Airfoil type drag reduction and lift augmentation device composed of triangular micro-ribs and airfoil type drag reduction and lift augmentation method

Abstract

The invention discloses an airfoil type drag reduction and lift enhancement device composed of triangular micro ribs and a method, and belongs to the technical field of airfoil type aerodynamic performance optimization. The unmanned aerial vehicle comprises a fixing mechanism and wings mounted on the fixing mechanism, the rib component is mounted on the upper surface and / or the lower surface of the wing, and the rib component is hermetically connected with the attached part of the wing; the performance testing system is in line connection with the fixing mechanism, the fixing mechanism is a rigid platform of a wing-shaped structure, and the wing is connected with the rigid platform; the performance test system comprises a main control module, a force sensor and a flow field monitoring module, wherein the force sensor and the flow field monitoring module are respectively connected with the main control module through wires; the force sensor and the fixing mechanism are in line connection, and the flow field monitoring module and the fixing mechanism are in line connection. According to the invention, a multi-working-condition test design is adopted, the critical states of different surface arrangements of the micro ribs are covered, the difference of resistance reduction and lift enhancement performance under different arrangements can be comprehensively reflected, and a more comprehensive experimental basis is provided for optimization of an airfoil structure.

Description

Technical Field

[0001] This invention relates to the field of airfoil aerodynamic performance optimization technology, specifically to an airfoil drag reduction and lift enhancement device and method composed of triangular microribs. Background Technology

[0002] Flow separation on the airfoil surface is a key factor leading to increased drag and a decreased lift-to-drag ratio. Traditional drag reduction techniques often employ fixed grooves or vortex generators, but their parameter design lacks quantitative standards, and their placement is arbitrary, making it difficult to precisely control the flow field characteristics of different airfoil surfaces. For example, covering the entire surface with microstructures may lead to increased local drag, while a single placement cannot adapt to complex flow field changes, resulting in unstable drag reduction effects. Existing testing methods have the following drawbacks: firstly, the microstructure parameters (such as height and spacing) have poor adaptability to the airfoil, and dimensionless dimensions exceed the effective drag reduction range (…). 25 or 30); secondly, the drag reduction differences of different surface arrangements were not compared, making it impossible to determine the optimal solution; and thirdly, the test system lacked a standardized calibration process, resulting in insufficient data reliability.

[0003] Therefore, it is necessary to provide an airfoil drag reduction and lift enhancement device and method composed of triangular microribs. Summary of the Invention

[0004] The purpose of this invention is to provide an airfoil drag reduction and lift enhancement device and method composed of triangular microribs, so as to solve the problem in the prior art that the drag reduction differences of different surface arrangements cannot be systematically compared and the optimal solution cannot be determined.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] An airfoil drag reduction and lift enhancement device composed of triangular microribs, comprising:

[0007] The fixing mechanism and the wing mounted on the fixing mechanism;

[0008] Rib assemblies are installed on the upper and / or lower surfaces of the wing, and the rib assemblies are sealed to the wing at their contact points.

[0009] A performance testing system for measuring the wing, the performance testing system being connected to the fixed mechanism line.

[0010] Furthermore, the fixing mechanism is a rigid platform with an airfoil structure, and the wing is connected to the rigid platform.

[0011] Furthermore, the performance testing system includes: a main control module, a force sensor, and a flow field monitoring module, wherein the force sensor and the flow field monitoring module are respectively connected to the main control module by wires; the force sensor and the fixing mechanism, and the flow field monitoring module and the fixing mechanism are both connected by wires.

[0012] Furthermore, sealant is filled between the bottom of the rib assembly and the surface of the wing.

[0013] Furthermore, the rib assembly includes a plurality of ribs arranged and connected, the ribs being strip-shaped structures with an isosceles triangular cross-section, and the rib assembly having a length of 128 mm and a width of 45 mm;

[0014] The rib assembly is 45mm away from the leading edge of the wing, 60mm away from the trailing edge of the wing, and 86mm away from both sides of the wingspan, and occupies 12.8% of the total wing surface area.

