Double-blade vortex generator suitable for subsonic airfoil and design method

Abstract

The invention provides a double-blade vortex generator suitable for subsonic airfoils and a design method.The double-blade vortex generator comprises a supporting plate and two fins fixed to the upper portion of the supporting plate, the supporting plate is fixed to the surface of an airfoil in the incoming flow direction, the two fins are symmetrically arranged about the plane where the supporting plate is located, and the two fins are fixed to the upper portion of the supporting plate. The two fins extend in the incoming flow direction. The vortex generator provided by the invention is mounted in front of a separation area, and can generate stronger flow vortexes to improve the aerodynamic characteristics of wings at a large attack angle, weaken the flow separation of a leeside and improve the aerodynamic performance of an aircraft, and compared with a vortex generator-free state, the vortex generator has the advantages that the resistance is reduced, and the lift-drag ratio is increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of aerospace, and relates to a vortex generator for a wing, specifically to a double - blade vortex generator applicable to subsonic airfoils and a design method thereof. Background Technique

[0002] Flow separation is a common flow phenomenon in the field of aerodynamics, usually occurring under flow conditions with a large angle of attack. When flow separation occurs on a wing, it will lead to a decrease in lift, an increase in flow loss, and severe flow separation will even cause the wing to stall, thus triggering accidents. To solve this problem, flow control techniques are usually adopted to improve the flow characteristics of the wing at a large angle of attack. Flow control techniques can be further divided into active control techniques and passive control techniques according to whether external energy input is required. Passive control techniques have been widely applied in the field of aerodynamics because they do not require additional energy input.

[0003] A vortex generator is a typical passive control technique, and its mechanism of action is mainly to generate wing - tip vortices with higher energy and act on the downstream low - energy fluid region, forcing the low - energy fluid to transfer from the surface to the mainstream and bringing the high - energy fluid from the mainstream down to the wing surface, so that the near - wall fluid can resist the adverse pressure gradient, thereby delaying separation and improving performance. Summary of the Invention

[0004] The purpose of the present invention is to provide a double - blade vortex generator applicable to subsonic airfoils and a design method thereof, so as to solve the serious flow separation phenomenon that occurs on the upper wing surface under the flight condition of a large angle of attack of the wing.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] As one aspect of the present invention, a double - blade vortex generator applicable to subsonic airfoils is provided, which includes a support plate and two fins fixed on the upper part of the support plate. The support plate is fixed on the wing surface along the oncoming flow direction, the two fins are symmetrically arranged with respect to the plane where the support plate is located, and the two fins extend along the oncoming flow direction.

[0007] Furthermore, a front - inclination angle is set at the leading edge of the vortex generator. The front - inclination angle is set along the leading edge of the fin and extends from the root of the leading edge of the fin to the leading edge of the support plate.

[0008] Furthermore, the included angle between the two fins ranges from 67° to 107°, and the value range of the front - inclination angle is from 15° to 45°.

[0009] Furthermore, a plurality of the double - blade vortex generators are arranged on the wing surface along the chord direction of the wing at a set interval.

[0010] As another aspect of the present invention, a design method for a double - leaf vortex generator applicable to subsonic airfoils is provided, including the following steps:

[0011] Select the airfoil of the wing as the research object, determine the geometric parameters of the wing, establish the geometric model of the wing, and determine the flight parameters of the airfoil of the wing under standard working conditions;

[0012] Use fluid mechanics software to calculate the flow field of the original wing and obtain the flow characteristics of the original wing;

[0013] According to the geometric parameters of the wing and the flow characteristics of the original wing, determine the geometric dimensions and installation positions of the vortex generator, and obtain the wing with the vortex generator;

[0014] Use fluid mechanics software to calculate the flow field of the wing with the vortex generator and obtain the flow characteristics of the wing with the vortex generator, and verify the effectiveness of the vortex generator in controlling separation.

[0015] Furthermore, the geometric parameters of the wing at least include the wing chord length, and the flight parameters of the airfoil of the wing under standard working conditions at least include the flight angle of attack and the flight speed.

[0016] Furthermore, the step of using fluid mechanics software to calculate the flow field of the original wing and obtain the flow characteristics of the original wing specifically includes the following steps:

[0017] Establish the computational domain of the original wing, superimpose the computational domain of the original wing on the geometric model of the wing to obtain the computational model, and perform discretization and surface encryption processing;

[0018] Set the turbulence model on the computational model and obtain the flow field structure of the original wing through simulation;

[0019] Collect the flow characteristics of the original wing, and the flow characteristics of the original wing at least include the thickness of the oncoming flow boundary layer, the drag coefficient, the lift coefficient, and the lift - to - drag ratio on the upper surface of the wing.

