A biomimetic near-space vehicle wing modification design method

Abstract

This invention provides a biomimetic near-space vehicle wing modification design method, comprising the following steps: obtaining the wing chamber structure on the surface of a dragonfly wing and the folded corrugated structure on the cross-section of the dragonfly wing; designing a biomimetic wing chamber structure based on the wing chamber structure on the dragonfly wing surface; smoothly connecting the extreme points of the folded corrugated structure of the dragonfly cross-section to obtain a biomimetic wing cross-sectional structure; fabricating the wing based on the biomimetic wing cross-sectional structure, and arranging the biomimetic wing chamber structure at a position before the initiation point of boundary layer transition on the wing surface. This biomimetic near-space vehicle wing modification design method, by designing a biomimetic modified wing based on the cross-sectional structure and wing chamber structure of a dragonfly wing, and by arranging a suitable dragonfly-inspired wing chamber structure on the wing, controls the initiation position of boundary layer transition on the wing surface, prompting the boundary layer to transition to a turbulent boundary layer earlier, thus making the wing surface boundary layer more stable.

Description

Technical Field

[0001] This invention belongs to the field of aviation technology, and in particular relates to a design method for modifying the wings of a biomimetic near-space aircraft. Background Technology

[0002] Near-space vehicles are a class of aircraft that operate in the airspace between 20km and 100km above sea level. This altitude is above the maximum controllable flight altitude of existing aircraft, but below the minimum altitude for satellites to maintain low Earth orbit. Within this altitude range, compared to ground-based communication relay stations, they offer wider communication coverage; compared to satellite communication, they have shorter latency, are reusable, and their information systems can be updated in a timely manner. A more significant advantage is their high solar energy utilization rate within this altitude range. Therefore, recent near-space vehicle designs have leaned towards high-altitude, solar-powered, long-endurance unmanned aerial vehicles (UAVs). Thus, designing a new type of wing with high payload and operational efficiency is particularly important for near-space vehicle design.

[0003] Boundary layer flow on the wing surface is a major factor affecting its operational efficiency and is closely related to flow separation. At high Reynolds numbers, the boundary layer rapidly transitions upon contact with the wing surface fluid, resulting in a turbulent boundary layer covering most of the wing surface. However, at low Reynolds numbers, due to increased viscous forces, the boundary layer on the wing surface is mostly laminar. Although the drag generated by the laminar boundary layer is smaller than that of the turbulent boundary layer, its resistance to interference is weaker in the presence of an adverse pressure gradient. Therefore, the turbulent boundary layer is more resistant to boundary layer separation. If laminar separation occurs, the drag generated by the wing will be far greater than the drag increase from the turbulent boundary layer compared to the laminar boundary layer.

[0004] Currently, active and passive flow control techniques are commonly used to control flow within the boundary layer. Traditional methods for controlling the boundary layer of airfoils include adding flaps and boundary layer blow-and-suction devices, but these suffer from problems such as complex structures, low reliability, large weight, and difficulty in implementation in practical applications. Summary of the Invention

[0005] In view of this, the present invention aims to propose a biomimetic near-space vehicle wing modification design method to solve the problem that the application of existing active flow control within the boundary layer of wings to near-space vehicle wings is difficult to implement.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] This invention provides a method for modifying the wing of a biomimetic near-space aircraft, comprising the following steps:

[0008] Obtain the wing chamber structure on the surface of the dragonfly wing, as well as the fold and ripple structure on the cross-section of the dragonfly wing;

[0009] A biomimetic wing chamber structure was designed based on the wing chamber structure of the dragonfly wing surface.

[0010] By smoothly connecting the extreme points of the folded and wavy structure of the dragonfly cross section, a biomimetic airfoil cross section structure is obtained.

[0011] The wing was fabricated based on the biomimetic wing cross-sectional structure, and a biomimetic wing chamber structure was arranged at the position before the starting point of boundary layer transition on the wing surface.

[0012] Furthermore, the design of the biomimetic wing chamber structure based on the wing chamber structure of the dragonfly wing surface includes:

[0013] The shape of the biomimetic wing chamber structure was designed based on the shape of the wing chamber structure on the surface of the dragonfly wing.

[0014] The dimensions of the biomimetic wing chamber structure are obtained by comparing the characteristic length of the wing chamber structure on the surface of the dragonfly wing with the wingspan of the dragonfly wing.

[0015] The depth of the biomimetic wing chamber structure is determined based on the boundary layer thickness at the corresponding position on the wing surface.

[0016] The arrangement of the biomimetic wing chamber structure was designed based on the arrangement of the wing chamber structure on the surface of the dragonfly wing.

[0017] Furthermore, the shape of the biomimetic wing chamber structure is at least one of quadrilateral, pentagonal and hexagonal.

[0018] Furthermore, the arrangement of the biomimetic wing chamber structure is at least one of staggered arrangement and aligned arrangement.

