Circumferential plane flow field scanning device and method

Abstract

The invention provides a circumferential plane flow field scanning device and method. The device comprises a PIV testing system, a circular sliding rail, a controller and a control system, and the PIV testing system comprises a PIV camera and a PIV laser and is used for collecting PIV images and measuring a flow field; the PIV camera and the PIV laser are installed on the circular sliding rail, the circumferential positions of the PIV camera and the PIV laser are changed through the controller, and it is always guaranteed that the axis of the PIV camera is perpendicular to the axis of the PIV laser in the moving process; and the control system controls the PIV test system to perform acquisition, controls the circular slide rail to move, and completes flow field scanning at different circumferential positions of the model according to a prepared circumferential angle sequence.

Description

Technical Field

[0001] The invention develops a circumferential plane flow field scanning device and method, belonging to the technical field of fluid measurement and automatic control. Background Art

[0002] Particle image velocimetry (PIV) is an important means to obtain full-field flow information. The traditional 2D-PIV measurement process requires that the laser sheet light be directed to the position to be measured, and then the camera is focused on the laser plane, the image is calibrated, and then the tracer particle image on the plane is captured. When using 2D-PIV to measure the flow field of sections at different positions, the above calibration process needs to be repeated. This process is extremely cumbersome and easily introduces human operation errors. For some rotating body aircraft, such as missiles and submarines, it is particularly important to obtain the flow field information of the circumferential plane (i.e., the plane passing through the axis of the rotating body). It is an important reference for judging the flow separation and vortex structure generation on the model surface, so as to inspect or optimize the design of the aircraft. However, these aircraft are not axisymmetric models, and there are differences in the flow field information of different circumferential planes. Measuring the flow field of different circumferential planes is the key to inspecting or optimizing the performance of the aircraft. There are difficulties in using traditional 2D-PIV to measure the flow field of different circumferential planes. It is necessary to manually adjust the shooting position and angle of the camera and laser, which is easy to introduce measurement uncertainty and low measurement efficiency. Summary of the invention

[0003] The technical problem solved by the present invention is to provide a circumferential plane flow field scanning device and method to realize rapid scanning measurement of the flow field at different circumferential positions of the model, and obtain flow field information at different circumferential positions that is difficult to obtain by conventional experimental means.

[0004] The solution of the present invention is: a circumferential plane flow field scanning device, including: a PIV test system, a circular slide rail and a controller, a control system

[0005] The PIV test system includes a PIV camera and a PIV laser, which are used to collect PIV images and measure flow fields;

[0006] The PIV camera and the PIV laser are installed on a circular slide rail, and the circumferential positions of the PIV camera and the PIV laser are synchronously changed by a controller, so that the rotation angles of the PIV camera and the PIV laser are the same each time, so as to ensure that the axis of the PIV camera is perpendicular to the axis of the PIV laser;

[0007] The control system controls the PIV test system to collect data, controls the circular slide rail to move, and completes the flow field scanning at different circumferential positions of the model according to the proposed circumferential angle sequence.

[0008] Preferably, the mold is mounted at the center of the circular slide rail.

[0009] Preferably, the circumferential angle sequence is given in the control system according to experimental needs, and the angle sequence should traverse the model feature positions of interest. Near protrusions on the model surface, the angle sequence should be set densely.

[0010] A circumferential plane flow field scanning method, comprising:

[0011] Build the scanning device described in claim 1, install the model to be tested, and ensure that the axial direction of the model to be tested is consistent with the incoming flow direction; install the PIV camera and the PIV laser on the circular slide rail, ensure that the axis of the PIV camera is perpendicular to the axis of the laser, and complete the camera focusing and camera calibration;

[0012] Set the measurement angle sequence and the number of image logarithms taken by the PIV camera at a single point;

[0013] Given the incoming wind speed, the circular slide is controlled to move the PIV camera and the PIV laser to the angle in the measurement angle sequence, triggering the PIV camera and the PIV laser to work. The PIV camera captures the flow field image according to the set single-point image logarithm, and the PIV camera image is collected. After the collection is completed, the circular slide is controlled to move to the next angle in the measurement angle sequence, and the execution is repeated until all angles in the measurement angle sequence are completed.

