A noise suppression method and device for jet impact inclined plate

Abstract

This invention provides a noise suppression method and device for a jet impact inclined plate. The method employs porous media layouts with different physical properties to specifically reduce various types of noise from jet impact, including the following steps: establishing a baseline model and multiple optimized models for numerical calculation of the jet impact inclined plate, and setting calculation conditions for each model; performing noise reduction analysis on the baseline model and multiple optimized models based on the calculation conditions to obtain the noise reduction results for each model; comparing the noise reduction results of the multiple optimized models and the baseline model to evaluate the optimal noise reduction model among the multiple optimized models; and performing mechanistic analysis on the optimal noise reduction model to obtain its underlying mechanism. The baseline model for the jet impact inclined plate is a non-porous medium inclined plate, and the optimized models are non-uniform porous medium inclined plates. The method provided by this invention achieves equipment noise control without changing the existing design.

Description

Technical Field

[0001] This invention relates to the field of noise reduction technology, and in particular to a noise suppression method and device for a jet impact inclined plate. Background Technology

[0002] Jet impact on a ramp refers to a physical phenomenon in which a high-speed fluid (such as gas or liquid) ejected from a nozzle or other device impacts a fixed or movable inclined plate at a certain angle. This phenomenon has wide applications in engineering fields, involving fluid mechanics, heat transfer, noise control, and energy conversion. The core characteristics of jet impact on a ramp include: The jet direction is not perpendicular to the ramp: the jet typically impacts the ramp at a certain angle (e.g., 22.5°, 65°, etc.), rather than perpendicularly; Complex flow and acoustic field interactions exist: after the jet impacts the ramp, boundary layer separation, vortex shedding, shock wave reflection, and other phenomena occur, especially under supersonic conditions. The physical phenomenon of jet impact on inclined plates is widely used in the following engineering applications: Energy field: such as the use of high-speed water jets to impact the runner blades of a water turbine to generate electricity; Thermal management field: jet impact on inclined plates is used to enhance heat exchange, such as post-rolling cooling of medium and heavy plates and heat dissipation of chips; Noise control: studying the impact of jet impact on inclined plates on noise (such as shock wave howling and turbulent noise); Flow measurement: impact flow meters calculate the flow rate by measuring the impact force of the material on the inclined plate. The main applications of jet impact inclined plates are as follows: Inclined-impact water turbines: The nozzle jet impacts the turbine blades at an angle of approximately 22.5°, achieving efficient kinetic energy conversion; Ultra-fast cooling systems: In steel rolling, jet impact inclined plate structures (such as slit nozzles or high-density array nozzles) are used to improve cooling uniformity and intensity; Aero-engine / gas turbine cooling: Inclined jets impact the turbine blade surface, optimizing local heat transfer; Noise mechanism research: By changing the distance (L) and angle (β) between the jet and the inclined plate, the changes in noise components are analyzed.

[0003] In existing technologies, noise control methods for jet impact ramps are mainly divided into active noise control strategies and passive noise control strategies. Passive noise control strategies typically aim to suppress noise sources such as jet shear layers, shock waves, impact stagnation zones, and transverse flow on the wall by optimizing the nozzle / ramps structure, adding porous media / sound-absorbing materials, or optimizing impact geometry, without introducing external energy. This disrupts the noise self-excitation feedback loop and achieves noise reduction for the jet impact ramp. Both active noise reduction strategies and passive noise control measures based on nozzle reshaping will change existing designs.

[0004] How to achieve noise control without changing the existing design is a core issue for researchers and a technical problem that urgently needs to be solved. Summary of the Invention

[0005] To address the aforementioned issues, this application provides a noise suppression method and device for jet impact on an inclined plate. This method is based on the sound absorption and vibration reduction mechanism of porous media. By exploring the influence of non-uniform porous media arrangements with different physical properties and area ratios on the total sound pressure level of a high-speed jet impacting an inclined plate, the optimal structural configuration with the best noise reduction performance is selected. Furthermore, by combining flow field evolution characteristics and multi-source noise components of jet impact, the suppression mechanism of this structure on typical noise sources such as turbulent broadband noise, impact howling noise, and separation vortex-induced noise is analyzed, fully revealing its noise reduction mechanism.

[0006] The specific technical solution of the present invention is as follows:

[0007] In a first aspect, the present invention provides a noise suppression method for a jet impact inclined plate, which employs porous media layouts with different physical properties to specifically reduce various types of noise from jet impact, including the following steps:

[0008] A baseline model and several optimized models for numerical calculation of jet impact on inclined plates were established, and the calculation conditions for each model were set.

