metamaterial, achieves broadband suppression of slat cavity noise by periodically arranging multiple acoustic metamaterial units along the spanwise direction of the slat in the interface of the slat skeleton, while maintaining the original aerodynamic shape and lift characteristics. Experimental results show that the average noise reduction of this leading-edge slat reaches 1.3 dB in the frequency range of 1030-2000 Hz, demonstrating excellent engineering applicability and noise reduction potential, and providing an effective technical means for the design of a new generation of low-noise, high-lift systems. Attached Figure Description

[0038] The above and / or other features and advantages of the present invention will become more readily understood from the following description with reference to the accompanying drawings, which are not drawn to scale and some features are enlarged or reduced to show details of specific parts.

[0039] Figure 1 This is a schematic diagram of the noise reduction interface required by the slat acoustic metamaterial in this embodiment of the invention;

[0040] Figure 2 This is a schematic diagram of the structure of the slat acoustic metamaterial unit in an embodiment of the present invention;

[0041] Figure 3 This is a flowchart of the acoustic metamaterial design method in an embodiment of the present invention;

[0042] Figure 4 This is a schematic diagram of the finite element model of the slat acoustic metamaterial unit in an embodiment of the present invention;

[0043] Figure 5 This is a simulation curve of the sound absorption coefficient of the acoustic metamaterial unit in the embodiment of the present invention;

[0044] Figure 6 This is a schematic diagram of the digital model arrangement of the leading edge slats in the spanwise direction in an embodiment of the present invention;

[0045] Figure 7 This is a comparison curve of the sound pressure level between the baseline configuration and the noise reduction configuration using the acoustic metamaterial of this invention.

[0046] In the diagram: 1-Slat metamaterial unit; 2-Slat skeleton; 3-Background pressure field; 4-Perfect matching layer; 10-Noise reduction interface. Detailed Implementation

[0047] The present invention will now be described in detail with reference to the accompanying drawings and exemplary embodiments thereof. It should be noted that the following detailed description of the present invention is for illustrative purposes only and is not intended to limit the scope of the invention.

[0048] It should be noted that, in the context of this invention, the terms “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “inner,” “outer,” “clockwise,” and “counterclockwise,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0049] Furthermore, terms such as "first" and "second" are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0050] The present invention aims to resolve the contradiction between the extremely small internal space of the leading edge slat and the difficulty in effectively suppressing its low-frequency broadband noise.

[0051] Reference Figure 1The illustration shows the noise reduction interface 10 required for an acoustic metamaterial suitable for a leading-edge slat, as an exemplary embodiment of the present invention. This interface is located inside the leading-edge slat and is defined by the slat frame 2, within an extremely compact space. For example, in the 30P30N airfoil, the slat itself occupies only about 2.7% of the total airfoil volume, and the noise reduction interface 10 is designed within this extreme space.

[0052] To achieve conformity with this narrow space and complex curved surface, the present invention designs as follows: Figure 2 The acoustic metamaterial unit 1 shown is composed of multiple acoustic metamaterial sub-units, which can be obtained by 3D printing. In this embodiment, there are five sub-units, namely sub-unit 1-1, sub-unit 1-2, sub-unit 1-3, sub-unit 1-4, and sub-unit 1-5. Those skilled in the art will understand that the specific number of sub-units is not limited to this and can be adjusted according to the actual slat geometry and noise reduction requirements. Each sub-unit includes a micro-perforated plate and a cavity. The micro-perforated plate covers the open end of the cavity, and one or more perforations as sound wave inlets are formed on the micro-perforated plate.

[0053] These sub-units are designed with different shapes according to the slat geometry of their location: sub-units 1-1 and 1-2 are straight, and their internal channels are also straight; while sub-units 1-3, 1-4 and 1-5 are curved, and their internal channels are correspondingly tortuous. The tortuous channels include at least one 90° bend or at least one 180° bend, so that the sound wave propagation path forms a corresponding L-shaped structure, U-shaped structure, S-shaped structure or a tortuous structure with more bends.