[0014] Based on the measurement results, the three-dimensional time-averaged velocity field is reconstructed.

[0015] Preferably, the acquisition status of the PIV test system and the movement status of the circular slide are obtained. When the PIV system completes the acquisition, the controller is triggered to control the movement of the circular slide, so that the PIV camera and the PIV laser are rotated to the next angle; when the circular slide has finished moving, the PIV test system is triggered to collect the flow field data at the current angle.

[0016] Preferably, the number of images taken by the PIV camera at each angular position should meet the convergence requirements of the average velocity of the flow field and the Reynolds stress characteristic quantity.

[0017] Preferably, the flow field measurement results at all angle positions in the angle sequence are combined, and the three-dimensional time-averaged velocity field is reconstructed by interpolation to obtain the spatial distribution of the velocity components of the flow field in the radial direction and the axial direction of the model.

[0018] The beneficial effects of the present invention compared with the prior art are:

[0019] Traditional 2D-PIV has difficulties in measuring different circumferential plane flow fields. It is necessary to manually adjust the shooting position and angle of the camera and laser, and repeat the calibration. This process is very easy to introduce measurement uncertainty and has low measurement efficiency. The circumferential plane flow field scanning device and method provided by the present invention can quickly obtain circumferential position flow field information that is difficult to obtain by conventional experimental means, improve efficiency, and reduce measurement uncertainty. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of a circumferential plane flow field scanning measurement system provided by an embodiment of the present invention

[0021] In the figure:

[0022] 1. PIV camera, 2. PIV laser (2-1: laser surface), 3. Circular slide rail (3-1~3-2: slide table), 4. Model to be tested, 5. Motor and reduction box, 6. Motor controller, 7. Control system

[0023] Figure 2 It is a logic block diagram of a control system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with the embodiments.

[0025] like Figure 1 As shown, a circumferential plane flow field scanning device includes a PIV test system, a circular slide rail and a controller, and a control system:

[0026] 1. PIV test system

[0027] It includes a PIV camera 1 and a PIV laser 2, which are used to collect PIV images and measure flow fields.

[0028] 1. The PIV laser 2 is installed on a circular slide rail through slides 3-1 and 3-2 to ensure that the axis of the PIV camera is perpendicular to the axis of the laser.

[0029] 2. Circular slide rail and controller

[0030] It is used to change the circumferential position of the PIV camera and the PIV laser, and ensure that the axis of the PIV camera is always perpendicular to the axis of the PIV laser during the movement. The control system sends instructions to the motor controller 6, which controls the motor and the reduction box 5. The output of the motor and the reduction box acts on the circular slide rail to change the angle and direction of rotation of the circular slide rail.

[0031] 3. Control system

[0032] Control triggering the PIV test system to collect data; control the circular slide rail to move; complete the flow field scanning at different circumferential positions of the model according to the proposed circumferential angle sequence. The control logic block diagram is shown in the attached figure. Figure 2 1) Build the test system. Install the model to be tested, with the axial direction of the model consistent with the incoming flow direction (z direction);

[0033] Ensure that the axis of the model coincides with the axis of the circular slide; install the PIV camera and PIV laser on the slide, ensure that the axis of the PIV camera is perpendicular to the axis of the laser, so that the focal plane of the camera coincides with the laser surface. 2) Before the experiment, complete the camera focus and camera calibration. The general method is as follows: a) Place the ruler or calibration plate on the plane of the laser surface; b) Focus the camera to make the image clear; c) Measure the pixel size of the known feature size on the ruler or calibration plate displayed on the camera image, and divide the known size by the pixel size to obtain the camera calibration coefficient.

