A bionic sinusoidal leading edge wing for air-to-air docking of a tandem wing uav

Abstract

The application discloses a bionic sinusoidal leading edge wing for aerial docking of tandem wing unmanned aerial vehicles, and belongs to the field of aircraft design and mechanics. The bionic sinusoidal leading edge wing for aerial docking comprises a wing main body and a bionic sinusoidal leading edge structure arranged near a wing tip of the wing main body. The application is suitable for unmanned aerial vehicles, low-speed fixed wings and airfoils requiring induced vortex control capability. The application can weaken the wing tip vortex energy, reduce the wing root bending moment of the wing, thereby reducing the operation difficulty in the docking process of the unmanned aerial vehicle, and through the reserved flat wing section, the lift coefficient and the lift-drag ratio of the wing under the small attack angle and low Reynolds number working condition are ensured from being obviously reduced.

Description

Technical Field

[0001] This invention belongs to the field of aerodynamic shape and docking control technology for unmanned aerial vehicles (UAVs), specifically relating to a biomimetic sinusoidal leading-edge wing for aerial docking of chain-wing UAVs and its configuration design method. Background Technology

[0002] A chain-wing UAV connects multiple small fixed-wing modules at their wingtips in mid-air to form a variable-configuration aircraft. This aircraft performs wingtip docking in the stratosphere, a process characterized by complex boundary conditions at low angles of attack and low Reynolds numbers. The wing-to-wing docking process exhibits significant unsteady aerodynamic coupling effects, specifically manifested as mutual interference between the wake and wingtip vortices at close range, and drastic changes in induced velocity with wing spacing. This leads to increased lift fluctuations, lateral disturbances, and attitude control burden during docking.

[0003] Bionics is a science that mimics the special abilities of living organisms, utilizing the results and functional principles of organisms in nature to design and develop machinery and various new technologies. Many inspirations for aircraft design and manufacturing come from organisms in nature. For example, the leading edge of the humpback whale's flipper has a sinusoidal protrusion; research has shown that this sinusoidal protrusion can effectively improve the humpback whale's hydrodynamic characteristics. Summary of the Invention

[0004] Existing straight leading-edge wings are prone to generating strong wingtip vortices and unstable shear layer structures during close-range docking. A sinusoidal leading edge with a fixed wavelength can delay stall and influence vortex structure to some extent. This influence can weaken the intensity of wingtip vortices, reduce wing root bending moment, and lower handling difficulty. However, compared to wings with straight leading edges, its disturbances lead to a decrease in the wing's lift coefficient and lift-to-drag ratio at low angles of attack. Therefore, a wing leading-edge configuration specifically designed for wingtip docking is needed. This configuration should possess the potential to weaken wingtip vortices with a biomimetic sinusoidal leading edge while ensuring that the lift coefficient and lift-to-drag ratio do not significantly decrease at low angles of attack and low Reynolds numbers by retaining the straight wing section.

[0005] This invention provides a biomimetic sinusoidal leading-edge wing for aerial docking of chain-wing UAVs, which solves the problem that the wingtip vortices of straight wings interfere strongly with each other at close range during the docking process of chain-wing UAVs, while the biomimetic sinusoidal leading-edge wing has a low lift-drag ratio under low Reynolds number and small angle of attack conditions.

[0006] The invention is implemented as follows: the end of the wing facing the incoming flow is called the leading edge of the wing, and the leading edge portion of the wingtip segment is sinusoidal in shape; the position of the sinusoidal wave crest on the outer surface of the wingtip segment is the leading edge crest position, and the position of the sinusoidal wave trough on the outer surface of the wingtip segment is the leading edge trough position; the leading edge portion of the wing fuselage segment is straight in shape.

[0007] Furthermore, the leading edge of the wingtip segment is sinusoidal in shape, and the wingtip segment accounts for more than 5% and less than 95% of the total length of the wing.

[0008] Furthermore, the amplitude of the sine wave at the leading edge of the wingtip section is less than 20% of the wing chord length.

[0009] Furthermore, the wavelength of the sine wave at the leading edge of the wingtip segment is greater than 2% of the wing chord length and less than 50% of the wing chord length.

[0010] Furthermore, the leading edge of the fuselage wing section is in the shape of a straight wing, and the straight wing section accounts for more than 5% and less than 95% of the total length of the wing.

[0011] Furthermore, the wing is divided into at least two segments along the span, each segment employing a different leading-edge distribution function.

[0012] Furthermore, the application scenarios of the wing include at least two wings, each of the at least two wings being any of the sinusoidal leading-edge wingtip wings as described above, and the wing spacing between adjacent wings during wingtip docking is less than or equal to 0.5 times the chord length.

