Airfoil profile for hydrodynamic and noise performance regulation

Abstract

The invention relates to an airfoil profile for hydrodynamic and noise performance regulation and control, the airfoil profile comprises an airfoil profile body, the airfoil profile body comprises an airfoil profile main body and an airfoil profile trailing edge, the surface of the airfoil profile main body is provided with a slippage coating for forming a slippage surface, and the slippage surface is used for improving the lift-drag ratio of the surface of the airfoil profile. A plurality of sawtooth structures arranged in the extension direction of the airfoil profile are arranged on the airfoil profile trailing edge and used for improving the noise performance of the airfoil profile. The lift-drag ratio of the surface of the airfoil can be improved through the sliding surface, then the hydrodynamic performance of the airfoil is improved, the loss of the hydrodynamic performance of the airfoil caused by the sawtooth structure can be overcome through coupling of the sawtooth structure and the sliding surface, noise increase caused by only adopting the sawtooth structure or a sliding coating can be avoided through the coupling effect of the sawtooth structure and the sliding surface, and the hydrodynamic performance of the airfoil is improved. Noise can be further reduced, and the hydrodynamic performance and the noise performance of the airfoil profile are improved.

Description

Technical Field

[0001] The present application relates to the technical field of airfoils, and in particular to an airfoil for regulating hydrodynamic and noise performance. Background Art

[0002] Airfoils are important components of surface ships and underwater vehicles, and are often used in tail rudders, anti-roll fins and other devices of surface ships and underwater vehicles. As an important component for the manipulation and navigation of ships and underwater vehicles, the hydrodynamic and noise performance of airfoils has an important impact on the speed and quietness of ships and underwater vehicles. Therefore, it is of great significance to improve the hydrodynamic and noise performance of airfoils. How to improve the hydrodynamic and noise performance of airfoils has become a technical problem that needs to be solved urgently in this field. Summary of the invention

[0003] Based on this, it is necessary to provide an airfoil for regulating hydrodynamic and noise performances, which can improve the hydrodynamic and noise performances of the airfoil, in order to address the above technical problems.

[0004] In a first aspect, the present application provides an airfoil for regulating hydrodynamic and noise performance, the airfoil comprising an airfoil body, the airfoil body comprising an airfoil main body and an airfoil trailing edge, the surface of the airfoil main body being provided with a slip coating for forming a slip surface, the slip surface being used to improve the lift-to-drag ratio of the airfoil surface, the airfoil trailing edge being provided with a plurality of serration structures arranged along the span direction of the airfoil, the serration structures being used to improve the noise performance of the airfoil.

[0005] In one embodiment, the slip coating includes 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 sawtooth structure has a shape of at least one of a triangle and a sinusoid.

[0009] In one of the embodiments, a ratio of a length of the sawtooth structure in a chord direction of the airfoil to a length in a span direction is not less than 2 and not more than 4.

[0010] In one of the embodiments, the length of the sawtooth structure in the chord length 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.

[0011] In one of the embodiments, a slip coating is provided on the surface of the sawtooth structure.

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

[0013] In one embodiment, the sawtooth structures are arranged at equal intervals and / or unequal intervals in the lengthwise direction.

[0014] The above-mentioned airfoil for regulating hydrodynamic and noise performance comprises an airfoil body, the airfoil body comprises 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, and the airfoil trailing edge is provided with a plurality of sawtooth structures arranged along the span direction of the airfoil, the sawtooth structure is used to improve the noise performance of the airfoil. The lift-to-drag ratio of the airfoil surface can be improved by the slip surface, thereby achieving the improvement of the hydrodynamic performance of the airfoil, and the coupling of the sawtooth structure and the slip surface can overcome the loss of hydrodynamic performance of the airfoil caused by the sawtooth structure, and the coupling effect of the two can avoid the increase of noise caused by only using the sawtooth structure or the slip coating, and can also further reduce the noise, thereby improving the hydrodynamic performance and noise performance of the airfoil. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related technologies, the drawings required for use in the embodiments or the related technical descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 It is an airfoil for regulating hydrodynamic and noise performance provided in an embodiment of the present application;