[0015] A method of using an airfoil drag reduction and lift enhancement device composed of triangular microribs as described above includes the following steps:

[0016] S1, fix the wing to the fixed mechanism, adjust the angle to ensure that there is no relative displacement between the airfoil and the fixed mechanism;

[0017] S2, Arrange the rib assembly according to the preset plan, calibrate the position of the rib assembly, and seal the joint between the rib assembly and the wing surface with sealant;

[0018] S3, Set the test conditions, and use the performance testing system to collect the total resistance F of the ribless assembly and different layout schemes. The total lift L is sampled for ≥60s for each operating condition;

[0019] S4. Calculate the drag reduction ratio according to the following formula. and lift-to-drag ratio Select and arrange layout plans;

[0020]

[0021]

[0022] In the formula: F is the drag force on the wing when the rib assembly is not installed; The drag experienced by the wing when rib assemblies are arranged.

[0023] Furthermore, in step S3, the sampling time for each operating condition is ≥60s.

[0024] The present invention has the following beneficial effects:

[0025] 1. This invention adopts a multi-condition (4 preset arrangement states) test design, which covers the critical state of microribs from non-existence to presence and different surface arrangements. It can comprehensively reflect the differences in drag reduction and lift enhancement performance under different arrangements, provide more comprehensive experimental basis for airfoil structure optimization, and solve the problem in the prior art that it failed to systematically compare the drag reduction differences of different surface arrangements and could not determine the optimal solution.

[0026] 2. This invention achieves selective arrangement of the upper and lower surfaces of the airfoil through rib assembly, which can simulate the control of the airfoil flow field by microribs on different surfaces, solves the problem of the disconnect between traditional fixed structure drag reduction and actual aerodynamic requirements, and makes the test data more valuable for reference. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the rib assembly in this invention;

[0028] Figure 2 This is a cross-sectional schematic diagram of the NACA0012 airfoil in this invention;

[0029] Figure 3 This is a schematic diagram showing the arrangement of the rib assembly on the upper surface of the NACA0012 airfoil in this invention;

[0030] Figure 4 This is a schematic diagram showing the arrangement of the rib assembly on the lower surface of the NACA0012 airfoil in this invention;

[0031] Figure 5 This is a schematic diagram of the shape of the ribs on the upper surface of the wing in this invention;

[0032] Figure 6 This is a schematic diagram of the shape of the ribs on the lower surface of the wing in this invention;

[0033] Figure 7 This is a schematic diagram showing the arrangement of the rib assembly on the upper and lower surfaces of the NACA0012 airfoil in this invention;

[0034] Figure 8 This is a schematic diagram showing the positional parameters of the rib assembly in the NACA0012 airfoil of the present invention;

[0035] Figure 9 The streamlines and flow velocity contours of the NACA0012 airfoil section without or without microrib structure in this invention;

[0036] Figure 10 This is a structural schematic diagram comparing the vorticity cloud diagrams of different rib assembly arrangement schemes in this invention. Detailed Implementation

[0037] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present application.

[0038] Example

[0039] like Figure 1-8 As shown, the present invention discloses an airfoil drag reduction and lift enhancement device composed of triangular microribs, a fixing mechanism, and an airfoil mounted on the fixing mechanism; the rib assembly is mounted on the upper surface and / or lower surface of the airfoil, and the rib assembly is sealed to the airfoil at the contact point; the performance testing system is connected to the fixing mechanism for measuring the airfoil.

[0040] Specifically, the rib assembly includes multiple triangular microribs arranged and connected together. The cross-section of each triangular microrib is an isosceles triangle with a height h of 0.5 mm and a width s of 0.5 mm. The wing is the NACA0012 airfoil, and the airfoil fixing mechanism is a rigid platform used to fix the NACA0012 airfoil. The NACA0012 airfoil has a chord length of 150 mm, a wingspan of 300 mm, and a fixed angle of attack of 8°.

