Airfoil for hydrodynamic and noise performance regulation

Abstract

The application relates to a wing profile for water power and noise performance regulation, which comprises a wing profile body, the wing profile body comprises a wing profile main body and a wing profile trailing edge, the surface of the wing profile main body is provided with a slip coating for forming a slip surface, the slip surface is used for improving the lift-drag ratio of the surface of the wing profile, and a plurality of sawtooth structures arranged along the span length direction of the wing profile are arranged on the wing profile trailing edge, the sawtooth structures are used for improving the noise performance of the wing profile. The lift-drag ratio of the surface of the wing profile can be improved through the slip surface, so that the water power performance of the wing profile is improved, the coupling of the sawtooth structures and the slip surface can overcome the loss of the water power performance of the wing profile caused by the sawtooth structures, the coupling of the two can avoid the noise increase caused by only using the sawtooth structures or the slip coating, can further reduce the noise, and can improve the water power performance and the noise performance of the wing profile.

Description

Technical Field

[0001] This application relates to the field of airfoil technology, and in particular to an airfoil for hydrodynamic and noise performance control. Background Technology

[0002] Airfoils are essential components of surface vessels and underwater vehicles, commonly used in rudders, anti-roll fins, and other devices. As crucial components for the maneuvering and navigation of ships and underwater vehicles, the hydrodynamic and noise performance of airfoils significantly impacts their speed and quietness. Therefore, improving the hydrodynamic and noise performance of airfoils is of great importance, and how to achieve this is a pressing technical problem in this field. Summary of the Invention

[0003] Therefore, it is necessary to provide an airfoil for hydrodynamic and noise performance control that can improve the hydrodynamic and noise performance of the airfoil, in order to address the above-mentioned technical problems.

[0004] In a first aspect, this application provides an airfoil for hydrodynamic and noise performance control. The airfoil includes an airfoil body, which includes an airfoil main body and an airfoil trailing edge. The surface of the airfoil main body is provided with a slip coating for forming a slip surface. The slip surface is used to improve the lift-to-drag ratio of the airfoil surface. The trailing edge of the airfoil is provided with a plurality of serrated structures arranged along the span direction of the airfoil. The serrated structures are used to improve the noise performance of the airfoil.

[0005] In one embodiment, the slip coating comprises a carbon-based coating or a fluorine-containing coating.

[0006] In one embodiment, the thickness of the carbon-based coating is not less than 2 micrometers and not more than 5 micrometers, and the thickness of the fluorine-containing coating is not less than 1 micrometer and not more than 10 micrometers.

[0007] In one embodiment, the slip coating is applied to the surface of the airfoil body by spraying, coating or spin coating.

[0008] In one embodiment, the shape of the sawtooth structure includes at least one of triangle and sine.

[0009] In one embodiment, the ratio of the length of the serrated structure in the chord direction of the airfoil to its length in the spanwise direction is not less than 2 and not greater than 4.

[0010] In one embodiment, the length of the serrated structure in the chord direction of the airfoil is not less than 0.0065 times the chord length of the airfoil and not greater than 0.1 times the chord length.

[0011] In one embodiment, the surface of the serrated structure is provided with a slip coating.

[0012] In one embodiment, the serrated structure is a structure formed at the trailing edge of the airfoil by removing material.

[0013] In one embodiment, the serrated structures are arranged at equal intervals and / or non-equal intervals in the elongation direction.

[0014] The aforementioned airfoil for hydrodynamic and noise performance control includes an airfoil body, which comprises a main body and a trailing edge. The main body has a slip coating to form a slip surface, which improves the airfoil's lift-to-drag ratio. The trailing edge has multiple serrated structures arranged along the airfoil's span, which improve its noise performance. The slip surface increases the airfoil's lift-to-drag ratio, thus enhancing its hydrodynamic performance. The coupling between the serrated structures and the slip surface overcomes the hydrodynamic performance loss caused by the serrated structures. This coupling also avoids the noise increase caused by using only serrated structures or slip coatings, and can further reduce noise, thus improving both the airfoil's hydrodynamic and noise performance. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This application provides an airfoil for hydrodynamic and noise performance control.