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

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

[0019] Figure 4 is a schematic diagram of the reduction in sound pressure level of a hydrofoil at a 0° angle of attack provided in an embodiment of the present application;

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

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

[0022] Figure 7 is a schematic diagram of the reduction in sound pressure level of a hydrofoil at a 6° angle of attack provided in an embodiment of the present 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 the present application;

[0024] Fig. 9 is a schematic diagram of a sound pressure level spectrum of a hydrofoil at an attack angle of 10° provided in an embodiment of the present application;

[0025] Fig.10 It is a schematic diagram of the reduction in sound pressure level of a hydrofoil at an attack angle of 10° provided in an embodiment of the present application. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0027] Airfoils are important components of surface ships and underwater vehicles, and are often used in tail rudders, anti-roll fins and other devices of surface ships and underwater vehicles. As an important component for the manipulation and navigation of ships and underwater vehicles, the hydrodynamic and noise performance of airfoils has an important impact on the speed and quietness of ships and underwater vehicles. Therefore, it is of great significance to improve the hydrodynamic and noise performance of airfoils. How to improve the hydrodynamic and noise performance of airfoils has become a technical problem that needs to be solved urgently in this field.

[0028] In order to solve the above technical problems, the embodiment of the present application provides an airfoil for regulating hydrodynamic and noise performance, such as Figure 1 As shown, Figure 1 An airfoil for regulating hydrodynamic and noise performance is provided in an embodiment of the present application. The airfoil includes an airfoil body, the airfoil body includes an airfoil body 11 and an airfoil trailing edge, the surface of the airfoil body 11 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, and a plurality of sawtooth structures 12 arranged along the span direction of the airfoil are provided on the airfoil trailing edge, the sawtooth structures 12 are used to improve the noise performance of the airfoil.

[0029] In the current related technologies, the main methods for regulating the hydrodynamic performance of airfoils include applying microstructures on the airfoil surface or optimizing the geometric shape of the airfoil body. However, applying microstructures on the airfoil surface has problems such as complex processing, difficult implementation, limited drag reduction effect, and easy attachment of organisms underwater, which causes microstructure failure. The optimization of the shape of the airfoil body has problems such as complex process, high cost of calculation optimization, and inability to improve the performance of existing airfoils. In this embodiment, a slip coating for forming a slip surface is provided on the surface of the airfoil body 11, so that the fluid in contact with the slip surface generates a certain slip speed when flowing through the slip surface, reducing the velocity gradient near the wall, thereby reducing the shear stress and friction resistance at the fluid-solid interface. At the same time, slip can change the pressure distribution on the airfoil surface, reduce the pressure difference resistance of the airfoil, and increase the lift of the airfoil, thereby increasing the lift-to-drag ratio of the airfoil surface and achieving the improvement of the hydrodynamic performance of the airfoil. Among them, the lift-to-drag ratio refers to the ratio of lift to drag. Moreover, compared with applying a microstructure or optimizing the geometric shape of the airfoil body, the slip surface formed by the slip coating has the advantages of being easy and simple to implement, being able to improve the hydrodynamic performance of the existing airfoil, and enhancing the drag reduction effect.

[0030] In the current related technologies, the methods for regulating the noise performance of airfoils are divided into active regulation and passive regulation. The active regulation method requires the input of energy from the outside to the controlled system, such as actively applying a phase-cancelling sound source, etc. The passive regulation method does not require the application of external energy, including optimizing the geometric shape of the airfoil itself and improving the structure of the airfoil. Active noise regulation has the problems of high energy consumption and complex control. The airfoil geometry optimization method in passive noise regulation also has the problems of complex calculation optimization process, high calculation optimization cost, and inability to improve the performance of existing airfoils. In this embodiment, a plurality of serrated structures 12 arranged along the span direction of the airfoil are provided on the trailing edge of the airfoil to improve the noise performance of the airfoil. The serrated trailing edge structure breaks up the turbulent vortex structure in the flow field, thereby reducing the turbulent pulsation and pulsating pressure on the airfoil surface, thereby reducing the radiated noise, and can achieve performance improvement of existing airfoils. The existing airfoil may be commonly used airfoils such as NACA 0009, NACA 0012, NACA 0015, NACA 0018, NACA 0020, NACA 0021, Clark Y, NACA 66 (mod), etc.