[0054] All these straight and curved sub-units are achieved through, for example Figure 2 The adaptive arrangement shown forms an overall structure conforming to the geometric contour of the leading-edge slat. In the figure, the x-axis direction is the direction of sound wave incidence, and the z-axis direction is the spanwise direction of the slat. The adaptive arrangement referred to here is a comprehensive three-dimensional spatial arrangement process, mainly including two aspects: First, contour adaptation within the airfoil section (the plane defined by the x-axis and y-axis), that is, the projection and combination of sub-units on the slat airfoil section must ensure that the overall structure matches the airfoil airfoil profile; Second, positional distribution and combination within the section perpendicular to the airfoil section and along the leading and trailing edges of the slat (the section defined by the x-axis and z-axis), including assembly and combination within this section, in the spanwise direction (z-axis direction) and the leading-to-trailing-edge direction (the direction perpendicular to the spanwise direction, y-axis direction), which must ensure that they can closely fit the slat's cross-sectional shape.

[0055] Through collaborative design in the two dimensions mentioned above, all sub-units together form an overall structure that is highly conformal to the complex three-dimensional profile of the leading-edge slats, maximizing space utilization.

[0056] To enhance the sound absorption performance of individual subunits, particularly low-frequency absorption, the perforations on the micro-perforated plate are intentionally positioned away from the center of the cavity. For linear subunits, the perforations are located at the ends along their length; for curved subunits, the perforations are offset towards the convex side of their curved profile. This design forces incident sound waves to undergo a longer propagation path after entering the cavity, thereby increasing the friction and heat loss between the sound energy and the perforation walls and air, effectively extending the sound path. In particular, for curved subunits, the tortuous channels inside the cavity (e.g., containing 90° or 180° bends) can extend the sound wave path several times over within a limited space through multiple bends, thus achieving strong absorption of low-frequency noise on the subwavelength scale.

[0057] like Figure 2 As shown, in this embodiment, five sub-units are adaptively interleaved within the airfoil profile: the first curved sub-unit 1-3 is located at the leading edge of the slat; the second straight sub-unit 1-2 and the third curved sub-unit 1-4 are located in the middle; the first straight sub-unit 1-1 and the second curved sub-unit 1-5 are located at the trailing edge, such that in the two end faces of the formed acoustic metamaterial unit in the spanwise direction of the slat, one end face is composed of sub-units 1-1, 1-3, and 1-4, and the other end face is composed of sub-units 1-3 and 1-5, while sub-unit 1-2 is sandwiched in the middle. The sub-units partially overlap and interweave in the section perpendicular to the airfoil profile and along the leading and trailing edges, and in the spanwise and perpendicular directions, forming a compact and efficient layout. In this way, as... Figure 2 As indicated by the white arrows, the internal channels of the cavities of each sub-unit are either straight or curved in a section perpendicular to the airfoil and along the leading and trailing edges.

[0058] In addition, to balance processability and aeroacoustic requirements, the perforation diameter of the micro-perforated plate 101 does not exceed 1.5 mm.

[0059] The acoustic metamaterial of this invention can achieve excellent mid-to-low frequency noise reduction in the extremely confined space of the leading-edge slat. The principle lies in the synergistic effect of three core designs: First, the macroscopic conformal design maximizes the use of the irregular space inside the slat by assembling linear and curved sub-units, providing the largest physical volume for acoustic function; second, the tortuous channel design greatly extends the sound wave propagation path at the subwavelength scale by bending, thereby stimulating a strong low-frequency resonant sound absorption mechanism and overcoming the performance barrier of traditional materials in the low-frequency range; finally, the modular broadband design combines multiple sub-units tuned to different frequencies in parallel, so that their sound absorption peaks are connected and merged in the frequency domain, thereby achieving effective coverage of broadband noise of the slat.