[0009] Based on the aforementioned computational conditions, a noise reduction analysis is performed on the baseline model and multiple optimized models to obtain the noise reduction results for each model.

[0010] The denoising results of multiple optimized models and benchmark models are compared to evaluate the best denoising model among the multiple optimized models;

[0011] Mechanism analysis was performed on the optimal noise reduction model to obtain its underlying mechanism;

[0012] The baseline model of the jet impact inclined plate is a non-porous medium inclined plate, and the optimized model is a non-uniform porous medium inclined plate.

[0013] Preferably, the establishment of the baseline model and multiple optimized models for numerical calculation of jet impact inclined plate specifically includes:

[0014] A baseline model and several optimized models of jet impacting an inclined plate are modeled, the modeled models are meshed, and the process of jet impacting the inclined plate is simulated.

[0015] Preferably, obtaining the noise reduction results of each model specifically includes: obtaining the total sound pressure level of each model, and using the total sound pressure level of each model as the noise reduction result of each model;

[0016] The comparison of denoising results from multiple optimized models and a benchmark model to evaluate the best denoising model among the multiple optimized models specifically includes:

[0017] The total sound pressure level of multiple optimized models is compared with that of the benchmark model, and the best noise reduction model among the multiple optimized models is determined based on the comparison results.

[0018] Preferably, the setting of calculation conditions for each model specifically includes: setting the condition number and multiple physical property parameters for each model, wherein the multiple physical property parameters include: porosity, porous area ratio and PPI of each corresponding porosity for each model.

[0019] Preferably, the non-uniform porous medium inclined plate is a segmented porous medium inclined plate, wherein the upper and lower parts of the segmented porous medium inclined plate have the same porosity PPI, and the middle part has a different porosity PPI than the upper and lower parts.

[0020] Preferably, the specific pore density values ​​of the upper, middle and lower parts of the segmented porous medium inclined plate are 10, 5 and 10, or 30, 10 and 30, or 30, 50 and 30.

[0021] Preferably, after evaluating the best noise reduction model among multiple optimization models, the method further includes: obtaining the PPI of the porosity corresponding to the best noise reduction model;

[0022] The aforementioned mechanistic analysis of the optimal noise reduction model to obtain its underlying mechanism specifically includes:

[0023] Based on the PPI of the porosity corresponding to the obtained optimal noise reduction model, a mechanism analysis is performed on the optimal noise reduction model to obtain its intrinsic mechanism.

[0024] Preferably, the mechanism analysis of the optimal noise reduction model specifically includes: performing mechanism analysis of the optimal model from the perspectives of turbulent kinetic energy, Q-criterion vorticity, spectrum diagram, and coherence.

[0025] After performing mechanistic analysis on the optimal noise reduction model, the method further includes: adjusting multiple physical property parameters of the optimal noise reduction model based on the mechanistic analysis to optimize the optimal noise reduction model.

[0026] Secondly, the present invention also provides a device in which the noise suppression method for jet impacting an inclined plate as described in the first aspect is applied.

[0027] Preferably, the equipment includes carrier-based aircraft that take off and land on the aircraft carrier deck.

[0028] The noise suppression method for jet impact inclined plate of the present invention has the following advantages over the prior art:

[0029] 1. The noise suppression method for jet impact inclined plate provided by the present invention establishes a benchmark model and multiple optimized models for numerical calculation of jet impact inclined plate, sets the calculation conditions for each model, performs noise reduction analysis on the benchmark model and multiple optimized models based on the calculation conditions, obtains the noise reduction results of each model, compares the noise reduction results of multiple optimized models and benchmark model, evaluates the best noise reduction model among multiple optimized models, performs mechanism analysis on the best noise reduction model, and obtains the intrinsic mechanism of the best noise reduction model. The benchmark model of jet impact inclined plate is a non-porous medium inclined plate, and the optimized model is a non-uniform porous medium inclined plate. This method takes the sound absorption and vibration reduction mechanism of porous media as its core. By exploring the influence of non-uniform arrangement of porous media with different physical properties and different area ratios on the total sound pressure level of high-speed jet impact on inclined plate, the optimal structural configuration with the best noise reduction performance is selected. Furthermore, by combining the flow field evolution characteristics and the multi-source noise components of jet impact, the suppression mechanism of this structure on typical noise sources such as turbulent broadband noise, impact howling noise, and separation vortex-induced noise is analyzed, and its noise reduction mechanism is fully revealed.