[0017] Figure 2 This is a schematic diagram of a hydrofoil test installation at 0° angle of attack provided in an embodiment of this application;

[0018] Figure 3 This is a schematic diagram of the sound pressure level spectrum of a hydrofoil with a 0° angle of attack provided in an embodiment of this application;

[0019] Figure 4 This is a schematic diagram illustrating the sound pressure level reduction of a hydrofoil at a 0° angle of attack, provided in an embodiment of this application.

[0020] Figure 5 This is a schematic diagram of a hydrofoil test installation at a 6° angle of attack, provided in an embodiment of this application;

[0021] Figure 6 This is a schematic diagram of the sound pressure level spectrum of a hydrofoil with a 6° angle of attack provided in an embodiment of this application;

[0022] Figure 7 This is a schematic diagram illustrating the sound pressure level reduction of a hydrofoil at a 6° angle of attack, provided in an embodiment of this application.

[0023] Figure 8 This is a schematic diagram of a hydrofoil test installation at a 10° angle of attack, provided in an embodiment of this application.

[0024] Figure 9 This is a schematic diagram of the sound pressure level spectrum of a hydrofoil with a 10° angle of attack provided in an embodiment of this application;

[0025] Figure 10 This is a schematic diagram illustrating the sound pressure level reduction of a hydrofoil with a 10° angle of attack, provided in an embodiment of this application. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0027] Airfoils are essential components of surface vessels and underwater vehicles, commonly used in rudders, anti-roll fins, and other devices. As crucial components for the maneuvering and navigation of ships and underwater vehicles, the hydrodynamic and noise performance of airfoils significantly impacts their speed and quietness. Therefore, improving the hydrodynamic and noise performance of airfoils is of great importance, and how to achieve this is a pressing technical problem in this field.

[0028] To address the aforementioned technical problems, embodiments of this application provide an airfoil for hydrodynamic and noise performance control, such as... Figure 1 As shown, Figure 1 This application provides an airfoil for hydrodynamic and noise performance control. The airfoil includes an airfoil body, which includes an airfoil main body 11 and an airfoil trailing edge. The surface of the airfoil main body 11 is provided with a slip coating for forming a slip surface, which is used to improve the lift-to-drag ratio of the airfoil surface. The trailing edge of the airfoil is provided with a plurality of serrated structures 12 arranged along the span direction of the airfoil, which are used to improve the noise performance of the airfoil.

[0029] Current technologies for controlling the hydrodynamic performance of airfoils mainly involve applying microstructures to the airfoil surface or optimizing the geometry of the airfoil body. However, applying microstructures to the airfoil surface presents challenges such as complex processing, implementation difficulties, limited drag reduction effects, and susceptibility to biofouling underwater, leading to microstructure failure. Optimizing the airfoil body shape, on the other hand, suffers from complex processes, high computational costs, and the inability to improve the performance of existing airfoils. In this embodiment, a slip coating is applied to the surface of the airfoil body 11 to form a slip surface. This allows the fluid in contact with the slip surface to generate a certain slip velocity, reducing the velocity gradient near the wall and thus reducing shear stress and frictional drag at the fluid-solid interface. Simultaneously, slip can alter the pressure distribution on the airfoil surface, reducing pressure drag and increasing lift, thereby improving the lift-to-drag ratio and enhancing the airfoil's hydrodynamic performance. The lift-to-drag ratio refers to the ratio of lift to drag. Furthermore, the slip surface formed by the slip coating has the advantages of being easy and simple to implement compared to applying microstructures or optimizing the geometry of the airfoil body, improving the hydrodynamic performance of existing airfoils, and enhancing drag reduction.

[0030] Current technologies for controlling airfoil noise performance categorize it into active and passive methods. Active control requires external energy input to the controlled system, such as actively applying a destructive noise source. Passive control, on the other hand, does not require external energy input and involves optimizing the airfoil's geometry or structural modifications. Active noise control suffers from high energy consumption and complex control, while passive noise control methods, such as airfoil geometry optimization, also suffer from complex computational optimization processes, high computational costs, and an inability to improve the performance of existing airfoils. In this embodiment, multiple serrated structures 12 arranged along the airfoil's span direction are provided on the trailing edge to improve the airfoil's noise performance. The serrated trailing edge structure breaks up turbulent vortex structures in the flow field, thereby reducing turbulent pulsations and pulsating pressures on the airfoil surface, and thus reducing radiated noise, enabling performance improvement of existing airfoils. Existing airfoils include common airfoils such as NACA 0009, NACA0012, NACA 0015, NACA 0018, NACA 0020, NACA 0021, Clark Y, and NACA 66 (mod).

