An airfoil configuration capable of improving separation characteristics at high angles of attack

Abstract

The invention discloses an airfoil configuration capable of improving separation characteristics at large angles of attack and a design method thereof. The airfoil configuration comprises a main wing and an elliptical wing, wherein the elliptical wing is arranged on the suction surface of the leading edge point of the main wing through a chord structure, and under the action of the incoming flow, alternating downward vortices are generated on both sides of the elliptical wing; the chord structure comprises a first fixing ring lock, a second fixing ring lock and a rotating bolt, wherein the first fixing ring lock is arranged at 25% of the span direction of the main wing, the second fixing ring lock is arranged at 75% of the span direction of the main wing, and the rotating bolt is arranged at 100% of the span direction of the main wing; the airfoil configuration can effectively suppress airflow separation at large angles of attack of the airfoil without consuming energy and generating less additional resistance, and can improve the lift coefficient of the airfoil while reducing the drag coefficient, and has the characteristics of greatly improving the lift-to-drag ratio of the airfoil and improving the aerodynamic performance at large angles of attack.

Description

Technical Field

[0001] The invention relates to the technical field of wing aerodynamic shape design, and in particular to an airfoil configuration capable of improving separation characteristics at large attack angles. Background Art

[0002] Under high angle of attack flow conditions, large-scale wing flow separation will occur on aircraft, resulting in a significant reduction in the lift coefficient of the airfoil, while increasing the drag coefficient and sharply deteriorating aerodynamic performance. When the airflow separates in the boundary layer on the airfoil, it will cause serious consequences such as stalling, which is very likely to cause aviation accidents. Therefore, studying effective solutions to improve the flow field and suppress airfoil flow separation is of great significance to improving the maneuverability and safety of aircraft under high angle of attack conditions.

[0003] The essence of flow control is to exert physical quantities such as force, mass, and energy on local flow, utilize the interaction of fluid dynamics between fluids, and induce local or global flow changes in the flow field. Depending on whether there is additional auxiliary energy consumption, flow control methods can be divided into two categories: active control methods and passive control methods. The most typical engineering application of passive flow control technology is the vortex generator. Its main control mechanism is to generate vortices through the vortex generator to transmit energy to the low-energy boundary layer, so as to overcome the adverse pressure gradient and delay the separation of airflow, thereby increasing the stall angle of attack and the maximum lift coefficient of the wing. The cost of the lift-enhancing effect is an increase in drag and a decrease in the lift-to-drag ratio. In addition to vortex generators, slotted airfoils, bionic nodules and groove technologies all belong to the category of passive flow control. Active flow control is to directly apply appropriate disturbances in the flow field, and couple with the airfoil flow to control the flow. The main ways to suppress airflow separation include jet, blowing and suction, plasma release, etc. Compared with passive flow control technology, active flow control technology can still effectively control the airfoil flow in non-design state, but it will increase the weight and energy consumption of the aircraft accordingly; the leading edge vibrating elliptical wing configuration of the airfoil is a flow control method, and its working principle is similar to that of vortex generators. Conventional vortex generators are usually installed on the surface of the fuselage, and increase the mixing of the internal fluid of the boundary layer and the external fluid by generating longitudinal vortices, thereby transferring momentum to the boundary layer, so that the boundary layer flow field in the adverse pressure gradient can continue to adhere to the surface of the fuselage after obtaining additional energy, so as to achieve the purpose of delaying or eliminating flow separation;

[0004] At present, the main technology for suppressing the airflow separation at high angles of attack of the airfoil and thus improving the aerodynamic performance of the airfoil is flow control technology. According to whether external energy is required for control, flow control technology can be divided into two categories: active flow control technology and passive flow control technology. Active flow control controls the flow around the airfoil by means of synthetic jets, air blowing and suction, plasma release, etc., thereby improving the aerodynamic characteristics of the airfoil. Its main disadvantage is that it requires additional energy consumption, and the arrangement of related equipment for active flow control inside the wing will increase the take-off weight of the aircraft, affecting the economic performance of the aircraft to a certain extent. Passive control technology includes passive vortex generators, stall strips, flaps, micro inserts, ribs, etc. Its main disadvantage is that while affecting the flow around the airfoil, it will generate additional resistance. Moreover, since the control method and control effect of passive flow control are pre-designed, when the aircraft deviates from the design state, the passive flow control cannot function normally, and even has an adverse effect on the aerodynamic characteristics of the airfoil. Summary of the invention