[0019] Furthermore, the step of obtaining the dimensions of the biomimetic wing chamber structure based on the ratio of the characteristic length of the wing chamber structure on the dragonfly wing surface to the wingspan of the dragonfly wing includes:

[0020] The ratio of the characteristic length of the wing chamber structure on the surface of the dragonfly wing to the wingspan of the dragonfly wing is selected as any value between 0.008 and 0.04;

[0021] Obtain the wingspan length of the wing, and based on the selected value, obtain the dimensions of the biomimetic wing chamber structure.

[0022] Furthermore, determining the depth of the biomimetic wing chamber structure based on the boundary layer thickness at the corresponding position on the wing surface includes:

[0023] Obtain the thickness value of the boundary layer at the location of the biomimetic wing chamber structure on the wing surface;

[0024] The thickness value is used as the depth value of the biomimetic wing chamber structure.

[0025] Furthermore, after designing the biomimetic wing chamber structure based on the wing chamber structure of the dragonfly wing surface, the method further includes:

[0026] The biomimetic wing chamber structure was chamfered.

[0027] Furthermore, after fabricating the wing based on the biomimetic wing profile structure and arranging the biomimetic wing chamber structure at a position before the initiation point of boundary layer transition on the wing surface, the method further includes:

[0028] The shape, size, depth, and arrangement of the bionic wing chamber structure are adjusted according to the different transition modes on the wing surface.

[0029] Compared with existing technologies, the biomimetic near-space vehicle wing modification design method described in this invention has the following advantages:

[0030] This invention discloses a biomimetic near-space vehicle wing modification design method. By designing a biomimetic modified wing based on the cross-sectional structure and wing chamber structure of a dragonfly wing, and arranging suitable dragonfly-inspired wing chamber structures on the wing, the starting position of the boundary layer transition on the wing surface is controlled. This induces the boundary layer to transition to a turbulent boundary layer earlier, making the wing surface boundary layer more stable. Consequently, the wing exhibits higher anti-interference capabilities, reduces flow losses caused by flow separation, and thus improves the flow field, which is beneficial for increasing wing loading and enhancing its aerodynamic performance. Furthermore, this invention only requires a simple arrangement of biomimetic wing chamber structures on the wing surface, offering advantages such as simple structure, convenient design, and easy adjustment. The chamfering treatment of the biomimetic wing chamber structures also increases engineering feasibility. Attached Figure Description

[0031] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0032] Figure 1 This is a flowchart illustrating a biomimetic near-space vehicle wing modification design method provided in Embodiment 1 of the present invention;

[0033] Figure 2 The velocity cloud diagram of the folded plate of the dragonfly wing cross section in a biomimetic near-space vehicle wing modification design method provided in Embodiment 1 of the present invention;

[0034] Figure 3 This is a schematic diagram of the cross-sectional structure of the wing and the biomimetic wing profile structure in a biomimetic near-space vehicle wing modification design method provided in Embodiment 1 of the present invention.

[0035] Figure 4 This is a cloud map showing the turbulence intensity and boundary layer thickness distribution of a prototype wing in a biomimetic near-space vehicle wing modification design method provided in Embodiment 1 of the present invention.

[0036] Figure 5 This is a flowchart illustrating a biomimetic near-space vehicle wing modification design method provided in Embodiment 2 of the present invention;

[0037] Figure 6 This is a schematic diagram of a typical dragonfly wing surface structure in a biomimetic near-space vehicle wing modification design method provided in Embodiment 2 of the present invention;

[0038] Figure 7 This is a schematic diagram of the simulation results showing the influence of different biomimetic wing chamber depths on the transition initiation position in a biomimetic near-space vehicle wing modification design method provided in Embodiment 2 of the present invention.

[0039] Figure 8 This is a schematic diagram of the modified wing in a biomimetic near-space vehicle wing modification design method provided in Embodiment 2 of the present invention;

[0040] Figure 9 The friction coefficient diagrams for a 50% spanwise plane prototype wing, aligned and staggered modified wings in a biomimetic near-space vehicle wing modification design method provided in Embodiment 2 of the present invention are shown.

[0041] Figure 10 This is a boundary layer shape factor distribution diagram of the prototype wing and the modified wing in a biomimetic near-space vehicle wing modification design method provided in Embodiment 2 of the present invention;

[0042] Figure 11 This is a surface shear stress cloud diagram of a modified wing model in a biomimetic near-space vehicle wing modification design method provided in Embodiment 2 of the present invention;

[0043] Figure 12 This is a flowchart illustrating a biomimetic near-space vehicle wing modification design method provided in Embodiment 3.

[0044] Figure 13 This is a schematic diagram of the biomimetic wing chamber structure after chamfering treatment in the biomimetic near-space aircraft wing modification design method provided in Embodiment 3. Detailed Implementation

[0045] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0046] Example 1

[0047] Figure 1 This is a flowchart illustrating a biomimetic near-space vehicle wing modification design method according to Embodiment 1 of the present invention. This embodiment can be used for the modification design of near-space vehicle wings and specifically includes the following steps:

[0048] Step 101: Obtain the wing chamber structure on the surface of the dragonfly wing and the folded and wavy structure on the cross-section of the dragonfly wing.