[0031] It should be noted that, due to the simplicity and convenience of applying a slip surface, existing airfoils can be easily controlled. This avoids the shortcomings of existing technologies that improve aerodynamic / hydrodynamic performance by optimizing airfoil geometry, which leads to complex implementation and the inability to control existing airfoils.

[0032] In this embodiment, the airfoil includes an airfoil body, which includes an airfoil main body 11 and an airfoil trailing edge. The surface of the airfoil main body 11 is provided with a slip coating to form a slip surface. The slip surface is used to improve the lift-to-drag ratio of the airfoil surface. Multiple serrated structures 12 arranged along the span direction of the airfoil are formed on the airfoil trailing edge. The serrated structures 12 are used to improve the noise performance of the airfoil. The slip surface can improve the lift-to-drag ratio of the airfoil surface, thereby improving the hydrodynamic performance of the airfoil. Through the coupling of the serrated structures 12 and the slip surface, the loss of hydrodynamic performance of the airfoil caused by the serrated structures 12 can be overcome. The coupling effect of the two can avoid the noise increase caused by using only the serrated structures 12 or the slip coating, and can also further reduce noise, thereby improving the hydrodynamic and noise performance of the airfoil.

[0033] In one embodiment, the slip coating comprises a carbon-based coating or a fluorine-containing coating. The carbon-based or fluorine-containing coating is a coating that does not significantly alter the surface roughness of the airfoil body 11, and has the advantages of being easy to implement and having strong durability.

[0034] Current technologies improve airfoil hydrodynamic performance by applying superhydrophobic surfaces. However, when the airfoil is underwater, the superhydrophobic surface layer is lost within a short time, leading to drag reduction failure or even increased drag. This embodiment addresses this by applying a carbon-based or fluorine-containing coating to the surface of the airfoil body 11, which improves durability compared to superhydrophobic surfaces. This allows for a longer-term increase in the lift-to-drag ratio of the airfoil surface, thereby enhancing hydrodynamic performance.

[0035] In this embodiment, by using a slip coating with a carbon-based coating or a fluorine-containing coating, the surface roughness of the airfoil body 11 can be changed without significantly altering it, and the process is convenient and durable.

[0036] In one embodiment, the thickness of the carbon-based coating is not less than 2 micrometers and not more than 5 micrometers, and the thickness of the fluorine-containing coating is not less than 1 micrometer and not more than 10 micrometers.

[0037] In this embodiment, airfoil surface slippage can be achieved by using a carbon-based coating with a thickness of not less than 2 micrometers and not more than 5 micrometers or a fluorine-containing coating with a thickness of not less than 1 micrometer and not more than 10 micrometers. Moreover, airfoil surface slippage does not significantly change the surface roughness of the airfoil, and has the advantages of being easy to implement and having strong durability.

[0038] In one embodiment, the slip coating is applied to the surface of the airfoil body 11 by spraying, plating, or spin coating.

[0039] In this embodiment, a slip coating is applied to the surface of the airfoil body 11 by spraying, coating or spin coating, so the implementation of the slip coating is relatively convenient.

[0040] In one embodiment, the shape of the sawtooth structure 12 includes at least one of a triangle and a sine.

[0041] In this embodiment, the triangular and sinusoidal sawtooth structure 12 has the advantages of simple structure and convenient processing.

[0042] In one embodiment, the ratio of the length of the serrated structure 12 in the chord direction of the airfoil to its length in the spanwise direction is not less than 2 and not greater than 4.

[0043] like Figure 1 As shown, the length of the sawtooth structure 12 in the chord direction of the airfoil refers to... Figure 1 The serration height shown in the figure, and the length of the serration structure 12 in the spanwise direction refer to... Figure 1 The serration width is shown in the figure. That is to say, the ratio of the height to the width of the serration structure 12, i.e., the aspect ratio, is not less than 2 and not greater than 4.

[0044] In this embodiment, the serrated trailing edge structure can break up the turbulent vortex structure in the flow field, thereby reducing the turbulent pulsation and pulsating pressure on the airfoil surface, and thus reducing radiated noise. In addition, the structure is simple and easy to process.

[0045] In one embodiment, the length of the serrated structure 12 in the chord direction of the airfoil is not less than 0.0065 times the chord length of the airfoil and not greater than 0.1 times the chord length.

