A wing for flapping wing dynamic stall control based on a biomimetic fin type leading edge

Abstract

The present application relates to a kind of wing based on bionic fin type leading edge for flapping wing dynamic stall control, belong to aircraft design and manufacturing technical field, solve the problem that flapping wing dynamic stall cannot be effectively controlled while considering flapping wing aerodynamic characteristics in prior art.The present application enhances the spanwise and normal motion of fluid by bionic fin type leading edge, passively introduces multiple groups of flow direction vortex to enhance the vortex and momentum exchange between fluids, which can effectively improve the safety and stability of flapping wing aircraft during actual flight;Using bionic fin type leading edge instead of traditional linear leading edge, all hardware designs can be completed at one time by using integrated molding process, which simplifies the structure, is easy to form, light maintenance and easy to use;Without consuming the energy of flapping wing, the flapping wing aircraft has better endurance service performance;By directional adjustment of wave height and wavelength, the dynamic stall control efficiency can be effectively improved without affecting the flapping wing aerodynamic characteristics.

Description

Technical Field

[0001] This invention relates to the field of aircraft design and manufacturing technology, specifically to a wing based on a biomimetic fin-shaped leading edge for dynamic stall control of flapping wings. Background Technology

[0002] With the increasing demands for space perception and detection, aircraft are evolving towards "low, slow, and small" designs, requiring high stealth and maneuverability to meet deployment requirements in complex terrains such as urban areas and mountainous regions. However, traditional aerodynamic design theory is limited by the small size (<20cm) and low Reynolds number (10⁻⁶) of these aircraft. 3 ~10 5 Facing significant challenges, including low aerodynamic efficiency, difficulty in miniaturizing propulsion, poor maneuverability, and weak anti-interference capabilities, biomimetic flapping wings are being developed, prompting research into novel unsteady high-lift flapping wings. Bionic flapping wings are a new type of artificial wing that mimics the movement of natural biological wings, integrating lift, hovering, and propulsion functions. They align with the design concepts and requirements of modern aircraft and hold significant application potential in the future of new aircraft.

[0003] However, the periodic, large-angle vibrations of flapping wings cause the large vortex structure to continuously detach or break during motion, resulting in dynamic stall in each wing cycle. Dynamic stall has a significant negative impact on the aircraft's lift, thrust, and stability. Furthermore, the resulting torsional forces and mechanical vibrations can lead to material fatigue, posing safety hazards and potentially causing crashes. Existing methods for controlling dynamic stall often sacrifice some aerodynamic performance or energy of the flapping wing to mitigate the safety and stability issues, such as reducing the flapping angle or introducing air intake / exhaust systems, making it difficult to fully realize the aerodynamic advantages of flapping wings.

[0004] In summary, existing technologies have the problem of not being able to effectively control the dynamic stall of flapping wings while also taking into account the aerodynamic characteristics of flapping wings. Summary of the Invention

[0005] In view of the above problems, the present invention provides an airfoil based on a biomimetic fin-shaped leading edge for dynamic stall control of flapping wings, which solves the problem in the prior art that it is impossible to effectively control the dynamic stall of flapping wings while taking into account the aerodynamic characteristics of flapping wings.

[0006] This invention provides a wing for flapping wing dynamic stall control based on a biomimetic fin-shaped leading edge, comprising a biomimetic fin-shaped leading edge 1 and a curved wing body 2; the biomimetic fin-shaped leading edge 1 is wavy along the entire wing span, referencing the forefin of a whale, and is constrained by a cosine function; the cosine function has characteristic parameters including wavelength and wave height; the wavelength at mid-span is smaller than the wavelength at the wingtip and / or wing root, and the wave height at mid-span is greater than the wave height at the wingtip and / or wing root.

[0007] Furthermore, the biomimetic fin-shaped leading edge 1 includes multiple waveform units along the entire wing span, each waveform unit including one crest and two troughs.

[0008] Furthermore, wavelength refers to the width along the wingspan of the center line of the waveform unit; wave height refers to the vertical distance between adjacent wave crests and troughs.

[0009] Furthermore, with the chordal direction of the wing as the x-axis and the spanwise direction as the y-axis, and the center of each waveform unit as the first origin, the cosine function is specifically expressed as:

[0010]

[0011] Where y is the position along the wingspan of the center line of the waveform unit; x is the height of the waveform unit at y; h is the wave height; and ω is the circular frequency.

[0012] Adjacent waveform units are connected by tangent through the troughs, and the overall biomimetic fin-shaped leading edge 1 has a continuous and smooth wave shape.

