A three-dimensional flow field monitoring device and monitoring method in a wind tunnel test

Abstract

The present invention relates to the technical field of wind tunnel testing, and discloses a three-dimensional flow field monitoring device and a monitoring method in wind tunnel testing, including: a flow field monitoring system and a support device. The support device includes: a first support rod, a second support rod, and a third support rod. The flow field monitoring system includes: a first CCD camera, a second CCD camera, a double-pulse laser, and a main control unit. The first CCD camera is installed on a first placement platform, the second CCD camera is installed on a second placement platform, and the double-pulse laser is installed on a third placement platform. The double-pulse laser is used to emit laser light into the wind tunnel test section and form a laser emission plane in the wind tunnel test section. The first CCD camera and the second CCD camera are used to photograph the laser emission plane formed in the wind tunnel test section and send the photographed laser emission plane to the main control unit. The main control unit is used to monitor the three-dimensional flow field in the wind tunnel test according to the laser emission plane.

Description

Technical Field

[0001] The present invention relates to the technical field of wind tunnel tests, and particularly to a three-dimensional flow field monitoring device and a monitoring method in wind tunnel tests. Background Art

[0002] With the increasing development of wind tunnel laboratory technology, new wind tunnel laboratories represented by tornado wind tunnel laboratories have been put into use, resulting in an increase in turbulence and an accelerated change rate of the flow field in wind tunnel tests. The original two-dimensional monitoring technology can no longer meet the monitoring requirements of the wind tunnel flow field. Therefore, it is necessary to introduce three-dimensional monitoring technology into the flow field monitoring of wind tunnel tests to improve the accuracy of wind tunnel test flow field monitoring. Currently, when monitoring the wind tunnel flow field, it is necessary to use a monitoring device to completely capture the flow conditions of different height sections in the wind tunnel flow field. If you want to completely capture the flow conditions of different height sections in the wind tunnel flow field, you need to change the shooting angles of the camera and the laser many times during the monitoring process, and you also need to focus the camera after fixing the shooting position each time to ensure the clarity of the shooting. A large amount of time is consumed during this process, which is not conducive to the smooth progress of the monitoring. It can be seen that the existing monitoring devices have problems of needing to adjust the shooting position and the focal length many times during the measurement process. Summary of the Invention

[0003] The present invention provides a three-dimensional flow field monitoring device and a monitoring method in wind tunnel tests to solve the problems that the existing monitoring devices need to adjust the shooting position and the focal length many times during the measurement process.

[0004] To achieve the above object, the present invention is realized through the following technical solutions:

[0005] In a first aspect, the present invention provides a three-dimensional flow field monitoring device in wind tunnel tests, including: a flow field monitoring system and a support device. The support device includes: a first support rod, a second support rod, and a third support rod. The first support rod and the second support rod are respectively installed on the front side of the wind tunnel test section in the monitoring area through a first fixed platform and a second fixed platform. The third support rod is installed on the rear side of the wind tunnel test section in the monitoring area through a third fixed platform. A first placement platform, a second placement platform, and a third placement platform are respectively installed on the first support rod, the second support rod, and the third support rod. The flow field monitoring system includes: a first CCD camera, a second CCD camera, a double-pulse laser, and a main control unit. The first CCD camera is installed on the first placement platform, the second CCD camera is installed on the second placement platform, and the double-pulse laser is installed on the third placement platform;

[0006] The double-pulse laser is used to emit laser light into the wind tunnel test section and form a laser emission plane in the wind tunnel test section;

[0007] The first CCD camera and the second CCD camera are used to photograph the laser emission plane formed in the wind tunnel test section and send the photographed laser emission plane to the main control unit;

[0008] The main control unit is used to monitor the three-dimensional flow field in the wind tunnel test according to the laser emission plane.

[0009] Optionally, N first placement platforms are arranged on the first support rod, N second placement platforms are arranged on the second support rod, and N third placement platforms are arranged on the third support rod, where N is a positive integer greater than 1;

[0010] The number of first CCD cameras in the flow field monitoring system is equal to the number of first placement platforms, the number of second CCD cameras is equal to the number of second placement platforms, and the number of double-pulse lasers is equal to the number of third placement platforms.