[0005] In view of the above-mentioned problems, the present invention aims to provide an airfoil configuration and a design method thereof that can improve the separation characteristics at large angles of attack. By adding tiny elliptical wings near the leading edge of the airfoil to form a composite wing and giving it a certain vibration form, the elliptical wings can guide and control the incoming flow, exchange energy with the main wing, and improve the main wing's ability to resist flow separation, so as to achieve the effect of increasing the wing's stall angle of attack and improving the aerodynamic characteristics at large angles of attack. This airfoil configuration can effectively suppress the airflow separation at large angles of attack of the airfoil without consuming much energy and generating little additional resistance, thereby increasing the lift coefficient of the airfoil and reducing the drag coefficient, and has the characteristics of greatly improving the lift-to-drag ratio of the airfoil and improving the aerodynamic performance at large angles of attack.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A wing configuration capable of improving separation characteristics at large angles of attack comprises a main wing and an elliptical wing, wherein the elliptical wing is arranged on the leading edge point suction surface of the main wing through a chord structure, and under the action of an incoming flow, alternating downward vortices are generated on both sides of the elliptical wing; the chord structure comprises a first fixing ring lock, a second fixing ring lock and a rotating bolt, wherein the first fixing ring lock is arranged at 25% of the span direction of the main wing, the second fixing ring lock is arranged at 75% of the span direction of the main wing, the rotating bolt is arranged at 100% of the span direction of the main wing, and the other ends of the first fixing ring lock, the second fixing ring lock and the rotating bolt are all connected to the elliptical wing.

[0008] Preferably, the elliptical wing is a front-rear symmetrical airfoil, and the chord length of the elliptical wing is 1% of the chord length of the main wing.

[0009] Preferably, the elliptical wing has two arrangements: arranged in front of and above the suction surface of the leading edge point of the main wing airfoil, and when arranged, the distance between the elliptical wing center and the leading edge point is 4% to 6% of the chord length of the main wing airfoil.

[0010] Preferably, the vibration form of the elliptical wing can be pitch motion or heave motion, and the motion equation is: y=Asin(2πft).

[0011] Preferably, when the elliptical wing performs pitch motion, the amplitude is 0.1 to 0.3 rad and the frequency is 16 to 64 Hz.

[0012] Preferably, when the elliptical wing performs sinking and floating motions, the frequency has little influence on its control effect, and the amplitude is 0.5% to 1% of the main wing chord length.

[0013] A design method for an airfoil configuration capable of improving separation characteristics at high angles of attack comprises the following steps

[0014] S1. First, the numerical simulation method based on the two-dimensional Reynolds-averaged Navier-Stokes equation is used to optimize the shape parameters of the static elliptical wing configuration set at the leading edge of the airfoil:

[0015] S2. On the basis of setting a static elliptical wing configuration at the leading edge of the airfoil, using the static elliptical wing configuration with the best effect, giving the elliptical wing a certain vibration form, optimizing the design of the vibrating elliptical wing configuration set at the leading edge of the airfoil, and taking the frequency and amplitude of the vibration as design variables respectively;

[0016] S3. Calculate it under high angle of attack conditions, take the maximum lift-to-drag ratio and the effect of suppressing flow separation on the wing surface as the optimization goal, select the appropriate elliptical wing vibration parameters, and complete the design of the airfoil configuration.

[0017] Preferably, the process of optimizing the shape parameters of the static elliptical wing configuration at the leading edge of the airfoil by using a numerical simulation method based on the two-dimensional Reynolds-averaged Navier-Stokes equations described in step S1 includes:

[0018] S101. taking the chord length of the elliptical wing and the positional relationship between the elliptical wing and the airfoil as design variables, and calculating the lift-to-drag ratio of the airfoil configurations of the elliptical wing with different chord lengths at different positions of the airfoil leading edge under a high angle of attack condition;

[0019] S102. Compare the calculated result with the original airfoil, take the maximum lift-to-drag ratio as the optimization target, and select the appropriate elliptical wing size and setting position.

[0020] The beneficial effects of the present invention are as follows: the present invention discloses an airfoil configuration and a design method thereof that can improve the separation characteristics at large angles of attack. Compared with the prior art, the improvements of the present invention are as follows:

[0021] (1) In view of the problems existing in the prior art, the present invention designs an airfoil configuration that can improve the separation characteristics at high angles of attack. This configuration can effectively suppress the airflow separation at high angles of attack of the airfoil without consuming much energy and generating little additional drag, thereby increasing the lift coefficient of the airfoil and reducing the drag coefficient, greatly improving the lift-to-drag ratio of the airfoil and improving the aerodynamic performance at high angles of attack.

