An apparatus and experimental method for taking tomo-piv

Abstract

This invention provides a device and experimental method for photographing Tomo-PIV, belonging to the field of flow field visualization measurement. The device includes: a water prism, a cavitation water cylinder, a laser, and a Tomo-PIV support assembly. The cavitation water cylinder is mounted on the Tomo-PIV support assembly, and multiple high-speed cameras are located on the exterior of the cavitation water cylinder. The Tomo-PIV support assembly includes a vertical lifting device, a horizontal moving device, and a calibration device. The calibration device includes two support frames connected by a crossbeam. A ball screw slide is mounted on the crossbeam, and a calibration plate fixing device is mounted on the ball screw slide. A calibration plate is mounted on the calibration plate fixing device. A water prism bracket is mounted on the support frame, and a water prism is installed in the water prism bracket. This invention achieves accurate measurement of three-dimensional flow fields without repeated calibration, has high calibration efficiency and good measurement data consistency, and can effectively reveal complex three-dimensional flow structures. It is suitable for visualization measurement scenarios of flow fields inside cavitation water cylinders.

Description

Technical Field

[0001] This invention belongs to the field of flow field visualization measurement, specifically relating to a device and experimental method for capturing Tomo-PIV images. Background Technology

[0002] Particle Image Velocimetry (PIV) is a non-invasive flow field measurement method that visualizes the flow field. It involves scattering tracer particles into the water, irradiating them with a high-energy laser to excite them, and simultaneously recording the particle trajectories with a high-speed camera. Algorithms then calculate the motion state of each particle, reflecting the flow field's dynamics. Traditional PIV captures a single plane illuminated by a laser sheet, using only one camera and outputting a two-dimensional velocity field (2D2C). Stereoscopic PIV, while also capturing a single plane illuminated by a laser sheet, uses two cameras. By utilizing the parallax between the two cameras, the velocity vector W perpendicular to the captured plane can be calculated, thus outputting a three-dimensional velocity field (2D3C).

[0003] Tomo-PIV, short for Tomographic-Particle Image Velocimetry, typically uses four cameras to capture an image of a particle illuminated by a laser. It simultaneously captures the instantaneous 3D velocity vectors of all points within a 3D volume, outputting the 3D velocity field of the entire volume—a 3D, three-component (3D3C) velocity field—revealing complex 3D flow structures. To achieve the precise geometric calibration required for 3D flow field reconstruction, the correspondence between multiple cameras at different viewpoints must be obtained. Current techniques often require manually moving each camera individually for multi-position calibration, which cannot guarantee that their relative positions remain constant during movement. Small, inconsistent positional shifts can lead to accumulated errors in multiple calibration steps, affecting the final calibration accuracy and 3D reconstruction quality.

[0004] Furthermore, even after initial calibration, equipment such as cameras and supports may experience micron-level deformation or displacement due to vibrations and changes in ambient temperature throughout the experimental period. This slow parameter drift cannot be corrected in traditional static calibration models, leading to a gradual decrease in the accuracy of subsequent measurement data reconstruction over time, thus affecting the overall quality of large-scale, long-term flow field scanning experiments. Therefore, an integrated calibration and measurement solution capable of continuous self-correction during the measurement process is urgently needed. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical problems and provide a device and experimental method for shooting Tomo-PIV.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A device for photographing Tomo-PIV includes: a water prism, a cavitation water tube, a laser, and a Tomo-PIV support assembly, wherein the cavitation water tube is mounted on the Tomo-PIV support assembly and the cavitation water tube has multiple high-speed cameras on its exterior.

[0008] The Tomo-PIV support system includes a vertical lifting device, a horizontal moving device, and a calibration device.

[0009] The calibration device includes two support frames connected by a crossbeam. A ball screw slide is mounted on the crossbeam, a calibration plate fixing device is mounted on the ball screw slide, and a calibration plate is mounted on the calibration plate fixing device. A water prism bracket is mounted on the support frame, and a water prism is mounted in the water prism bracket.