[0049] Compared to active control technology, passive control technology is characterized by low cost and ease of implementation, and has shown high efficiency in recent research, with great application potential. The excellent flight ability of dragonflies at low Reynolds numbers, combined with bionics, provides new research ideas for the design of wings for near-space vehicles.

[0050] To address the passive control and regulation of boundary layer flow on the wing surface of near-space vehicles operating under low Reynolds number conditions, this invention proposes a biomimetic wing modification design method. Since dragonflies possess exceptional flight capabilities, research has shown that their wing structure can effectively regulate surface airflow. Therefore, by designing a modified wing based on the structural characteristics of dragonfly wings, the wing can effectively regulate surface airflow.

[0051] Step 102: Design a biomimetic wing chamber structure based on the wing chamber structure on the surface of dragonfly wings;

[0052] Analysis of dragonfly wings reveals two main structural features: a folded cross-section and wing chambers with varying shapes and arrangements on the wing surface. Therefore, by extracting the wing chamber structures from dragonfly wings and designing modification schemes corresponding to near-space aircraft wings, subsequent wing modifications and optimizations can be facilitated.

[0053] Step 103: Smoothly connect the extreme points of the dragonfly cross-section folded ripple structure to obtain the biomimetic wing profile structure;

[0054] Figure 2 The velocity cloud diagram of the dragonfly wing cross-section folded plate in the biomimetic near-space vehicle wing modification design method provided in Embodiment 1 of the present invention is shown below. Figure 2As shown, by extracting the typical folded and wavy structure from the cross-section of a dragonfly wing, a folded plate with the same folded shape was modeled. Simulation software was used to determine the basic flow field information of the folded plate when it ran at a 0° angle of attack. The velocity contour plot shows that the distribution range of the low-speed region in the flow field on the surface of the folded plate fills the folded grooves. Based on this idea, the extreme points of the folded structure in the dragonfly cross-section were smoothly connected to obtain a novel biomimetic airfoil profile structure, which can meet the needs of airfoil modification.

[0055] Furthermore, this embodiment only takes the airfoil section after connecting the extreme points of the folded structure, and does not make any design requirements for the internal skeleton support of the airfoil. Since the biomimetic airfoil section structure plays a major role, those skilled in the art can select a suitable internal skeleton support for the airfoil according to actual needs in practical applications, which will not be elaborated here.

[0056] Figure 3 This diagram illustrates the wing cross-sectional structure and biomimetic wing profile of a biomimetic near-space vehicle wing modification design method provided in Embodiment 1 of the present invention. In practical applications, the biomimetic wing profile can be obtained by extracting the cross-sectional structure of the middle portion of a dragonfly wing. Those skilled in the art can also extract the cross-sectional structures of other locations on the dragonfly wing according to actual needs and conduct corresponding comparative experiments to obtain the optimal biomimetic wing profile, thereby improving the subsequent wing modification effect. Furthermore, in actual design, the biomimetic wing profile can be specifically determined for different locations on the wing based on the cross-sectional structures of different locations on the dragonfly wing, thereby obtaining a wing modification structure that more closely resembles the dragonfly wing. Those skilled in the art can choose according to actual needs to achieve better flight performance; further details are omitted here.

[0057] Step 104: Fabricate the wing based on the biomimetic wing cross-sectional structure, and arrange the biomimetic wing chamber structure at the position before the starting point of the boundary layer transition on the wing surface.

[0058] In practical applications, to fabricate an airfoil, two steps are required: First, based on the wavy, corrugated structure of a dragonfly's wing cross-section, the extreme points of the corrugation structure need to be smoothly connected to obtain a new airfoil profile. Second, referencing the wing chamber structure composed of veins and membranes on the dragonfly's wing surface, a reasonable arrangement needs to be made on the airfoil surface. This results in a biomimetic passive control method for non-smooth surfaces, enabling passive control of flow within the boundary layer.

[0059] By arranging a suitable dragonfly-shaped wing-like chamber structure on the aircraft wing at a position before the starting point of boundary layer transition, the starting position of boundary layer transition on the wing surface can be controlled. This can induce the boundary layer to transition into a turbulent boundary layer earlier, thereby making the boundary layer on the wing surface more stable, giving it higher anti-interference ability, and reducing flow losses caused by flow separation.

[0060] Figure 4 This is a cloud map showing the prototype turbulence intensity and boundary layer thickness distribution in a biomimetic near-space vehicle wing modification design method provided in Embodiment 1 of the present invention. Figure 4 As shown, this invention uses the chord Reynolds number (Rex) as a reference, first determines the chord Reynolds number at the transition starting point, and then arranges biomimetic wing chamber structures with specific parameters at different positions before that point.