[0020] Furthermore, the step of determining the geometric dimensions and installation positions of the vortex generator according to the geometric parameters of the wing and the flow characteristics of the original wing specifically includes the following steps:

[0021] According to the flow characteristics of the original wing, calculate the geometric dimensions of the vortex generator. The geometric dimensions of the vortex generator include:

[0022] b = 0.02δ

[0023] s = 1.2δ

[0024] H = 1δ

[0025] h = 0.3δ

[0026] wherein, δ is the thickness of the oncoming flow boundary layer on the upper surface of the wing; b is the thickness of the strut and fin; s is the total length of the vortex generator, H is the total height of the vortex generator, and h is the height of the strut;

[0027] Set the initial value of the included angle between the two fins and the initial value of the rake angle of the vortex generator;

[0028] According to the geometric parameters of the wing, determine the installation position of the vortex generator, and the installation position of the vortex generator includes:

[0029] x = (0.1 ± 0.05)c

[0030] Δy = (0.1 ± 0.05)c

[0031] wherein, x is the distance of the vortex generator from the leading edge of the wing, Δy is the interval between the vortex generator arrays arranged along the span of the wing, and c is the chord length of the wing.

[0032] Furthermore, the flow characteristics of the wing with the vortex generator at least include the drag coefficient, lift coefficient, and lift-to-drag ratio of the wing with the vortex generator;

[0033] The effectiveness of the vortex generator in controlling separation is judged by using the Q-criterion.

[0034] Furthermore, the design method of the double-leaf vortex generator further includes the following steps:

[0035] If the improvement effects of the drag coefficient, lift coefficient, and lift-to-drag ratio of the wing with the vortex generator relative to the original wing do not meet the requirements, or the effectiveness of the vortex generator in controlling separation does not meet the requirements, then optimize the geometric size and / or installation position of the vortex generator;

[0036] Optimizing the geometric size of the vortex generator includes adjusting the included angle between the two fins and the rake angle of the vortex generator;

[0037] Optimizing the installation position of the vortex generator includes adjusting the distance of the vortex generator from the leading edge of the wing and the interval between the vortex generator arrays arranged along the span of the wing.

[0038] The beneficial effects of the present invention compared with the prior art:

[0039] In order to solve the serious flow separation phenomenon that occurs on the upper wing surface under the flight condition of a large angle of attack, the present invention proposes a double - blade vortex generator. The vortex generator mainly consists of a lower support plate and two upper fins. The vortex generator is installed in front of the separation area and can generate stronger streamwise vortices to improve the aerodynamic characteristics of the wing at a large angle of attack, weaken the flow separation on the leeward side, improve the aerodynamic performance of the aircraft, reduce the drag compared with the state without the vortex generator, and increase the lift - to - drag ratio. At the same time, the vortex generator has a simple structure and is easy to install, and is applicable to different types of subsonic airfoils.

[0040] In order to optimize the use effect of the double - blade vortex generator, the present invention also provides a design method for the double - blade vortex generator applicable to subsonic airfoils. Through the simulation comparison of the flow characteristics of the original wing and the wing with the vortex generator, the effectiveness of the vortex generator in controlling separation can be verified, and at the same time, it can feedback and guide the optimization of the size parameters and installation layout of the vortex generator. Brief Description of the Drawings

[0041] The included drawings are used to provide a further understanding of the embodiments of the present invention. They form a part of the specification, are used to illustrate the embodiments of the present invention, and together with the written description, explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0042] Figure 1 Structural schematic diagrams of the vortex generator provided for specific embodiments of the present invention, (a) front view, (b) side view, (c) front view, (d) top view;

[0043] Figure 2 Structural schematic diagram of the wing model with the vortex generator provided for specific embodiments of the present invention;

[0044] Figure 3 Schematic diagrams of the cross - section streamlines in the wing model provided for specific embodiments of the present invention, (a) without the vortex generator, (b) with the vortex generator;

[0045] Figure 4 Q - criterion isosurface diagrams provided for specific embodiments of the present invention, (a) without the vortex generator, (b) with the vortex generator. Detailed Description of the Invention

[0046] The specific embodiments of the present invention will be described in detail below. In the following description, for purposes of explanation rather than limitation, specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced in other embodiments without departing from these specific details.

[0047] It should be noted here that in order to avoid obscuring the present invention with unnecessary details, only the device structures and / or processing steps closely related to the solution of the present invention are shown in the drawings, while other details less related to the present invention are omitted.