[0030] 2. This method can be applied to carrier-based aircraft. In response to the hazards caused by the strong impact noise induced by the high-speed wake jet of carrier-based aircraft impacting the deflector, such as seriously threatening the physical and mental health of personnel working on the aircraft carrier deck and restricting the safe take-off of carrier-based aircraft, deflectors are usually installed behind carrier-based aircraft that take off and land on the aircraft carrier deck without changing the shape of the aircraft engine nozzle. This can increase the utilization rate of deck space and prevent the high-speed and high-temperature tail jet generated by the carrier-based aircraft from injuring the personnel behind the aircraft and the safety of other aircraft. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a flowchart illustrating the noise suppression method for jet impacting an inclined plate in an embodiment of the present invention.

[0033] Figures 2(a) and 2(c) are schematic diagrams of Model A of the noise suppression method applicable to jet impact inclined plate in the embodiments of the present invention.

[0034] Figures 2(b) and 2(d) are schematic diagrams of Model B of the noise suppression method applicable to the jet impact inclined plate in the embodiment of the present invention.

[0035] Figure 3This is a microphone array arrangement diagram for a noise suppression method applicable to a jet impact inclined plate in an embodiment of the present invention.

[0036] Figure 4 This is a schematic diagram of the mesh generation for a noise suppression method applicable to a jet impact inclined plate in an embodiment of the present invention.

[0037] Figure 5 In the noise suppression method for jet impacting the inclined plate in this embodiment of the invention, under operating conditions A-B4, 100Hz-1×10 4 A graph showing the total sound pressure level at a frequency of Hz.

[0038] Figures 6(a) and 6(b) are comparison diagrams of turbulent kinetic energy based on working conditions A and B3 as shown in Figure 6(c) in the noise suppression method of jet impacting inclined plate in the embodiment of the present invention.

[0039] Figures 7(a), 7(c), 7(b), and 7(d) are comparison diagrams of Q-criterion vorticity based on working condition A and working condition B3 in the noise suppression method of jet impact inclined plate in the embodiment of the present invention.

[0040] Figure 8 The above are the spectrum diagrams of upstream (130°) and downstream (30°) of models A and B3 in the noise suppression method of jet impact inclined plate in the embodiment of the present invention.

[0041] Figure 9 This is a schematic diagram of the model coherence monitoring point location for the noise suppression method of jet impact inclined plate in an embodiment of the present invention.

[0042] Figure 10 In the middle, the three small figures from left to right are the pressure coherence diagrams at (a), (b), and (c) of Model A and Model B3 of the noise suppression method for jet impacting inclined plate in the embodiment of the present invention.

[0043] Figure 11 In the middle, the three small figures from left to right are the velocity coherence diagrams at (a), (b), and (c) of Model A and Model B3 of the noise suppression method for jet impacting inclined plate in the embodiment of the present invention. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0045] To better understand the invention and not to limit its scope, all figures indicating amounts, percentages, and other numerical values ​​used in this application should, in all cases, be understood to be modified by the word "approximately." Therefore, unless specifically stated otherwise, the numerical parameters listed in the specification and appended claims are approximate values ​​and may vary depending on the desired properties being sought. Each numerical parameter should at least be considered as obtained based on reported significant figures and through conventional rounding methods.

[0046] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single digits within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0047] Porous media refers to a multiphase composite structure consisting of a solid framework and interconnected / closed pore spaces, in which fluids can seep, diffuse, dissipate, and exchange energy.

[0048] This invention proposes to suppress noise by using a porous deflector plate to regulate flow characteristics without altering the existing design of the aircraft carrier deck and carrier-based aircraft. Although there are existing reports on using uniform porous inclined plates to suppress high-speed jet impact noise, the types of noise that can be suppressed are limited, and there is a tendency for some noises to increase while others decrease, resulting in unsatisfactory noise reduction effects, with a maximum noise reduction of only 6.92 dB.

[0049] To address the limitations of existing uniform porous inclined plate noise reduction techniques in accurately resolving the complex multi-source, broadband noise issues in jet impact inclined plate systems, this invention proposes a non-uniformly distributed porous inclined plate noise reduction method. By rationally allocating the spatial arrangement of porous media and adjusting the ratio of pore size, material properties, and other physical parameters, the noise reduction potential of porous inclined plates is fully explored, achieving synergistic suppression of multiple noise components. This results in a more superior and robust overall noise reduction effect compared to uniform porous plates.

[0050] This invention proposes a noise reduction method using non-uniformly distributed porous inclined plates, applicable to equipment such as carrier-based aircraft capable of takeoff and landing on aircraft carrier decks. The following section uses the application of this method to carrier-based aircraft as an example to reveal and analyze the method.