[0011] Optionally, both the first CCD camera and the second CCD camera are cross-frame CCD cameras, and the shutter time is 1 ms.

[0012] Optionally, the double-pulse laser is a Quantel Evergreen double-pulse laser, and the maximum pulse power of the double-pulse laser is 200 mJ and the wave field is 532 nm.

[0013] In a second aspect, an embodiment of the present application provides a method for monitoring a three-dimensional flow field in a wind tunnel test, including:

[0014] Emitting laser light into the wind tunnel test section through a double-pulse laser;

[0015] Adjusting the shooting angle of the CCD camera so that the focal length of the CCD camera is aligned with the wind tunnel test section;

[0016] Spraying tracer particles into the wind tunnel test section, and displaying the flow field in the wind tunnel test section through the tracer particles;

[0017] Irradiating the tracer particles with the laser light emitted by the double-pulse laser to form a laser emission plane, which is photographed by the CCD cameras located in the same height interval. At the same time, whenever the CCD cameras on the placement platforms take pictures, the CCD cameras located in the top card slots also take pictures synchronously. After each shooting is completed, the laser emitter on the upper layer is turned off and then the laser emitter on the lower layer is turned on to ensure the clarity of the picture, and the time interval between every two shootings is controlled within 2 s;

[0018] Sending the video information photographed by the CCD camera to the main control unit, and using the main control unit to process the video information and complete the monitoring of the three-dimensional flow field in the wind tunnel test.

[0019] Optionally, the use of the main control unit to process video information and complete the monitoring of the three-dimensional flow field in the wind tunnel test includes:

[0020] S1. Take the captured images of two adjacent frames as a pair of particle images, and perform data processing on each pair of images;

[0021] S2. Set the coordinates of the particles on the image at time n to (x, y, z), and the coordinates of the particles on the image at time n+1 to (x1, y1, z1). Then the displacement between the two at adjacent times is:

[0022]

[0023] S3. The velocity vector can be obtained from the displacement at adjacent times obtained in step S2:

[0024]

[0025] S4. After obtaining the velocity vector in step S3, we can further write the streamline equation:

[0026]

[0027]

[0028] S5. Similarly, according to the velocity vector, we can calculate the vorticity:

[0029]

[0030] S6. For the vorticity obtained in step S5, based on the relationship between the vorticity and the vortex line equation, the three-dimensional vortex line equation can be written:

[0031]

[0032]

[0033] S7. During the shooting process, we obtain the particle images of multiple laser emission planes. Each laser emission plane can be regarded as a microelement, and the entire test section of the wind tunnel is thus divided into multiple microelements. In steps S2 - S6, we obtain the displacement, velocity vector, streamline equation, vorticity, and vortex line equation of each microelement. Based on this, the three-dimensional velocity field, flow field, and vortex field of the entire wind tunnel test section can be drawn.

[0034] Beneficial effects:

[0035] The three-dimensional flow field monitoring device provided by the present invention in a wind tunnel test includes: a flow field monitoring system and a support device. The support device includes: a first support rod, a second support rod, and a third support rod. The first support rod and the second support rod are respectively installed on the front side of the wind tunnel test section in the monitoring area through a first fixed platform and a second fixed platform. The third support rod is installed on the rear side of the wind tunnel test section in the monitoring area through a third fixed platform. A first placement platform, a second placement platform, and a third placement platform are respectively installed on the first support rod, the second support rod, and the third support rod. The flow field monitoring system includes: a first CCD camera, a second CCD camera, a double-pulse laser, and a main control unit. The first CCD camera is installed on the first placement platform, the second CCD camera is installed on the second placement platform, and the double-pulse laser is installed on the third placement platform;

[0036] The double-pulse laser is used to emit laser light into the wind tunnel test section and form a laser emission plane in the wind tunnel test section;

[0037] The first CCD camera and the second CCD camera are used to photograph the laser emission plane formed in the wind tunnel test section and send the photographed laser emission plane to the main control unit;

[0038] The main control unit is used to monitor the three-dimensional flow field in the wind tunnel test according to the laser emission plane;

[0039] Through the above settings, the problems that the existing monitoring devices need to adjust the shooting position and focal length multiple times during the measurement process can be solved. Description of the Drawings

