Low-Reynolds-number wing design method based on cavity pressure air-flexible coupling effect

Abstract

The invention provides a low-Reynolds-number wing design method based on a cavity pressure pneumatic flexible coupling effect, and relates to the technical field of aircraft design, the method comprises the following steps: detecting the flow separation position of a low-Reynolds-number wing to obtain the mounting position and laying length of an elastic wall plate; the method comprises the following steps: analyzing the airfoil shape of a wing by using the mounting position and laying length of an elastic wallboard, enabling the elastic wallboard to coincide with the shape of the mounting part of the wing in a non-deformation state to obtain the chordwise shape of the elastic wallboard, and testing by using the pressure value of the dynamic pressure in the flight process of the low-Reynolds-number wing. The thickness and material selection of the elastic wall plate are obtained, the cavity pressure value is obtained through calculation according to the lift force of the rigid wing body and the lift force of the wing body provided with the elastic wall plate, the low-Reynolds-number wing provided with the elastic wall plate is adjusted, and the improved low-Reynolds-number wing profile is obtained. The problems of how to improve the lift-drag ratio of the wings and prolong the endurance time of the aircraft are solved.

Description

TECHNICAL FIELD

[0001] The present specification relates to the technical field of aircraft design, in particular to a low Reynolds number wing design method based on cavity pressure-air-structure coupling effect. BACKGROUND

[0002] High-altitude long-endurance solar unmanned aerial vehicles generally cruise under low Reynolds number conditions, and nonlinear flow phenomena such as laminar separation, transition and reattachment easily occur on the upper surface of the airfoil, affecting the aerodynamic performance.

[0003] In recent years, flexible skin technology has attracted widespread attention due to its weight reduction and potential for in-plane functional integration. However, existing flexible skin solutions focus on passive deformation, lack active and real-time control means for flow separation zones, and do not fully consider the coupling effect between cavity pressure, structure vibration and flow pulsation. Therefore, there is an urgent need for an aerodynamic control technology that is simple in structure, fast in response, and can adapt to incoming flow conditions, to delay or weaken low Reynolds number flow separation, improve wing lift-drag ratio, and extend the endurance of the aircraft. SUMMARY

[0004] In view of the above problems in the prior art, the low Reynolds number wing design method based on cavity pressure-air-structure coupling effect provided by the present application solves the problem of how to improve the wing lift-drag ratio and extend the endurance of the aircraft.

[0005] In order to achieve the above-mentioned purposes, the technical scheme adopted by the present application is as follows: a low Reynolds number wing design method based on cavity pressure-air-structure coupling effect, comprising:

[0006] S1: detecting the flow separation position of the low Reynolds number airfoil to obtain the installation position and laying length of the elastic wallboard;

[0007] S2: analyzing the airfoil shape of the wing using the installation position and laying length of the elastic wallboard, so that the elastic wallboard coincides with the shape of the wing installation part in a non-deformed state, and obtaining the chordwise shape of the elastic wallboard;

[0008] S3: based on the chordwise shape of the elastic wallboard, using the pressure value of the dynamic pressure in the flight process of the low Reynolds number wing, testing the amplitude of different thicknesses and materials under various working conditions of the airfoil, until the amplitude is within the required range, to obtain the thickness and material selection of the elastic wallboard;

[0009] S4: using the thickness and material selection of the elastic wallboard, calculating the cavity pressure value according to the lift of the rigid wing body and the lift of the wing body with the elastic wallboard installed;

[0010] S5: Based on the cavity pressure value, the low Reynolds number wing with elastic panels is adjusted to obtain an improved low Reynolds number airfoil, thus completing the aerodynamic control of the low Reynolds number wing.

[0011] Further, S1 includes:

[0012] By solving the flow field around the wing and performing numerical calculations, the locations where laminar separation, turbulent reattachment, and turbulent separation occur on the upper surface of the airfoil at various flight angles of attack within its normal operating range are obtained under the condition of a completely rigid wall boundary.