[0048] The vortex generator is a typical passive control technology. Its action mechanism is mainly to generate high-energy wingtip vortices acting on the downstream low-energy fluid region, forcing the low-energy fluid to transfer from the surface to the mainstream, and bringing the high-energy fluid from the mainstream down to the wing surface, enabling the near-wall fluid to resist the adverse pressure gradient, thereby delaying separation and improving performance.

[0049] In order to solve the serious flow separation phenomenon that occurs on the upper wing surface under the flight condition of a large angle of attack of the wing, the present invention proposes a double-leaf vortex generator for the flow separation of the wing under a large angle of attack, as Figure 1 shown. The vortex generator mainly includes a lower support plate and an upper fin. The support plate is fixed on the wing surface along the oncoming flow direction. The two fins are symmetrically arranged with respect to the plane where the support plate is located, and the two fins extend along the oncoming flow direction. The vortex generator is installed in front of the wing separation region and can generate stronger streamwise vortices to improve the aerodynamic characteristics of the wing under a large angle of attack, weaken the flow separation on the leeward side, and improve the aerodynamic performance of the aircraft.

[0050] Preferably, the leading edge of the vortex generator is provided with a forward rake angle, which is provided along the leading edge of the fin and extends from the root of the leading edge of the fin to the leading edge of the support plate. As Figure 1 shown, in the side view of the vortex generator, the leading edge of the vortex generator forms a forward rake angle at a set angle, and the forward rake angle covers the leading edge structures of the fin and the support plate locally. By adopting this configuration, the aerodynamic drag of the vortex generator can be better reduced.

[0051] Preferably, the included angle between the two fins ranges from 67° to 107°, and the forward rake angle ranges from 15° to 45°. Through multiple verification tests, by adopting this configuration, the effect of the vortex generator in controlling separation can be optimized.

[0052] Preferably, in order to optimize the effect of the vortex generator in controlling separation, multiple double-leaf vortex generators are arranged on the wing surface at a set interval along the direction perpendicular to the oncoming flow. As Figure 2 shown, on the upper surface of the wing, multiple double-leaf vortex generators are arranged along the chord direction of the wing to form an array layout.

[0053] To optimize the use effect of the double - leaf vortex generator, the present invention also provides a design method of a double - leaf vortex generator applicable to subsonic airfoils, including the following steps:

[0054] First, select the airfoil model of the wing as the research object, determine the main geometric parameters of the research object, and complete the creation of the geometric model. And determine the flight conditions of the wing: mainly including but not limited to the angle of attack, atmospheric parameters, etc.

[0055] After that, use computational fluid dynamics software to complete the flow field calculation of the original wing at a large angle of attack, and obtain the flow characteristics of the original wing at a large angle of attack.

[0056] Then, according to the flow separation characteristics and boundary layer thickness of the wing at a large angle of attack, determine the main geometric dimensions of the vortex generator and the installation position, that is, complete the wing model with the vortex generator.

[0057] Finally, perform simulation processing on the wing model containing the vortex generator again using computational fluid dynamics software, obtain the flow characteristics of the wing with the vortex generator, and verify the effectiveness of its separation control.

[0058] A design method of a double - leaf vortex generator applicable to subsonic airfoils provided by the present invention can verify the effectiveness of the vortex generator's separation control through the simulation comparison of the flow characteristics of the original wing and the wing with the vortex generator. At the same time, it can feedback and guide the optimization of the size parameters and installation layout of the vortex generator. Using this design method, the vortex generator can generate a highly energetic streamwise vortex, improve the flow characteristics of the wing at a large angle of attack, and weaken the separation area and separation intensity on the leeward side. Compared with the state without the vortex generator, the drag is reduced and the lift - to - drag ratio is increased.

[0059] The following will explain in detail the specific implementation manner of the method of the present invention with reference to the accompanying drawings. The embodiments are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0060] A design method of a double - leaf vortex generator applicable to subsonic airfoils includes the following steps:

[0061] Step 1, select the original wing model, and determine the geometric dimensions and flight conditions of the wing: angle of attack, atmospheric pressure, etc.

[0062] S1: Select an appropriate airfoil of the wing and determine the main geometric parameters of the wing, and establish a geometric model. In this embodiment, the wing selects the NACA0012 airfoil, and the chord length is set to 300 mm.

[0063] S2: Determine the flight parameters of the wing. The flight parameters of one working condition of the wing can be selected for the optimization design. In this embodiment, the flight parameters under the standard working condition of the airfoil are adopted. For the NACA0012 airfoil, the flight parameters are selected as the flight angle of attack of 12°, the flight speed of 0.3 Mach, the ambient pressure of one standard atmosphere, and the air density of 1.225 kg / m 3 , and the ambient temperature of 288.15 K.