[0051] Carrier-based aircraft that perform short takeoff and landing (STOVL) on the deck are typically equipped with deflectors. This increases deck space utilization and prevents the high-speed, high-temperature exhaust jets generated during takeoff from injuring personnel and other aircraft. However, the presence of deflectors also significantly increases the noise radiation intensity on the deck. Studies show that the exhaust velocity of carrier-based aircraft typically exceeds the speed of sound, with exhaust impact noise reaching up to 170 dB. Even with noise-protected headphones, the ambient noise level remains as high as 140 dB, severely damaging the physical and mental health of ground crew working at close range for extended periods and affecting mission execution. Furthermore, the high-intensity impact noise can cause structural vibrations, leading to fatigue damage and destruction of precision instruments and engines within the aircraft, threatening flight safety. With the rapid development of my country's aircraft carriers and the increasing number of carrier-based aircraft, the demand for all-weather training is growing daily. To establish a precise and effective carrier deck noise and safety protection system and ensure the flight safety and mission execution of carrier-based aircraft, research on noise suppression from carrier-based aircraft exhaust impact deflectors is urgently needed.

[0052] This invention addresses the hazards posed by the strong impact noise induced by the high-speed wake jet of carrier-based aircraft impacting the deflector plate, such as seriously threatening the physical and mental health of personnel working on the aircraft carrier deck and restricting the safe takeoff of carrier-based aircraft. Without changing the shape of the carrier-based aircraft engine nozzle, a passive deformation and noise reduction strategy using a non-uniformly distributed multi-hole inclined plate is proposed.

[0053] The steps and underlying mechanisms of this method are explained below.

[0054] This invention provides a noise suppression method for jet impact on inclined plates, employing porous media layouts with different physical properties to specifically reduce various types of noise from jet impact, such as... Figure 1 As shown, it includes the following steps:

[0055] S1. Establish a baseline model and multiple optimized models for numerical calculation of jet impact inclined plate, and set the calculation conditions for each model;

[0056] S2. Based on the calculation conditions, perform noise reduction analysis on the benchmark model and multiple optimized models to obtain the noise reduction results of each model;

[0057] S3. Compare the denoising results of multiple optimized models and the benchmark model, and evaluate the best denoising model among the multiple optimized models;

[0058] S4. Conduct a mechanism analysis on the optimal noise reduction model to obtain its underlying mechanism;

[0059] The baseline model of the jet impact inclined plate is a non-porous medium inclined plate, and the optimized model is a non-uniform porous medium inclined plate.

[0060] It should be noted that the noise suppression method for jet impact inclined plate provided by the present invention establishes a benchmark model and multiple optimized models for numerical calculation of jet impact inclined plate, sets the calculation conditions for each model, performs noise reduction analysis on the benchmark model and multiple optimized models based on the calculation conditions, obtains the noise reduction results of each model, compares the noise reduction results of multiple optimized models and the benchmark model, evaluates the best noise reduction model among multiple optimized models, performs mechanism analysis on the best noise reduction model, and obtains the intrinsic mechanism of the best noise reduction model. The benchmark model of the jet impact inclined plate is a non-porous medium inclined plate, and the optimized model is a non-uniform porous medium inclined plate. This method takes the sound absorption and vibration reduction mechanism of porous media as its core. By exploring the influence of non-uniform arrangement of porous media with different physical properties and different area ratios on the total sound pressure level of high-speed jet impact on inclined plate, the optimal structural configuration with the best noise reduction performance is selected. Furthermore, by combining the flow field evolution characteristics and the multi-source noise components of jet impact, the suppression mechanism of this structure on typical noise sources such as turbulent broadband noise, impact howling noise, and separation vortex-induced noise is analyzed, and its noise reduction mechanism is fully revealed.

[0061] In some embodiments, establishing a baseline model and multiple optimized models for numerical calculation of jet impact inclined plate specifically includes:

[0062] A baseline model and several optimized models of jet impacting an inclined plate are modeled, the modeled models are meshed, and the process of jet impacting the inclined plate is simulated.

[0063] Specifically, SOLIDWORKS was used to model the jet impact inclined plate model, and ICEM was used to mesh the model (see reference). Figure 4 The jet impacting the inclined plate process was simulated using FLUENT. The baseline model A and the optimized model B are shown in Figure 2. In both models, the nozzle inner diameter d = 56 mm, the nozzle outer diameter is 96 mm, the airflow inlet inner diameter is 200 mm, and the airflow inlet outer diameter is 230 mm. The distance from the nozzle to the inclined plate is 4d = 224 mm, the angle between the inclined plate and the horizontal plane is 55°, and the inclined plate parameters are 600 mm × 600 mm × 20 mm. The nozzle tip is set as a pressure outlet, the default gas is a compressible ideal gas, and the nozzle outlet pressure is 1.6 × 10⁻⁶. 5The non-uniform porous medium region has parameters of 600mm × 600mm × 20mm, with a lateral distribution, and is set as internal. To ensure accurate evaluation of the noise generated by the jet impact, the sound integral surface spatial parameters are 30d × 30d × 18d (1680mm × 1680mm × 1008mm), also set as internal. To ensure sufficient space for accurate capture of fluid characteristics, the space outside the computational domain is 36d × 36d × 30d (2016mm × 2016mm × 1680mm). The ambient temperature ratio Tr is set to 1, meaning the temperature at the nozzle exit is the same as the ambient temperature. The nozzle inner wall and the inclined plate surface are both set as no-slip solid wall boundary conditions. All surfaces of the external flow field are set as pressure outlets, and the ambient pressure is set to 9.6 × 10⁻⁶. 4 Pa, ambient temperature set to 300 K.