[0041] The dimensionless dimensions of the triangular microribs satisfy =14、 =14 ( ≤25 and (≤30), which can be selectively arranged on the upper surface, lower surface, or both surfaces simultaneously at 0.3c-0.6c of the wing, with 256 ribs symmetrically arranged on each of the upper and lower surfaces, distributed symmetrically on both sides of the wingspan center. By rationally planning the position, spacing, and shape of the rib assembly, the airfoil structural stiffness is enhanced, aerodynamic loads are evenly distributed, local stress concentration is reduced, and the airflow field is optimized in conjunction with the airfoil surface to reduce surface disturbance and additional drag.

[0042] The performance testing system includes a main control module, force sensors, and a flow field monitoring module. The force sensors and flow field monitoring module are wiredly connected to the main control module. The force sensors and the stationary mechanism, as well as the flow field monitoring module and the stationary mechanism, are also wiredly connected. The main control module includes a CFD simulation unit, which uses the SST k-ω turbulence model and can simulate a Reynolds number of 77000 (free velocity U). ∞ The flow field characteristics under the condition of 7.7 m / s were measured. Drag and lift were measured in the range of 0-10 N using force sensors and a flow field monitoring module to evaluate the drag reduction and lift enhancement effect of the microribs.

[0043] A method for reducing drag and increasing lift in an airfoil composed of triangular microribs, implemented using the aforementioned device, comprises the following steps:

[0044] S1: Install the NACA0012 airfoil onto the fixed mechanism, adjust the angle of attack to 8°, and ensure that there is no relative displacement between the airfoil and the fixed mechanism;

[0045] S2: Arrange the triangular micro-rib assembly according to the preset scheme (arranged on the upper surface, lower surface, or both surfaces simultaneously), calibrate the position by positioning slide rail, so that the rib is 45mm from the front edge and 60mm from the rear edge, and seal the edges with sealant.

[0046] S3: Set test conditions (free flow velocity U) ∞ =7.7m / s, Reynolds number 77000), the total resistance F was collected through a performance testing system under different arrangement schemes and without ribs. For the total lift L, the sampling time for each working condition is ≥60s;

[0047] S4, calculate the drag reduction rate according to the formula. and lift-to-drag ratio The drag reduction and lift enhancement effects under different working conditions were analyzed to determine the optimal parameter combination.

[0048]

[0049]

[0050] In the formula: F is the drag force on the wing when the rib assembly is not installed; This invention relates to the drag experienced by an airfoil when rib assemblies are arranged. By using rib assemblies to selectively arrange the upper and lower surfaces of the airfoil, it can simulate the airfoil flow field control conditions caused by microribs on different surfaces. This solves the problem of the disconnect between traditional fixed-structure drag reduction and actual aerodynamic requirements, making the test data more valuable.

[0051] This invention employs a multi-condition (four preset arrangement states) test design, covering the critical states of microribs from absence to presence and different surface arrangements. It comprehensively reflects the differences in drag reduction and lift enhancement performance under different arrangements, providing a more comprehensive experimental basis for airfoil structure optimization. This solves the problem in existing technologies that fail to systematically compare drag reduction differences between different surface arrangements, making it impossible to determine the optimal solution.

[0052] The airfoil drag reduction and lift enhancement device of this invention, composed of triangular microribs, has a simple structure, is easy to operate, and its modular design makes it easy to replace microribs of different sizes for testing. It is suitable for improving the aerodynamic efficiency of airfoils of low-speed aircraft, wind turbine blades, etc.

[0053] In practice, install the micro-ribs according to the following steps:

[0054] The NACA0012 airfoil is fixedly installed on the fixing mechanism.