[0013] Furthermore, the biomimetic sinusoidal leading-edge wingtip makes the leading-edge disturbance more compatible with the aerodynamic requirements of different spanwise positions, thereby achieving better overall performance compared to straight leading-edge wings and sinusoidal leading-edge wings under the same operating conditions, reducing wingtip vortex intensity and unsteady coupling fluctuations; improving the robustness of attitude control during docking; maintaining sufficient lift and increasing stall angle of attack.

[0014] Furthermore, the leading edge crest position can generate stronger flow adhesion, and the flow acceleration at the leading edge trough position generates flow vortices. The flow vortices can mix with the low-energy boundary layer flow, transferring energy to the boundary layer. This allows the boundary layer flow field in the adverse pressure gradient to gain additional energy and continue to adhere to the wing surface, thereby delaying the separation of the leeward side at high angles of attack, strengthening the energy of the fluid on the wing surface in the direction of the incoming flow, weakening the flow on the wing surface in the spanwise direction, thereby weakening the wingtip vortex energy, reducing the wing root bending moment, and thus reducing the operational difficulty during the UAV docking process.

[0015] The wavelength of the leading edge of the biomimetic sinusoidal wing section changes the lateral spacing between the leading edge crest and trough positions, while the amplitude of the leading edge changes the drastic change in the flow state at the leading edge crest and trough positions. Both of these factors jointly affect the spanwise flow of airflow on the wing surface and can influence the intensity of the wingtip vortex, thereby weakening the wingtip vortex to some extent, suppressing the three-dimensional effect, mitigating the change in wing root bending moment during wingtip docking, and reducing the difficulty of docking.

[0016] This invention introduces a biomimetic sinusoidal leading-edge wingtip, which makes the leading-edge disturbance more compatible with the aerodynamic requirements of different spanwise positions. As a result, under the same operating conditions, it achieves better overall performance than straight leading-edge wings and sinusoidal leading-edge wings: reducing wingtip vortex intensity and unsteady coupling fluctuations; improving the robustness of attitude control during docking; maintaining sufficient lift and increasing stall angle of attack. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of a biomimetic sinusoidal leading-edge wing for aerial docking of a chain-wing UAV according to the present invention.

[0018] Figure 2 A schematic diagram of the leading edge of the fin of a humpback whale;

[0019] Figure 3 An image of a sinusoidal leading edge and a straight leading edge function is provided as an embodiment of the present invention;

[0020] Figure 4 This is a top view of the biomimetic sinusoidal leading-edge wingtip wing of the present invention;

[0021] Figure 5 This is a left view of the biomimetic sinusoidal leading-edge wingtip wing of the present invention;

[0022] Figure 6 This is a front view of the biomimetic sinusoidal leading-edge wingtip wing of the present invention;

[0023] Figure 7 This is a schematic diagram of the wingtip docking process of an aircraft provided in an embodiment of the present invention, with the wingtip spacing being 0.5 times the chord length. Specific implementation methods

[0024] To facilitate understanding and implementation of the present invention by those skilled in the art, embodiments of the present invention will be described below in conjunction with the accompanying drawings.

[0025] like Figure 1 As shown, the wing of the present invention includes a wing leading edge, the end of the wing facing the oncoming airflow being called the wing leading edge. Existing wing leading edges are smooth, straight leading edges. In this embodiment, it is referred to as a "straight leading edge," meaning that the wing leading edge on a straight leading edge wing is a smooth, straight leading edge.

[0026] like Figure 2 This is a schematic diagram of the leading edge of a humpback whale's fin. The invention utilizes the irregular protrusions on the leading edge of the humpback whale's fin to design the wingtip segment with a biomimetic sinusoidal leading edge.

[0027] Figure 1The example shown divides the wing into two segments. The segment closer to the fuselage is called the "fuselage wing segment" and is labeled 1 in the figure; the segment closer to the wingtip is called the "wingtip wing segment" and is labeled 2 in the figure. In this embodiment, a biomimetic sinusoidal leading edge is used in the wingtip wing segment; in this embodiment, a straight leading edge is used in the fuselage wing segment.

[0028] Figure 3 The image shows the function curves of the sinusoidal leading edge and the straight leading edge of the wingtip section and fuselage section of the biomimetic sinusoidal leading edge wing used for aerial docking of a chain-wing UAV, as described in this invention.

[0029] Figure 4 This is a top view of the overall structure of a biomimetic sinusoidal leading-edge wing for aerial docking of a chain-wing UAV according to the present invention; Figure 5 This is a side view of the overall structure of the present invention; Figure 6 This is a front view of the overall structure of the present invention.