[0046] In this embodiment, by limiting the length of the sawtooth structure 12 in the chord direction of the airfoil, the size of the sawtooth structure can be diversified to meet the application requirements under different working conditions.

[0047] In one embodiment, the surface of the serrated structure 12 is provided with a slip coating.

[0048] In this embodiment, by providing a slip coating on the surface of the serrated structure 12, the lift-to-drag ratio of the airfoil surface can be further improved, thereby enhancing the hydrodynamic performance of the airfoil.

[0049] In one embodiment, the serrated structure 12 is a structure formed at the trailing edge of the airfoil by removing material.

[0050] In this embodiment, the sawtooth structure 12 is formed by removing material, which can ensure high structural strength and avoid the situation where the sawtooth structure oscillates under large hydrodynamic loads, resulting in a surge in noise.

[0051] In one embodiment, the serrated structures 12 are arranged at equal intervals and / or at non-equal intervals in the elongation direction.

[0052] In this embodiment, the sawtooth structure 12 is arranged at equal intervals and / or non-equal intervals in the span direction, which can adapt to different scenario requirements. Through the coupling of the equally and / or non-equally spaced sawtooth structure 12 with the sliding surface, the loss of hydrodynamic performance of the airfoil caused by the sawtooth structure 12 can be overcome, and the coupling effect of the two can improve the hydrodynamic performance and noise performance of the airfoil.

[0053] The airfoil provided in this embodiment has its chord length and span selectable according to actual conditions. The operating condition of the airfoil is a flow Reynolds number of 3.6, with the chord length as the characteristic length and the free flow velocity as the characteristic velocity. 10 5 -1.0 10 6 The range of angle of attack is from 0° to the airfoil stall angle of attack. Angle of attack refers to the angle between the incoming flow direction and the chord length of the airfoil.

[0054] To provide a clearer description of the embodiments of this application, the specific technical effects of the technical solutions proposed in this application will be described below in conjunction with specific embodiments.

[0055] It should be noted that, in the subsequent description of specific embodiments, for the sake of conformity with the conventions of this technical field, the airfoil will be referred to as a hydrofoil. Taking the NACA 0012 hydrofoil with a chord length of 100 mm and a span of 224 mm as an example, the hydrofoil surface has a carbon-based coating with a thickness of approximately 2.5-3 μm, and the trailing edge of the hydrofoil has a triangular serrated structure with an aspect ratio of 2. The serrated structure has two sizes: one is a large serrated structure, where the serration height is 0.1 times the hydrofoil chord length, the serration height is equal to 10 mm, and the corresponding serration width is 5 mm; the other is a small serrated structure, where the serration height is 0.025 times the hydrofoil chord length, the serration height is equal to 2.5 mm, and the corresponding serration width is 1.25 mm. The hydrofoil with the above coating and serrated structure simultaneously controlled is referred to as "large serration-coated hydrofoil" and "small serration-coated hydrofoil," respectively. The above hydrofoil is placed in the test section of a cavitation water cylinder device, wherein the cross-section of the test section is 225 mm. The test section was 1.6 m long and consisted of a 225 mm square section. The experimental water velocity was set at 6 m / s, corresponding to a chord characteristic Reynolds number of 6. 10 5The hydrofoil flow conditions were adjusted to 0°, 6° and 10° angle of attack by the angle of attack adjustment device, all of which are within the angle of attack range before stall. At the same time, a force balance was installed in the hydrofoil base to measure the lift and drag on the hydrofoil. A hydrophone was installed on the wall of the water cylinder above the trailing edge of the hydrofoil to measure the noise data of different hydrofoils. During the test, pressurization was applied to ensure that the hydrofoil was free of cavitation, so as to measure the hydrofoil noise in the free cavitation state, which is convenient for subsequent comparison of results. Among them, the airfoil noise performance is measured by the sound pressure level index, that is, the expression of sound pressure level (SPL) is as follows (1):

[0056]

[0057] in, For reference sound pressure. In water medium. = 1 10 -6 Pa, Represents the i-th frequency The corresponding sound pressure level at that location.