[0013] Furthermore, the biomimetic fin-shaped leading edge 1, with the mid-span of the wingspan as the second origin, exhibits wave height variations along the wingspan towards the wingtip and wing root using a first power function. The constraint condition for this first power function variation is expressed as follows:

[0014] h = a × |y b |+c;

[0015] Wherein, wave height h>0; first power coefficient a<0; first power exponent b>1; first constant c>0;

[0016] Wave height h near the wingtip at the same distance from the second origin t The wave height h is less than that near the wing root. r .

[0017] Furthermore, the biomimetic fin-shaped leading edge 1, with the mid-span of the wingspan as the origin, exhibits a second power function variation in wavelength along the wingspan towards the wingtip and wing root, respectively. The constraint condition for this second power function variation is expressed as follows:

[0018] λ=m×|y n |+q;

[0019] Where wavelength λ>0; second power coefficient m>0; second power exponent n>1; second constant q>0;

[0020] The wavelength λ near the wingtip at the same distance from the origin t Greater than the wavelength λ near the wing root r .

[0021] Furthermore, the airfoil changes continuously with the wave height along the wingspan, and the continuously changing airfoil parameters are the chord length and leading edge radius; the remaining airfoil parameters remain unchanged, including the maximum thickness, mid-curvature, maximum camber, and trailing edge angle; the maximum chord length and minimum leading edge radius are at the mid-span of the wingspan, and the minimum chord length and maximum leading edge radius are at the trough of the wave element.

[0022] Furthermore, the biomimetic fin-shaped leading edge 1 and the curved wing body 2 are integrally formed, and the tail of the biomimetic fin-shaped leading edge 1 is tangentially connected to the curved wing body 2.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects:

[0024] (1) Compared with the traditional linear flapping wing leading edge, the wing based on the biomimetic fin leading edge of the present invention for flapping wing dynamic stall control enhances the spanwise and normal motion of the fluid through the biomimetic fin leading edge, passively introduces multiple sets of flow vortex pairs to enhance the vortex and momentum exchange between the fluids, which helps to suppress or weaken the dynamic stall at the large angle of attack of the flapping wing, avoid the generation of large reverse lift and reverse torque gradient, and can effectively improve the safety and stability of flapping wing aircraft during actual flight.

[0025] (2) Compared with the existing dynamic stall control design, the wing of the present invention based on the biomimetic fin leading edge for flapping wing dynamic stall control uses the biomimetic fin leading edge to replace the traditional linear leading edge. All hardware design can be completed at one time by adopting an integrated molding process. There is no need to build complex paths or structures on the surface or inside of the wing, nor is it necessary to transmit relevant flow control commands and receive feedback signals in flapping wing flight state. The present invention has a simple overall structure, is easy to form, requires little maintenance, and is easy to use.

[0026] (3) Compared with the energy consumption of existing dynamic stall control, the wing based on the bionic fin leading edge of the present invention for flapping wing dynamic stall control is a passive flow control method that uses the bionic fin leading edge to control flapping wing dynamic stall. It achieves effective control by directly changing the flow structure around the wing through its unique shape, without consuming the flapping wing's own energy, thus enabling flapping wing aircraft to have better endurance and service performance.

[0027] (4) Compared with the efficiency of existing dynamic stall control, the wing based on the biomimetic fin leading edge of the present invention for flapping wing dynamic stall control has a biomimetic fin leading edge based on the spatial distribution law of the wing flow field. Its waveform unit shape changes irregularly along the span. By directional adjustment of wave height and wavelength, the dynamic stall control efficiency can be effectively improved without affecting the flapping wing aerodynamic characteristics. Attached Figure Description

[0028] The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention.

[0029] Figure 1 This is a schematic diagram of the overall structure of the wing for flapping wing dynamic stall control based on a biomimetic fin-shaped leading edge disclosed in this invention.

[0030] Figure 2 This is a top view schematic diagram of the wing for flapping wing dynamic stall control based on a biomimetic fin-shaped leading edge disclosed in this invention.

[0031] Figure 3 This is a schematic diagram of the shape of the waveform unit disclosed in this invention;

[0032] Figure 4 This is a schematic diagram showing the variation of the wave height of the waveform unit along the span of the wing as disclosed in this invention;

[0033] Figure 5 This is a schematic diagram showing the wavelength of the waveform unit disclosed in this invention varying along the wing span.