[0060] Reference Figure 3The design method of acoustic metamaterials, as an exemplary embodiment of the present invention, includes the following steps:

[0061] Step S1: Based on the slat noise spectrum, determine the target noise reduction frequency band (e.g., 400-3000 Hz), and determine the number of sub-units (e.g., five) based on the geometric space of the slat interface, dividing the broadband target into multiple target sound absorption frequencies corresponding to the number of sub-units;

[0062] Step S2: Assign each target sound absorption frequency to the corresponding sub-unit;

[0063] Step S3: For each subunit, based on its assigned target sound absorption frequency, adjust the structural parameters such as the perforation diameter, number of holes, and effective length of the internal channel of the micro-perforated plate to make its acoustic impedance optimal at that frequency.

[0064] Step S4: Combine all the designed sub-units into a complete acoustic metamaterial unit;

[0065] Step S5: Calculate the total acoustic impedance of the unit based on the impedance parallel formula, evaluate its broadband performance through the sound absorption coefficient, and iteratively optimize the parameters of step S3 until the requirements are met.

[0066] The sound absorption coefficient is calculated using the following formula:

[0067]

[0068]

[0069] In the formula, The total acoustic impedance of the acoustic metamaterial unit. The number of acoustic metamaterial subunits. For the first The acoustic impedance of each acoustic metamaterial subunit is calculated as follows:

[0070]

[0071] In the formula, and The first Acoustic impedance of the micro-perforated plate and cavity in each acoustic metamaterial subunit and These are the density of air and the speed of sound, respectively. Let be the area of ​​the incident sound wave's cross-section. , This represents the side length of the cross-section of the incident sound wave.

[0072] The acoustic impedances of the micro-perforated plate and the cavity are calculated as follows:

[0073] Z p i = j ω p 0 n i S h i { t [ 1 − 2 B 1 ( x − j ) x − j B 0 ( x − j ) ] − 1 + 0 . 8 5 d i } + 2 m x n i S h i d i

[0074]

[0075] In the formula, The imaginary unit, This represents the cross-sectional area of ​​a single perforation. For the number of holes, The diameter of the perforation hole. and These are the 0th and 1st order Bessel functions of the first kind, respectively. For the thickness of the micro-perforated plate, The dynamic viscosity of air. Angular frequency, The perforation constant; The effective length of the internal channel of the cavity. This represents the cross-sectional area of ​​the internal channel of the cavity; and These are the effective characteristic impedance and effective wavenumber of the air inside the cavity, respectively. and The expressions are as follows:

[0076]

[0077]

[0078] In the formula, and These are the length and width of the internal channel of the cavity, respectively. and The number of iterations in the calculation process. , , , , and These are the thermal conductivity and specific heat at constant volume of air, respectively. Atmospheric pressure Specific heat ratio.

[0079] As an exemplary embodiment of the present invention, the leading edge slat includes a slat frame 2 and a plurality of acoustic metamaterial units 1 composed of a plurality of acoustic metamaterial subunits, wherein the plurality of acoustic metamaterial units 1 are arranged in the slat interface of the slat frame 2 along the spanwise direction of the slat.

[0080] To verify the design, a pressure acoustic module was built in COMSOL Multiphysics as follows: Figure 4The finite element model is shown. In this model, 1 represents the slat metamaterial element, whose tortuous cavity uses a pressure acoustic domain, while the micro-perforations use a thermoviscous acoustic domain to accurately calculate losses; 3 represents the background pressure field, applied with plane wave radiation; and 4 represents the perfectly matched layer, used to simulate a non-reflective boundary. Based on the aforementioned design method, the detailed structural parameters and final simulation performance of the slat metamaterial element are as follows:

[0081] Table 1 Structural parameters of the slat acoustic metamaterial subunit

[0082]

[0083] In this embodiment, all micro-perforated plates are 1.5 mm thick and the perforation diameter is 1 mm, satisfying the requirement of "not exceeding 1.5 mm". The effective channel length of each sub-unit is specially designed according to its target frequency. The effective length of the curved sub-units (1-3, 1-4, 1-5) is greater than that of the straight sub-units, reflecting the design concept of extending the sound path through tortuous channels.