[0064] In some embodiments, setting the calculation conditions for each model specifically includes: setting the condition number and multiple physical property parameters for each model, wherein the multiple physical property parameters include: the porosity, the percentage of porous area, and the PPI of each corresponding porosity for each model.

[0065] In some embodiments, the non-uniform porous medium inclined plate is a segmented porous medium inclined plate, wherein the upper and lower parts of the segmented porous medium inclined plate have the same porosity PPI, and the middle part has a different porosity PPI than the upper and lower parts.

[0066] In some embodiments, the specific porosity values ​​of the upper, middle and lower parts of the segmented porous medium inclined plate are 10, 5 and 10, or 30, 10 and 30, or 30, 50 and 30.

[0067] Specifically, the calculation conditions for setting the baseline model and the optimization model can be shown in Table 1.

[0068] Table 1

[0069]

[0070] This invention uses 10 PPI and 50 PPI in the middle of the inclined plate to investigate the effects of two different physical properties on jet impact noise and vortex changes, and selects 30 PPI on the upper and lower sides of the plate to dissipate and absorb small vortices.

[0071] In some embodiments, obtaining the noise reduction results of each model specifically includes: obtaining the total sound pressure level of each model and using the total sound pressure level of each model as the noise reduction result of each model;

[0072] The comparison of denoising results from multiple optimized models and a benchmark model to evaluate the best denoising model among the multiple optimized models specifically includes:

[0073] The total sound pressure level of multiple optimized models is compared with that of the benchmark model, and the best noise reduction model among the multiple optimized models is determined based on the comparison results.

[0074] In some embodiments, after evaluating the best noise reduction model among multiple optimization models, the method further includes: obtaining the porosity PPI corresponding to the best noise reduction model;

[0075] The aforementioned mechanistic analysis of the optimal noise reduction model to obtain its underlying mechanism specifically includes:

[0076] Based on the PPI of the porosity corresponding to the obtained optimal noise reduction model, a mechanism analysis is performed on the optimal noise reduction model to obtain its intrinsic mechanism.

[0077] In some embodiments, the mechanism analysis of the optimal noise reduction model specifically includes: performing mechanism analysis of the optimal model from the perspectives of turbulent kinetic energy, Q-criterion vorticity, spectrum diagram, and coherence.

[0078] After performing mechanistic analysis on the optimal noise reduction model, the method further includes: adjusting multiple physical property parameters of the optimal noise reduction model based on the mechanistic analysis to optimize the optimal noise reduction model.

[0079] Specifically, in steady-state flow field calculations, a k-ω SST (shear stress transport) turbulence model is used to ensure computational accuracy; in transient flow field calculations, Large Eddy Simulation (LES) is employed to accurately predict aerodynamic noise and capture the evolution of transient vortex structures. Spatial discretization uses a second-order upwind scheme, and the subgrid-scale model used in LES is the WALE model. Time term discretization uses a second-order implicit scheme. To ensure computational accuracy, the time step is set to 1×10⁻⁶. -5 s. In far-field noise calculations based on the FW-H (Fowcs Williams-Hawkings) acoustic analogy theory, to comprehensively evaluate acoustic characteristics and verify calculation results, reference is made to... Figure 3 The microphone array is used to deploy far-field monitoring points: with the nozzle center as the base point, monitoring points are set every 10° along the azimuth angle from 30° to 140° on the side of the nozzle axis, for a total of 12 monitoring points. All monitoring points are distributed in an arc shape with a distribution radius of 3.55 × 10⁻⁶. 3 mm.

[0080] Coherence analysis is a quantitative assessment method based on the linear correlation between the frequency domain cross power spectral density and the self power spectral density. It is used to characterize the degree of linear correlation and causal transmission characteristics of two random signals at different frequencies.