[0064] Step 2: Establish the computational domain of the original wing, and use computational fluid dynamics simulation software to perform the flow analysis of the original airfoil to obtain the boundary layer thickness and separation structure.

[0065] S3: Establish the computational domain and discretize it. The flow direction length of the computational domain of the original wing is taken as 15 times the chord length, and the spanwise length is taken as 30 times the chord length. After determining the computational domain, perform the subtraction operation of the Boolean operation on the computational domain of the original wing and the geometric model determined in S1 to obtain the computational model. Use the software to complete the discretization process of the calculation, and perform encryption processing on the wing surface area.

[0066] S4: Use CFD software for calculation. The SA model widely used in external flow calculations is selected for the turbulence model to obtain the flow field structure of the original airfoil of the wing, and based on this, the flow characteristics of the original wing are obtained. The flow characteristics of the original wing mainly include: measuring the oncoming boundary layer thickness δ = 10 mm on the upper surface of the wing, calculating that the drag coefficient of the original wing is 0.0695, the lift coefficient is 0.8991, and the lift-to-drag ratio is 12.94.

[0067] Step 3: Determine the geometric dimensions and installation positions of the vortex generators according to the oncoming boundary layer thickness and the chord length; construct the computational domain of the wing model containing the vortex generators and perform computational fluid dynamics simulation analysis.

[0068] S5: The established vortex generator model is as Figure 1 shown. The vortex generator is mainly composed of a lower strut and fins connected to the strut. The thickness of the strut and fins of the vortex generator is b = 0.02δ = 0.2 mm, the total length of the vortex generator is s = 1.2δ = 12 mm, the total height of the vortex generator is H = 1δ = 10 mm, the height of the strut is h = 0.3δ = 3 mm, the initial angle between the two fins is α = 87°, and the initial forward tilt angle of the vortex generator is β = 30°.

[0069] S6: Analyze the flow field characteristics of the original wing obtained in S4, and determine that the vortex generators are installed in the flow direction at x = 0.1c = 30 mm, and the spanwise array interval is Δy = 0.08c = 25 mm; perform the addition operation of the Boolean operation on the vortex generators determined in S5 and the wing model to obtain the wing model with vortex generators as Figure 2 shown.

[0070] S7: Establish a computational domain using the wing model with vortex generators obtained in S6. The size of the computational domain is the same as that in S3, and discretize the computational domain with the same mesh encryption method as in S3.

[0071] S8: Use software to calculate the flow field structure of the wing with vortex generators, and the calculation settings are the same as those in S4.

[0072] Step Four: Analyze the effects of the vortex generators

[0073] S9: Analyze the beneficial effects of using vortex generators, such as Figure 3 As shown, from the streamline of the wing mid-section, it can be seen that after adding the vortex generators, the separation area decreases, and the separation is effectively weakened. In addition, the Q-criterion is a method for vortex identification in fluid mechanics, and it can visually show the vorticity isosurface with a certain value. As Figure 4 shown, from the Q-criterion isosurface, it can be seen that the vortex generators generate obvious streamwise vortices, effectively controlling the downstream separation region.

[0074] Meanwhile, for the wing with vortex generators arranged, the calculated drag coefficient is 0.0562, the lift coefficient is 1.008, and the lift-to-drag ratio is 17.94. The lift-to-drag ratio is significantly improved, verifying the effectiveness of the vortex generators in controlling separation.

[0075] Based on the above embodiments, it can be seen that a vortex generator for a wing provided by the present invention can effectively achieve flow control at a large angle of attack. By generating extremely high-energy streamwise vortices, it improves the flow characteristics of the wing at a large angle of attack and weakens the separation area and separation intensity on the leeward side. Compared with the state without vortex generators, the drag is reduced and the lift-to-drag ratio is increased.

[0076] Features described and / or illustrated for one embodiment above can be used in the same or similar manner in one or more other embodiments, and / or combined with the features in other embodiments or replace the features in other embodiments.

[0077] It should be emphasized that the term "comprising / including" when used herein refers to the presence of features, whole things, steps or components, but does not exclude the presence or addition of one or more other features, whole things, steps, components or their combinations.

[0078] Many features and advantages of these embodiments will be apparent from this detailed description, and thus the appended claims are intended to cover all such features and advantages of these embodiments that fall within their true spirit and scope. Further, since many modifications and changes will readily occur to those skilled in the art, it is not intended to limit the embodiments of this invention to the exact construction and operation shown and described, but rather all suitable modifications and equivalents that fall within its scope may be covered.