[0055] According to the test plan, the triangular micro-rib assembly is symmetrically installed on the upper and lower surfaces of the wing at 0.3c-0.6c on both sides of the wingspan center, or simultaneously. The rib assembly is 128mm long and 45mm wide, 45mm from the leading edge of the wing, 60mm from the trailing edge of the wing, and 86mm from each side of the wingspan.

[0056] All joints (where the ribs meet the wing surface) are sealed with sealant to ensure that airflow only flows along the wing surface and there is no additional leakage.

[0057] Operating conditions settings:

[0058] The test conditions covered a comparison of three arrangement schemes: no ribs, ribs on the upper surface, ribs on the lower surface, or ribs on both the upper and lower surfaces.

[0059] Data collection process:

[0060] Selected micro-free flow velocity U ∞ =7.7m / s, Reynolds number is 77000.

[0061] Under each operating condition, the total resistance F is collected through CFD simulation or force sensor data. The total lift L and the sampling time meet the requirement of 95% confidence interval ±0.5% (simulation iteration until residual <1e). -6 (Experimental sampling time: 60s).

[0062] Simultaneous measurement of airfoil surface flow field characteristics (based on flow field visualization standards), with microribs remaining installed during testing and flow velocity consistent with that during measurement.

[0063] Performance calculation:

[0064] Calculate the drag reduction ratio using the formula:

[0065]

[0066] Calculate the lift-to-drag ratio using the formula:

[0067]

[0068] The total aerodynamic drag and aerodynamic lift results before and after the microrib arrangement are shown in Table 1.

[0069] Table 1. Drag reduction rate and lift-to-drag ratio of wing surface

[0070] Wing surface Total resistance (N) Total lift (N) drag reduction rate (%) Rise-to-drag ratio No ribs were arranged. 0.062937 1.39845 0 22.22 Ribs are arranged on the upper surface 0.058317 1.363661 7.3 23.38 Ribs are arranged on the lower surface. 0.05790 1.382036 8.0 23.87 Ribs are arranged on both the upper and lower surfaces. 0.057984 1.3765 7.8 23.78

[0071] It can be observed that placing ribs on the upper surface of the wing reduces drag by 7.3%, while placing ribs on the lower surface reduces drag by 8.0%. This demonstrates that drag reduction can be achieved on either the upper or lower surface of the wing. Regarding lift-to-drag ratio, the lift-to-drag ratio is 22.22 without ribs, 23.38 with ribs on the upper surface, and 23.87 with ribs on the lower surface. Therefore, it is evident that placing ribs on the wing not only reduces drag but also improves the lift-to-drag ratio, with the effect being better when placed on the lower surface.

[0072] Depend on Figure 9 Analyzing the drag reduction differences of ribs at different locations reveals that the separation zone is shortest when ribs are placed on the lower surface, followed by ribs on both the upper and lower surfaces, then ribs on the upper surface, and finally, no ribs. This explains why ribs on the lower surface provide the best drag reduction. The presence of ribs makes the fluid flow within the boundary layer more orderly, reducing lateral pulsations and mixing of fluid particles. This is reflected in a more stable velocity distribution on the velocity contour map, reducing the extent of high velocity gradient regions. Furthermore, ribs interfere with fluid flow and suppress flow separation. When fluid flows over the lower surface of an airfoil, without ribs, boundary layer separation may occur under certain conditions, forming a low-pressure zone after the separation point and generating significant pressure drag. The presence of ribs delays boundary layer separation, resulting in a more uniform pressure distribution on the lower surface of the airfoil and reducing pressure drag caused by flow separation. Ribs optimize the near-wall flow structure, suppress turbulent pulsations, and reduce drag. The drag reduction effect is better when ribs are placed on the lower surface. Compared with ribs placed on the upper surface, ribs placed on the lower surface significantly reduce the high vorticity region and make the flow more orderly. The ribs are more effective in optimizing the near-wall flow structure and have a better drag reduction effect.