[0031] It should be noted that, since the application of the sliding surface is simple and convenient, the existing airfoil can be easily adjusted, thereby avoiding the shortcomings of the prior art of improving aerodynamic / hydrodynamic performance by optimizing the airfoil geometry, which leads to complex implementation and inability to adjust the existing airfoil.

[0032] In this embodiment, the airfoil includes an airfoil body, the airfoil body 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, the slip surface is used to improve the lift-to-drag ratio of the airfoil surface, and a plurality of sawtooth structures 12 arranged along the span direction of the airfoil are provided on the airfoil trailing edge, the sawtooth structure 12 is used to improve the noise performance of the airfoil. The lift-to-drag ratio of the airfoil surface can be improved by the slip surface, thereby achieving the improvement of the hydrodynamic performance of the airfoil, and the loss of the hydrodynamic performance of the airfoil caused by the sawtooth structure 12 can be overcome by coupling the sawtooth structure 12 with the slip surface, and the coupling effect of the two can avoid the increase of noise caused by only using the sawtooth structure 12 or the slip coating, and can also further reduce the noise, thereby improving the hydrodynamic performance 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 coating or the fluorine-containing coating is a coating that does not significantly change the roughness of the surface of the airfoil body 11 and has the advantages of being easy to implement and having strong durability.

[0034] In some current related technologies, the hydrodynamic performance of the airfoil is improved by applying a super-hydrophobic surface on the airfoil surface. However, when the airfoil is underwater, the air layer on the super-hydrophobic surface will be lost in a short time, resulting in the failure of the entire super-hydrophobic surface to reduce drag or even increase drag. In this embodiment, a sliding surface with a carbon-based coating or a fluorine-containing coating is applied to the surface of the airfoil body 11, which improves the durability relative to the super-hydrophobic surface, and can improve the lift-to-drag ratio of the airfoil surface for a long time, thereby improving the hydrodynamic performance.

[0035] In this embodiment, by using a slip coating of a carbon-based coating or a fluorine-containing coating, the roughness of the surface of the airfoil body 11 can be kept unchanged, and the implementation is convenient and the durability is strong.

[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 slip can be achieved by a carbon-based coating with a thickness of not less than 2 microns and not more than 5 microns or a fluorine-containing coating with a thickness of not less than 1 micron and not more than 10 microns, and the airfoil surface slip does not significantly change the airfoil surface roughness, which has the advantages of easy implementation and strong durability.

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

[0039] In this embodiment, the slip coating is applied on 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 sawtooth structure 12 has a shape of at least one of a triangle and a sinusoid.

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

[0042] In one embodiment, the ratio of the length of the sawtooth structure 12 in the chord direction of the airfoil to the length in the span direction is not less than 2 and not more than 4.

[0043] like Figure 1 As shown, the length of the sawtooth structure 12 in the chord length direction of the airfoil is Figure 1 The sawtooth height shown in FIG. 1 is the length of the sawtooth structure 12 in the span direction. Figure 1 That is, the ratio of the height to the width of the sawtooth structure 12, that is, the aspect ratio, is not less than 2 and not more 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 further reducing the radiation noise, and the structure is simple and easy to process.

[0045] In one embodiment, the length of the sawtooth structure 12 in the chord length 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.

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

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

[0048] In this embodiment, by providing a slip coating on the surface of the sawtooth 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 sawtooth structure 12 is a structure formed by removing material from the trailing edge of the airfoil.