[0013] Based on the locations of laminar separation, turbulent reattachment, and turbulent separation occurring on the upper surface at various flight angles of attack, the flow separation locations of low Reynolds number airfoils are detected. The front installation location of the elastic wall panel is determined as the front location where laminar separation occurs, and the rear installation location of the elastic wall panel is determined as the tail or the rear location where turbulent reattachment occurs, thus obtaining the installation location and laying length of the elastic wall panel.

[0014] Further, S2 includes:

[0015] By analyzing the airfoil shape of the wing using the installation position and laying length of the elastic wall panel, the shape of the elastic wall panel is made to coincide with the shape of the wing installation part in a non-deformed state, thus obtaining the chordal shape of the elastic wall panel.

[0016] Further, S3 includes:

[0017] Using the flow field analysis method in S2, the Lagrangian finite element method based on structural mesh is adopted, combined with the structural solution method of the geometric nonlinear wall panel vibration equation, to obtain the vibration amplitude of the maximum displacement point on the surface of the flexible wall panel under different material selections and thicknesses when the cavity pressure is equal to the static pressure under common working conditions. The material thickness is selected with the amplitude between 1 / 1000 and 1 / 200 of the chord length.

[0018] Further, S5 includes:

[0019] Based on the cavity pressure value, the low Reynolds number wing is adjusted so that the lift of the wing with the elastic panel is greater than that of the wing without the elastic panel, and the drag of the wing with the elastic panel is less than that of the wing without the elastic panel, thus obtaining the aerodynamic control result and completing the aerodynamic control of the low Reynolds number wing.

[0020] This invention provides a low Reynolds number wing design device based on the cavity pressure-gas flexible coupling effect, comprising:

[0021] The wing body comprises a main body, connecting screws, sealing strips, elastic panels, a sealing cavity, valves, a high-pressure air source, a first pressure sensing device, and a second pressure sensing device. The sealing cavity is located inside the main body, and the pressure within the cavity is controlled by the high-pressure air source and an air inlet pipe connecting the high-pressure air source and the sealing cavity. A valve controlling the inflation and deflation of the air is installed on the air inlet pipe. The first and second pressure sensing devices are located on the exterior of the sealing cavity and the main body. The elastic panels are installed at the position of the original main wing panel being replaced. Sealing strips are installed between the protrusions around the concave structure of the main body and the protrusions of the elastic panels. The elastic panels are sequentially connected to the main body by connecting screws.

[0022] The beneficial effects of this invention are as follows: This invention provides a low Reynolds number wing design method based on the cavity pressure-air-flexible coupling effect. It is jointly controlled by a sealed cavity and dynamic cavity pressure / back pressure. Through the deformation and vibration of the elastic wall panel, the lift coefficient of the wing is increased and the drag coefficient is decreased, effectively extending the aircraft's cruise time. The structure is simple and can be adaptively controlled by the incoming flow conditions. Attached Figure Description

[0023] This specification will be further described by way of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. These embodiments are not limiting; in these embodiments, the same reference numerals denote the same structures, wherein:

[0024] Figure 1 This is an exemplary flowchart illustrating a low Reynolds number wing design method based on the cavity pressure air-flexible coupling effect, according to some embodiments of this specification.

[0025] Figure 2 This is an exemplary schematic diagram of a design process for improving the aerodynamic performance of low Reynolds number wings by utilizing the cavity pressure air-flexible coupling effect, as shown in some embodiments of this specification.

[0026] Figure 3 This is an exemplary schematic diagram of the geometry of a low Reynolds number wing design device based on the cavity pressure air-flexible coupling effect, according to some embodiments of this specification.

[0027] Figure 4 This is an exemplary schematic diagram showing the connection between a resilient wall panel and a wing according to some embodiments of this specification;

[0028] Figure 5 This is an exemplary top view of a resilient wall panel and wing structure according to some embodiments of this specification;

[0029] Figure 6 This is an exemplary schematic diagram showing the deformation state of an elastic wall panel according to some embodiments of this specification;

[0030] Figure 7 This is an exemplary schematic diagram of the flow field on the upper surface of an airfoil following the vibration and vortex shedding of an elastic panel, according to some embodiments of this specification.