[0081] In the model coherence analysis, analysis points were taken 20 mm vertically above the inclined plate of model A (10 mm above the inclined plate of model B). Points ① and ② are located at 30 PPI, and points ③ and ④ are located at 10 PPI. (a) represents the coherence between points ③ and ④, (b) represents the coherence between points ② and ③, and (c) represents the coherence between points ① and ②. This is used to further analyze the mechanism of jet flow at 10 PPI and 30 PPI.

[0082] Comparison of total sound pressure levels from models A to B4 ( Figure 5 As can be seen, models B0-B4 all exhibit significant noise reduction effects compared to the baseline model, achieving a systematic reduction in noise levels at the sound source level. Among models B0-B3, model B3 (porosity 0.95; upper, middle, and lower area ratios of 10%, 80%, and 10%, respectively; corresponding to PPI 30 / 10 / 30) has the lowest total sound pressure level across almost all three stages, achieving an average noise reduction of 13.74 dB from multiple angles. While model B4 shows better noise reduction in the middle stage, the sound pressure levels in the upper and lower stages remain relatively high, indicating a boundary effect. Furthermore, further reducing the PPI based on the porous parameters of model B4 would, strictly speaking, exceed the range of porous materials. Therefore, model B3 is determined to be the optimal noise reduction model. Next, the noise reduction mechanism of model B2 will be analyzed from multiple aspects, including turbulent kinetic energy, Q-criterion vorticity, spectrum diagram, and coherence.

[0083] Comparing the turbulent kinetic energy (TKE) of the baseline plate and model B3 (Figure 6), it was found that, compared with the baseline plate, the red and white Mach ring regions in the high-energy region (region I), the interaction between the jet shear layer vortex structure and the impact region (region III), the jet shear layer vortex structure and the free jet region (region II) of model B3 were significantly reduced, and the reduction was significant. This phenomenon indicates that the porous distribution structure adopted by model B3 can effectively intervene in the vortex evolution process inside the flow field, greatly weaken the generation and transfer of turbulent kinetic energy in the interaction region between the free jet region of region II and region III, and effectively suppress the turbulent kinetic energy in the high-energy region of region I. The reduction of turbulent kinetic energy is directly positively correlated with the generation of flow field noise, further achieving the purpose of noise reduction. Based on the structural design of Model B3, it can be seen that the red and white areas in Region I of the turbulent kinetic energy diagram of Model B3 do not involve the 30 PPI area on the upper side of the inclined plate. This feature is closely related to the layered porous structure design of the model: the central 10 PPI area, with its specific porosity and pore size, can break up and dissipate the large eddies in the middle, and then guide these small-scale eddies into the 30 PPI porous area on the upper side of the inclined plate. The 30 PPI porous structure has a finer pore structure than the 10 PPI porous structure, which can further break up the small-scale eddies. Through the viscous dissipation effect of the porous medium, the energy of the small-scale eddies is absorbed, which promotes the continuous decay of turbulent kinetic energy and thus significantly suppresses the noise generated by eddy current interaction. The synergistic effect of this segmented porous structure realizes the graded breaking up and energy dissipation of eddies of different scales. Compared with the single structure of the reference plate, its control accuracy of turbulent kinetic energy and noise reduction effect are significantly improved, providing an effective structural optimization idea for flow field noise control.

[0084] The Q-criterion vorticity isosurfaces describing the jet impact on the inclined plate in the positive and inclined directions are used (Figure 7), where the Q-criterion vortex intensity is set as Q = 9 × 10⁻⁶. 4This threshold effectively identifies vortex-dominated regions and captures vortex structures with significant influence in the flow field. By comparing the vortex isosurface distribution differences between the reference plate and model B3 at this vortex intensity, it can be found that when the jet impacts the reference plate, a large number of continuously distributed large-scale vortices exist on the surface of the reference plate, and the red area representing high velocity amplitude above the inclined plate is more extensive and darker in color. This phenomenon indicates that when the jet impacts the reference plate, the high-speed amplitude of the fluid in the wall impact region directly leads to enhanced turbulent pulsation in the flow field, resulting in stronger noise. In contrast, the number of large-scale vortices above the inclined plate in model B3 is significantly reduced, and the vortex size is noticeably smaller. Simultaneously, the small-scale vortices on the left and right sides and below the inclined plate also show a clear attenuation trend. Correspondingly, the areas of the red and white highlighted regions corresponding to the velocity amplitude are significantly reduced in size and brightness. This confirms that the 10 PPI portion of the non-uniform porous medium structure used in model B3 can disrupt the large-scale vortex structure formed during jet impact, preventing further development of large-scale vortices. At the same time, the viscous dissipation and pore blockage effects of the 30 PPI porous medium can absorb energy from the broken small-scale vortices, suppressing the pulsation intensity of small-scale vortices and reducing noise sources generated by vortex interactions. Ultimately, this achieves the dual effect of optimizing the flow field vortex structure and suppressing noise, verifying the effectiveness of the non-uniform porous distribution structure in flow field noise control.