[0030] The biomimetic sinusoidal leading-edge wing for aerial docking of chain-wing UAVs is characterized in that the amplitude of the sinusoidal wave at the leading edge of the wingtip section is less than 20% of the wing chord length.

[0031] The biomimetic sinusoidal leading-edge wing for aerial docking of chain-wing UAVs is characterized in that the wavelength of the sinusoidal wave at the leading edge of the wingtip segment is greater than 2% of the wing chord length and less than 50% of the wing chord length.

[0032] The biomimetic sinusoidal leading-edge wing for aerial docking of chain-wing UAVs is characterized in that the leading edge portion of the fuselage wing section is in the shape of a straight wing, and the straight wing section accounts for more than 5% and less than 95% of the total wing length. Correspondingly, the leading edge of the wingtip section is in the shape of a sine wave, and the wingtip section accounts for more than 5% and less than 95% of the total wing length.

[0033] Wherein, the position of the sine wave peak on the outer surface of the leading edge of the biomimetic sine wing segment is the leading edge peak position, and the position of the sine wave trough on the outer surface of the leading edge of the biomimetic sine wing segment is the leading edge trough position.

[0034] This invention utilizes the biomimetic sinusoidal wing section's leading edge crest to generate stronger flow adhesion, and at the leading edge trough, the flow accelerates to generate directional vortices. These directional vortices mix with the low-energy boundary layer flow, transferring energy to the boundary layer. This allows the boundary layer flow field, situated in the adverse pressure gradient, to gain additional energy and continue to adhere to the wing surface, thereby delaying the separation of the leeward side at high angles of attack. This strengthens the energy of the fluid on the wing surface in the incoming flow direction, weakens the flow on the wing surface in the spanwise direction, and thus reduces the energy of the wingtip vortex, decreasing the wing root bending moment and reducing the operational difficulty during UAV docking.

[0035] The leading edge of a biomimetic sinusoidal wing segment has two independent parameters: wavelength and amplitude. By changing the amplitude and wavelength of the leading edge, leading edges with different performance characteristics can be obtained. The amplitude and wavelength of the leading edge of the biomimetic sinusoidal wing segment can be determined based on the wing chord length, which refers to the distance between the leading and trailing edges of the wing.

[0036] In addition, the amplitude and wavelength of the leading edge of the biomimetic sinusoidal airfoil section can be determined by technicians based on factors such as usage conditions, and this embodiment does not impose specific limitations here.

[0037] In this embodiment, the difference in aerodynamic characteristics between the leading edge of the biomimetic sinusoidal airfoil section and the leading edge of the straight leading edge airfoil section mainly lies in the difference in flow states at the leading edge crest and trough positions. The larger the amplitude of the leading edge of the biomimetic sinusoidal airfoil section, the greater the difference in flow states between the leading edge crest and trough positions, and the greater the change in flow states, resulting in a greater difference in aerodynamic characteristics compared to the leading edge of the straight leading edge airfoil section.

[0038] The wavelength of the leading edge of the biomimetic sinusoidal wing section changes the lateral spacing between the leading edge crest and trough positions, while the amplitude of the leading edge changes the drastic change in the flow state at the leading edge crest and trough positions. Both of these factors jointly affect the spanwise flow of airflow on the wing surface and can influence the intensity of the wingtip vortex, thereby weakening the wingtip vortex to some extent, suppressing the three-dimensional effect, mitigating the change in wing root bending moment during wingtip docking, and reducing the difficulty of docking.

[0039] The straight leading edge section retains the original geometry of the wing, ensuring that the overall lift and lift-to-drag ratio of the wing will not be significantly reduced due to the introduction of too many biomimetic sinusoidal leading edges.

[0040] Furthermore, this invention divides the wing along its span into at least two segments, each employing a different leading-edge distribution function. Any other wing composed of multiple segments employing different leading-edge distribution functions is also within the scope of this invention.

[0041] Figure 7 This is a schematic diagram of an aircraft provided in an embodiment of the present invention. The present invention provides an aircraft including a main body and a wing. The wing includes a wingtip section and a fuselage section. The wingtip section adopts a biomimetic sinusoidal leading edge, and the outer surface of the leading edge of the biomimetic sinusoidal wing section has a sinusoidal shape along the direction from the end near the wingtip. The fuselage section adopts a straight leading edge, and the outer surface of the straight leading edge wing section is linearly distributed along the direction from the end near the fuselage.

[0042] This invention is designed for aerial wingtip connection of a chain-winged unmanned aerial vehicle (UAV). The aircraft performs wingtip docking in the stratosphere, and the docking condition is a flow under complex boundary conditions with a small angle of attack and a low Reynolds number.