[0058] The formula for calculating the Overall Sound Pressure Level (OASPL) is as follows (2):

[0059]

[0060] To effectively compare the technical effects of the proposed solution, we simultaneously tested a basic hydrofoil without any improvements, a coated hydrofoil with only coating adjustment, and a large-tooth hydrofoil and a small-tooth hydrofoil with only serrated structure adjustment. The test conditions and procedures were consistent with those for the large-tooth coated hydrofoil and the small-tooth coated hydrofoil. The specific results are as follows.

[0061] In one embodiment, the hydrofoil test installation at a 0° angle of attack is as follows: Figure 2 As shown, Figure 2 This is a schematic diagram of a hydrofoil test installation at a 0° angle of attack, provided in an embodiment of this application. The noise test results for each hydrofoil are as follows: Figure 3 As shown in (a), (b), (c), and (d), Figure 3This is a schematic diagram of the sound pressure level spectrum of a hydrofoil at a 0° angle of attack, provided in an embodiment of this application. As shown in the figure, a series of peaks appear in the sound pressure level spectrum of both the basic hydrofoil and other experimental hydrofoils. The basic hydrofoil exhibits relatively significant peaks at f1, f2, and f3. The reason for these line spectrum peaks is that the hydrofoil was installed with a single-sided cantilever in the experiment, and the fluid and hydrofoil structure may have been coupled under the scouring of the water flow, resulting in strong line spectrum peaks at the modal frequencies of the hydrofoil structure. Besides the basic hydrofoil, a series of peaks also appear in the sound pressure level spectrum of other experimental hydrofoils. In addition to the line spectrum peaks at f1, f2, and f3, other experimental hydrofoils also show peaks at frequencies around f1. - or f1 + The same location also exhibits a relatively significant peak.

[0062] Extract Figure 3 The sound pressure level at each characteristic peak in the sound pressure level spectrum shown is used to calculate the sound pressure level reduction compared to the basic airfoil, with reference to... Figure 4 , Figure 4 This is a schematic diagram illustrating the sound pressure level reduction of a hydrofoil at a 0° angle of attack, provided in an embodiment of this application. (See diagram below.) Figure 4 As shown in (a) of the figure, at frequencies f1, f2, and f3, compared to the basic hydrofoil, the coated hydrofoil, small sawtooth hydrofoil, large sawtooth hydrofoil, small sawtooth coated coupled hydrofoil, and large sawtooth coated coupled hydrofoil all exhibited a decrease in sound pressure level. Taking f1 as an example, the sound pressure level reduction of each hydrofoil was 7.1 dB, 9.2 dB, 17.7 dB, 12.4 dB, and 19.2 dB, respectively. The noise reduction effect of the coated sawtooth coupled hydrofoil at f1 frequency was better than that of the coated hydrofoil or sawtooth hydrofoil alone. Similar conclusions were reached at frequencies f2 and f3. In addition to the decrease in sound pressure level at f1, f2, and f3 frequencies, the coated hydrofoil, small sawtooth hydrofoil, large sawtooth hydrofoil, small sawtooth coated coupled hydrofoil, and large sawtooth coated coupled hydrofoil all showed a decrease in sound pressure level at f1. - or f1 + Linear noise is generated at certain frequencies, and the linear noise produced by small-toothed and large-toothed hydrofoils is more intense at f1. - The sound pressure level amplitude at the frequency exceeds the sound pressure level amplitude of the basic airfoil at the f1 frequency, thus adversely affecting the noise performance of the hydrofoil.

[0063] Furthermore, the total sound pressure level of the hydrofoil in the 100-5000 Hz frequency range was calculated, and the reduction in total sound pressure level compared to the basic airfoil was also calculated. The results are as follows: Figure 4 As shown in (b) of the figure. It can be seen from the figure that due to the small sawtooth hydrofoil and the large sawtooth hydrofoil... The generated line spectral peaks at certain frequencies resulted in a 5 dB and 2 dB increase in total sound pressure level compared to the basic hydrofoil. The coated hydrofoil, the small-serrated coated hydrofoil, and the large-serrated coated hydrofoil all exhibited a reduction in total sound pressure level, with reductions of 3 dB, 5 dB, and 4 dB, respectively. This indicates that at a 0° angle of attack, the coupling between the serrated structure and the coating improves the noise characteristics of the serrated hydrofoil, transforming it from an unfavorable increase in noise to a favorable reduction, and demonstrating a superior noise reduction effect compared to the coated hydrofoil. This highlights the advantage of the serrated coating coupling control scheme.