[0061] To clearly illustrate the arrangement of the dragonfly-wing-like chamber structure, this embodiment uses numerical simulation based on actual operating parameters of near-space spacecraft. For example, according to... Figure 4 It can be seen that the chord Reynolds number is 1.5 * 10. 6 The turbulence intensity in the nearby boundary layer begins to change, and the boundary layer thickness δ(x) begins to increase. Based on this, it can be determined that the boundary layer transition process begins near this location. Therefore, as long as the biomimetic wing structure is arranged before this location, the boundary layer can be transitioned to a turbulent boundary layer in advance, thereby making the boundary layer on the wing surface more stable and reducing the flow loss caused by flow separation.

[0062] During aircraft flight, the boundary layer on the wing surface undergoes transition, evolving into a turbulent boundary layer. Before transition, the laminar boundary layer has weak anti-interference capabilities, while the turbulent boundary layer, although increasing drag, effectively improves its anti-interference capabilities. For example, at zero angle of attack, the abrupt change in the friction coefficient clearly indicates the starting point of the boundary layer transition. Within the boundary layer, fluid exchange with the main flow intensifies, leading to increased shear stress. After transition, the friction coefficient stabilizes, at which point the boundary layer has developed into a fully developed turbulent boundary layer.

[0063] Compared with existing technologies, this embodiment designs a wing with a biomimetic wing chamber structure and a biomimetic wing profile structure based on the wing chamber structure on the surface of a dragonfly wing and the folded and corrugated structure on the cross-section of a dragonfly wing. This can improve the flight performance of the wing when flying in near space. Furthermore, this embodiment also controls the starting position of the boundary layer transition on the wing surface by arranging a suitable dragonfly-like wing chamber structure on the wing, causing the boundary layer to transition to a turbulent boundary layer in advance, making the boundary layer on the wing surface more stable. This results in the wing having higher anti-interference ability, reducing flow losses caused by flow separation, and further improving the flight performance of the wing.

[0064] Example 2

[0065] Figure 5 This is a flowchart illustrating a biomimetic near-space vehicle wing modification design method provided in Embodiment 2 of the present invention. This embodiment is based on the above embodiment and optimized. In this embodiment, the step of designing the biomimetic wing chamber structure based on the wing chamber structure of the dragonfly wing surface is specifically optimized as follows: designing the shape of the biomimetic wing chamber structure based on the shape of the wing chamber structure of the dragonfly wing surface; obtaining the size of the biomimetic wing chamber structure based on the ratio of the characteristic length of the wing chamber structure of the dragonfly wing surface to the wingspan of the dragonfly wing; determining the depth of the biomimetic wing chamber structure based on the boundary layer thickness of the biomimetic wing chamber structure at the corresponding position on the wing surface; and designing the arrangement of the biomimetic wing chamber structure based on the arrangement of the wing chamber structure of the dragonfly wing surface.

[0066] Accordingly, the biomimetic near-space vehicle wing modification design method provided in this embodiment specifically includes:

[0067] Step 201: Obtain the wing chamber structure on the surface of the dragonfly wing and the folded and wavy structure on the cross-section of the dragonfly wing;

[0068] Step 202: Design the shape of the biomimetic wing chamber structure based on the shape of the wing chamber structure on the surface of the dragonfly wing;

[0069] Figure 6 This is a schematic diagram of a typical dragonfly wing surface structure in a biomimetic near-space vehicle wing modification design method provided in Embodiment 2 of the present invention, as shown in the figure. Figure 6 As shown, analysis of the distribution of wing chamber structures on the surface of dragonfly wings reveals that the shapes of these structures are primarily quadrilaterals, pentagons, and hexagons; their arrangement is either staggered or equidistantly aligned. Extracting and modeling typical wing chamber structures from the dragonfly wing surface yields five typical structures: aligned quadrilaterals, staggered quadrilaterals, aligned pentagons, staggered pentagons, and staggered hexagons. Therefore, the shape of a biomimetic wing chamber structure can be at least one of quadrilaterals, pentagons, and hexagons.

[0070] Step 203: Obtain the dimensions of the biomimetic wing chamber structure based on the ratio of the characteristic length of the wing chamber structure on the surface of the dragonfly wing to the wingspan of the dragonfly wing.

[0071] The ratio of the characteristic length of the biomimetic wing chamber structure to the wingspan of the wing designed in this invention is based on the ratio of the characteristic length of the wing chamber to the wingspan of a dragonfly wing, thus ensuring the universality of the design method. The characteristic length of the biomimetic wing chamber structure is the diameter of the circumscribed circle of the designed biomimetic wing chamber shape (i.e., quadrilateral, pentagonal, or hexagonal). In practical applications, actual measurements on the surface of dragonfly wings show that the ratio of the characteristic length of the wing chamber structure to the wing length is in the range of 0.008 to 0.04. This invention aims to achieve better aerodynamic characteristics in the flow field with minimal structural adjustments; therefore, a smaller ratio is chosen for setting the dimensional parameters of the biomimetic wing chamber structure.