[0010] Furthermore, the vertical lifting device includes an upper frame and a lower reinforcing frame. Lifting legs are installed between the upper frame and the lower reinforcing frame. A sliding table is installed on the upper frame, and a fixed crossbeam is installed on the lower reinforcing frame.

[0011] Furthermore, the horizontal moving device is connected to the slide of the vertical lifting device via a slider, so that the horizontal moving device moves in a direction perpendicular to the water flow of the bubble tube.

[0012] Furthermore, the horizontal movement device includes a camera base and a laser base, on which a laser is mounted.

[0013] Furthermore, the laser base has a three-dimensional adjustment mechanism.

[0014] Furthermore, multiple high-speed cameras, including high-speed camera one, high-speed camera two, high-speed camera three, and high-speed camera four, are respectively mounted and fixed on the camera base of the horizontal moving device, so that they are respectively located on the left, left rear, right, and right rear sides of the cavitation water cylinder, with high-speed camera two and high-speed camera four perpendicular to the water prism.

[0015] The present invention may also include:

[0016] An experimental method for using the device described above to photograph Tomo-PIV, comprising the following steps:

[0017] Perform initial positioning and debugging of the equipment. After the initial positioning and debugging are completed, start the calibration software to perform the first calibration operation, collect the imaging data of the four cameras and generate a calibration file, which is then saved to the system storage directory.

[0018] The control system of the ball screw slide drives the carrier platform to move along the Y direction by a set distance. After moving into position, the calibration plate is kept in a stable position. The above focusing and Sham angle fine-tuning process is repeated. After ensuring that the image quality meets the requirements, the second calibration is performed, and the calibration file is generated and saved.

[0019] Repeat the calibration process as described above. After each calibration, move the calibration plate a set distance along the Y direction. Move the plate five times in total to complete six calibration operations. The center positions of the calibration plate in the six calibrations are evenly distributed along the Y direction, completely covering the target measurement area.

[0020] After all calibrations are completed, the six sets of calibration files are checked for consistency using calibration software to ensure that the deviation of each set of calibration parameters is within ±0.5 pixels. Once the check is passed, the entire calibration process is complete.

[0021] After the calibration process is completed, remove the calibration plate fixing device inside the cavitation water cylinder and take it out to ensure that there are no foreign objects left inside the cavitation water cylinder; then put the top cover of the cavitation water cylinder on and seal it with the sealing device to prevent water leakage during the experiment.

[0022] Clean water is added to the cylinder to the rated level through the liquid injection system of the cavitation water cylinder. During the filling process, the water flow rate is controlled to avoid the generation of air bubbles. After the liquid level reaches the preset value, tracer particles of appropriate particle size are added to the water, and the tracer particles are evenly dispersed in the water by the stirring device.

[0023] Turn on the laser and preheat for 10 minutes. After the laser output stabilizes, start the four cameras to work synchronously with the laser through the synchronizer. Perform the first set of flow field data acquisition according to the preset shooting parameters. The acquisition time is 10 seconds. After the acquisition is completed, save the data to the folder.

[0024] The imaging component is driven to move along the Y direction by a horizontal moving device, and the moving distance is precisely controlled to a set distance. After moving into position, the system is kept stable for a period of time to ensure that the flow field returns to stability. Then, the second set of flow field data is collected and saved.

[0025] Repeat the above-described movement and acquisition process until data acquisition is completed at all preset locations within the target measurement area. During the acquisition process, monitor the imaging quality and tracer particle distribution in real time using monitoring software to ensure data validity.

[0026] Furthermore, the initial positioning and debugging of the equipment includes:

[0027] Perform the pre-experiment preparation procedure and assemble the water prism and high-speed camera into the preset installation positions;

[0028] Connect the signal output terminals of multiple high-speed cameras to the signal input terminal of the synchronizer and the network port of the switch, respectively.