[0085] In the complex flow field of a jet impacting an inclined plate, the upstream region is the ideal area for capturing high-frequency acoustic features, the downstream region is the dominant area for the evolution of the jet on the wall, and the midstream region is a transition section, where the acoustic features are a combination of upstream and downstream mechanisms. Therefore, by comparing and analyzing the acoustic features of the upstream and downstream regions and eliminating the interference of the midstream transition flow field, we can more specifically explain the evolution law in the jet impact process.

[0086] contrast Figure 8 The spectrum analysis of the two models reveals that model B3 significantly reduces the sound pressure level across the entire frequency range. At 130° upstream, the non-uniform porous structure represented by model B3 not only effectively reduces low-frequency turbulent mixing noise but also eliminates discrete single tones with an attenuation of up to 26.8 dB. This demonstrates that the non-uniform porous structure can effectively disrupt the acoustic feedback loop formed by the interaction between the jet shear layer and the near-wall region. Specifically, the 10 PPI porous medium absorbs most of the momentum during jet impact, weakening the initial sound wave generated by the collision. The viscous dissipation of the 30 PPI porous medium significantly absorbs the residual acoustic energy generated by the impact, leading to a decrease in the intensity of the sound wave propagating upstream. This greatly reduces the sound pressure feedback loop, preventing the resonance between the jet shear layer and the near-wall region from being maintained, thus achieving the reduction of discrete single tones.

[0087] Although the downstream noise of Model A decreases with increasing frequency, it still remains high in the mid-to-high frequency range. Model B3 maintains a significant noise reduction advantage in this region, with a more pronounced decrease in sound pressure level in the mid-to-high frequency range. This indicates that the 30PPI porous medium dissipates energy from the residual vortices generated by separation on the upper side of the inclined plate through dissipation, reducing the migration speed and interaction intensity of the small vortices and effectively suppressing sound radiation in the downstream region.

[0088] contrast Figure 10 and Figure 11 The pressure and velocity coherence at points (a), (b), and (c) show that at 10 PPI: large-scale eddies (jet shear layers) brought by the jet are cut and broken by the porous structure after entering the 10 PPI region, resulting in decreased pressure coherence; some of the energy of the large eddies in the velocity field is redistributed to the mid-frequency range, forming coherent eddies induced by pores. Small-scale eddies are dissipated by viscosity within the porous structure, resulting in extremely low velocity coherence. At 10 PPI flowing through 30 PPI: large eddies are reorganized during the crossing process, resulting in enhanced velocity coherence, but pressure coherence has decreased; at high frequencies, velocity / pressure coherence decreases significantly, small eddies decouple, and the interface between materials with different porosities is a strong absorbing boundary for pressure waves. At 30 PPI: the flow is more impeded, large eddies are broken up more thoroughly, and overall velocity coherence decreases. However, small-scale channels with dense pores may generate high-frequency micro-jet streams, forming weak coherence at specific frequencies (significantly enhanced at 8000 Hz). The coherence of the pressure field is generally reduced due to the sound absorption effect of the dense pores, but the local pressure pulsations generated by the microjets in the high-frequency band may still have a weak correlation.

[0089] Pressure coherence showed a significant decrease at 2400 Hz, consistent with the better elimination of whistling by model B3. This also aligns with the Q-criterion vorticity diagram conclusions: porous media with a pore size of 10 PPI dissipate large eddies and absorb small eddies, while those with a pore size of 30 PPI further dissipate and absorb small eddies. While eliminating mid-to-low frequency whistling and reducing jet shear noise, other noises were introduced. Due to the difference in pore size between 10 PPI and 30 PPI and the influence of internal pore flow disturbances, small-scale turbulent pulsations were generated when the fluid passed through the pore interface, thus introducing a small amount of noise.

[0090] In summary, compared to the baseline plate, model B3, using a non-uniform porous medium, exhibits superior noise reduction performance on the jet impact inclined plate. From the flow field evolution (Figures 6 and 7), the porous medium effectively breaks up large-scale vortex structures near the wall and suppresses their development and merging. Simultaneously, it absorbs small-scale vortex energy through pore blockage and viscous dissipation, reducing turbulent pulsation intensity and weakening vortex-induced noise sources at their source. From the acoustic field performance (… Figure 8 , Figure 10 , Figure 11From the perspective of the data, Model B3 significantly reduces the sound pressure level in the initial jet stage, the shear layer turbulence stage behind the inclined plate, and the wake evolution part of the jet impacting the upper part of the inclined plate, effectively suppressing both the noise peak and broadband noise. However, when the fluid flows through porous media with different parameters, additional noise is still introduced due to local shearing. Overall, the magnitude of the additional noise is much smaller than the noise reduction benefit brought by the regional porous structure control, ultimately achieving the effect of overall flow field noise suppression, further verifying the effectiveness of porous distribution structures in flow field noise control.