[0022] (2) At the same time, the main mechanism of this configuration to suppress airflow separation and improve the aerodynamic performance of the wing at high angles of attack is that the shedding vortex generated by the elliptical wing set at the leading edge of the main wing and the tail vortex generated by the vibration interact with the boundary layer of the airfoil, thereby introducing momentum into the boundary layer, which plays a role in delaying airflow separation, increasing lift and reducing drag; at the same time, due to the backward movement of the stagnation point at the rear of the lift surface, the lower surface pressure of the elliptical wing configuration set at the leading edge is higher than that of the original airfoil, which makes the airfoil have better aerodynamic characteristics at high angles of attack; and through the experiment, the elliptical wing configuration with leading edge vibration of this airfoil is compared with the airfoil without the elliptical wing. The elliptical wing has a significant effect on suppressing flow separation. The original large separation bubble on the airfoil completely disappears or becomes a very small separation bubble near the trailing edge of the airfoil. At the same time, the lift coefficient is increased, the drag coefficient is reduced, and the lift-to-drag ratio is greatly improved to about 3 times that of the original airfoil. Therefore, this airfoil configuration has the advantages of greatly improving the lift-to-drag ratio of the airfoil and improving the aerodynamic performance at high angles of attack. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a global view of the configuration of the elliptical wing of the present invention arranged in front of the leading edge point of the airfoil.

[0024] Figure 2 It is a partial view of the elliptical wing of the present invention arranged at the leading edge of the airfoil of the configuration forward of the leading edge point of the airfoil.

[0025] Figure 3 This is a global view of the configuration in which the elliptical wing of the present invention is arranged above the leading edge point of the airfoil.

[0026] Figure 4 It is a partial view of the leading edge of the airfoil of the present invention in which the elliptical wing is arranged above the leading edge point of the airfoil.

[0027] Figure 5 It is a global view of the installation form of the elliptical wing and the main wing of the present invention.

[0028] Figure 6 This is a partial view of the fixed ring rope arranged at 25% of the main wing span of the present invention.

[0029] Figure 7 It is the flow field streamline diagram of the original airfoil and the front vibrating elliptical wing configuration of Example 2 of the present invention.

[0030] Figure 8This is the Mach number cloud diagram (Ma=0.15) of the original airfoil and the front-mounted vibrating elliptical wing configuration of Example 2 of the present invention.

[0031] Fig. 9 This is a comparison chart of aerodynamic performance parameters of the original airfoil of Example 2 of the present invention and the configuration designed by the present invention.

[0032] Fig.10 It is the flow field streamline diagram of the original airfoil and the front vibrating elliptical wing configuration of Example 3 of the present invention.

[0033] Fig.11 This is the Mach number cloud diagram (Ma=0.15) of the original airfoil and the front-mounted vibrating elliptical wing configuration of Example 3 of the present invention.

[0034] Fig.12 This is a comparison chart of aerodynamic performance parameters of the original airfoil of Example 3 of the present invention and the configuration designed by the present invention.

[0035] Fig.13 It is the flow field streamline diagram of the original airfoil and the front vibrating elliptical wing configuration of Example 4 of the present invention.

[0036] Fig.14 It is the Mach number cloud diagram (Ma=0.15) of the original airfoil and the front-mounted vibrating elliptical wing configuration of Example 4 of the present invention.

[0037] Fig.15 This is a comparison chart of aerodynamic performance parameters of the original airfoil of Example 4 of the present invention and the configuration designed by the present invention.

[0038] in: Figure 7-1 This is the flow field streamline diagram of the original NACA0012 airfoil configuration of Example 2 of the present invention. Figure 7-2 This is a flow field streamline diagram of the front vibrating elliptical wing configuration according to Example 2 of the present invention; Figure 8-1 This is the Mach number cloud diagram of the original airfoil configuration of NACA0012 in Example 2 of the present invention. Figure 8-2 This is a Mach number cloud diagram of the front vibrating elliptical wing configuration of Example 2 of the present invention; Figure 9-1 This is a comparison chart of the lift coefficients of the original airfoil of Example 2 of the present invention and the configuration designed by the present invention. Figure 9-2 This is a comparison chart of the drag coefficients of the original airfoil of Example 2 of the present invention and the configuration designed by the present invention. Figure 9-3 A comparison chart of lift-to-drag ratios between the original airfoil of Example 2 of the present invention and the configuration designed by the present invention;