[0073] From the vorticity cloud map, as follows Figure 10 As shown, without ribs, the flow is turbulent, the vorticity distribution is chaotic, and the high vorticity region is extensive, resulting in strong turbulent pulsations and high drag. When ribs are arranged on the lower surface, the high vorticity region is relatively small, meaning there is less area of ​​strong rotational motion and lower energy dissipation. This is because the ribs effectively suppress flow separation on the lower surface, allowing the fluid to flow smoothly and reducing vortex generation, thus achieving the best drag reduction effect. When ribs are arranged on both the upper and lower surfaces, the flow on the upper and lower surfaces interferes with each other, generating new vorticity sources or making vortex dissipation difficult. The high vorticity region is slightly larger than when ribs are arranged on the lower surface alone, resulting in a slightly less effective drag reduction effect. When ribs are arranged on the upper surface, the high vorticity region is significantly larger, indicating that it is difficult to suppress flow separation and vortex generation. The incoming flow forms more strong rotational flow, resulting in high energy dissipation and high drag, thus achieving the worst drag reduction effect.

[0074] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0075] Optionally, specific examples in this embodiment can refer to the examples described in the above embodiments, and will not be repeated here.

[0076] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0077] In the above embodiments of this application, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0078] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. An airfoil drag reduction and lift enhancement device composed of triangular microribs, characterized in that, include: The fixing mechanism and the wing mounted on the fixing mechanism; Rib assemblies are installed on the upper and / or lower surfaces of the wing, and the rib assemblies are sealed to the wing at their contact points. A performance testing system for measuring the wing, the performance testing system being connected to the fixed mechanism line.

2. The airfoil drag reduction and lift enhancement device composed of triangular microribs according to claim 1, characterized in that, The fixing mechanism is a rigid platform with an airfoil structure, and the wing is connected to the rigid platform.

3. The airfoil drag reduction and lift enhancement device composed of triangular microribs according to claim 1, characterized in that, The performance testing system includes a main control module, a force sensor, and a flow field monitoring module. The force sensor and the flow field monitoring module are respectively connected to the main control module by wires. The force sensor and the fixed mechanism, and the flow field monitoring module and the fixed mechanism are also connected by wires.

4. The airfoil drag reduction and lift enhancement device composed of triangular microribs according to claim 1, characterized in that, The bottom of the rib assembly is filled with sealant between itself and the surface of the wing.

5. The airfoil drag reduction and lift enhancement device composed of triangular microribs according to claim 1, characterized in that, The rib assembly includes a plurality of ribs arranged and connected together. The ribs are strip-shaped structures with an isosceles triangular cross-section. The length of the rib assembly is 128 mm and the width is 45 mm. The rib assembly is 45mm away from the leading edge of the wing, 60mm away from the trailing edge of the wing, and 86mm away from both sides of the wingspan, and occupies 12.8% of the total surface area of ​​the wing.

6. A method of using the airfoil drag reduction and lift enhancement device composed of triangular microribs as described in any one of claims 1-5, characterized in that, Includes the following steps: S1, fix the wing to the fixed mechanism, adjust the angle to ensure that there is no relative displacement between the airfoil and the fixed mechanism; S2, Arrange the rib assembly according to the preset plan, calibrate the position of the rib assembly, and seal the joint between the rib assembly and the wing surface with sealant; S3, Set the test conditions, and use the performance testing system to collect the total resistance F of the ribless assembly and different layout schemes. Total lift L; S4. Calculate the drag reduction ratio according to the following formula. and lift-to-drag ratio Select and arrange layout plans; In the formula: F is the drag force on the wing when the rib assembly is not installed; The drag experienced by the wing when rib assemblies are arranged.

7. The method of using the airfoil drag reduction and lift enhancement device composed of triangular microribs according to claim 6, characterized in that, In step S3, the sampling time for each operating condition is ≥60s.

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