[0072] Therefore, in practical applications, the ratio of the characteristic length of the wing chamber structure on the dragonfly wing surface to the wingspan of the dragonfly wing is selected as any value between 0.008 and 0.04. Then, the wingspan of the wing is obtained, and the dimensions of the biomimetic wing chamber structure are calculated based on the selected value. Specifically, the ratio of the characteristic length of the wing chamber structure on the dragonfly wing surface to the wingspan should be the same as the ratio of the characteristic length of the biomimetic wing chamber structure to the wingspan of the wing. Knowing the wingspan of the wing, the characteristic length of the biomimetic wing chamber structure can be calculated, and then, based on the selected shape of the biomimetic wing chamber structure, the actual dimensions of the biomimetic wing chamber structure can be obtained.

[0073] For example, the shape of the biomimetic wing chamber structure is selected as a quadrilateral, and the diameter of the circumcircle of the quadrilateral should be equal to the characteristic length of the biomimetic wing chamber structure. Similarly, the same applies to pentagons and hexagons, which will not be elaborated upon here. Therefore, by calculating the characteristic length of the biomimetic wing chamber structure, the dimensional parameters of the biomimetic wing structure can be obtained.

[0074] Step 204: Determine the depth of the biomimetic wing chamber structure based on the boundary layer thickness at the corresponding position on the wing surface.

[0075] Specifically, the thickness of the boundary layer at the location corresponding to the biomimetic wing chamber structure on the wing surface is obtained; and this thickness value is used as the depth value of the biomimetic wing chamber structure to determine its depth. By using the thickness of the boundary layer at the corresponding location of the biomimetic wing chamber structure as the depth of the biomimetic wing chamber structure, the biomimetic wing chamber structure can have a better control over the flow field.

[0076] Figure 7 This is a schematic diagram illustrating the simulation results of the influence of different biomimetic wing chamber depths on the transition initiation position in a biomimetic near-space vehicle wing modification design method provided in Embodiment 2 of the present invention. Figure 7As shown, two biomimetic wing chamber structures with different depths were arranged at the chordal Reynolds number of 0 on the wing: 1 mm and 3 mm, equivalent to the boundary layer thickness at the transition position. Compared with the prototype, it can be seen that the 1 mm depth scheme has little effect on the transition, only slightly advancing the transition initiation position. The 3 mm depth scheme, however, causes the transition to begin immediately at the location of the biomimetic wing chamber structure. This clearly demonstrates that structural depth has a significant impact on flow field regulation, and using a depth equivalent to the boundary layer thickness allows the biomimetic structure to have a better flow field regulation effect.

[0077] Step 205: Design the arrangement of the biomimetic wing chamber structure based on the arrangement of the wing chamber structure on the surface of the dragonfly's wing;

[0078] Optionally, the arrangement of the biomimetic wing chamber structures can be at least one of staggered and aligned arrangements. For example, taking a quadrilateral biomimetic wing chamber structure as an example, at least one row of quadrilateral biomimetic wing chamber structures can be arranged on the wing. The quadrilateral biomimetic wing chamber structures can be arranged in an equidistant aligned manner and / or staggered arrangement to modify the wing. Specifically, when the biomimetic wing chamber structures are arranged in a staggered manner, the three adjacent biomimetic wing chamber structures are arranged in a triangular pattern. Similarly, the pentagonal and hexagonal biomimetic wing chamber structures can be arranged similarly. The pentagonal biomimetic wing chamber structures can be arranged in a staggered manner to modify the wing, while the hexagonal biomimetic wing chamber structures can be arranged in a staggered manner to modify the wing.

[0079] Figure 8 This is a schematic diagram of the modified wing in a biomimetic near-space vehicle wing modification design method provided in Embodiment 2 of the present invention, as shown below. Figure 8 As shown, the wing is equipped with two rows of biomimetic wing chamber structures, with the quadrilateral biomimetic wing chamber structures arranged alternately on the wing. Using a single row of quadrilateral biomimetic wing chamber structures can achieve the purpose of controlling transition, while using multiple rows of quadrilateral biomimetic wing chamber structures will have a certain effect on reducing the surface drag of the wing. Therefore, those skilled in the art can also set the number of rows of quadrilateral biomimetic wing chamber structures according to actual needs.

[0080] Figure 9 This is a friction coefficient diagram of a 50% spanwise plane prototype wing, aligned and staggered modified wings in a biomimetic near-space vehicle wing modification design method provided in Embodiment 2 of the present invention. Figure 9 As shown, by comparing and analyzing three examples—the prototype wing, the modified wing with aligned and staggered quadrilateral bionic wing chamber structures arranged in the downstream direction at a chord Reynolds number of 0—it can be seen that compared to the prototype where the transition begins at about 60% of the chord length, both wing modifications cause the modified boundary layer to transition earlier due to the presence of the bionic structure.

[0081] Specifically, analysis of the friction coefficient diagram in the 50% spanwise plane of the model shows that the prototype diagram has a chord Reynolds number of approximately 1.6 x 10⁻⁶. 6 The friction coefficient suddenly increases sharply at approximately 60% of the chord length, indicating that the boundary layer begins to transition at this point. Comparing two identical biomimetic wing structure shapes—aligned quadrilaterals and staggered quadrilaterals—but with different arrangements, it is clear that the boundary layer on the modified wing surface rapidly transitions to a turbulent boundary layer at the location of the biomimetic wing structure. Simultaneously, the abrupt change in friction coefficient at the location of the biomimetic structure is also clearly visible.