[0091] Based on the above analysis, the beneficial effects of this invention can be summarized as follows:

[0092] 1. The porous arrangement and area ratio of the non-uniform porous medium were determined, and the corresponding porous parameters for the non-uniform distribution were also determined.

[0093] 2. This solution is effective in reducing the noise from the jet impact ramp, and can reduce the damage to personnel and aircraft carrier components from noise while ensuring the quality of carrier-based aircraft takeoff operations.

[0094] 3. The intrinsic mechanism of noise reduction in non-uniform porous media was analyzed in detail.

[0095] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A noise suppression method for a jet impact inclined plate, characterized by, Targeted noise reduction of various types of jet impact noise is achieved using porous media layouts with different physical properties, including the following steps: A baseline model and several optimized models for numerical calculation of jet impact on inclined plates were established, and the calculation conditions for each model were set. Based on the aforementioned computational conditions, a noise reduction analysis is performed on the baseline model and multiple optimized models to obtain the noise reduction results for each model. The denoising results of multiple optimized models and benchmark models are compared to evaluate the best denoising model among the multiple optimized models; Mechanism analysis was performed on the optimal noise reduction model to obtain its underlying mechanism; The baseline model of the jet impact inclined plate is a non-porous medium inclined plate, and the optimized model is a non-uniform porous medium inclined plate.

2. The noise suppression method for a jet-impact inclined plate as described in claim 1, characterized in that, The establishment of the baseline model and multiple optimized models for numerical calculation of jet impact inclined plate specifically includes: A baseline model and several optimized models of jet impacting an inclined plate are modeled, the modeled models are meshed, and the process of jet impacting the inclined plate is simulated.

3. The noise suppression method for a jet-impact inclined plate as described in claim 1, characterized in that, The process of obtaining the noise reduction results of each model specifically includes: obtaining the total sound pressure level of each model and using the total sound pressure level of each model as the noise reduction result of each model; The comparison of denoising results from multiple optimized models and a benchmark model to evaluate the best denoising model among the multiple optimized models specifically includes: The total sound pressure level of multiple optimized models is compared with that of the benchmark model, and the best noise reduction model among the multiple optimized models is determined based on the comparison results.

4. The noise suppression method for a jet-impact inclined plate as described in claim 1, characterized in that, The setting of calculation conditions for each model specifically includes: setting the condition number and multiple physical property parameters for each model, including: porosity, porous area ratio and PPI of each corresponding porosity for each model.

5. The noise suppression method for a jet-impact inclined plate as described in claim 4, characterized in that, The non-uniform porous medium inclined plate is a segmented porous medium inclined plate. The upper and lower parts of the segmented porous medium inclined plate have the same porosity PPI, while the middle part has a different porosity PPI than the upper and lower parts.

6. The noise suppression method for a jet-impact inclined plate as described in claim 5, characterized in that, The specific pore density values ​​of the upper, middle and lower parts of the segmented porous medium inclined plate are 10, 5 and 10, or 30, 10 and 30, or 30, 50 and 30.

7. The noise suppression method for a jet-impact inclined plate as described in claim 6, characterized in that, After evaluating the best noise reduction model among multiple optimization models, the method further includes: obtaining the porosity PPI corresponding to the best noise reduction model; The aforementioned mechanistic analysis of the optimal noise reduction model to obtain its underlying mechanism specifically includes: Based on the PPI of the porosity corresponding to the obtained optimal noise reduction model, a mechanism analysis is performed on the optimal noise reduction model to obtain its intrinsic mechanism.

8. The noise suppression method for a jet-impact inclined plate as described in claim 7, characterized in that, The mechanism analysis of the optimal noise reduction model specifically includes: mechanism analysis of the optimal model from the perspectives of turbulent kinetic energy, Q-criterion vorticity, spectrum diagram, and coherence. After performing mechanistic analysis on the optimal noise reduction model, the method further includes: adjusting multiple physical property parameters of the optimal noise reduction model based on the mechanistic analysis to optimize the optimal noise reduction model.

9. A device, characterized in that, The noise suppression method for jet impact inclined plate as described in any one of claims 1 to 8 is applied to the device.

10. The device as claimed in claim 9, characterized in that, The equipment includes carrier-based aircraft that take off and land on the aircraft carrier deck.

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