[0050] In this embodiment, the sawtooth structure 12 is formed by removing material, which can ensure a high structural strength and avoid the situation in which the sawtooth structure 12 caused by adding material under a large hydrodynamic load causes the sawtooth structure to oscillate and cause a surge in noise.

[0051] In one embodiment, the sawtooth structures 12 are arranged at equal intervals and / or unequal intervals in the lengthwise direction.

[0052] In this embodiment, the sawtooth structure 12 is arranged at equal intervals and / or unequal intervals in the span direction, which can adapt to the needs of different scenarios. Through the coupling of the equally spaced and / or unequally spaced sawtooth structures 12 and 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 chord length and span of the airfoil provided in the embodiment of the present application can be selected according to actual conditions. The working condition of the airfoil is that the chord length of the airfoil is the characteristic length, the free flow velocity is the characteristic velocity, and the flow Reynolds number is 3.6. 10 5 -1.0 10 6 The range of angle of attack is from 0° angle of attack to the airfoil stall angle of attack. The angle of attack refers to the angle between the incoming flow direction and the chord length of the airfoil.

[0054] In order to provide a clearer introduction to the embodiments of the present application, the specific technical effects of the technical solutions proposed in the present application will be introduced below in conjunction with specific embodiments.

[0055] It should be noted that, when introducing specific embodiments later, in order to comply with the custom in this professional and 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 surface of the hydrofoil has a carbon-based coating with a thickness of about 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, that is, the serration height is 0.1 times the chord length of the hydrofoil, the serration height is equal to 10 mm, and the corresponding serration width is 5 mm; the other is a small serration structure, the serration height is 0.025 times the chord length of the hydrofoil, that is, the serration height is equal to 2.5 mm, and the corresponding serration width is 1.25 mm. The hydrofoils with the above-mentioned coating and serration structure regulated simultaneously are respectively recorded as "large serration-coated hydrofoil" and "small serration-coated hydrofoil". The above-mentioned hydrofoil is placed in the test section of the cavitation water cylinder equipment, where the cross-section of the test section is 225 mm The square of 225 mm, the length of the test section is 1.6 m, the experimental water velocity is set to 6 m / s, and the corresponding chord length characteristic Reynolds number is 6 10 5, the angle of attack adjustment device is used to adjust the flow conditions of the hydrofoil to 0°, 6° and 10° angles of attack, all of which are within the pre-stall angle of attack range. At the same time, a force balance is installed in the base of the hydrofoil to measure the lift and drag of the hydrofoil. A hydrophone is 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 is used to ensure that the hydrofoil is free of cavitation during the test, so that the hydrofoil noise in the non-cavitation state is measured, 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 sound pressure level (SPL) expression is as follows (1):

[0056]

[0057] in, is the reference sound pressure. = 1 10 -6 Pa, represents the i-th frequency The corresponding sound pressure.

[0058] The calculation formula for the overall sound pressure level (OASPL) is as follows (2):

[0059]

[0060] In order to effectively compare the technical effects of the technical solution proposed in the present invention, the basic hydrofoil without improvement, the coated hydrofoil with only coating regulation, and the large sawtooth hydrofoil and small sawtooth hydrofoil with only sawtooth structure regulation were tested at the same time. The test conditions and test process were consistent with those of the large sawtooth-coated hydrofoil and the small sawtooth-coated hydrofoil. The specific results are as follows.

[0061] In one embodiment, the hydrofoil test installation at 0° angle of attack is as follows Figure 2 As shown, Figure 2 Schematic diagram of a hydrofoil test installation at a 0° attack angle provided in an embodiment of the present application. Figure 3 As shown in (a), (b), (c) and (d) in Figure 3It is a schematic diagram of the sound pressure level spectrum of a hydrofoil at a 0° angle of attack provided in an embodiment of the present application. As can be seen from the figure, a series of peaks appear in the sound pressure level spectra of the basic hydrofoil and other experimental hydrofoils. The basic hydrofoil has more significant peaks at f1, f2, and f3. The reason for the appearance of the line spectrum is that the hydrofoil is installed in a single-sided cantilever installation in the experiment. The fluid and the hydrofoil structure may have a coupling effect under the scouring of the water flow, thereby generating a strong line spectrum peak at the modal frequency of the hydrofoil structure. In addition to the basic hydrofoil, a series of peaks also appear in the sound pressure level spectra of other experimental hydrofoils. In addition to the line spectrum peaks at f1, f2, and f3, other experimental hydrofoils have line spectrum peaks on both sides of the f1 frequency. - or f1 + There is also a significant peak at the