[0082] In the verification case, six rows of identical quadrilateral wing chamber structures were arranged on the leading edge of the model, starting at a point where the chordal Reynolds number was 0, and spaced out along the airflow direction. Verification revealed that the six and three wave-like trends exhibited by aligned and staggered quadrilaterals respectively on the 50% spanwise plane, along with the starting positions of these waves, correspond precisely to the arrangement positions of the six wing chamber structures contained in the aligned quadrilaterals and the three wing chamber structures contained in the staggered quadrilaterals on the same plane. This demonstrates that arranging dragonfly-inspired wing chamber structures on the wing provides effective control over boundary layer transition.

[0083] Figure 10 This is a boundary layer shape factor distribution diagram of the prototype wing and the modified wing in a biomimetic near-space vehicle wing modification design method provided in Embodiment 2 of the present invention, as shown in the diagram. Figure 10 As shown, considering the characteristics of the near-space vehicle's operating environment, boundary and initial conditions were set. By comparing the prototype with an aligned quadrilateral and an interlaced square wing chamber structure, the preliminary effects of the modification were explored. The modification effects are as follows. Figure 10 As shown, compared to the prototype, the wing transition point of the modified wing is moved forward to the location of the biomimetic structure, and the transition is completed near the location of the biomimetic structure, developing into full turbulence.

[0084] Among them, such as Figure 10 As shown, the shape factor H is a parameter used to measure the flow state of the boundary layer. It is generally believed that the shape factor for laminar flow should be greater than 2, while the shape factor for turbulent flow is generally around 1.5. A smaller H value indicates a fuller velocity profile shape, meaning stronger momentum exchange between layers, thus making boundary layer separation less likely. Figure 10 It is evident that the shape factor of the modified wing is lower than that of the original wing. Therefore, a quantitative analysis of the rate of change of the shape factor is performed, with R representing the rate of change of the modified wing surface relative to the smooth surface. This value can be calculated using the following formula:

[0085]

[0086] Wherein, H prototype represents the shape factor H value corresponding to the prototype curve in the figure, and H modified represents the shape factor H value corresponding to the aligned and staggered curves in the figure.

[0087] refer to Figure 10 It can be seen that the prototype value of H is 1.42045, the modified value of H with aligned arrangement is 1.352849, and the modified value of H with staggered arrangement is 1.359966. Based on the above formulas, it can be calculated that arranging aligned wing chambers on the wing can reduce the shape factor at the wing trailing edge by approximately 4.7591%; while arranging staggered wing chambers can reduce the shape factor at the wing trailing edge by approximately 4.2581%. Therefore, both aligned and staggered biomimetic wing chamber structures have good modification effects on the wing, but the aligned arrangement can reduce the shape factor value more significantly.

[0088] Figure 11 This is a surface shear stress cloud diagram of a modified wing model in a biomimetic near-space vehicle wing modification design method provided in Embodiment 2 of the present invention, such as... Figure 11 As shown in the figure, simulation software analysis reveals that, comparing the shear stress on the wing surface under the two arrangement methods, Figure 11 (a) The shear stress on the wall of the aligned modified wing is approximately 2.5, while Figure 11 (b) The shear stress on the staggered modified wing wall is approximately 2.7. The shear stress value on the wing surface obtained using simulation software is existing technology; those skilled in the art can select appropriate simulation software according to actual needs, and will not be elaborated further here.

[0089] In summary, the analysis shows that both modification methods can induce earlier boundary layer transition in the modified wing and significantly reduce its boundary layer shape factor, resulting in a fuller boundary layer velocity profile and higher anti-interference capability. Furthermore, comparing the surface shear stress values ​​of the modified wing surface (i.e., the surface friction drag values ​​generated by the two arrangements), simulation results indicate that the aligned arrangement results in a greater reduction in shape factor and lower drag. Therefore, using an equidistant aligned arrangement of the bionic wing chamber structure yields a better modification effect on the wing.

[0090] Step 206: Smoothly connect the extreme points of the dragonfly cross-section folded ripple structure to obtain the biomimetic wing profile structure;

[0091] Step 207: Fabricate the wing according to the biomimetic wing cross-sectional structure, and arrange the biomimetic wing chamber structure at the position before the starting point of boundary layer transition on the wing surface.

[0092] In this second embodiment, the shape of the biomimetic wing chamber structure is designed based on the shape of the wing chamber structure on the surface of the dragonfly wing; then, the size of the biomimetic wing chamber structure is obtained based on the ratio of the characteristic length of the wing chamber structure on the surface of the dragonfly wing to the wingspan of the dragonfly wing; then, the depth of the biomimetic wing chamber structure is determined based on the boundary layer thickness of the biomimetic wing chamber structure at the corresponding position on the wing surface; finally, based on the arrangement of the wing chamber structure on the surface of the dragonfly wing, the biomimetic wing chamber structure is designed to adopt a quadrilateral equidistant alignment arrangement, which can obtain the optimal wing modification design.