[0031] Figure 8 This is an exemplary schematic diagram of a three-dimensional structure of an elastic wall panel according to some embodiments of this specification.

[0032] The components include: 1. Wing body; 2. Connecting screws; 3. Sealing strip; 4. Elastic wall panel; 5. Sealing cavity; 6. Valve; 7. High-pressure air source; 8. First pressure sensing device; and 9. Second pressure sensing device. Detailed Implementation

[0033] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0034] Example 1

[0035] Figure 1 This is an exemplary flowchart illustrating a low Reynolds number wing design method based on the cavity pressure-air flexible coupling effect, according to some embodiments of this specification. Figure 1 and Figure 2 As shown, the process includes the following steps. In some embodiments, the process may be executed by a processor.

[0036] S1: By detecting the separation location of the low Reynolds number airfoil flow, the installation position and laying length of the elastic wall panel are obtained.

[0037] In some embodiments, the processor can use the compressible unsteady Reynolds-averaged Navier-Stokes equations based on the ALE (Arbitrary Lagrangian Eulerian) method to solve the flow field around the wing. The transition model adopts the SST transition model, based on the structured mesh finite volume method, combined with the third-order MUSCL (Monotone upstreamcentered schemes for conservation laws) reconstruction scheme, the SIMPLE (Semi-Implicit Method for Pressure-Linked Equations) scheme, and the Second-Order scheme. The Implicit time discretization method is used for numerical calculation to obtain the locations where laminar separation, turbulent reattachment, and turbulent separation occur on the upper surface of the airfoil at various flight angles of attack within its normal operating range (small angle of attack) under completely rigid wall boundary conditions. Based on the location range of the three points obtained, the front mounting position of the elastic wall panel is determined as the front position where laminar separation occurs, and the rear mounting position of the elastic wall panel is determined as the tail or the rear position where turbulent reattachment occurs.

[0038] In some embodiments, the processor can perform numerical calculations by solving the flow field around the wing to obtain the locations where laminar separation, turbulent reattachment, and turbulent separation occur on the upper surface of the airfoil at various flight angles of attack within its normal operating range under completely rigid wall boundary conditions.

[0039] Based on the locations of laminar separation, turbulent reattachment, and turbulent separation occurring on the upper surface at various flight angles of attack, the flow separation locations of low Reynolds number airfoils are detected. The front installation location of the elastic wall panel is determined as the front location where laminar separation occurs, and the rear installation location of the elastic wall panel is determined as the tail or the rear location where turbulent reattachment occurs, thus obtaining the installation location and laying length of the elastic wall panel.

[0040] S2: Analyze the airfoil shape of the wing by utilizing the installation position and laying length of the elastic wall panel, so that the shape of the elastic wall panel coincides with the shape of the wing installation part in the non-deformed state, and obtain the chordal shape of the elastic wall panel.

[0041] In some embodiments, the processor can determine the chordal shape of the elastic panel by utilizing its installation position and laying length, so that it coincides with the shape of the wing mounting portion in a non-deformed state.

[0042] In some embodiments, the processor can analyze the airfoil shape of the wing by utilizing the installation position and laying length of the elastic wall panel, so that the elastic wall panel coincides with the shape of the wing installation part in a non-deformed state, thereby obtaining the chordal shape of the elastic wall panel.

[0043] S3: Based on the chordal shape of the elastic panel, the dynamic pressure value during the flight of a low Reynolds number wing is used to test the amplitude of different thicknesses and materials under various working conditions of the airfoil until the amplitude is within the required range, thus obtaining the thickness of the elastic panel and the material selection.