[0034] Figure 6 This is a schematic diagram of the airfoil for flapping wing dynamic stall control based on a biomimetic fin leading edge disclosed in this invention at different spanwise positions.

[0035] Figure label:

[0036] 1- Bionic fin-shaped leading edge; 2- Curved wing body. Detailed Implementation

[0037] To better understand the above-described objectives, features, and advantages of the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other. Furthermore, the present invention can be implemented in other ways different from those described herein; therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0038] This invention addresses the challenge of dynamic stall in the development and design of flapping-wing aircraft by proposing a biomimetic fin-shaped leading edge for dynamic stall control. Utilizing the unique shape and passive flow control principle of the biomimetic fin-shaped leading edge, spanwise and normal velocities are introduced to enhance vorticity and energy mixing between fluids. This suppresses or improves the separation and shedding of the wing boundary layer or large vortex structure at high angles of attack in the flapping mode, avoiding the generation of large adverse lift and adverse torque gradients. Thus, dynamic stall control is effectively achieved without sacrificing the aerodynamic performance of the flapping wing. To achieve more effective dynamic stall control, the biomimetic fin-shaped leading edge is irregularly varied along the wing span. Tall and dense waveform elements are provided at the mid-span where flow separation is most severe to enhance flow control. Correspondingly, moderately high and dense waveform elements are provided at the wing root where flow separation is relatively mild, while low and sparse waveform elements are provided at the wingtip where flow separation is weakest.

[0039] This invention discloses a wing for flapping wing dynamic stall control based on a biomimetic fin-shaped leading edge, comprising a biomimetic fin-shaped leading edge 1 and a curved wing body 2; the biomimetic fin-shaped leading edge 1 is wavy along the entire wing span, referencing the forefin of a whale, and is constrained by a cosine function; the cosine function has characteristic parameters including wavelength and wave height; the wavelength at mid-span is smaller than the wavelength at the wingtip and / or wing root, and the wave height at mid-span is greater than the wave height at the wingtip and / or wing root.

[0040] The biomimetic fin-shaped leading edge 1 includes multiple waveform units along the entire wing span, each waveform unit including one crest and two troughs.

[0041] It is not difficult to understand that the waveform units are of different sizes, and the waveforms are higher and denser in the wingspan, while they are smaller and sparser at the wing root and wingtip; the waveform structure at the wing root has a larger wave height and a smaller wavelength compared to the wingtip.

[0042] Wavelength refers to the width along the wingspan of the center line of the waveform unit; wave height refers to the vertical distance between adjacent wave crests and troughs.

[0043] The biomimetic fin-shaped leading edge 1, with the chordal direction of the wing as the x-axis and the spanwise direction of the wing as the y-axis, and the center of each waveform unit as the first origin, is specifically represented by the cosine function as follows:

[0044]

[0045] Where y is the position along the wingspan of the center line of the waveform unit; x is the height of the waveform unit at y; h is the wave height; and ω is the circular frequency.

[0046] Adjacent waveform units are connected by tangent through the troughs, and the overall biomimetic fin-shaped leading edge 1 has a continuous and smooth wave shape.

[0047] The biomimetic fin-shaped leading edge 1 takes the mid-span of the wingspan as the second origin, and the wave height varies along the wingspan towards the wingtip and wing root according to the first power function. The constraint condition for the variation of the first power function is expressed as follows:

[0048] h = a × |y b |+c;

[0049] Wherein, wave height h>0; first power coefficient a<0; first power exponent b>1; first constant c>0.

[0050] Wave height h near the wingtip at the same distance from the second origin t The wave height h is less than that near the wing root. r .

[0051] The biomimetic fin-shaped leading edge 1, with the mid-span of the wingspan as the origin, exhibits wavelength variations along the wingspan towards the wingtip and wing root as a second power function. The constraint condition for this second power function variation is expressed as follows:

[0052] λ=m×|y n |+q;

[0053] Wherein, wavelength λ>0; second power coefficient m>0; second power exponent n>1; second constant q>0.

[0054] The wavelength λ near the wingtip at the same distance from the origin t Greater than the wavelength λ near the wing root r .

[0055] The airfoil changes continuously with the wave height along the wingspan. The continuously changing airfoil parameters are the chord length and leading edge radius. The remaining airfoil parameters remain unchanged, including the maximum thickness, mid-curvature, maximum camber, and trailing edge angle. The maximum chord length and minimum leading edge radius are located at the mid-span of the wingspan, while the minimum chord length and maximum leading edge radius are located at the troughs of the wave elements.