[0039] Figure 10-1 This is the flow field streamline diagram of the original NACA0012 airfoil configuration of Example 3 of the present invention. Figure 10-2 This is a flow field streamline diagram of the front vibrating elliptical wing configuration of Example 3 of the present invention; Figure 11-1 This is the Mach number cloud diagram of the original airfoil configuration of NACA0012 in Example 3 of the present invention. Figure 11-2This is a Mach number cloud diagram of the front vibrating elliptical wing configuration of Example 3 of the present invention; Figure 12-1 This is a comparison chart of the lift coefficients of the original airfoil of Example 3 of the present invention and the configuration designed by the present invention, Figure 12-2 This is a comparison chart of the drag coefficients of the original airfoil of Example 3 of the present invention and the configuration designed by the present invention. Figure 12-3 A comparison chart of lift-to-drag ratios between the original airfoil of Example 3 of the present invention and the configuration designed by the present invention;

[0040] Figure 13-1 This is the flow field streamline diagram of the original airfoil configuration of NACA0012 in Example 4 of the present invention. Figure 13-2 This is a flow field streamline diagram of the front vibrating elliptical wing configuration of Example 4 of the present invention; Figure 14-1 This is the Mach number cloud diagram of the original airfoil configuration of NACA0012 in Example 4 of the present invention. Figure 14-2 This is a Mach number cloud diagram of the front vibrating elliptical wing configuration of Example 4 of the present invention; Figure 15-1 This is a comparison chart of the lift coefficients of the original airfoil of Example 4 of the present invention and the configuration designed by the present invention, Figure 15-2 This is a comparison chart of the drag coefficients of the original airfoil of Example 4 of the present invention and the configuration designed by the present invention, Figure 15-3 A comparison chart of lift-to-drag ratios between the original airfoil of Example 4 of the present invention and the configuration designed by the present invention;

[0041] 1. Main wing, 2. Elliptical wing, 3. Leading edge point, 4. Elliptical wing center, 5. First fixing ring lock, 6. Second fixing ring lock, 7. Rotation bolt. DETAILED DESCRIPTION

[0042] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0043] The main technology to overcome the current suppression of airflow separation at high angles of attack of airfoils and improve the aerodynamic performance of airfoils is flow control technology. According to whether external energy is required during control, flow control technology can be divided into two categories: active flow control technology and passive flow control technology. Active flow control controls the flow around the airfoil by means of synthetic jets, blowing and inhaling, and releasing plasma, thereby improving the aerodynamic characteristics of the airfoil. Its main disadvantage is that it requires additional energy consumption, and the arrangement of related equipment for active flow control inside the wing will increase the take-off weight of the aircraft, which will affect the economic performance of the aircraft to a certain extent. Passive control technology includes passive vortex generators, stall strips, flaps, micro inserts, ribs, etc. Its main disadvantage is that while affecting the flow around the airfoil, it will generate additional resistance. Moreover, since the control method and control effect of passive flow control are pre-designed, passive flow control cannot function normally when the aircraft deviates from the design state, and even has an adverse effect on the aerodynamic characteristics of the airfoil.

[0044] See attached Figure 1-9 As shown, an airfoil configuration capable of improving separation characteristics at large angles of attack and a design method thereof, the airfoil configuration capable of improving separation characteristics at large angles of attack comprises a main wing 1 and an elliptical wing 2, the elliptical wing 2 being arranged on the suction surface of the leading edge point 3 of the main wing 1 through a chord structure, the elliptical wing 2 being extremely small relative to the main wing 1, under the action of the incoming flow, alternating downward vortices are generated on both sides of the elliptical wing 2, so that the elliptical wing 2 is subjected to pulsating pressure in the lateral and flow directions, thereby causing vibration; the chord structure is a structure similar to a stringed instrument, and during the installation process of the elliptical wing 2, fixed keys are arranged at intervals to control the elliptical wing 2, a first fixing ring lock 5, a second fixing ring lock 6 and a rotating bolt 7 are respectively arranged at 25% of the main wing span direction, 75% of the main wing span direction and 100% of the main wing span direction, and the other ends of the first fixing ring lock 5, the second fixing ring lock 6 and the rotating bolt 7 are all connected to the elliptical wing 2, that is, the elliptical wing is divided into three sections according to 0% to 25%, 25% to 75% and 75% to 100% of the main wing span length through the first fixing ring lock 5, the second fixing ring lock 6 and the rotating bolt 7, and the tightness of the elliptical wing 2 is adjusted through the rotating bolt 7 at the end of the main wing.

