An aerodynamic profile suitable for use in a wind tunnel and a method of designing the same

Abstract

The application relates to an aerodynamic profile suitable for a wind tunnel and a design method thereof, and belongs to the technical field of aviation aerodynamic wind tunnel tests. The front end surface of the aerodynamic profile is a square section, the rear end surface of the aerodynamic profile is a circular section, the middle part of the aerodynamic profile is a transition section, and the front and rear sections are connected through the change of the section shape from front to back. The research and development purpose is to provide a novel aerodynamic profile design method for the transition from a square section to a circular section, the flow field can be smoothly transitioned from a square to a circle, the influence on the flow field quality is minimized, the pressure loss is reduced, and the method of rounding the right angle and gradually increasing the rounding radius is adopted to realize the smooth transition from the square section to the circular section. The circular arc curve is gradually lengthened, the right angle side is gradually shortened, and finally the profile line is completely changed into a circular shape. The transition mode is natural and smooth, the change is gentle, the aerodynamic performance is good, and the interference on the flow field due to the change of the section shape can be obviously reduced.

Description

Technical Field

[0001] This invention relates to an aerodynamic profile design method applicable to wind tunnels, belonging to the field of aerodynamic wind tunnel testing technology. Background Technology

[0002] Aerodynamics is a fundamental science for the development of aerospace technology and other industrial technologies, and wind tunnel testing is one of the basic methods in aerodynamic research. As the most basic equipment in wind tunnel testing, the wind tunnel has always played a very important role in aerodynamic research and aircraft aerodynamic design. The shape and size of the internal surfaces of different sections of the wind tunnel vary, and the connections and transitions between these sections affect the overall flow field quality of the wind tunnel. The aerodynamic profiles of these connecting and transition sections are crucial; poorly designed aerodynamic profiles will directly affect the wind tunnel's velocity uniformity, airflow deflection angle, turbulence intensity, and other flow field indicators, and will also increase the pressure loss of the airflow and the power consumption of the wind tunnel operation.

[0003] In wind tunnel piping, an intermediate section is needed to connect and transition between the front and rear cross sections. The profile of this transition section requires careful design. Currently, there is no clear and effective design method for the transition section profiles in existing high- and low-speed wind tunnels; many transition profiles have not even undergone detailed design. These profiles reduce flow field quality and increase pressure loss.

[0004] Therefore, there is an urgent need to propose a new type of aerodynamic profile suitable for wind tunnels to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to address the problem of providing a novel aerodynamic profile design method that transitions from a square cross-section to a circular cross-section, enabling a smooth transition of the flow field from square to circular while minimizing its impact on flow quality and reducing pressure loss. A brief overview of this invention is provided below to offer a basic understanding of certain aspects of the invention. It should be understood that this overview is not an exhaustive summary of the invention. It is not intended to identify key or essential parts of the invention, nor is it intended to limit the scope of the invention.

[0006] The technical solution of the present invention:

[0007] Option 1: An aerodynamic profile design method suitable for wind tunnels, specifically as follows:

[0008] Step 1: Set the front end face of the aerodynamic profile to a square cross section, define 4 sides EF, FG, GH, HE, with an initial side length of N; set the rear end face of the aerodynamic profile to a circular cross section, define the radius as R, and the length of the transition section from the front end face to the rear end face of the aerodynamic profile as L.

[0009] Step 2: Set 4 points A, B, C, and D on the circular curve of the rear end face. A is located on the vertical midline of EF, B is located on the vertical midline of FG, C is located on the vertical midline of GH, and D is located on the vertical midline of HE.

[0010] Step 3: Connect points E and F to point A to obtain line segments EA and EF. Connect points F and G to point B to obtain line segments FB and GB. Connect points G and H to point C to obtain line segments GC and HC. Connect points H and E to point D to obtain line segments HD and ED. This will give you four isosceles triangles: AEF, BFG, CGH, and DHE.