[0093] Example 3

[0094] Figure 12 This is a flowchart illustrating a biomimetic near-space vehicle wing modification design method provided in Embodiment 3. This embodiment is an optimization based on the above embodiment. In this embodiment, after designing the biomimetic wing chamber structure according to the wing chamber structure on the surface of the dragonfly wing, the following step is added: chamfering the biomimetic wing chamber structure.

[0095] Accordingly, the biomimetic near-space vehicle wing modification design method provided in this embodiment specifically includes:

[0096] Step 301: Obtain the wing chamber structure on the surface of the dragonfly wing and the folded and wavy structure on the cross-section of the dragonfly wing;

[0097] Step 302: Design the shape of the biomimetic wing chamber structure based on the shape of the wing chamber structure on the surface of the dragonfly wing;

[0098] Step 303: Obtain the dimensions of the biomimetic wing chamber structure based on the ratio of the characteristic length of the wing chamber structure on the surface of the dragonfly wing to the wingspan of the dragonfly wing.

[0099] Step 304: Determine the depth of the biomimetic wing chamber structure based on the boundary layer thickness at the corresponding position on the wing surface.

[0100] Step 305: Design the arrangement of the biomimetic wing chamber structure based on the arrangement of the wing chamber structure on the surface of the dragonfly's wing.

[0101] Step 306: Chamfer the biomimetic wing chamber structure;

[0102] Figure 13This is a schematic diagram of the biomimetic wing chamber structure after chamfering treatment in the biomimetic near-space aircraft wing modification design method provided in Embodiment 3. Since the wing chamber structure, composed of wing veins and wing membranes on the dragonfly's surface, has a smooth, arc-shaped transition at the connection point, chamfering treatment during the biomimetic wing chamber structure design creates a smooth, arc-shaped transition on the surface. This makes the biomimetic wing chamber structure more closely resemble the wing chamber structure of a dragonfly, which is beneficial for further improving the wing's flight performance and facilitating subsequent engineering applications.

[0103] In practical applications, research on actual dragonfly wing chambers reveals that the edges of dragonfly wing chambers are connected in an arc shape. By comparing the two wing chamber structures with and without chamfers, it can be found that the two schemes have little difference in controlling the starting position of the transition in the flow field. However, the bionic wing chamber with chamfer treatment is beneficial to improving the flight performance of the wing. Considering the practicality of engineering practice in actual applications, this design adopts the scheme of adding chamfers.

[0104] Step 307: Smoothly connect the extreme points of the dragonfly cross-section folded ripple structure to obtain the biomimetic wing profile structure;

[0105] Step 308: Fabricate the wing according to the biomimetic wing cross-sectional structure, and arrange the biomimetic wing chamber structure at the position before the starting point of boundary layer transition on the wing surface.

[0106] In this embodiment, after designing the biomimetic wing chamber structure based on the wing chamber structure of the dragonfly wing surface, a chamfering treatment is added to the biomimetic wing chamber structure. Through the above steps, the surface of the biomimetic wing chamber structure can form a smooth arc-shaped transition, thereby making the biomimetic wing chamber structure closer to the wing chamber structure of the dragonfly wing, which is convenient for subsequent engineering practice applications.

[0107] Transition, the transition from laminar to turbulent flow, characterizes a flow phenomenon. Transitions can be classified into three types: natural transition, bypass transition, and separation transition. Natural transition occurs at low turbulence intensities (Tu < 1%) and is considered the most common form of transition. Bypass transition, on the other hand, is caused by strong disturbances from external airflow (free-flow turbulence). Its boundary layer disturbances exhibit algebraic growth, no longer following an exponential law; that is, it directly transitions from laminar to turbulent flow without undergoing a small disturbance growth process involving the TS wave. A typical example is the transition process in turbomachinery.

[0108] The Reynolds number is often used to determine the flow state of viscous fluids. Under low Reynolds number operating conditions, viscous forces dominate, and viscous effects are important in the entire flow field. The surface of the wing is mostly in a laminar flow state.

[0109] The chordal Reynolds number is a local Reynolds number whose value changes with the chord length. The friction coefficient, or coefficient of frictional resistance, is defined as the ratio of the flow-direction wall shear stress to the inlet dynamic pressure, and its calculation formula is:

[0110]

[0111] Among them U ∞ For the local mainstream velocity, τ w This represents the wall shear stress.

[0112] Displacement thickness δ * Defined as the distance by which free flow is deflected outward due to the presence of the boundary layer, it is the ratio of the mass flow rate effective due to the boundary layer to the mass flow rate under ideal conditions. Its calculation formula is as follows:

[0113]

[0114] Momentum thickness θ is defined as the ratio of the momentum deficit caused by the presence of the boundary layer to the fluid momentum under ideal conditions. Its calculation formula is as follows:

[0115]

[0116] The shape factor is defined as the ratio of displacement thickness to momentum thickness, and its expression is as follows:

[0117]

[0118] Where h is the boundary layer height, and ρ and v are the actual density and actual flow velocity within the boundary layer, respectively. e v e These represent the density and velocity of the fluid in the mainstream region, respectively.