[0040] Figure 1 is a schematic diagram of the three-dimensional flow field device in the wind tunnel test disclosed in the embodiment of the present invention;

[0041] Figure 2 is a top view schematic diagram of the three-dimensional flow field device in the wind tunnel test disclosed in the embodiment of the present invention;

[0042] Figure 3 is a schematic diagram of the principle disclosed in the embodiment of the present invention;

[0043] Figure 4 is a schematic diagram of the camera body placed perpendicular to the shooting plane disclosed in the embodiment of the present invention;

[0044] Figure 5 is a schematic diagram of the camera body placed obliquely to the shooting plane disclosed in the embodiment of the present invention;

[0045] In the figure: 1. First fixed platform; 2. Second fixed platform; 3. Third fixed platform; 4. First support rod; 5. Second support rod; 6. Third support rod; 7. First placement platform; 8. Second placement platform; 9. Third placement platform; 10. First CCD camera; 11. Second CCD camera; 12. Double-pulse laser; 13. Three-dimensional flow field. Detailed implementation manners

[0046] The technical solutions of the present invention will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0047] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the art to which the present invention belongs. The "first", "second" and similar terms used in the present invention do not denote any order, quantity or importance, but are only used to distinguish different components. Similarly, terms such as "a" or "one" do not denote a quantity limitation, but mean that there is at least one. The terms "connected" or "coupled" and the like are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms "upper", "lower", "left", "right" and the like are only used to represent relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship also changes accordingly.

[0048] Please refer to Figure 1-2 , an embodiment of the present application provides a three-dimensional flow field 13 monitoring device in a wind tunnel test, including: a flow field monitoring system and a support device. The support device includes: a first support rod 4, a second support rod 5 and a third support rod 6. The first support rod 4 and the second support rod 5 are respectively installed on the front side of the wind tunnel test section in the monitoring area through the first fixed platform 1 and the second fixed platform 2. The third support rod 6 is installed on the rear side of the wind tunnel test section in the monitoring area through the third fixed platform 3. A first placement platform 7, a second placement platform 8 and a third placement platform 9 are respectively installed on the first support rod 4, the second support rod 5 and the third support rod 6. The flow field monitoring system includes: a first CCD camera 10, a second CCD camera 11, a double-pulse laser 12 and a main control unit. The first CCD camera 10 is installed on the first placement platform 7, the second CCD camera 11 is installed on the second placement platform 8, and the double-pulse laser 12 is installed on the third placement platform 9;

[0049] The double-pulse laser 12 is used to emit laser light into the wind tunnel test section and form a laser emission plane in the wind tunnel test section;

[0050] The first CCD camera 10 and the second CCD camera 11 are used to photograph the laser emission plane formed in the wind tunnel test section and send the photographed laser emission plane to the main control unit;

[0051] The main control unit is used to monitor the three-dimensional flow field 13 in the wind tunnel test according to the laser emission plane.

[0052] Optionally, N first placement platforms 7 are arranged on the first support rod 4, N second placement platforms 8 are arranged on the second support rod 5, and N third placement platforms 9 are arranged on the third support rod 6, where N is a positive integer greater than 1;

[0053] In the flow field monitoring system, the number of the first CCD cameras 10 is equal to the number of the first placement platforms 7, the number of the second CCD cameras 11 is equal to the number of the second placement platforms 8, and the number of the double-pulse lasers 12 is equal to the number of the third placement platforms 9.

[0054] Optionally, both the first CCD camera 10 and the second CCD camera 11 are cross-frame CCD cameras, and the shutter time is 1 ms.

[0055] Optionally, the double-pulse laser 12 is a Quantel Evergreen double-pulse laser 12, and the maximum pulse power of the double-pulse laser 12 is 200 mJ and the wave field is 532 nm.