[0045] Preferably, the elliptical wing 2 is a front-rear symmetrical airfoil, and the chord length of the elliptical wing 2 is 1% of the chord length of the main wing 1 , and the specific size is determined according to the chord length of the main wing 1 .

[0046] Preferably, the elliptical wing 2 is arranged on the main wing 1 in two forms: in front of and above the suction surface of the leading edge point of the airfoil of the main wing 1, and when set, the distance between the elliptical wing center 4 of the elliptical wing 2 and the leading edge point 3 is 4% to 6% of the chord length of the airfoil of the main wing 1.

[0047] Preferably, the vibration form of the elliptical wing 2 can be pitching motion or heaving motion, and the motion equation is: y = Asin (2πft), and both vibration forms can achieve good control effects;

[0048] (1) When the elliptical wing 2 performs pitch motion, the amplitude is 0.1 to 0.3 rad and the frequency is 16 to 64 Hz;

[0049] (2) When the elliptical wing performs sinking and floating motions, the frequency has little effect on its control effect, and the amplitude is 0.5% to 1% of the chord length of the main wing 1.

[0050] Preferably, the airfoil of the main wing 1 is a NACA0012 airfoil, which is a commonly used airfoil for subsonic high lift. Other airfoils can be selected according to the actual needs of the aircraft.

[0051] Embodiment 1: A design method for an airfoil configuration as described above that can improve separation characteristics at high angles of attack, comprising the following steps:

[0052] S1. Firstly, the numerical simulation method based on the two-dimensional Reynolds-averaged Navier-Stokes equations is used to optimize the shape parameters of the static elliptical wing configuration set at the leading edge of the airfoil;

[0053] S2. On the basis of setting a static elliptical wing configuration at the leading edge of the airfoil, using the static elliptical wing configuration with the best effect, giving the elliptical wing a certain vibration form, optimizing the design of the vibrating elliptical wing configuration set at the leading edge of the airfoil, and taking the frequency and amplitude of the vibration as design variables respectively;

[0054] S3. Calculate it under high angle of attack conditions, take the maximum lift-to-drag ratio and the effect of suppressing flow separation on the wing surface as the optimization goal, select the appropriate elliptical wing vibration parameters, and complete the design of the airfoil configuration.

[0055] Preferably, the process of optimizing the shape parameters of the static elliptical wing configuration at the leading edge of the airfoil by using a numerical simulation method based on the two-dimensional Reynolds-averaged Navier-Stokes equations described in step S1 includes:

[0056] S101. taking the chord length of the elliptical wing and the positional relationship between the elliptical wing and the airfoil as design variables, and calculating the lift-to-drag ratio of the airfoil configurations of the elliptical wing with different chord lengths at different positions of the airfoil leading edge under a high angle of attack condition;

[0057] S102. Compare the calculated result with the original airfoil, take the maximum lift-to-drag ratio as the optimization target, and select the appropriate elliptical wing size and setting position.

[0058] Embodiment 2: This embodiment adopts a numerical simulation method based on the Reynolds averaged Navier-Stokes equation to perform numerical simulation on the high angle of attack aerodynamic characteristics of an elliptical wing configuration with airfoil leading edge vibration, verifying that the elliptical wing configuration with airfoil leading edge vibration of the present invention can effectively suppress airflow separation and significantly improve the high angle of attack aerodynamic characteristics of the wing. The simulation process includes:

[0059] S1. The simulation object is to set a vibrating elliptical wing configuration in front of the leading edge of the airfoil. The main wing airfoil is a NACA0012 airfoil. The elliptical wing chord length is 1% of the main wing chord length. It is set just in front of the leading edge point of the airfoil. The distance between the center of the elliptical wing and the leading edge point is 4% of the main wing chord length. Taking the elliptical wing doing sinking and floating motion as an example, the motion equation is: y = Asin (2πft), the amplitude is 1% of the main wing chord length, and the frequency is 16Hz;

