A high speed wind tunnel for three-dimensional PIV

Abstract

The application discloses a high-speed wind tunnel applied to three-dimensional PIV, which comprises a nozzle section and an experimental section, wherein the experimental section is provided with an experimental area capable of placing an experimental model or a real aircraft; a concave cavity is arranged on the wall surface downstream of the experimental area of the experimental section, and an observation window is arranged on the wall surface of the concave cavity and faces the experimental area. The application is applied to the field of aerodynamics, and the angle of the observation window can be flexibly adjusted according to the characteristics of the supersonic flow field. The camera lens can be arranged vertically to the observation window during flow field observation, the imaging blur problem caused by the refraction of the observation window glass is avoided, clear flow field images are ensured to be shot, and the three-dimensional velocity field can be accurately calculated.

Description

Technical Field

[0001] This invention relates to the field of aerodynamic equipment technology, specifically a high-speed wind tunnel applied to three-dimensional PIV measurement. Background Technology

[0002] High-speed (sonic / hypersonic) wind tunnels are key equipment for researching and engineering high-speed aircraft flow mechanisms. The most important components of the wind tunnel's main structure are the nozzle section and the test section. The nozzle section accelerates the incoming flow, creating a uniform supersonic / hypersonic flow, providing the high-speed airflow experimental environment for the test section. Experimental models or actual aircraft are placed inside the test section to simulate the flow field during actual flight. To observe the flow field, optical observation windows are typically provided on the walls of the test section, such as... Figure 1 As shown.

[0003] Three-dimensional PIV typically employs a Scheimpflug mechanism to tilt the camera lens. Theoretically, a clear image can be formed on the CCD chip when the observed plane, the lens's equivalent plane, and the CCD chip intersect on a single line in space. During three-dimensional PIV measurements, the camera lens is generally at a 45° angle to the observation window. Figure 2 As shown. However, because the camera lens is not perpendicular to the wind tunnel observation window, the light rays pass through the observation window at an angle due to the refraction of the glass, resulting in a blurred image. This ultimately leads to the inability to calculate or the inaccuracy of the three-dimensional velocity field. Summary of the Invention

[0004] To address the shortcomings of the existing technology, this invention provides a high-speed wind tunnel for three-dimensional PIV measurement. During flow field observation, the camera lens can be arranged perpendicularly to the observation window, avoiding the imaging blurring problem caused by the refraction of the observation window glass, and effectively improving the experimental results of three-dimensional PIV.

[0005] To achieve the above objectives, the present invention provides a high-speed wind tunnel for three-dimensional PIV, comprising a nozzle section and an experimental section, wherein the experimental section has an experimental area capable of housing experimental models or real aircraft.

[0006] A cavity is provided on the wall of the experimental section located downstream of the experimental area, and an observation window facing the experimental area is provided on the wall of the cavity.

[0007] In one embodiment, the cavity includes a first wall and a second wall, one end of the first wall is connected to the wall of the experimental section, the other end of the first wall is connected to one end of the second wall, and the other end of the second wall is connected to the wall of the experimental section.

[0008] The first wall is located upstream of the second wall, and the first wall and the second wall form a concave cavity with a triangular cross section. The observation window is located on the second wall.

[0009] In one embodiment, the first wall surface and the second wall surface are perpendicular to each other, and both the first wall surface and the second wall surface form a 45° angle with the wall surface of the experimental section.

[0010] In one embodiment, the width of the cavity is less than or equal to the width of the experimental segment.

[0011] In one embodiment, there are two cavities, which are symmetrically arranged on the upper and lower walls of the experimental section.

[0012] This invention provides a high-speed wind tunnel for three-dimensional PIV. Based on the characteristics of supersonic flow fields, the angle of the observation window can be flexibly adjusted. During flow field observation, the camera lens can be arranged perpendicular to the observation window, avoiding the imaging blurring problem caused by the refraction of the observation window glass, thereby ensuring that clear flow field images are captured for accurate calculation of the three-dimensional velocity field. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0014] Figure 1 A schematic diagram of wind tunnel window openings in existing technology;

[0015] Figure 2 This is a schematic diagram of a three-dimensional PIV measurement using the Scheimpflug mechanism in the prior art;

[0016] Figure 3 This is a schematic diagram of the high-speed wind tunnel in an embodiment of the present invention;

[0017] Figure 4 This is a schematic diagram of a high-speed wind tunnel in an embodiment of the present invention;

[0018] Figure 5 This is a schematic diagram of the three-dimensional flow channel profile in an embodiment of the present invention;

[0019] Figure 6 This is a three-dimensional configuration diagram of the cavity on the wall of the experimental section in an embodiment of the present invention;

[0020] Figure 7This is a schematic diagram of another embodiment of the high-speed wind tunnel in this invention.

[0021] Reference numerals: Nozzle section 1, Experimental section 2, Cavity 3, First wall 301, Second wall 302, Side wall 303, Observation window 4, Experimental model or real aircraft 5.