[0056] The biomimetic fin-shaped leading edge 1 and the curved wing body 2 are integrally formed, and the tail of the biomimetic fin-shaped leading edge 1 is tangentially connected to the curved wing body 2.

[0057] To illustrate the effectiveness of the method proposed in this invention, the following detailed description of the above technical solution is provided through a specific embodiment:

[0058] Example 1

[0059] Figure 1 This is a schematic diagram of the overall structure of the wing for flapping wing dynamic stall control based on the biomimetic fin-shaped leading edge proposed in this invention. The traditional linear leading edge structure is replaced by the wave-shaped biomimetic fin-shaped leading edge of this invention. The wave-shaped units are irregularly and asymmetrically distributed from the wing root to the wingtip. The biomimetic fin-shaped leading edge and the curved wing body are smoothly connected and formed in one piece using a tangential method. The minimum chord length of the wing is 30mm, the maximum chord length is 42mm, and the span is 100mm.

[0060] Figure 2 This is a top view schematic diagram of the wing for flapping wing dynamic stall control based on the biomimetic fin leading edge proposed in this invention. Preferably, the biomimetic fin leading edge is composed of 10 waveform units of different sizes. The characteristic parameters of each waveform unit include wavelength λ and wave height h. The waveform unit has a minimum wavelength of 4 mm and a maximum wave height of 12 mm at the mid-wing span, and a maximum wavelength of 39 mm and a minimum wave height of 4 mm at the wingtip.

[0061] It should be noted that the number of waveform units, wave height, and wavelength of the biomimetic fin leading edge are determined by the actual flapping fin flow field characteristics and are not fixed values.

[0062] Figure 3This is a schematic diagram of the shape of the waveform unit proposed in this invention. Each waveform unit includes one crest and two troughs. Adjacent waveform units are connected by tangents through the troughs. The leading edge is a continuous, smooth wave shape. With the chordal direction of the wing as the x-axis and the spanwise direction of the wing as the y-axis, the center of each waveform unit is the first origin. Figure 3 The shape of the waveform unit is constrained to be h and ω change with their position along the spanwise direction of the wing.

[0063] Figure 4 and Figure 5 These are schematic diagrams illustrating the variation of wavelength and wave height of the waveform units proposed in this invention along the wingspan. The wavelength and wave height of each waveform unit change continuously along the wingspan. The waveform units are higher and denser in the middle of the wingspan, while they are smaller and sparser at the wing root and wingtip. The waveform at the wing root has a larger wave height and a smaller wavelength compared to the wingtip. With the chord direction of the wingspan as the x-axis, the wingspan as the y-axis, and the middle of the wingspan as the second origin, the constraint function for the variation of wave height along the wingspan at the wingtip is h = -0.0016 × y. 2 +6, while the constraint function for the change towards the wing root is h = -0.0012 × y 2 +6, it can be seen that the wave height near the wingtip at the same distance from the second origin is smaller than that near the wing root; the constraint function for the variation of the waveform wavelength along the spanwise wingtip is λ=0.007×y 2 +2, while the constraint function for the change towards the wing root is λ = 0.0053 × y 2 +2, it can be seen that the wavelength near the wingtip at the same distance from the origin is greater than that near the wing root.

[0064] Figure 6 This is a schematic diagram of the airfoil for flapping wing dynamic stall control based on a biomimetic fin-shaped leading edge proposed in this invention at different spanwise positions. The airfoil changes continuously along the spanwise with the wave element, but the main airfoil parameters that change are the chord length and leading edge radius. The maximum chord length of 42 mm and the minimum leading edge radius of 0.09 mm are at the mid-span of the wingspan, while the minimum chord length of 30 mm and the maximum leading edge radius of 0.54 mm are at the trough of the wings. Other airfoil parameters such as maximum thickness, maximum camber, and trailing edge angle remain unchanged.