[0084] By solving the scattered sound pressure of the background pressure field With background sound pressure The ratio of these two values ​​can be used to calculate the reflection coefficient:

[0085]

[0086] The sound absorption coefficient can then be calculated using the relationship between the sound absorption coefficient and the reflection coefficient.

[0087]

[0088] By using the formula for the sound absorption coefficient, a time-domain solution is performed in COMSOL Multiphysics to obtain the sound absorption coefficient curve, as shown below. Figure 5 As shown in Table 2, the sound absorption coefficient of this design is greater than 0.5 in the 1030-2000 Hz range, and the average sound absorption coefficient is 0.80 in this range. The absorption frequencies and peak values ​​of the five sound-absorbing units are shown in Table 2, which verifies the effectiveness of achieving broadband noise reduction through the combination of multiple sub-units.

[0089] Table 2 Sound absorption performance of slat metamaterial subunits

[0090]

[0091] Finally, refer to Figure 6This paper demonstrates an implementation scheme that applies multiple of the aforementioned acoustic metamaterial units to a leading-edge slat. As shown in the digital model, five locations of the aforementioned acoustic metamaterial are arranged along the spanwise direction of the slat, each comprising multiple acoustic metamaterial units 1, and fixed by a slat frame 2, thereby forming a continuous noise reduction zone across the entire slat span. The slat frame 2 is machined from metal to ensure its experimental strength in the acoustic wind tunnel and to prevent significant bending or other phenomena.

[0092] To verify the noise reduction capability of the slat acoustic metamaterial, an acoustic wind tunnel experiment was conducted at a flow velocity of 60 m / s and an angle of attack of 8°. The microphone measuring point was located 6.3 m directly below the slat. Figure 7 The sound pressure level comparison curve. From Figure 7 As can be seen, compared to the baseline configuration (curve with square dots), the noise reduction configuration using the acoustic metamaterial of this invention (curve without scattering points) achieves an average noise reduction of 1.3 dB in the design frequency range of 1030-2000 Hz. Due to the flow effect of the metamaterial, the sound absorption peak shifts, resulting in an even higher average noise reduction of 1.7 dB in the 1500-2200 Hz range, fully demonstrating its effectiveness and reliability in real airflow environments.

[0093] In summary, this invention, through conformal design, tortuous extension, and modular combination, successfully achieves efficient suppression of mid-to-low frequency broadband noise within the slat limit space, providing an innovative and feasible solution for the field of aviation noise reduction.

[0094] Finally, it should be noted that the features mentioned and / or shown in the above description of exemplary embodiments of the present invention can be combined in the same or similar manner with one or more other embodiments, combined with or substituted for corresponding features in other embodiments. These combined or substituted technical solutions should also be considered to be included within the scope of protection of the present invention.

Claims

1. An acoustic metamaterial suitable for use in a leading edge slat, characterized by: The acoustic metamaterial subunit comprises a micro-perforated plate and a cavity, the micro-perforated plate is covered on the open end of the cavity, and one or more perforations on the micro-perforated plate are used as sound wave incidence ports. At least one of the acoustic metamaterial subunits is linear, and the internal passage of the cavity is linear; at least one of the acoustic metamaterial subunits is curved, and the internal passage of the cavity is curved. The linear subunit and the curved subunit are adaptively arranged to form an overall structure conforming to the geometric profile of the leading edge slat; the adaptive arrangement includes profile adaptation within the airfoil profile and position distribution and combination within the profile perpendicular to the airfoil profile and along the leading and trailing edges. The perforations on the micro-perforated plate are arranged away from the central region of the cavity to maximize the propagation path of the sound wave in the cavity.

2. An acoustic metamaterial suitable for use in a leading edge slat according to claim 1 characterised in that: The internal zigzag passage of the cavity of the curved subunit comprises at least one 90° bending section or at least one 180° bending section.