[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. Figure 4 , Figure 4 Schematic diagram of the reduction in sound pressure level of a hydrofoil at a 0° attack angle provided in an embodiment of the present application. Figure 4 As shown in (a) in the figure. It can be seen from the figure that at the frequencies of f1, f2, and f3, compared with the basic hydrofoil, the coated hydrofoil, small serrated hydrofoil, large serrated hydrofoil, small serrated coated coupled hydrofoil, and large serrated coated coupled hydrofoil all show a reduction in sound pressure level. Taking the f1 frequency as an example, the reduction in sound pressure level of each hydrofoil is 7.1 dB, 9.2 dB, 17.7 dB, 12.4 dB, and 19.2 dB, respectively. The noise reduction effect of the coated serrated coupled hydrofoil at the f1 frequency is better than that of a single coated hydrofoil or serrated hydrofoil, and similar conclusions are reached at the f2 and f3 frequencies. In addition to the reduction in sound pressure level at the f1, f2, and f3 frequencies, the coated hydrofoil, small serrated hydrofoil, large serrated hydrofoil, small serrated coated coupled hydrofoil, and large serrated coated coupled hydrofoil have - or f1 + Line spectrum noise will be generated at the frequency, and the line spectrum noise generated by small and large sawtooth hydrofoils is more intense. - The sound pressure level amplitude at the frequency exceeds the sound pressure level amplitude of the basic airfoil at the f1 frequency, which has an adverse effect on the noise performance of the hydrofoil.

[0063] Furthermore, the total sound pressure level of the hydrofoil in the frequency range of 100-5000 Hz is calculated, and the reduction in the total sound pressure level compared with the basic airfoil is calculated. The results are as follows: Figure 4 As shown in (b) in the figure, it can be seen that due to the small sawtooth hydrofoil and the large sawtooth hydrofoil The line spectrum peak with higher amplitude was generated at the frequency, which caused a 5 dB and 2 dB increase in the total sound pressure level compared with the basic hydrofoil. The coated hydrofoil, small serrated coating coupled hydrofoil, and large serrated coating coupled hydrofoil all showed a reduction in the total sound pressure level, with a reduction amplitude of 3 dB, 5 dB, and 4 dB, respectively. That is, at a 0° attack angle, the coupling of the serrated structure and the coating improved the noise characteristics of the serrated hydrofoil, turning it from an unfavorable noise increase to a favorable noise reduction, and showed a better noise reduction effect than the coated hydrofoil, indicating the advantages of the serrated coating coupling control scheme.

[0064] In addition, the hydrofoil can also improve the hydrodynamic performance at a 0° angle of attack. The hydrodynamic performance at a 6° angle of attack is more significantly improved than that at a 0° angle of attack. The subsequent combined data will mainly compare the hydrodynamic performance of the hydrofoil at a 6° angle of attack.