[0044] In some embodiments, the processor may employ the flow field analysis method in step 2, and use the structural mesh-based Lagrange finite element method combined with the structural solution method of the geometric nonlinear wall panel vibration equation to obtain the vibration amplitude of the maximum displacement point on the surface of the flexible wall panel when the cavity pressure / back pressure Pc is equal to the static pressure P∞ under common working conditions.

[0045] In some embodiments, the processor can adjust the thickness and material parameters of the flexible panel to make the amplitude A of the panel reach a suitable value.

[0046] In some embodiments, A = 1 / 1000 to 1 / 200c, where c is the chord length of the wing body.

[0047] In some embodiments, the processor can utilize the flow field analysis method in S2, employing a structured mesh-based Lagrange finite element method combined with a structural solution method for the geometric nonlinear wall panel vibration equation, to obtain the vibration amplitude of the maximum displacement point on the surface of the flexible wall panel under different material selections and thicknesses when the cavity pressure is equal to the static pressure under common working conditions, and select a material thickness with an amplitude between 1 / 1000 and 1 / 200 of the chord length.

[0048] In some embodiments, the differential equation of motion of the elastic wall plate considers geometric nonlinearity, the elastic wall plate is fixedly supported around its perimeter, and the equation of motion of the elastic wall plate is solved using the finite element method.

[0049] S4: Utilizing the thickness and material selection of the elastic wall panel, and based on the lift of the rigid wing body and the lift of the wing body with the elastic wall panel installed, the cavity pressure value is obtained through calculation.

[0050] S5: By utilizing the cavity pressure value, the low Reynolds number wing with elastic panels is adjusted to obtain an improved low Reynolds number airfoil, thus completing the aerodynamic control of the low Reynolds number wing.

[0051] In some embodiments, the processor may employ the numerical calculation method in step 3 to adjust the cavity pressure Pc within the cavity, i.e. the back pressure on the flexible wall panel, so that the lift of the wing with the elastic wall panel installed is greater than that of the wing without the elastic wall panel installed, and the drag of the wing with the elastic wall panel installed is less than that of the wing without the elastic wall panel installed.

[0052] In some embodiments, the processor can optimize the aerodynamic performance of the wing body by determining the cavity pressure / back pressure values.

[0053] In some embodiments, the processor can adjust the low Reynolds number wing based on the cavity pressure value, so that the lift of the wing with the elastic panel is greater than that of the wing without the elastic panel, and the drag of the wing with the elastic panel is less than that of the wing without the elastic panel, thereby obtaining aerodynamic control results and completing the aerodynamic control of the low Reynolds number wing.

[0054] In some embodiments of this specification, a low Reynolds number wing design method based on the cavity pressure-air-flexible coupling effect is provided. This method is jointly controlled by a sealed cavity and dynamic cavity pressure / back pressure. Through the deformation and vibration of the elastic panel, the lift coefficient of the wing is increased and the drag coefficient is decreased, effectively extending the aircraft's cruise time. The structure is simple and can be adaptively controlled by the incoming flow conditions.

[0055] Example 2

[0056] This invention provides a low Reynolds number wing design device based on the cavity pressure-gas flexible coupling effect, comprising:

[0057] The wing body 1, connecting screws 2, sealing strips 3, elastic wall panels 4, sealing cavity 5, valves 6, high-pressure air source 7, first pressure sensing device 8, and second pressure sensing device 9 are provided. The sealing cavity 5 is provided inside the wing body 1. The pressure inside the sealing cavity 5 is controlled by the high-pressure air source 7 and the air inlet pipe connecting the high-pressure air source 7 and the sealing cavity 5. The air inlet pipe is provided with a valve 6 for controlling the inflation and deflation of air. The sealing cavity 5 and the wing body 1 are provided with the first pressure sensing device 8 and the second pressure sensing device 9. The elastic wall panel 4 is installed at the position of the original wing body wall panel that is replaced. The wing body (1) cavity structure has a sealing strip 3 between the protrusions around the cavity structure and the protrusions of the elastic wall panel 4. The elastic wall panel 4 and the wing body 1 are connected in sequence by the connecting screws 2.