3. Acoustic metamaterial suitable for a leading edge slat according to claim 1 or 2, characterized in that: The linear subunit is provided with two, namely a first linear subunit (1-1) and a second linear subunit (1-2); the curved subunit is provided with three, the internal zigzag passage of the cavity of two of which comprises a 90° bending section, namely a first curved subunit (1-3) and a second curved subunit (1-5), and the internal zigzag passage of the cavity of one of which comprises a 180° bending section, namely a third curved subunit (1-4).

4. An acoustic metamaterial suitable for use in a leading edge slat according to claim 3, characterised in that: The plurality of acoustic metamaterial subunits are adaptively arranged within the airfoil profile of the leading edge slat; wherein the first curved subunit (1-3) is located in the front region of the slat, the second linear subunit (1-2) and the third curved subunit (1-4) are located in the middle region of the slat, the first linear subunit (1-1) and the second curved subunit (1-5) are located in the rear region of the slat, and each subunit is partially overlapped and staggered in the direction perpendicular to the airfoil profile and along the leading and trailing edges, in the spanwise direction and in the direction perpendicular to the spanwise direction.

5. An acoustic metamaterial suitable for use in a leading edge slat according to claim 4, characterised in that: The aperture of the perforation on the micro-perforated plate is not more than 1.5 mm.

6. An acoustic metamaterial suitable for use in a leading edge slat according to claim 1 or 2, characterised in that: The method comprises the following steps:

7. A method of designing an acoustic metamaterial according to any one of claims 1 to 6, characterized in that, Step 1: determining the target noise reduction frequency band according to the noise spectrum characteristics of the leading edge slat; and setting the number of acoustic metamaterial subunits according to the geometric space of the slat interface, and dividing the target noise reduction frequency into a plurality of target sound absorption frequencies corresponding to the number of subunits; Step 2: distributing the plurality of target sound absorption frequencies to each acoustic metamaterial subunit; Step 3: for each acoustic metamaterial subunit, matching the target acoustic impedance at the target sound absorption frequency assigned to it by adjusting its structural parameters; the structural parameters at least include the perforation aperture and the number of perforations of the micro-perforated plate, and the effective length of the internal passage of the cavity; Step 4: combining the plurality of acoustic metamaterial subunits with completed structural parameter design to form an acoustic metamaterial unit; The acoustic impedance of the micro-perforated plate and the cavity is calculated as follows: Step 5, calculate the overall sound absorption coefficient of the acoustic metamaterial unit based on the following formula And through iterative optimization of the structure parameters in step 3, the sound absorption coefficient Meets the preset requirements within the target noise reduction frequency band, wherein the sound absorption coefficient Is calculated by the following formula: In the formula, The total acoustic impedance of the acoustic metamaterial unit. The number of acoustic metamaterial subunits. For the first The acoustic impedance of each acoustic metamaterial subunit is calculated as follows: wherein and are the acoustic impedance of the micro-perforated panel and the cavity in the th acoustic metamaterial sub-unit, respectively, and are the density and the sound speed of air, respectively, is the area of the incident sound wave.

8. The method of designing according to claim 7, wherein, ​ wherein is the imaginary unit, denotes the cross-sectional area of a single perforation, is the number of perforations, is the perforation diameter, and are the zeroth and first order Bessel functions of the first kind, respectively, is the micro-perforated panel thickness, is the dynamic viscosity of air, is the angular frequency, is the perforation constant; is the effective length of the internal passage of the cavity, is the cross-sectional area of the internal passage of the cavity; and are the effective characteristic impedance and the effective wave number of the air inside the cavity, respectively, and are expressed as follows, respectively: where, and are the length and width of the internal passage of the cavity, respectively, and are the number of iterations, , , , , and are the thermal conductivity and the specific heat at constant volume of air, respectively, is the atmospheric pressure, is the ratio of specific heats.

9. A leading edge slat wing employing the acoustic metamaterial of any one of claims 1 to 6, characterized in that: The slat skeleton and a plurality of acoustic metamaterial units composed of the plurality of acoustic metamaterial subunits are arranged in a slat interface of the slat skeleton along a slat spanwise direction.

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