[0060] S2. Get Figure 7The flow field streamline diagram of a single NACA0012 airfoil and the improved configuration designed by the present invention when the incoming flow Mach number is 0.15 and the angle of attack is 18°; it can be seen that serious airflow separation occurs on the upper surface of a single NACA0012 airfoil at a large angle of attack, and most of the area on the upper surface of the airfoil is covered by a large separation bubble, resulting in a significant increase in the pressure on the upper surface of the airfoil and a serious loss of the lift characteristics of the wing at a large angle of attack; compared with the original airfoil, the front vibrating elliptical wing configuration designed by the present invention can play a good role in suppressing flow separation at a large angle of attack, and the original large separation bubble on the airfoil becomes a smaller separation bubble at the trailing edge of the airfoil, which is of great significance for improving the aerodynamic performance of the airfoil at a stall angle of attack and a large angle of attack;

[0061] S3. Figure 8 It is the Mach number cloud diagram of the NACA0012 original airfoil and the airfoil leading edge vibration elliptical wing configuration at an angle of attack of 18°; Figure 8 It can be seen that compared with the original airfoil, the flow velocity on the lower surface of the leading edge vibration elliptical wing configuration designed by the present invention is relatively low, while the flow velocity on the upper surface is relatively high, which is of great significance for improving the pressure difference between the upper and lower surfaces of the lift surface;

[0062] S3. Fig. 9 The aerodynamic performance parameters of the original airfoil and the airfoil leading edge vibration elliptical wing configuration designed by the present invention are compared when the incoming flow angle of attack is 0° to 20° under the condition that the incoming flow Mach number is 0.15; Fig. 9 It can be seen that under small angles of attack, the vibrating elliptical wing configuration of the leading edge of the airfoil has no adverse effect on the aerodynamic performance of the airfoil, and the lift-to-drag ratio is slightly higher than that of the original airfoil. When the incoming flow angle of attack is greater than 12°, the drag coefficient of the configuration designed by the present invention increases slightly, and the lift-to-drag ratio decreases. The original airfoil enters the stall region at an angle of attack of 16°, and the lift-to-drag ratio drops sharply. The configuration designed by the present invention has an obvious lift-increasing effect at large angles of attack, and the stall angle is delayed to 18°.

[0063] The results of the numerical simulation method mentioned above show that the leading edge vibrating elliptical wing configuration of the airfoil designed in this example can effectively suppress airflow separation under subsonic high angle of attack conditions, greatly improve the lift characteristics and lift-to-drag ratio of the airfoil without generating any additional drag, delay the stall angle of attack, effectively improve the aerodynamic performance, and significantly improve the maneuverability and economy of the aircraft.

[0064] Embodiment 3: This embodiment adopts a numerical simulation method based on the Reynolds averaged Navier-Stokes equation to perform numerical simulation on the high angle of attack aerodynamic characteristics of an elliptical wing configuration with airfoil leading edge vibration, verifying that the elliptical wing configuration with airfoil leading edge vibration of the present invention can effectively suppress airflow separation and significantly improve the high angle of attack aerodynamic characteristics of the wing. The simulation process includes:

[0065] S1. The simulation object is to set a vibrating elliptical wing configuration in front of the leading edge of the airfoil. The main wing airfoil is a NACA0012 airfoil. The elliptical wing chord length is 1% of the main wing chord length. It is set just in front of the leading edge point of the airfoil. The distance between the center of the elliptical wing and the leading edge point is 5% of the main wing chord length. Taking the elliptical wing doing sinking and floating motion as an example, the motion equation is: y = Asin (2πft), the amplitude is 1% of the main wing chord length, and the frequency is 16Hz;

[0066] S2. Get Fig.10 The figure is a flow field streamline diagram of a single NACA0012 airfoil and an improved configuration designed by the present invention when the incoming flow Mach number is 0.15 and the angle of attack is 18°; it can be seen that at a large angle of attack, serious airflow separation occurs on the upper surface of a single NACA0012 airfoil, and most of the area on the upper surface of the airfoil is covered by a large separation bubble, resulting in a significant increase in the pressure on the upper surface of the airfoil and a serious loss of the lift characteristics of the wing at a large angle of attack; compared with the original airfoil, the front vibrating elliptical wing configuration designed by the present invention can play a good role in suppressing flow separation at a large angle of attack, and the original large separation bubble on the airfoil becomes a very small separation bubble at the trailing edge of the airfoil, which is of great significance for improving the aerodynamic performance of the airfoil at a stall angle of attack and a large angle of attack;