[0022] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0025] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0026] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two elements or the interaction between two elements, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0027] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0028] like Figure 3 The diagram shows a high-speed wind tunnel for three-dimensional PIV disclosed in this embodiment, comprising a nozzle section 1 and an experimental section 2 connected in a straight line. The experimental section 2 has an experimental area capable of housing an experimental model or a real aircraft 5. Based on the characteristic that downstream disturbances in supersonic flow cannot affect the upstream, a cavity 3 is provided on the wall of the experimental section 2 downstream of the experimental area. An observation window 4 facing the experimental area is provided on the wall of the cavity 3. (Reference) Figure 4 Since the cavity 3 is located downstream of the experimental model or real aircraft 5, expansion waves and shock waves will only be generated downstream of the experimental model or real aircraft 5. Therefore, the camera lens can be arranged perpendicular to the observation window 4 without affecting the required flow field, thus avoiding the imaging blurring problem caused by the refraction of the glass of the observation window 4 and effectively improving the three-dimensional PIV experimental effect.

[0029] In the specific implementation process, the cavity 3 includes a first wall surface 301 and a second wall surface 302. One end of the first wall surface 301 is connected to the wall of the experimental section 2, and the other end of the first wall surface 301 is connected to one end of the second wall surface 302. The other end of the second wall surface 302 is also connected to the wall of the experimental section 2. The first wall surface 301 is located upstream of the second wall surface 302, and the first wall surface 301 and the second wall surface 302 form a cavity 3 with a triangular cross-section. The observation window 4 is located on the second wall surface 302. Figure 3 Line segment ab represents the first wall 301, and line segment bc represents the second wall 302. Preferably, the first wall 301 and the second wall 302 are perpendicular to each other, and both the first wall 301 and the second wall 302 form a 45° angle with the wall of experimental section 2. Of course, in specific applications, the angle between the walls can be adjusted adaptively according to the position of the experimental model and the starting performance requirements of the wind tunnel. As for the lengths of the first wall 301 and the second wall 302, i.e. Figure 3 The lengths of line segments ab and bc can be adaptively adjusted according to the size of observation window 4.

[0030] join Figure 5 ,exist Figure 3 A three-dimensional flow channel profile can be formed by stretching a two-dimensional flow channel wall. Figure 5 In the diagram, surface ABCD represents the sidewall profile of experimental section 2 on the wind tunnel. Since the 3D PIV observation window 4 does not need to fill the entire height of experimental section 2, the height (h) of the cavity 3 is determined based on the size of the observation window 4 and the model's placement. This design minimizes the interference of the flow in the cavity 3 on the wind tunnel's start-up performance. Finally, based on the aerodynamic profile of the observation window 4 device, the structural thickness is designed, and a small observation window 4 is created on surface bcc′b′, completing the wind tunnel's structural design.

[0031] refer to Figure 6 This is a three-dimensional configuration diagram of the cavity 3 on the wall of experimental section 2. In addition to the first wall 301 and the second wall 302, the cavity 3 also has two side walls 303. The various walls of the cavity 3 are fixed to the wall of experimental section 2 by welding, bolting, or integral molding. The second wall 302 is specifically a rectangular frame structure, and the observation window 4 is fixed within the frame of the second wall 302 by bolts or clips.

[0032] In a preferred embodiment, the number of cavities 3 can be set to two, and the two cavities 3 are symmetrically arranged on the upper and lower walls of the experimental section 2, that is... Figure 7 As shown, by simultaneously acquiring images of the flow field under test using two cameras, the three-dimensional velocity field can be calculated more accurately, effectively improving the experimental results of three-dimensional PIV.

[0033] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A high-speed wind tunnel for use in three-dimensional PIV, characterized in that, It includes a nozzle section and an experimental section, wherein the experimental section has an experimental area that can accommodate experimental models or real aircraft. A cavity is provided on the wall of the experimental section located downstream of the experimental area, and an observation window facing the experimental area is provided on the wall of the cavity. The cavity includes a first wall and a second wall. One end of the first wall is connected to the wall of the experimental section, and the other end of the first wall is connected to one end of the second wall. The other end of the second wall is connected to the wall of the experimental section. The first wall is located upstream of the second wall, and the first wall and the second wall form a concave cavity with a triangular cross section. The observation window is located on the second wall.

2. The high-speed wind tunnel applied to three-dimensional PIV as described in claim 1, characterized in that, The first wall and the second wall are perpendicular to each other, and both the first wall and the second wall form a 45° angle with the wall of the experimental section.

3. The high-speed wind tunnel applied to three-dimensional PIV according to claim 1 or 2, characterized in that, The width of the cavity is less than or equal to the width of the experimental section.

4. The high-speed wind tunnel applied to three-dimensional PIV according to claim 1 or 2, characterized in that, The number of the recesses is two, and the two recesses are symmetrically arranged on the upper and lower walls of the experimental section.

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