[0065] In one embodiment, the hydrofoil test installation at 6° angle of attack is as follows Figure 5 As shown, Figure 5 6° angle of attack. Figure 6 As shown in (a), (b), (c) and (d) in Figure 6 It is a schematic diagram of the sound pressure level spectrum of a hydrofoil at a 6° angle of attack provided in an embodiment of the present application. As can be seen from 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. Different from the 0° angle of attack, the basic hydrofoil has more significant peaks at the f1 and f2 frequencies, and also produces an extremely strong peak at the f0 frequency, which far exceeds the sound pressure levels at the f1 and f2 frequencies, and exceeds the broadband sound pressure level at the f0 frequency by nearly 30 dB. At the same time, a sharp sound can be heard during the experimental test, indicating that a strong shedding vortex may have been generated on the surface of the hydrofoil at a 6° angle of attack, and the shedding vortex frequency is also f0, thereby generating resonance with the hydrofoil structure and forming a singing sound. The coated hydrofoil, small serrated hydrofoil, and small serrated coated coupled hydrofoil also produce strong line spectra at the f0 frequency, while the large serrated hydrofoil and large serrated coated coupled hydrofoil do not show significant line spectra at the f0 frequency, and the corresponding f0 frequency values ​​of each airfoil fluctuate around 680-690 Hz.

[0066] The sound pressure level amplitude of each airfoil at the characteristic frequencies of f0, f1, and f2 is extracted, and the reduction in sound pressure level compared with the basic airfoil is calculated. Figure 7 , Figure 7 Schematic diagram of the reduction in sound pressure level of a hydrofoil at a 6° attack angle provided in an embodiment of the present application. Figure 7As shown in (a) in the figure. It can be seen from the figure that the large serrated hydrofoil and the large serrated coating coupled hydrofoil do not show significant line spectra at the f0 frequency. The disappearance of the line spectrum frequency of the large serrated hydrofoil and the large serrated coating coupled hydrofoil at the f0 frequency indicates that the resonance between the shedding vortex and the airfoil structure is destroyed and the singing sound is eliminated. The reason for the elimination of the singing sound is that the large serrated structure breaks up the periodic vortex shedding structure with the f0 characteristic frequency on the surface of the hydrofoil, eliminates the excitation source that causes the hydrofoil resonance, and thus eliminates the singing sound. On the basis of eliminating the singing sound, the large serrated coating coupled hydrofoil shows a lower broadband sound pressure level than the large serrated hydrofoil.

[0067] Correspondingly, both the coated hydrofoil and the small sawtooth hydrofoil failed to eliminate the singing noise, while the small sawtooth coated coupled hydrofoil showed a partial effect of eliminating singing noise. This phenomenon indicates that the coating may have caused a change in the flow state on the hydrofoil surface, delaying the location of vortex shedding on the hydrofoil surface to the range where the small sawtooth structure can effectively act, so that the small sawtooth structure can produce a crushing effect on the delayed shedding vortex structure, thereby reducing the strength of the shedding vortex and achieving a reduction in the line spectrum noise of the sawtooth coated coupled hydrofoil.

[0068] In addition, at the characteristic frequencies of f1 and f2, the coated hydrofoil, serrated hydrofoil and serrated coating coupled hydrofoil all showed a reduction in sound pressure level, and at the frequency of f1, the coated hydrofoil, small serrated hydrofoil, large serrated hydrofoil, small serrated coating coupled hydrofoil and large serrated coating 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 frequency range of 100-5000 Hz at an angle of attack of 6° was calculated, and the reduction in the total sound pressure level compared with the basic airfoil was calculated. The results are as follows: Figure 7 As shown in (b) in the figure. As can be seen from the figure, due to the strengthening of the line spectrum peak at the f0 frequency of the coated hydrofoil and the small serrated hydrofoil, the total sound pressure level increased by 7 dB and 17 dB compared with the basic hydrofoil. The large serrated hydrofoil, the small serrated coating coupled hydrofoil, and the large serrated coating coupled hydrofoil all showed a reduction in the total sound pressure level, with a reduction amplitude of 8 dB, 10 dB and 12 dB, respectively. That is, at an angle of attack of 6°, the coupling of the small serrated structure and the coating improved the noise characteristics of the coated hydrofoil and the small serrated hydrofoil, turning it from noise increase to noise reduction. In addition, the coupling of the large serrated structure and the coating improved the noise characteristics of the coated hydrofoil, turning it from noise increase to noise reduction, and showed a better noise reduction effect than the large serrated hydrofoil, indicating the advantages of the serrated coating coupling control scheme.