[0067] S3. Fig.11 It is the Mach number cloud diagram of the NACA0012 original airfoil and the airfoil leading edge vibration elliptical wing configuration at an angle of attack of 18°; Fig.11 It can be seen that compared with the original airfoil, the flow velocity on the lower surface of the leading edge vibration elliptical wing configuration designed by the present invention is relatively low, while the flow velocity on the upper surface is relatively high, which is of great significance for improving the pressure difference between the upper and lower surfaces of the lift surface;

[0068] S3. Fig.12 The aerodynamic performance parameters of the original airfoil and the airfoil leading edge vibration elliptical wing configuration designed by the present invention are compared when the incoming flow angle of attack is 0° to 20° under the condition that the incoming flow Mach number is 0.15; Fig.12 It can be seen that at small angles of attack, the vibrating elliptical wing configuration at the leading edge of the airfoil has no adverse effect on the aerodynamic performance of the airfoil, and the lift-to-drag ratio is slightly higher than that of the original airfoil. The original airfoil enters the stall region at an angle of attack of 16°, and the lift-to-drag ratio drops sharply, while the configuration designed by the present invention has a significant lift-increasing effect at large angles of attack, and the stall angle of attack is delayed to 19°.

[0069] Embodiment 4: This embodiment adopts a numerical simulation method based on the Reynolds averaged Navier-Stokes equation to perform numerical simulation on the high angle of attack aerodynamic characteristics of an elliptical wing configuration with airfoil leading edge vibration, verifying that the elliptical wing configuration with airfoil leading edge vibration of the present invention can effectively suppress airflow separation and significantly improve the high angle of attack aerodynamic characteristics of the wing under high angle of attack conditions. The simulation process includes:

[0070] S1. The simulation object is to set a vibrating elliptical wing configuration in front of the leading edge of the airfoil. The main wing airfoil is a NACA0012 airfoil. The elliptical wing chord length is 1% of the main wing chord length. It is set just in front of the leading edge point of the airfoil. The distance between the center of the elliptical wing and the leading edge point is 6% of the main wing chord length. Taking the elliptical wing doing sinking and floating motion as an example, the motion equation is: y=Asin(2πft), the amplitude is 1% of the main wing chord length, and the frequency is 16Hz;

[0071] S2. Get Fig.13 The flow field streamline diagram of a single NACA0012 airfoil and the improved configuration designed by the present invention when the incoming flow Mach number is 0.15 and the angle of attack is 18°; it can be seen that serious airflow separation occurs on the upper surface of a single NACA0012 airfoil at a large angle of attack, and most of the area on the upper surface of the airfoil is covered by a large separation bubble, resulting in a significant increase in the pressure on the upper surface of the airfoil and a serious loss of the lift characteristics of the wing at a large angle of attack; compared with the original airfoil, the front vibrating elliptical wing configuration designed by the present invention can better suppress the flow separation at a large angle of attack, and the original large separation bubble on the airfoil becomes a smaller separation bubble, and the separation point moves backward, which is of great significance for improving the stall angle of attack of the airfoil and the aerodynamic performance at a large angle of attack;

[0072] S3. Fig.14 It is the Mach number cloud diagram of the NACA0012 original airfoil and the airfoil leading edge vibration elliptical wing configuration at an angle of attack of 18°; Fig.14 It can be seen that compared with the original airfoil, the flow velocity on the lower surface of the leading edge vibration elliptical wing configuration designed by the present invention is relatively low, while the flow velocity on the upper surface is relatively high, which is of great significance for improving the pressure difference between the upper and lower surfaces of the lift surface;

[0073] S3. Fig.15 The aerodynamic performance parameters of the original airfoil and the airfoil leading edge vibration elliptical wing configuration designed by the present invention are compared when the incoming flow angle of attack is 0° to 20° under the condition that the incoming flow Mach number is 0.15; Fig. 9 It can be seen that under small angles of attack, the vibrating elliptical wing configuration of the leading edge of the airfoil does not have an adverse effect on the aerodynamic performance of the airfoil, and the lift-to-drag ratio is slightly higher than that of the original airfoil. When the incoming flow angle of attack is greater than 12°, the drag coefficient of the configuration designed by the present invention increases slightly, and the lift-to-drag ratio decreases. The original airfoil enters the stall region at an angle of attack of 16°, and the lift-to-drag ratio drops sharply, while the configuration designed by the present invention has an obvious lift-increasing effect at large angles of attack, and the stall angle of attack is slightly delayed.