[0119] The shape factor H is a parameter reflecting the shape of the velocity profile distribution within the boundary layer. The smaller the H, the fuller the velocity profile shape, indicating stronger momentum exchange between flow layers and making boundary layer separation less likely. It is generally believed that the shape factor for laminar flow should be greater than 2, while the shape factor for turbulent flow is generally around 1.5.

[0120] This invention primarily targets the wings of near-space vehicles operating under low Reynolds number conditions. Referring to the typical wing chamber structure of a dragonfly wing, and considering the typical shape and arrangement of these chambers, a novel biomimetic non-smooth surface is proposed. Based on this, a novel biomimetic airfoil design method based on the cross-sectional structure of a dragonfly wing is proposed. The principles and methods utilized in this invention differ from existing passive flow control methods for non-smooth surfaces. They primarily combine bionics, rationally analyzing and applying different typical structures of the dragonfly wing cross-section and surface chambers to improve the flow field, thereby increasing wing loading and enhancing its aerodynamic performance.

[0121] This invention primarily relates to a novel biomimetic passive flow control method for non-smooth surfaces, and proposes a biomimetic near-space vehicle wing modification design method based on this method. The invention involves detailed analysis of the dragonfly wing cross-section and surface wing chamber structure, extracting and modeling its typical structure, and finally applying it to the wing surface of a near-space vehicle under low Reynolds number conditions. The biomimetic wing profile structure is obtained by smoothly connecting the extreme points of the folded, corrugated structure of its cross-section, and the biomimetic wing chamber structure on the wing surface is used as a non-smooth surface structure as a passive flow control scheme. Flow field regulation is achieved by rationally arranging the biomimetic wing chamber structure on the wing surface, while the edges of the biomimetic wing chamber structure are chamfered during arrangement, making engineering applications easier to implement.

[0122] Furthermore, by arranging the biomimetic wing chamber structure before the boundary layer transition position, the present invention can reduce the shape factor value of the modified wing while controlling the transition start point, thereby improving the anti-interference capability of the turbulent boundary layer on the surface of the modified wing after the transition.

[0123] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for modifying the wing of a biomimetic near-space aircraft, characterized in that, Includes the following steps: Obtain the wing chamber structure on the surface of the dragonfly wing, as well as the fold and ripple structure on the cross-section of the dragonfly wing; A biomimetic wing chamber structure was designed based on the wing chamber structure of the dragonfly wing surface. By smoothly connecting the extreme points of the folded and wavy structure of the dragonfly cross section, a biomimetic airfoil cross section structure is obtained. The wing was fabricated based on the biomimetic wing cross-sectional structure, and a biomimetic wing chamber structure was arranged at the position before the boundary layer transition point on the wing surface. The design of the biomimetic wing chamber structure based on the wing chamber structure of the dragonfly wing surface includes: The shape of the biomimetic wing chamber structure was designed based on the shape of the wing chamber structure on the surface of the dragonfly wing. The dimensions of the biomimetic wing chamber structure are obtained by comparing the characteristic length of the wing chamber structure on the surface of the dragonfly wing with the wingspan of the dragonfly wing. The depth of the biomimetic wing chamber structure is determined based on the boundary layer thickness at the corresponding position on the wing surface. The arrangement of the biomimetic wing chamber structure was designed based on the arrangement of the wing chamber structure on the surface of the dragonfly wing. The method of determining the dimensions of the biomimetic wing chamber structure based on the ratio of the characteristic length of the wing chamber structure on the dragonfly wing surface to the wingspan of the dragonfly wing includes: The ratio of the characteristic length of the wing chamber structure on the surface of the dragonfly wing to the wingspan of the dragonfly wing is selected as any value between 0.008 and 0.04; Obtain the wingspan length of the wing, and based on the selected value, obtain the dimensions of the biomimetic wing chamber structure.

2. The method according to claim 1, characterized in that: The shape of the biomimetic wing chamber structure is at least one of quadrilateral, pentagonal and hexagonal.

3. The method according to claim 1, characterized in that: The arrangement of the biomimetic wing chamber structure is at least one of staggered arrangement and aligned arrangement.

4. The method according to claim 1, characterized in that, The process of determining the depth of the biomimetic wing chamber structure based on the boundary layer thickness at the corresponding position on the wing surface includes: Obtain the thickness value of the boundary layer at the location of the biomimetic wing chamber structure on the wing surface; The thickness value is used as the depth value of the biomimetic wing chamber structure.

5. The method according to claim 1, characterized in that, After designing the biomimetic wing chamber structure based on the wing chamber structure of the dragonfly wing surface, the method further includes: The biomimetic wing chamber structure was chamfered.

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