[0070] In addition, in terms of hydrodynamic performance, the lift and drag of different hydrofoils at an angle of attack of 6° were experimentally measured, and the results are shown in Table 1 below. As can be seen from the table, compared with the basic hydrofoil, the coated hydrofoil can achieve a 0.6% lift increase and a 11.1% drag reduction, thereby achieving an increase in lift-to-drag ratio of about 13.2%. Both the small serrated hydrofoil and the large serrated hydrofoil showed a reduction in lift and drag, and the lift reduction was large, resulting in a reduction in lift-to-drag ratio, and the large serrated hydrofoil had a greater reduction in lift-to-drag ratio (6.8%). For the serrated coated coupled hydrofoil, compared with the serrated hydrofoil, its lift characteristics showed a certain improvement, and the lift-to-drag ratio reduction rate decreased. Compared with the basic hydrofoil, the lift-to-drag ratio of the small serrated coated coupled hydrofoil and the large serrated coated coupled hydrofoil decreased by 0.8% and 4.6%, respectively. It can be seen that the coating has a significant beneficial effect on improving the hydrodynamic performance of the hydrofoil, while the serrated structure has an adverse effect on the hydrodynamic performance. The coupling of the serrated structure and the coating can improve the degradation of the hydrodynamic performance of the hydrofoil caused by the serrated structure.

[0071]

[0072] Table 1

[0073] In summary, the coated hydrofoil showed a relatively excellent improvement in hydrodynamic performance, the small serrated hydrofoil showed no improvement in hydrodynamic performance and noise performance, the large serrated hydrofoil showed an excellent noise reduction effect, but the hydrodynamic performance loss was large, and the serrated-coated coupled hydrofoil overcame the shortcomings of the coating and serrated structure in terms of noise performance, combined the advantages of the coating in hydrodynamic performance regulation, overcame the loss of hydrodynamic performance caused by the serrated structure, and achieved an improvement in the comprehensive performance of the hydrofoil. It has the potential for practical application and provides a new idea for improving the performance of the hydrofoil. At an angle of attack of 6°, the hydrofoil can generate a relatively significant lift, and the drag value increases. Therefore, the subsequent comparison is mainly about the hydrodynamic performance of the hydrofoil at an angle of attack of 6°.

[0074] In one embodiment, the hydrofoil test installation at a 10° angle of attack is as follows: Figure 8 As shown, Figure 8 1 is a schematic diagram of a hydrofoil test installation at a 10° attack angle provided in an embodiment of the present application. The noise test results of each hydrofoil are as follows: Fig. 9 As shown in (a), (b), (c) and (d) in Fig. 9 : is a schematic diagram of the sound pressure level spectrum of a hydrofoil at an attack angle of 10° provided in an embodiment of the present application. Fig. 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. Fig.10 , Fig.10 1 is a schematic diagram of the reduction in sound pressure level of a hydrofoil at an attack angle of 10° provided in an embodiment of the present application. Fig.10As shown in (a) in the figure. As can be seen from the figure, compared with the basic hydrofoil, at the frequencies of f0, f1, and f2, the coated hydrofoil shows a decrease in the sound pressure level, while at f0 and f1, the small serrated hydrofoil shows an increase in the sound pressure level (increased by 20.8 dB and 6.6 dB respectively), while the large serrated hydrofoil has a smaller reduction in the sound pressure level, which can be almost ignored. The small serrated coating coupled hydrofoil and the large serrated coating coupled hydrofoil improve the sound pressure level characteristics of the serrated hydrofoil. At the frequency of f0, the small serrated coating coupled hydrofoil reduces the increase in the sound pressure level from 20.8 dB to 2.5 dB, while at the frequency of f1, the small serrated coating coupled hydrofoil improves the change in the sound pressure level from an increase of 6.6 dB to a decrease of 3.1 dB, showing a significant noise reduction advantage compared to the existing small serrated hydrofoil. The large serrated coating coupled hydrofoil has a similar improvement in the sound pressure level characteristics compared to the large serrated hydrofoil.