[0058] In some embodiments, such as Figures 3-5As shown, the low Reynolds number wing structure with elastic panels provided by the present invention includes a wing body 1 and an elastic panel 4. A sealed cavity 5 is provided within the wing body. The pressure within the sealed cavity is controlled by a high-pressure air source 7 and an air inlet pipe connecting the high-pressure air source and the sealed cavity 5. A valve 6 for controlling inflation and deflation is provided on the air inlet pipe. Pressure sensing devices 8 and 9 are provided on the sealed cavity and the outside of the wing body. The elastic panel 4 is installed at the position of the original wing body panel it replaces. A sealing strip 3 is provided between the protrusions around the concave structure of the wing body 1 and the protrusions of the elastic panel 4. The elastic panel 4 and the wing body 1 are sequentially connected by connecting screws 2. Figure 8 As shown, the elastic wall panel provided by this invention has bosses and through holes around its perimeter, and a concave cavity in its central area, with the central area of ​​the wall panel being smaller than the surrounding bosses. When the wing begins to operate, the separation bubble generated by the interaction between the incoming flow and the boundary layer acts on the elastic wall panel area, creating a pressure difference between the upper and lower surfaces of the wall panel. The wall panel begins to vibrate under forced vibration, and the separation bubble on the upper surface of the wing fluctuates with the vibration of the wall panel, thereby suppressing the influence of the separation bubble on the aerodynamic performance of the wing and achieving the effect of improving the aerodynamic performance of the wing.

[0059] In some embodiments, the sealing cavity and the wing are integrated into a single design, with the cavity height sufficient to accommodate a certain amount of high-pressure gas, so that there is a sufficient pressure difference between the upper and lower surfaces of the elastic wall panel to cause deformation during operation; when the inflation / deflation valve is closed, the pressure in the sealing cavity remains constant. The dynamic cavity pressure / back pressure originates from the sealing cavity and is equivalent to the pressure inside the sealing cavity, which is controlled by a valve that can inflate and deflate the sealing cavity.

[0060] Working principle: When the flow field is not activated, the elastic wall panel 4 is in an undeformed state, with its upper surface aligned with the original shape of the wing body 1. When a flow field occurs on the upper surface of the wing body 1, the sensor 8 measures the external flow field parameters. Based on the measured dynamic pressure value, the high-pressure air source 7 charges and discharges air into the sealed cavity 5. Under the pressure difference between the upper and lower walls and the pressure pulsation on the upper surface, the elastic wall panel 4 begins to vibrate and deform. The deformation state of the elastic wall panel is as follows: Figure 6 As shown. Under the influence of panel deformation and vibration, the separation bubble on the upper surface of the wing body 1 undergoes periodic changes, which weakens its negative impact on the wing's aerodynamic performance, thereby improving the wing's aerodynamic performance. The morphological changes of the separation bubble are as follows: Figure 7 As shown.

[0061] The present invention aims to provide a method for improving the aerodynamic performance of low Reynolds number airfoils, and includes how to use this method to add a control device to an existing low Reynolds number airfoil in a practical situation. This method is designed to protect the airfoil from vibration caused by the combined effects of external flow field loads and cavity pressure, which in turn affects the flow field near the airfoil, thereby improving its aerodynamic performance.

Claims

1. A low Reynolds number wing design method based on the cavity pressure-air flexible coupling effect, characterized in that, include: S1: By detecting the separation location of the low Reynolds number airfoil flow, the installation position and laying length of the elastic wall panel are obtained; S2: Analyze the airfoil shape of the wing by using the installation position and laying length of the elastic wall panel, so that the shape of the elastic wall panel coincides with the shape of the wing installation part in the non-deformed state, and obtain the chordal shape of the elastic wall panel. S3: Based on the chordal shape of the elastic panel, the dynamic pressure value during the flight of a low Reynolds number wing is used to test the amplitude of different thicknesses and materials under various working conditions of the airfoil until the amplitude is within the required range, thus obtaining the thickness of the elastic panel and the material selection. S4: Utilizing the thickness and material selection of the elastic wall panel, and based on the lift of the rigid wing body and the lift of the wing body with the elastic wall panel installed, the cavity pressure value is obtained through calculation. S5: Based on the cavity pressure value, the low Reynolds number wing with elastic panels is adjusted to obtain an improved low Reynolds number airfoil, thus completing the design of the low Reynolds number wing.