[0029] The laser is positioned and its emission angle is adjusted by the three-dimensional adjustment mechanism of the laser base according to the spatial coordinate range of the target flow field, so that the laser beam can completely cover the flow field area to be measured; after the laser beam is positioned, the control signal terminal of the laser is connected to the signal output terminal of the synchronizer.

[0030] Open the top cover of the cavitation water cylinder, install the calibration plate on the calibration plate fixing device, place the fixing device with the calibration plate inside the cavitation water cylinder, and adjust the height of the calibration plate through the drive system of the ball screw slide according to the spatial position parameters of the target flow field so that the center plane of the calibration plate coincides with the Z-direction center plane of the flow field.

[0031] Adjust the height of the vertical lifting device so that the center of the lenses of the four cameras is at the same horizontal level as the center of the calibration plate; then focus the four cameras separately.

[0032] The beneficial effects of this invention are as follows:

[0033] This invention has strong anti-drift capability. Based on the online self-calibration algorithm of flow field image features, it can correct the camera pose parameters in real time during continuous scanning measurements for several hours. It can continuously suppress the systematic error caused by mechanical relaxation or temperature effect to less than 0.1 pixels, ensuring the data accuracy and repeatability of long-term experiments.

[0034] This invention is highly intelligent, with the system possessing self-state perception and parameter fine-tuning capabilities, reducing reliance on manual intervention and frequent repetitive calibration, and improving the level of automation and operational efficiency of experiments.

[0035] This invention offers better data consistency: by reconstructing all data points within the entire scanning measurement area using a continuously optimized unified geometric model, it eliminates the systematic bias caused by minor parameter differences in data collected at different time points, making the spliced ​​large-scale flow field data more physically coherent and consistent.

[0036] This invention employs a method that involves installing and debugging components in a preset posture, using a calibration plate to perform multi-position calibration by moving it step-by-step along the Y-axis of the target flow field, and then using a horizontal movement device to drive the imaging component to collect flow field data step-by-step. This method achieves accurate measurement of the three-dimensional flow field without the need for repeated calibration, resulting in high calibration efficiency and good consistency of measurement data. It effectively reveals complex three-dimensional flow structures and is suitable for visual measurement scenarios of flow fields within cavitation water cylinders. Attached Figure Description

[0037] Appendix Figure 1 This is a schematic diagram of the structure of the present invention;

[0038] Appendix Figure 2 This is a schematic diagram of the overall structure of the Tomo-PIV support frame of the present invention;

[0039] Appendix Figure 3 This is a schematic diagram of the vertical lifting device of the present invention;

[0040] Appendix Figure 4 This is a schematic diagram of the structure of the horizontal moving device of the present invention;

[0041] Appendix Figure 5 This is a schematic diagram of the calibration device of the present invention.

[0042] In the attached diagram: 1. High-speed camera one, 2. High-speed camera two, 3. High-speed camera three, 4. High-speed camera four, 5. Water prism, 6. Cavitation water tank, 7. Laser, 8. Tomo-PIV support frame, 9. Vertical lifting device, 10. Horizontal moving device, 11. Calibration device, 12. Lifting outrigger, 13. Lower reinforcement frame, 14. Fixed crossbeam, 15. Water prism, 16. Vertical moving device, 17. Laser base, 18. Water prism support, 19. Ball screw slide, 20. Calibration plate fixing device, 21. Support frame, 22. Calibration plate, 23. Crossbeam, 24. Upper frame. Detailed Implementation

[0043] The present invention will now be further described with reference to the accompanying drawings.

[0044] This invention provides a device for filming Tomo-PIV, as shown in the attached document. Figures 1-2 As shown, it includes: multiple high-speed cameras, a water prism, a cavitation water tank, a laser, and the entire Tomo-PIV support.

[0045] The Tomo-PIV support frame as a whole includes: a vertical lifting device 9, a horizontal moving device 10, and a calibration device 11;

[0046] The Tomo-PIV bracket 8 is installed directly below the cavitation water cylinder 6;

[0047] As attached Figure 3 As shown, the vertical lifting device 9 consists of lifting legs 12, a lower reinforcing frame 13, a calibration device fixing beam 14, an upper frame 24, and a slide table 15. The height of the lifting legs is adjusted to adjust the overall height of the device. The specific position of the overall height depends on the position of the flow field to be photographed.