[0064] In addition, hydrofoils can also improve hydrodynamic performance at 0° angle of attack, and the improvement in hydrodynamic performance at 6° angle of attack is more significant than that at 0° angle of attack. The following data will be used to mainly compare the hydrodynamic performance of hydrofoils at 6° angle of attack.

[0065] In one embodiment, the hydrofoil test installation at a 6° angle of attack is as follows: Figure 5 As shown, Figure 5 This is a schematic diagram of a hydrofoil test installation at a 6° angle of attack, provided in an embodiment of this application. The noise test results for each hydrofoil are as follows: Figure 6 As shown in (a), (b), (c), and (d), Figure 6 This is a schematic diagram of the sound pressure level spectrum of a hydrofoil at a 6° angle of attack, provided in an embodiment of this application. As shown in the figure, peaks similar to those at a 0° angle of attack appear in the sound pressure level spectra of the basic hydrofoil and other experimental hydrofoils. Unlike the 0° angle of attack, the basic hydrofoil, in addition to significant peaks at frequencies f1 and f2, also produces an extremely strong peak at frequency f0, far exceeding the sound pressure levels at f1 and f2, and exceeding the broadband sound pressure level at f0 by nearly 30 dB. Simultaneously, a sharp sound can be heard during experimental testing, indicating that strong shedding vortices may be generated on the surface of the hydrofoil at a 6° angle of attack. The frequency of these shedding vortices is also f0, thus generating resonance with the hydrofoil structure and producing a singing sound. Coated hydrofoils, small sawtooth hydrofoils, and small sawtooth coated coupled hydrofoils also produce strong line spectra at the f0 frequency, while large sawtooth hydrofoils and large sawtooth coated coupled hydrofoils do not show significant line spectra at the f0 frequency. The f0 frequency values ​​corresponding to each airfoil fluctuate around 680-690 Hz.

[0066] The sound pressure level amplitudes at the characteristic frequencies of f0, f1, and f2 for each airfoil were extracted, and the reduction in sound pressure level compared to the basic airfoil was calculated. Figure 7 , Figure 7 This is a schematic diagram illustrating the sound pressure level reduction of a hydrofoil at a 6° angle of attack, provided in an embodiment of this application. The results are as follows... Figure 7As shown in (a) of the figure, neither the sawtooth hydrofoil nor the sawtooth-coated coupled hydrofoil exhibits a significant line spectrum at the f0 frequency. The disappearance of the line spectrum frequency at f0 for both the sawtooth hydrofoil and the sawtooth-coated coupled hydrofoil indicates that the resonance between the shedding vortex and the airfoil structure is disrupted, and the singing sound is eliminated. The reason for the elimination of the singing sound is that the sawtooth structure eliminates the excitation source causing the hydrofoil resonance by breaking the periodic vortex shedding structure with the f0 characteristic frequency on the hydrofoil surface, thereby eliminating the singing sound. The sawtooth-coated coupled hydrofoil, on the other hand, exhibits a lower broadband sound pressure level than the sawtooth hydrofoil, even after the singing sound is eliminated.

[0067] Correspondingly, neither the coated hydrofoil nor the sawtooth hydrofoil eliminated singing, while the sawtooth coated hydrofoil exhibited partial singing reduction. This phenomenon suggests that the coating may have altered the flow state on the hydrofoil surface, delaying the vortex shedding from the hydrofoil surface to a range where the sawtooth structure can effectively act. This allows the sawtooth structure to disrupt the delayed vortex structure, thereby reducing the intensity of the vortex shedding and achieving a reduction in the line spectrum noise of the sawtooth coated hydrofoil.

[0068] Furthermore, at the characteristic frequencies of f1 and f2, the coated hydrofoil, sawtooth hydrofoil, and sawtooth coated coupled hydrofoil all exhibited a reduction in sound pressure level. At the f1 frequency, the coated hydrofoil, small sawtooth hydrofoil, large sawtooth hydrofoil, small sawtooth coated coupled hydrofoil, and large sawtooth coated coupled hydrofoil can reduce the sound pressure level by 1.9 dB, 0.9 dB, 7.6 dB, 9.9 dB, and 10.4 dB, respectively.