[0011] Step 4: Any cross section in the transition segment forms four lines of intersection with the isosceles triangle. These four lines of intersection form the legs of the right triangle. The formula for calculating the length 'a' of the right triangle is as follows:

[0012] Formula 1

[0013] Where x is the distance between the cross-section and the front end face;

[0014] Step 5: Connect the four right-angled sides with four 90° circular arcs. These four 90° circular arcs form four rounded arcs of this cross-section. The formula for calculating the radius r of the circular arcs is as follows:

[0015] Formula 2

[0016] Step 6: Obtain the contours of all cross sections on the transition section according to Formula 1 and Formula 2, and then obtain the complete profile of the transition section to complete the design of the aerodynamic profile.

[0017] Option 2: An aerodynamic profile suitable for wind tunnels, obtained according to the aerodynamic profile design method for wind tunnels described in Option 1, includes a front end face of the aerodynamic profile having a square cross section, a rear end face of the aerodynamic profile having a circular cross section, and a middle section of the aerodynamic profile having a transition section.

[0018] The present invention has the following beneficial effects:

[0019] 1. An aerodynamic profile suitable for wind tunnel applications according to the present invention employs a method of rounding right angles and gradually increasing the rounding radius to achieve a smooth transition from a square cross-section to a circular cross-section. The arc curve gradually lengthens while the right angle sides gradually shorten, until the profile becomes completely circular. This transition method is natural and smooth, with a gradual change and good aerodynamic performance, and can significantly reduce the interference to the flow field caused by changes in cross-sectional shape;

[0020] 2. The present invention provides an aerodynamic profile design method applicable to wind tunnels. Numerical simulation calculations show that, compared with previous transition profiles in wind tunnels, the wind tunnel flow field changes more smoothly and the pressure loss can be reduced by about 1% when the transition profile designed using this method is used. Attached Figure Description

[0021] Figure 1 It is a three-dimensional diagram of aerodynamic profiles suitable for use in wind tunnels;

[0022] Figure 2 yes Figure 1 MM cross-section;

[0023] Figure 3 It is a dot-line diagram of aerodynamic profiles suitable for use in wind tunnels. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below with reference to specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0025] The connections mentioned in this invention are divided into fixed connections and detachable connections. Fixed connections, also known as non-detachable connections, include but are not limited to conventional fixed connection methods such as folded connections, riveted connections, adhesive connections, and welded connections. Detachable connections include but are not limited to conventional disassembly methods such as threaded connections, snap-fit ​​connections, pin connections, and hinged connections. When a specific connection method is not explicitly defined, it is assumed that at least one existing connection method can always be found to achieve the function, and those skilled in the art can choose according to their needs. For example, a welded connection can be chosen for fixed connections, and a hinged connection can be chosen for detachable connections.

[0026] Specific implementation method one: Combining Figures 1-3 This embodiment describes an aerodynamic profile design method applicable to wind tunnels, comprising a front end face of the aerodynamic profile with a square cross-section, a rear end face with a circular cross-section, and a transition section in the middle of the aerodynamic profile. To achieve a smooth transition from the square cross-section to the circular cross-section, a method of rounding right angles and gradually increasing the rounding radius is employed, such as... Figure 1 Except for the rear end face being circular and the front end face being square, every other cross-section in this transition section is composed of four rounded arcs and four right-angled sides connected together, such as... Figure 2 The specific design process is as follows:

[0027] Step 1: Set the front end face of the aerodynamic profile to a square cross section, define 4 sides EF, FG, GH, HE, with an initial side length of N; set the rear end face of the aerodynamic profile to a circular cross section, define the radius as R, and define the transition section length between the front end face and the rear end face of the aerodynamic profile as L.

[0028] Step 2: Set 4 points A, B, C, and D on the circular curve of the rear end face. A is located on the vertical midline of EF, B is located on the vertical midline of FG, C is located on the vertical midline of GH, and D is located on the vertical midline of HE.

[0029] Step 3: Connect points E and F to point A to obtain line segments EA and EF. Connect points F and G to point B to obtain line segments FB and GB. Connect points G and H to point C to obtain line segments GC and HC. Connect points H and E to point D to obtain line segments HD and ED. This will give you four isosceles triangles: AEF, BFG, CGH, and DHE.