[0079] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0081] The parts not detailed in the present invention are well-known technologies to those skilled in the art.

Claims

1. A two-blade vortex generator suitable for subsonic airfoils, characterized in that: It comprises a support plate and two fins fixed on the upper part of the support plate, wherein the support plate is fixed on the wing surface along the incoming flow direction, the two fins are symmetrically arranged about the plane where the support plate is located, and the two fins extend along the incoming flow direction.

2. The double-blade vortex generator according to claim 1, characterized in that: The leading edge of the vortex generator is provided with a forward inclination angle, which is provided along the leading edge of the fin and extends from the root of the leading edge of the fin to the leading edge of the support plate.

3. The double-blade vortex generator according to claim 2, characterized in that: The included angle between the two fins ranges from 67° to 107°, and the forward inclination angle ranges from 15° to 45°.

4. The double-blade vortex generator according to any one of claims 1 to 3, characterized in that: A plurality of the double-blade vortex generators are arranged on the wing surface along the chord direction of the wing at set intervals.

5. A design method for a two-blade vortex generator suitable for a subsonic airfoil, characterized in that: Using the double-blade vortex generator described in any one of claims 1 to 4, the design method comprises the following steps: Select the wing airfoil as the research object, determine the geometric parameters of the wing, establish the wing geometric model, and determine the flight parameters of the wing airfoil under standard working conditions; The flow field of the original wing is calculated using fluid mechanics software to obtain the flow characteristics of the original wing; According to the geometric parameters of the wing and the flow characteristics of the original wing, the geometric size and installation position of the vortex generator are determined to obtain the wing with the vortex generator; The flow field of the wing with vortex generators is calculated using fluid mechanics software, the flow characteristics of the wing with vortex generators are obtained, and the effectiveness of the vortex generator in controlling separation is verified.

6. The design method according to claim 5, characterized in that: The geometric parameters of the wing include at least the chord length of the wing, and the flight parameters of the wing airfoil under standard working conditions include at least the flight angle of attack and the flight speed.

7. The design method according to claim 6, characterized in that: The method of calculating the original wing flow field by using fluid mechanics software to obtain the flow characteristics of the original wing specifically includes the following steps: Establish the computational domain of the original wing, superimpose the computational domain of the original wing on the wing geometric model, obtain the computational model, and perform discretization and surface encryption processing; A turbulence model is set on the computational model, and the flow field structure of the original wing is obtained through simulation; The flow characteristics of the original wing are collected, wherein the flow characteristics of the original wing at least include the thickness of the incoming flow boundary layer, the drag coefficient, the lift coefficient, and the lift-to-drag ratio on the upper surface of the wing.

8. The design method according to claim 7, characterized in that: The method of determining the geometric size and installation position of the vortex generator according to the geometric parameters of the wing and the flow characteristics of the original wing specifically includes the following steps: According to the flow characteristics of the original wing, the geometric dimensions of the vortex generator are calculated, and the geometric dimensions of the vortex generator include: b=0.02δ s=1.2δ H=1δ h=0.3δ Among them, δ is the thickness of the incoming boundary layer on the upper surface of the wing; b is the thickness of the support plate and fin; s is the total length of the vortex generator, H is the total height of the vortex generator, and h is the height of the support plate; Set the initial value of the angle between the two fins and the initial value of the forward tilt angle of the vortex generator; According to the geometric parameters of the wing, the installation position of the vortex generator is determined, and the installation position of the vortex generator includes: x=(0.1±0.05)c Δy=(0.1±0.05)c Where x is the distance between the vortex generator and the leading edge of the wing, Δy is the interval between the vortex generator arrays arranged along the span of the wing, and c is the chord length of the wing.

9. The design method according to claim 5, characterized in that: The flow characteristics of the wing with vortex generators include at least the drag coefficient, lift coefficient, and lift-to-drag ratio of the wing with vortex generators; The effectiveness of verifying the separation controlled by the vortex generator is judged by using the Q criterion.

10. The design method according to claim 5, characterized in that: The double-blade vortex generator design method also includes the following steps: If the drag coefficient, lift coefficient and lift-to-drag ratio improvement effect of the wing with vortex generators relative to the original wing does not meet the requirements, or the effectiveness of the vortex generators in controlling separation does not meet the requirements, the geometric dimensions and / or installation position of the vortex generators shall be optimized; The optimization of the geometric dimensions of the vortex generator includes adjusting the angle between the two fins and the forward tilt angle of the vortex generator; The optimizing the installation position of the vortex generator includes adjusting the distance between the vortex generator and the leading edge of the wing and the interval between the vortex generator arrays arranged along the span direction of the wing.

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