[0065] Compared with existing technologies, the wing based on a biomimetic fin-shaped leading edge for dynamic stall control of flapping wings in this invention enhances the spanwise and normal motion of the fluid through the biomimetic fin-shaped leading edge, passively introducing multiple sets of flow vortices to enhance the vortex and momentum exchange between the fluids. This helps to suppress or reduce dynamic stall at high angles of attack of the flapping wing, avoids the generation of large reverse lift and reverse torque gradients, and can effectively improve the safety and stability of flapping wing aircraft during actual flight. By using a biomimetic fin-shaped leading edge to replace the traditional linear leading edge, all hardware designs can be completed in one go using a one-piece molding process, eliminating the need to build complex pathways or structures on or inside the wing surface, and eliminating the need for additional components on the flapping wing itself. This invention transmits relevant flow control commands and receives feedback signals during flight. It features a simple overall structure, is easy to mold, requires minimal maintenance, and is convenient to use. Utilizing a biomimetic fin-shaped leading edge to control the dynamic stall of a flapping wing is a passive flow control method. It directly alters the wing's airflow structure through its unique shape to achieve effective control without consuming the flapping wing's own energy, thus improving the flapping wing's endurance and service performance. Based on the spatial distribution of the wing's flow field, the shape of its waveform units varies irregularly along the span. By directionally adjusting the wave height and wavelength, the dynamic stall control efficiency can be effectively improved without affecting the flapping wing's aerodynamic characteristics.

[0066] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A wing for dynamic stall control of flapping wings based on a biomimetic fin-shaped leading edge, characterized in that, It includes a biomimetic fin-shaped leading edge (1) and a curved wing body (2); the biomimetic fin-shaped leading edge (1) is wavy along the entire wingspan, referencing the forefin of a whale, and is constrained by a cosine function; the cosine function has characteristic parameters including wavelength and wave height; the wavelength at the mid-span is smaller than the wavelength at the wingtip and / or wing root, and the wave height at the mid-span is greater than the wave height at the wingtip and / or wing root.

2. The wing for dynamic stall control of flapping wings based on a biomimetic fin-shaped leading edge according to claim 1, characterized in that, The biomimetic fin-shaped leading edge (1) includes multiple waveform units along the entire wing span, each waveform unit including a crest and two troughs.

3. The wing for dynamic stall control of flapping wings based on a biomimetic fin-shaped leading edge according to claim 2, characterized in that, Wavelength refers to the width along the wingspan of the center line of the waveform unit; wave height refers to the vertical distance between adjacent wave crests and troughs.

4. The wing for flapping wing dynamic stall control based on a biomimetic fin-shaped leading edge according to claim 3, characterized in that, The biomimetic fin leading edge (1) takes the chord direction of the wing as the x-axis and the span direction of the wing as the y-axis, with the center of each waveform unit as the first origin. The cosine function is specifically expressed as: Where y is the position along the wingspan of the center line of the waveform unit; x is the height of the waveform unit at y; h is the wave height; and ω is the circular frequency. Adjacent waveform units are connected by tangent through the troughs, and the biomimetic fin-shaped leading edge (1) is a continuous and smooth wave shape.

5. The wing for flapping wing dynamic stall control based on a biomimetic fin-shaped leading edge according to claim 4, characterized in that, The biomimetic fin-shaped leading edge (1) takes the mid-wing span as the second origin, and the wave height varies along the wingspan towards the wingtip and wing root in the form of a first power function. The constraint condition for the variation of the first power function is expressed as follows: h=a×|y b |+c; Wherein, wave height h>0; first power coefficient a<0; first power exponent b>1; first constant c>0; Wave height h near the wingtip at the same distance from the second origin t The wave height h is less than that near the wing root. r .

6. The wing for dynamic stall control of flapping wings based on a biomimetic fin-shaped leading edge according to claim 5, characterized in that, The biomimetic fin-shaped leading edge (1) takes the mid-wing span as the origin, and the wavelength varies along the wingspan towards the wingtip and wing root in a second power function manner. The constraint condition for the variation of the second power function is expressed as follows: λ=m×|y n |+q; Where wavelength λ>0; second power coefficient m>0; second power exponent n>1; second constant q>0; The wavelength λ near the wingtip at the same distance from the origin t Greater than the wavelength λ near the wing root r .

7. The wing for flapping wing dynamic stall control based on a biomimetic fin-shaped leading edge according to claim 6, characterized in that, The airfoil changes continuously with the wave height along the wingspan. The continuously changing airfoil parameters are the chord length and leading edge radius. The remaining airfoil parameters remain unchanged, including the maximum thickness, mid-curvature, maximum camber, and trailing edge angle. The maximum chord length and minimum leading edge radius are located at the mid-span of the wingspan, while the minimum chord length and maximum leading edge radius are located at the troughs of the wave elements.

8. The wing for flapping wing dynamic stall control based on a biomimetic fin-shaped leading edge according to claim 7, characterized in that, The biomimetic fin-shaped leading edge (1) and the curved wing body (2) are integrally formed, and the tail of the biomimetic fin-shaped leading edge (1) is tangentially connected to the curved wing body (2).

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