[0056] Embodiment 2

[0057] Please refer to Figures 3-5 This application embodiment also provides a method for monitoring the three-dimensional flow field 13 in a wind tunnel test, including:

[0058] Emitting laser into the wind tunnel test section by the double-pulse laser 12;

[0059] Adjusting the shooting angle of the CCD camera so that the focal length of the CCD camera is aligned with the wind tunnel test section;

[0060] Spraying tracer particles into the wind tunnel test section, and displaying the flow field in the wind tunnel test section through the tracer particles;

[0061] Irradiating the tracer particles with the laser emitted by the double-pulse laser 12 to form a laser emission plane, and photographing by the CCD cameras located in the same height interval. At the same time, whenever the CCD cameras on the placement platform take pictures, the CCD cameras located in the top card slots also take pictures synchronously. After each shooting is completed, turn off the laser emitter on the upper layer and then turn on the laser emitter on the lower layer to ensure the clarity of the picture, and control the time interval between every two shootings within 2 s;

[0062] Send the video information captured by the CCD camera to the main control unit, and use the main control unit to process the video information and complete the monitoring of the three-dimensional flow field 13 in the wind tunnel test.

[0063] Optionally, the use of the main control unit to process the video information and complete the monitoring of the three-dimensional flow field 13 in the wind tunnel test includes:

[0064] S1. Take the captured images of two adjacent frames as a pair of particle images, and perform data processing on each pair of images;

[0065] S2. Set the coordinates of the particles on the image at time n to (x, y, z), and the coordinates of the particles on the image at time n+1 to (x1, y1, z1). Then the displacement between the two at adjacent times is:

[0066]

[0067] S3. The velocity vector can be obtained from the displacement at adjacent times obtained in step S2:

[0068]

[0069] S4. After obtaining the velocity vector in step S3, we can further write the streamline equation:

[0070]

[0071]

[0072] S5. Similarly, we can find the vorticity based on the velocity vector:

[0073]

[0074] S6. For the vorticity obtained in step S5, the three-dimensional vorticity line equation can be written according to the relationship between the vorticity and the vorticity line equation:

[0075]

[0076]

[0077] S7. During the shooting process, we obtained the particle images of multiple laser emission planes. Each laser emission plane can be regarded as a microelement, and the entire test section of the wind tunnel is divided into multiple microelements. In steps S2 - S6, we obtained the displacement, velocity vector, streamline equation, vorticity, and vorticity line equation of each microelement. Based on this, the three-dimensional velocity field, flow field, and vorticity field of the entire wind tunnel test section can be drawn.

[0078] Example 3

[0079] The principle of obtaining the out-of-plane coordinates is as follows:

[0080] As shown Figure 3 in the figure, the expressions of the velocity components (along the x-axis, y-axis, and z-axis respectively) can be derived:

[0081]

[0082]

[0083]

[0084] where α and β are the angles between the camera installation angle and the yz-plane and the xz-plane respectively.

[0085] Regarding the arrangement and orientation of the camera, there are two different correction mechanisms including lateral displacement and angular displacement. Lateral displacement correction means that the bodies and lenses of the two cameras are perpendicular to the plane to be photographed, ensuring the same magnification and a more suitable focal length. However, the resolution of the image is restricted by the viewing angle θ, as Figure 4 shown in the figure, the following relationship can be obtained:

[0086]

[0087] where σ Δz and σ Δx are the error values of the velocity component in the direction perpendicular to the photographing plane and within the photographing plane respectively.

[0088] When the viewing angle θ increases, the error in the direction perpendicular to the photographing plane will increase, and the viewing angle limitation can be eliminated by using the angular displacement adjustment method, as Figure 5 . The axis of the camera photographing is no longer parallel to the z-axis. Although the clarity in the z-direction can be improved to a certain extent, the inclined angle makes it impossible for the two cameras to obtain a uniform image.

[0089] Therefore, in the experiment, it is necessary to further adjust the relative positions of the lens and the body through the adjustment of lateral displacement and angular displacement to finally obtain a clear flow field diagram.

[0090] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field according to the concept of the present invention through logical analysis, reasoning, or limited experiments on the basis of the prior art should be within the protection scope determined by the claims.