[0075] Furthermore, the total sound pressure level of the hydrofoil in the frequency range of 100-5000 Hz is calculated, and the reduction in the total sound pressure level compared with the basic airfoil is calculated. The results are as follows: Fig.10 As shown in (b) in the figure. As can be seen from the figure, due to the high amplitude line spectrum peak generated by the small serrated hydrofoil at the f0 frequency, the total sound pressure level increased by 4 dB compared with the basic hydrofoil. The large serrated hydrofoil did not show a decrease in the total sound pressure level. The coated hydrofoil, the small serrated coating coupled hydrofoil, and the large serrated coating coupled hydrofoil all showed a decrease in the total sound pressure level, with a decrease of 3 dB, 5 dB and 4 dB respectively. That is, at an angle of attack of 10°, the coupling of the serrated structure and the coating improved the noise characteristics of the serrated hydrofoil, turning it from an unfavorable noise increase or no noise reduction to a favorable noise reduction, and showing a better noise reduction effect than the coated hydrofoil, indicating the advantages of the serrated coating coupling control scheme.

[0076] It can be seen from the above-mentioned embodiments that the coupling of the sawtooth structure and the coating changes the regulation of the noise performance of the sawtooth structure from noise increase to noise reduction, and can further enhance the noise reduction effect of the coating or improve the regulation effect of the coating on noise from noise increase to noise reduction, showing the advantages of the coupling regulation of the sawtooth structure and the coating surface proposed in the embodiments of the present application. At the same time, the coupling of the sawtooth structure and the coating surface greatly improves the hydrodynamic performance of the sawtooth structure. The above results show that the method for regulating the hydrodynamic and noise performance of the wing profile of the sawtooth structure and the sliding surface proposed in the embodiments of the present application has significant advantages over the prior art. In addition, the sawtooth structure and the sliding surface have the advantage of being easy to implement, and the sliding surface formed by the coating still shows a relatively stable test effect in experimental tests lasting several days, indicating that it has the advantage of strong endurance and has broad application prospects in the fields of surface ships, underwater navigation bodies, etc.

[0077] It should be understood that, although the various steps in the flowcharts involved in the above-mentioned embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps does not have a strict order restriction, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-mentioned embodiments can include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0078] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium 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), magnetoresistive 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. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. Non-relational databases may include distributed databases based on blockchains, etc., but are not limited to this. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., but are not limited to this.

[0079] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, 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 above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. An airfoil for regulating hydrodynamic and noise performance, characterized in that: 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, and the slip surface is used to improve the lift-to-drag ratio of the surface of the airfoil. The airfoil trailing edge is provided with a plurality of serration structures arranged along the span direction of the airfoil, and the serration structures are used to improve the noise performance of the airfoil.

2. The airfoil according to claim 1, characterized in that The slip coating includes a carbon-based coating or a fluorine-containing coating.

3. The airfoil according to claim 2, characterized in that 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.

4. The airfoil according to claim 1 or 2, characterized in that: The slip coating is applied to the surface of the airfoil body by spraying, coating or spin coating.

5. The airfoil according to claim 1 or 2, characterized in that: The sawtooth structure has a shape of at least one of a triangle and a sinusoid.

6. The airfoil according to claim 1 or 2, characterized in that: The ratio of the length of the sawtooth structure in the chord direction of the airfoil to the length in the span direction is not less than 2 and not more than 4.

7. The airfoil according to claim 1 or 2, characterized in that: The length of the sawtooth structure in the chord length 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.

8. The airfoil according to claim 1 or 2, characterized in that: The surface of the sawtooth structure is provided with the slip coating.

9. The airfoil according to claim 1 or 2, characterized in that: The sawtooth structure is a structure formed by removing material from the trailing edge of the airfoil.

10. The airfoil according to claim 1 or 2, characterized in that: The sawtooth structures are arranged at equal intervals and / or at unequal intervals in the extension direction.

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