[0069] Furthermore, the total sound pressure level of the hydrofoil in the 100-5000 Hz frequency range at a 6° angle of attack was calculated, and the reduction in total sound pressure level compared to the basic airfoil was also calculated. The results are as follows: Figure 7 As shown in (b) of the figure, the coated hydrofoil and the small sawtooth hydrofoil, due to the enhanced line spectrum peak at f0 frequency, caused an increase in total sound pressure level of 7 dB and 17 dB compared to the basic hydrofoil. The large sawtooth hydrofoil, the small sawtooth coated hydrofoil, and the large sawtooth coated hydrofoil all showed a decrease in total sound pressure level, with reductions of 8 dB, 10 dB, and 12 dB, respectively. That is, at a 6° angle of attack, the coupling between the small sawtooth structure and the coating improved the noise characteristics of the coated hydrofoil and the small sawtooth hydrofoil, turning the noise increase into a noise reduction. Furthermore, the coupling between the large sawtooth structure and the coating improved the noise characteristics of the coated hydrofoil, turning the noise increase into a noise reduction, and showed a better noise reduction effect than the large sawtooth hydrofoil, demonstrating the advantage of the sawtooth coating coupling control scheme.

[0070] In addition, regarding hydrodynamic performance, the lift and drag of different hydrofoils at a 6° angle of attack were measured experimentally, and the results are shown in Table 1 below. As can be seen from the table, compared to the basic hydrofoil, the coated hydrofoil achieves a 0.6% increase in lift and an 11.1% decrease in drag, resulting in an approximately 13.2% increase in lift-to-drag ratio. Both the small-serrated and large-serrated hydrofoils showed a decrease in lift and drag, with a larger decrease in lift leading to a decrease in lift-to-drag ratio, and the large-serrated hydrofoil showing a greater decrease (6.8%). For the serrated coating coupled hydrofoil, compared to the serrated hydrofoil, its lift characteristics showed a certain improvement, and the rate of decrease in lift-to-drag ratio was somewhat reduced. Compared to the basic hydrofoil, the lift-to-drag ratio of the small-serrated coating coupled hydrofoil and the large-serrated coating coupled hydrofoil decreased by 0.8% and 4.6%, respectively. Therefore, it can be seen that the coating has a significant beneficial effect on improving the hydrodynamic performance of the hydrofoil, while the sawtooth structure has a detrimental effect on hydrodynamic performance. The coupling between the sawtooth structure and the coating can improve the decline in hydrodynamic performance of the hydrofoil caused by the sawtooth structure.

[0071]

[0072] Table 1

[0073] In summary, the coated hydrofoil exhibits superior hydrodynamic performance improvement. The small-serrated hydrofoil shows no improvement in either hydrodynamic or noise performance, while the large-serrated hydrofoil demonstrates excellent noise reduction, albeit with significant hydrodynamic performance loss. The serrated-coated coupled hydrofoil overcomes the limitations of individually controlling noise performance through either the coating or the serrated structure, combining the advantages of the coating in hydrodynamic performance control and overcoming the hydrodynamic performance loss caused by the serrated structure. This achieves an overall improvement in hydrofoil performance and has potential for practical application, providing a new approach to hydrofoil performance enhancement. At a 6° angle of attack, the hydrofoil can generate significant lift, but drag increases. Therefore, subsequent comparisons will primarily focus on the hydrodynamic performance of the hydrofoil at a 6° angle of attack.

[0074] In one embodiment, the hydrofoil test installation at a 10° angle of attack is as follows: Figure 8 As shown, Figure 8 This is a schematic diagram of a hydrofoil test installation at a 10° angle of attack, provided in an embodiment of this application. The noise test results for each hydrofoil are as follows: Figure 9 As shown in (a), (b), (c), and (d), Figure 9 This is a schematic diagram of the sound pressure level spectrum of a hydrofoil with a 10° angle of attack, provided in an embodiment of this application. Extraction Figure 9 The sound pressure level at each characteristic peak in the sound pressure level spectrum shown is used to calculate the sound pressure level reduction compared to the basic airfoil, with reference to... Figure 10 , Figure 10 This is a schematic diagram illustrating the sound pressure level reduction of a hydrofoil with a 10° angle of attack, as provided in an embodiment of this application. Figure 10As shown in (a) of the figure, compared to the basic hydrofoil, the coated hydrofoil exhibits a decrease in sound pressure level at frequencies f0, f1, and f2. At f0 and f1, the small sawtooth hydrofoil shows an increase in sound pressure level (20.8 dB and 6.6 dB, respectively), while the large sawtooth hydrofoil shows a negligible decrease. The small and large sawtooth coated hydrofoils improve the sound pressure level characteristics of the sawtooth hydrofoil. At frequency f0, the small sawtooth coated hydrofoil reduces the increase in sound pressure level from 20.8 dB to 2.5 dB, and at frequency f1, it reduces the change from a 6.6 dB increase to a 3.1 dB decrease, demonstrating a significant noise reduction advantage compared to the existing small sawtooth hydrofoil. The large sawtooth coated hydrofoil shows a similar improvement in sound pressure level characteristics compared to the large sawtooth hydrofoil.