Claims

1. A three-dimensional flow field monitoring device in a wind tunnel test, characterized in that, it includes: a flow field monitoring system and a support device, the support device includes: a first support rod, a second support rod and a third support rod. The first support rod and the second support rod are respectively installed on the front side of the wind tunnel test section in the monitoring area through a first fixed platform and a second fixed platform. The third support rod is installed on the right side of the wind tunnel test section in the monitoring area through a third fixed platform. A first placement platform, a second placement platform and a third placement platform are respectively installed on the first support rod, the second support rod and the third support rod. The flow field monitoring system includes: a first CCD camera, a second CCD camera, a double-pulse laser and a main control unit. The first CCD camera is installed on the first placement platform, the second CCD camera is installed on the second placement platform, and the double-pulse laser is installed on the third placement platform; The double-pulse laser is used to emit laser light into the wind tunnel test section and form a laser emission plane in the wind tunnel test section; The first CCD camera and the second CCD camera are used to photograph the laser emission plane formed in the wind tunnel test section and send the photographed laser emission plane to the main control unit; The main control unit is used to monitor the three-dimensional flow field in the wind tunnel test according to the laser emission plane; N first placement platforms are vertically arranged on the first support rod, N second placement platforms are vertically arranged on the second support rod, and N third placement platforms are vertically arranged on the third support rod, where N is a positive integer greater than 1; The number of first CCD cameras in the flow field monitoring system is equal to the number of first placement platforms, the number of second CCD cameras is equal to the number of second placement platforms, and the number of double-pulse lasers is equal to the number of third placement platforms.

2. The three-dimensional flow field monitoring device in a wind tunnel test according to claim 1, characterized in that, both the first CCD camera and the second CCD camera are cross-frame CCD cameras, and the shutter time is 1 ms.

3. The three-dimensional flow field monitoring device in a wind tunnel test according to claim 1, characterized in that, the double-pulse laser is a Quantel Evergreen double-pulse laser, and the maximum pulse power of the double-pulse laser is 200 mJ and the wave field is 532 nm.

4. A three-dimensional flow field monitoring method in a wind tunnel test, applied to the three-dimensional flow field monitoring device in a wind tunnel test according to any one of claims 1-3, characterized in that, it includes: emitting laser light into the wind tunnel test section through a double-pulse laser; adjusting the shooting angle of the CCD camera so that the focal length of the CCD camera is aligned with the wind tunnel test section; spraying tracer particles into the wind tunnel test section, and displaying the flow field in the wind tunnel test section through the tracer particles; The tracer particles are irradiated by the laser emitted from a double-pulse laser to form a laser emission plane. The CCD camera in the same height range as the double-pulse laser is used for shooting. At the same time, whenever the CCD cameras on the first placement platform and the second placement platform in the same height range as the double-pulse laser are shooting, the CCD cameras on the top placement platforms of the first support rod and the second support rod also shoot synchronously. After each shooting, the laser emitter on the upper layer is turned off and then the laser emitter on the lower layer is turned on to ensure the clarity of the picture. The time interval between every two shootings is controlled within 2 s; The video information captured by the CCD camera is sent to the main control unit, and the main control unit is used to process the video information and complete the monitoring of the three-dimensional flow field in the wind tunnel test.

5. The method for monitoring the three-dimensional flow field in the wind tunnel test according to claim 4, characterized in that, the use of the main control unit to process the video information and complete the monitoring of the three-dimensional flow field in the wind tunnel test includes: S1. Take the captured images of two adjacent frames as a pair of particle images, and perform data processing on each pair of images; S2. Set the coordinates of the particles on the image at time n to (x, y, z), and the coordinates of the particles on the image at time n + 1 to (x1, y1, z1), then the displacement between the two at adjacent times is: ； S3. The velocity vector can be obtained from the displacement at adjacent times obtained in step S2; ； S4. After obtaining the velocity vector in step S3, we can further write the streamline equation: ； ； S5. Similarly, we can calculate the vorticity based on the velocity vector; ； S6. For the vorticity obtained in step S5, the three-dimensional vorticity equation can be written according to the relationship between the vorticity and the vorticity line equation; ； ； S7. During the shooting process, we obtain the particle images of multiple laser emission planes. Each laser emission plane can be regarded as a microelement, and the entire test section of the wind tunnel is divided into multiple microelements. In steps S2 - S6, we obtain the displacement, velocity vector, streamline equation, vorticity, and vorticity line equation of each microelement, and based on this, the three-dimensional velocity field, flow field, and vorticity field of the entire wind tunnel test section can be drawn.

Images