2. The low Reynolds number wing design method based on the cavity pressure-air flexible coupling effect according to claim 1, characterized in that, S1 includes: By solving the flow field around the wing and performing numerical calculations, the locations where laminar separation, turbulent reattachment, and turbulent separation occur on the upper surface of the airfoil at various flight angles of attack within its normal operating range are obtained under the condition of a completely rigid wall boundary. Based on the locations of laminar separation, turbulent reattachment, and turbulent separation occurring on the upper surface at various flight angles of attack, the flow separation locations of low Reynolds number airfoils are detected. The front installation location of the elastic wall panel is determined as the front location where laminar separation occurs, and the rear installation location of the elastic wall panel is determined as the tail or the rear location where turbulent reattachment occurs, thus obtaining the installation location and laying length of the elastic wall panel.

3. The low Reynolds number wing design method based on the cavity pressure-air flexible coupling effect according to claim 1, characterized in that, S2 includes: By analyzing the airfoil shape of the wing using the installation position and laying length of the elastic wall panel, the shape of the elastic wall panel is made to coincide with the shape of the wing installation part in a non-deformed state, thus obtaining the chordal shape of the elastic wall panel.

4. The low Reynolds number wing design method based on the cavity pressure-air flexible coupling effect according to claim 1, characterized in that, S3 includes: Using the flow field analysis method in S2, the Lagrangian finite element method based on structural mesh is adopted, combined with the structural solution method of the geometric nonlinear wall panel vibration equation, to obtain the vibration amplitude of the maximum displacement point on the surface of the flexible wall panel under different material selections and thicknesses when the cavity pressure is equal to the static pressure under common working conditions. The material thickness is selected with the amplitude between 1 / 1000 and 1 / 200 of the chord length.

5. The low Reynolds number wing design method based on the cavity pressure-air flexible coupling effect according to claim 1, characterized in that, S5 includes: Based on the cavity pressure value, the low Reynolds number wing is adjusted so that the lift of the wing with the elastic panel is greater than that of the wing without the elastic panel, and the drag of the wing with the elastic panel is less than that of the wing without the elastic panel, thus obtaining the aerodynamic control result and completing the aerodynamic control of the low Reynolds number wing.

6. A low Reynolds number wing design apparatus based on cavity pressure-gas flexible coupling effect, used to execute the low Reynolds number wing design method based on cavity pressure-gas flexible coupling effect as described in any one of claims 1 to 5, characterized in that, include: The wing body (1), connecting screws (2), sealing strips (3), elastic wall panels (4), sealing cavity (5), valves (6), high-pressure air source (7), first pressure sensing device (8) and second pressure sensing device (9) are provided inside the wing body (1). The pressure inside the sealing cavity (5) is controlled by the high-pressure air source (7) and the air inlet pipe connecting the high-pressure air source (7) and the sealing cavity (5). The air inlet pipe is equipped with a valve (6) to control the inflation and deflation of air. The sealing cavity (5) and the wing body (1) are equipped with the first pressure sensing device (8) and the second pressure sensing device (9) outside the wing body (1). The elastic wall panel (4) is installed at the position of the original wing body wall panel that is replaced. The wing body (1) cavity structure has a sealing strip (3) between the protrusions around the cavity structure and the protrusions of the elastic wall panel (4). The elastic wall panel (4) and the wing body (1) are connected in sequence by connecting screws (2).

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