[0074] It can be seen from the above three embodiments that when the distance from the center of the elliptical wing to the leading edge point is increased to 6% of the main wing chord length, the control effect of the airfoil leading edge vibrating elliptical wing configuration on flow separation at large angles of attack is weakened, but it can still effectively suppress the airflow separation at large angles of attack of the airfoil while generating less additional resistance, thereby improving the lift-to-drag ratio of the airfoil; when the distance from the center of the elliptical wing to the leading edge point exceeds 6% of the main wing chord length, the control effect of the airfoil leading edge vibrating elliptical wing configuration will be further weakened on this basis, and at this time it will be difficult to achieve the ideal effect of improving the aerodynamic performance at large angles of attack.

[0075] The working principle of the airfoil configuration that can improve the separation characteristics at large angles of attack is as follows: when working, the fluid flows through the elliptical wing 2 set at the leading edge of the airfoil, generating a shedding vortex, and under the action of the incoming flow, the elliptical wing will be subjected to the pulsating pressure in the lateral and flow directions, thereby inducing vibration, and the shedding vortex and the tail vortex generated by the vibration interact with the boundary layer of the main wing, thereby introducing momentum into the boundary layer, improving the ability of the boundary layer to resist the adverse pressure gradient, and playing a role in delaying airflow separation, increasing lift and reducing drag. At the same time, due to the rearward movement of the stagnation point at the rear of the lift surface, the lower surface pressure of the elliptical wing configuration set at the leading edge is higher than that of the original airfoil, thereby causing the airfoil to have better aerodynamic characteristics at large angles of attack; and it can be seen from the above embodiments that the elliptical wing configuration with the leading edge vibration of the airfoil is compared with the airfoil without the elliptical wing, and the elliptical wing has a significant inhibitory effect on flow separation, and the original large separation bubble on the airfoil completely disappears or becomes a very small separation bubble near the trailing edge of the airfoil, and at the same time, the lift coefficient is increased, the drag coefficient is reduced, and the lift-to-drag ratio is greatly increased to about 3 times of the original airfoil.

[0076] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A design method for an airfoil configuration capable of improving separation characteristics at high angles of attack. The airfoil configuration capable of improving separation characteristics at high angles of attack comprises: A main wing (1) and an elliptical wing (2), wherein the elliptical wing (2) is arranged on a suction surface of a leading edge point (3) of the main wing (1) through a chord structure; the chord structure comprises a first fixing ring lock (5), a second fixing ring lock (6) and a rotating bolt (7), wherein the first fixing ring lock (5) is arranged at 25% of the span direction of the main wing (1), the second fixing ring lock (6) is arranged at 75% of the span direction of the main wing (1), the rotating bolt (7) is arranged at 100% of the span direction of the main wing (1), and the other ends of the first fixing ring lock (5), the second fixing ring lock (6) and the rotating bolt (7) are all connected to the elliptical wing (2), characterized in that the design method comprises the following steps: S1. Firstly, the numerical simulation method based on the two-dimensional Reynolds-averaged Navier-Stokes equations is used to optimize the shape parameters of the static elliptical wing configuration set at the leading edge of the airfoil; S2. On the basis of setting a static elliptical wing configuration at the leading edge of the airfoil, using the static elliptical wing configuration with the best effect, giving the elliptical wing a certain vibration form, optimizing the design of the vibrating elliptical wing configuration set at the leading edge of the airfoil, and taking the frequency and amplitude of the vibration as design variables respectively; S3. Calculate it under high angle of attack conditions, take the maximum lift-to-drag ratio and the effect of suppressing flow separation on the wing surface as the optimization goal, select the appropriate elliptical wing vibration parameters, and complete the design of the airfoil configuration.

2. A method for designing an airfoil configuration capable of improving separation characteristics at high angles of attack according to claim 1, characterized in that: The process of optimizing the shape parameters of the static elliptical wing configuration at the leading edge of the airfoil by using the numerical simulation method based on the two-dimensional Reynolds-averaged Navier-Stokes equations described in step S1 includes: S101. taking the chord length of the elliptical wing and the positional relationship between the elliptical wing and the airfoil as design variables, and calculating the lift-to-drag ratio of the airfoil configurations of the elliptical wing with different chord lengths at different positions of the airfoil leading edge under a high angle of attack condition; S102. Compare the calculated result with the original airfoil, take the maximum lift-to-drag ratio as the optimization target, and select the appropriate elliptical wing size and setting position.

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