[0034] 3) Set the angle sequence and the number of images taken by PIV single point (such as Figure 2 ). The circumferential angle sequence is given in the control system according to the experimental needs. In order to improve the measurement resolution and measurement accuracy, the number of angle sequences should be as high as possible, and the angle sequence should traverse the model feature positions of interest. According to the measurement requirements, the angle sequence should be set densely near the protrusions on the model surface to ensure the measurement resolution of the flow field. The number of PIV single-point shooting logarithms should meet the convergence requirements of the measurement results such as time-averaged velocity and Reynolds stress.

[0035] 4) Given the incoming wind speed, run the control program, and the control system follows the following Figure 2 The control process shown is executed sequentially until the flow field measurement at all angle value positions in the angle sequence is completed.

[0036] 5) Combine the flow field measurement results of all angle positions contained in the angle sequence to reconstruct the three-dimensional time-averaged velocity field and obtain the spatial distribution of the velocity components of the flow field in the radial and axial directions of the model.

[0037] During the entire control process, the acquisition status of the PIV test system and the movement status of the circular slide are obtained. When the PIV system completes the acquisition, the controller is triggered to control the movement of the circular slide, so that the PIV camera and PIV laser move to the next angle; when the circular slide completes the movement, the PIV test system is triggered to collect the flow field data at the current angle.

[0038] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

[0039] Parts not described in detail in the present invention belong to common knowledge of those skilled in the art.

Claims

1. A circumferential plane flow field scanning device, characterized in that include: PIV test system, circular slide rail and controller, control system The PIV test system includes a PIV camera and a PIV laser, which are used to collect PIV images and measure flow fields; The PIV camera and the PIV laser are installed on a circular slide rail, and the circumferential positions of the PIV camera and the PIV laser are synchronously changed by a controller, so that the rotation angles of the PIV camera and the PIV laser are the same each time, so as to ensure that the axis of the PIV camera is perpendicular to the axis of the PIV laser; The control system controls the PIV test system to collect data, controls the circular slide rail to move, and completes the flow field scanning at different circumferential positions of the model according to the proposed circumferential angle sequence.

2. A circumferential plane flow field scanning device according to claim 1, characterized in that: The model is mounted in the center of a circular slide.

3. The circumferential plane flow field scanning device according to claim 1, characterized in that: The circumferential angle sequence is given in the control system according to experimental needs. The angle sequence should traverse the model feature positions of concern. Near the protrusions on the model surface, the angle sequence should be set densely.

4. A circumferential plane flow field scanning method, characterized in that include: Build the scanning device described in claim 1, install the model to be tested, and ensure that the axial direction of the model to be tested is consistent with the incoming flow direction; install the PIV camera and the PIV laser on the circular slide rail, ensure that the axis of the PIV camera is perpendicular to the axis of the laser, and complete the camera focusing and camera calibration; Set the measurement angle sequence and the number of image logarithms taken by the PIV camera at a single point; Given the incoming wind speed, the circular slide is controlled to move the PIV camera and the PIV laser to the angle in the measurement angle sequence, triggering the PIV camera and the PIV laser to work. The PIV camera captures the flow field image according to the set single-point image logarithm, and the PIV camera image is collected. After the collection is completed, the circular slide is controlled to move to the next angle in the measurement angle sequence, and the execution is repeated until all angles in the measurement angle sequence are completed. Based on the measurement results, the three-dimensional time-averaged velocity field is reconstructed.

5. A circumferential plane flow field scanning method according to claim 4, characterized in that: The acquisition status of the PIV test system and the movement status of the circular slide are obtained. When the PIV system completes the acquisition, the controller is triggered to control the circular slide to move, so that the PIV camera and PIV laser move to the next angle; when the circular slide moves, the PIV test system is triggered to collect flow field data at the current angle.

6. A circumferential plane flow field scanning method according to claim 4, characterized in that: The number of images taken by the PIV camera at each angle position should meet the convergence requirements of the average velocity of the flow field and the Reynolds stress characteristic quantity.

7. A circumferential plane flow field scanning method according to claim 4, characterized in that: The flow field measurement results at all angle positions in the angle sequence are combined, and the three-dimensional time-averaged velocity field is reconstructed by interpolation to obtain the spatial distribution of the velocity components of the flow field in the radial and axial directions of the model.

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