[0075] Furthermore, the total sound pressure level of the hydrofoil in the 100-5000 Hz frequency range was calculated, and the reduction in total sound pressure level compared to the basic airfoil was also calculated. The results are as follows: Figure 10 As shown in (b) of the figure, the small sawtooth hydrofoil generates a line spectrum peak with a higher amplitude at frequency f0, resulting in a 4 dB increase in total sound pressure level compared to the basic hydrofoil. The large sawtooth hydrofoil did not show a decrease in total sound pressure level. However, the coated hydrofoil, the small sawtooth coated hydrofoil, and the large sawtooth coated hydrofoil all showed a decrease in total sound pressure level, with reductions of 3 dB, 5 dB, and 4 dB, respectively. That is, at an angle of attack of 10°, the coupling between the sawtooth structure and the coating improves the noise characteristics of the sawtooth hydrofoil, turning it from an unfavorable increase in noise or no noise reduction into a favorable noise reduction, and showing a better noise reduction effect than the coated hydrofoil, indicating the advantage of the sawtooth coating coupling control scheme.

[0076] As demonstrated by the foregoing embodiments, the coupling between the serrated structure and the coating transforms the noise performance regulation of the serrated structure from noise amplification to noise reduction. Furthermore, it can further enhance the noise reduction effect of the coating or improve the noise regulation effect of the coating from noise amplification to noise reduction, showcasing the advantages of the serrated structure and coating surface coupling regulation proposed in this application. Simultaneously, the coupling between the serrated structure and the coating surface significantly improves the hydrodynamic performance of the serrated structure. These results indicate that the airfoil hydrodynamic and noise performance regulation method using a serrated structure and a sliding surface proposed in this application has significant advantages over existing technologies. Moreover, the serrated structure and sliding surface offer the advantage of convenient implementation, and the sliding surface formed by the coating exhibits relatively stable test results even during several days of experimental testing, demonstrating its strong durability and broad application prospects in the fields of surface vessels and underwater vehicles.

[0077] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0078] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments described above. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0079] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0080] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. An airfoil for hydrodynamic and noise performance regulation, characterized in that, The airfoil comprises an airfoil body, the airfoil body comprising an airfoil main body and an airfoil trailing edge, a surface of the airfoil main body is provided with a slip coating for forming a slip surface for improving the lift-drag ratio of the surface of the airfoil, and a plurality of sawtooth structures arranged along the spanwise direction of the airfoil are formed on the airfoil trailing edge, the sawtooth structures being used for improving the noise performance of the airfoil. The slip coating comprises a carbon-based coating or a fluorine-containing coating, and the surface of the sawtooth structures is provided with the slip coating.

2. The airfoil of claim 1, wherein The thickness of the carbon-based coating is not less than 2 microns and not more than 5 microns, and the thickness of the fluorine-containing coating is not less than 1 micron and not more than 10 microns.

3. The airfoil of claim 1, wherein The slip coating is applied on the surface of the airfoil main body by spraying, plating or spin coating.

4. The airfoil of claim 1, wherein The shape of the sawtooth structures comprises at least one of a triangle and a sinusoid.

5. The airfoil of claim 1, wherein The ratio of the length of the sawtooth structures in the chordwise direction of the airfoil to the length in the spanwise direction is not less than 2 and not more than 4.

6. The airfoil of claim 1, wherein The length of the sawtooth structures in the chordwise direction of the airfoil is not less than 0.0065 times the chord length of the airfoil and not more than 0.1 times the chord length.

7. The airfoil of claim 1, wherein The sawtooth structures are structures formed by removing material on the airfoil trailing edge.

8. The airfoil of claim 1, wherein The sawtooth structures are arranged at equal intervals and / or non-equal intervals in the spanwise direction.

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