[0030] Step 4: Any cross-section in the entire transition section forms four lines of intersection with the isosceles triangle. These four lines of intersection are the legs of the right triangle. The formula for calculating the length 'a' of the right triangle is as follows:

[0031] Formula 1

[0032] Where x is the distance between the cross-section and the front end face;

[0033] Step 5: Connect the four right-angled sides with four 90° circular arcs. These four 90° circular arcs form the four rounded arcs of this cross-section. The formula for calculating the radius r of the circular arc is as follows:

[0034] Formula 2

[0035] Step 6: Obtain the contours of all cross sections on the transition section according to Formula 1 and Formula 2, and then obtain the complete profile of the entire transition section to complete the design of the aerodynamic profile.

[0036] Specific Implementation Method Two: Combining Figures 1-3 This embodiment describes an aerodynamic profile suitable for use in a wind tunnel, based on specific embodiment one. The aerodynamic profile has a square cross-section at its front end, a circular cross-section at its rear end, and a transition section in the middle. The front and rear sections are connected by changing the shape of the cross-section from front to back.

[0037] The four right angles of the square cross-section of the front end are rounded, with the radii of the four rounded edges gradually increasing from front to back, eventually reaching the radius of the circular rear end face at the rear end. Simultaneously, the length 'a' of the four right-angled sides of the square front end face gradually decreases from front to back, eventually decreasing to zero at the rear end. This results in a complete circle on the rear end face formed by the four rounded edges, thus completing the transition of the entire aerodynamic profile. The transition section of the aerodynamic profile is smooth and gradual, exhibiting good aerodynamic performance and significantly reducing the impact on the flow field caused by changes in cross-sectional shape.

[0038] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0039] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0040] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0041] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0042] It should be noted that the terms "first," "second," etc., used 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 sequences other than those illustrated or described herein.

[0043] It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be permuted and combined. Those skilled in the art can exhaust all possibilities based on the mathematical knowledge of permutation and combination. Therefore, the present invention will not describe the technical solutions after permutation and combination one by one, but it should be understood that the technical solutions after permutation and combination have been disclosed by the present invention.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An aerodynamic profile suitable for use in wind tunnels, characterized in that: The front end of the aerodynamic profile has a square cross-section, the rear end of the aerodynamic profile has a circular cross-section, and the middle part of the aerodynamic profile is a transition section. It also includes an aerodynamic profile design method suitable for wind tunnels, which is based on the aforementioned aerodynamic profile suitable for wind tunnels, and includes: Step 1: Set the front end face of the aerodynamic profile to a square cross section, define 4 sides EF, FG, GH, HE, with an initial side length of N; set the rear end face of the aerodynamic profile to a circular cross section, define the radius as R, and define the transition section length between the front end face and the rear end face of the aerodynamic profile as L. Step 2: Set 4 points A, B, C, and D on the circular curve of the rear end face. A is located on the vertical midline of EF, B is located on the vertical midline of FG, C is located on the vertical midline of GH, and D is located on the vertical midline of HE. Step 3: Connect points E and F to point A to obtain line segments EA and EF. Connect points F and G to point B to obtain line segments FB and GB. Connect points G and H to point C to obtain line segments GC and HC. Connect points H and E to point D to obtain line segments HD and ED. This will give you four isosceles triangles: AEF, BFG, CGH, and DHE. Step 4: Any cross-section in the entire transition section forms four lines of intersection with the isosceles triangle. These four lines of intersection are the legs of the right triangle. The formula for calculating the length 'a' of the right triangle is as follows: Formula 1 Where x is the distance between the cross-section and the front end face; Step 5: Connect the four right-angled sides with four 90° circular arcs. These four 90° circular arcs form the four rounded arcs of this cross-section. The formula for calculating the radius r of the circular arc is as follows: Formula 2 Step 6: Obtain the contours of all cross sections on the transition section according to Formula 1 and Formula 2, and then obtain the complete profile of the entire transition section to complete the design of the aerodynamic profile.

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