[0043] Simulation results show that at a Reynolds number of 60,000, a biomimetic sinusoidal leading-edge wavelength of 0.2 times the chord length, an amplitude of 0.05 times the chord length, and a biomimetic sinusoidal wing section length of 1.5 times the chord length, the axial velocity of the wingtip vortex core decreases by 5.54%, and the vortex core pressure decreases by 17.4%. Furthermore, compared to a completely straight wing, this biomimetic sinusoidal wing reduces the root bending moment by 25.2% while only decreasing the lift-to-drag ratio by 5.05%. It effectively achieves the goal of possessing the wingtip vortex reduction potential of the biomimetic sinusoidal leading edge, while ensuring that the lift coefficient and lift-to-drag ratio do not significantly decrease under low angle-of-attack and low Reynolds number conditions by retaining the straight wing section.

Claims

1. A biomimetic sinusoidal leading-edge wing for aerial docking of chain-wing UAVs, characterized in that, The end of the wing facing the oncoming airflow is called the leading edge of the wing, and the leading edge of the wingtip section has a sinusoidal shape. The position of the sinusoidal wave crest on the outer surface of the wingtip segment is the leading edge crest position, and the position of the sinusoidal wave trough on the outer surface of the wingtip segment is the leading edge trough position. The leading edge of the fuselage section of the wing is in the shape of a straight wing.

2. The biomimetic sinusoidal leading-edge wing for aerial docking of chain-wing UAVs according to claim 1, characterized in that, The leading edge of the wingtip segment is sinusoidal in shape, and the wingtip segment accounts for more than 5% and less than 95% of the total length of the wing.

3. The biomimetic sinusoidal leading-edge wing for aerial docking of chain-wing UAVs according to claim 1, characterized in that, The amplitude of the sinusoidal wave at the leading edge of the wingtip section is less than 20% of the wing chord length.

4. The biomimetic sinusoidal leading-edge wing for aerial docking of chain-wing UAVs according to claim 1, characterized in that, The wavelength of the sine wave at the leading edge of the wingtip section is greater than 2% of the wing chord length and less than 50% of the wing chord length.

5. The biomimetic sinusoidal leading-edge wing for aerial docking of a chain-wing UAV according to claim 1, characterized in that, The leading edge of the fuselage wing section is in the shape of a straight wing, and the straight wing section accounts for more than 5% and less than 95% of the total length of the wing.

6. The biomimetic sinusoidal leading-edge wing for aerial docking of a chain-wing UAV according to claim 1, characterized in that, The wing is divided into at least two segments along the span, each segment using a different leading edge distribution function.

7. The biomimetic sinusoidal leading-edge wing for aerial docking of a chain-wing UAV according to claim 1, characterized in that, The application scenarios for the wing include at least two wings, and the distance between adjacent wings during wingtip docking is less than or equal to 0.5 times the chord length.

8. The biomimetic sinusoidal leading-edge wing for aerial docking of a chain-wing UAV according to claim 1, characterized in that, The biomimetic sinusoidal leading edge wingtip makes the leading edge disturbance better match the aerodynamic requirements of different spanwise positions, thus achieving better overall performance than straight leading edge wings and sinusoidal leading edge wings under the same operating conditions, and reducing wingtip vortex intensity and unsteady coupling fluctuations. Improve the robustness of attitude control during docking; maintain sufficient lift and increase stall angle of attack.

9. The biomimetic sinusoidal leading-edge wing for aerial docking of a chain-wing UAV according to claim 1, characterized in that, The aforementioned leading edge crest position can generate stronger flow adhesion, and the flow acceleration at the leading edge trough position generates flow vortices. The flow vortices can mix with the low-energy boundary layer flow, transferring energy to the boundary layer. This allows the boundary layer flow field in the adverse pressure gradient to gain additional energy and continue to adhere to the wing surface, thereby delaying the separation of the leeward side at high angles of attack, strengthening the energy of the fluid on the wing surface in the direction of the incoming flow, weakening the flow on the wing surface in the spanwise direction, thereby weakening the wingtip vortex energy, reducing the wing root bending moment, and thus reducing the operational difficulty during the UAV docking process. The wavelength of the leading edge of the biomimetic sinusoidal wing section changes the lateral spacing between the leading edge crest and trough positions, while the amplitude of the leading edge changes the drastic change in the flow state at the leading edge crest and trough positions. Both of these factors jointly affect the spanwise flow of airflow on the wing surface and can influence the intensity of the wingtip vortex, thereby weakening the wingtip vortex to some extent, suppressing the three-dimensional effect, mitigating the change in wing root bending moment during wingtip docking, and reducing the difficulty of docking.

10. A biomimetic sinusoidal leading-edge wing for aerial docking of a chain-wing UAV, as described in any one of claims 1 to 9, for use in an aircraft.

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