[0048] As attached Figure 4As shown, the horizontal moving device 10 consists of a slider 16, a camera base 25, and a laser base 17. The horizontal moving device is connected to the slide table of the vertical moving device through the slider, so that the moving device can move along a direction perpendicular to the water flow of the bubble tube.

[0049] Four high-speed cameras are placed on the corresponding sides of the cavitation water cylinder and are perpendicular to the side plate of the cavitation water cylinder or the optical surface of the water prism. The laser and the cameras are linked with the synchronizer to achieve synchronous control.

[0050] Furthermore, the high-speed camera 1, high-speed camera 2, high-speed camera 3, and high-speed camera 4 are mounted and fixed on the camera base 25 of the horizontal moving device 10, so that they are located on the left, left rear, right, and right rear sides of the cavitation water cylinder, respectively. The cameras of high-speed camera 2 and high-speed camera 4 need to be perpendicular to the water prism 5, and the specific positions depend on the flow field position to be captured.

[0051] The laser 7 is mounted on the laser fixing base 17 of the horizontal moving device 10, and its specific position depends on the location of the flow field to be illuminated.

[0052] As attached Figure 5 As shown, the calibration device 11 consists of a calibration plate fixing device 20, a ball screw slide 19, a water prism bracket 18, and a support rod 21. Angle steel is used to connect the support rod and the calibration device fixing beam 14 of the vertical lifting device 9.

[0053] The calibration plate 22 is installed on the calibration plate fixing device 20, which is fixed above the ball screw slide table 19. The ball screw slide table is fixed on the crossbeam 23. The calibration plate is moved in a direction perpendicular to the water flow of the cavitation water cylinder 6 by means of the ball screw slide table.

[0054] The water prism 5 is installed in the water prism bracket 18 of the calibration device 11, and the position of the water prism depends on the location of the flow field to be photographed.

[0055] Example 2:

[0056] The experimental method for capturing Tomo-PIV using the device described in Example 1 includes the following steps:

[0057] To perform the pre-experiment preparation procedure, first assemble the water prism into the preset installation position, and use a level to complete the attitude calibration of the water prism to ensure that its optical surface is coaxial with the subsequent measurement optical path; after calibration, add clean water into the water prism to the rated liquid level to ensure that the liquid level is stable and there are no air bubbles.

[0058] Subsequently, four high-speed cameras were deployed (High-speed camera 1, High-speed camera 2, High-speed camera 3, and High-speed camera 4). High-speed camera 1 and High-speed camera 3 were fixedly installed in an orientation perpendicular to the side plate of the cavitation water tank, while high-speed camera 2 and high-speed camera 4 were fixedly installed in an orientation perpendicular to one side optical surface of the water prism. During the assembly process, a rangefinder was used to control the accuracy, ensuring that the vertical distance deviation between high-speed camera 1 and high-speed camera 3 and the corresponding side plate of the cavitation water tank did not exceed ±0.1mm, and the vertical distance deviation between high-speed camera 2 and high-speed camera 4 and the corresponding side plate of the cavitation water tank did not exceed ±0.1mm.

[0059] After completing the mechanical installation of the cameras, connect the signal output terminals of the four cameras to the signal input terminals of the synchronizer and the network port of the switch respectively. Verify the smooth communication links between the cameras, synchronizer, and switch using debugging software to ensure stable data transmission and timely response of synchronization control signals.

[0060] The laser is fixedly mounted on a dedicated laser mounting base using fastening bolts. Based on the spatial coordinate range of the target flow field (with the flow field center as the reference), the spatial position and emission angle of the laser are adjusted through the three-dimensional adjustment mechanism of the base so that the laser beam can completely cover the flow field area to be measured. After the laser beam is positioned, the control signal terminal of the laser is connected to the signal output terminal of the synchronizer.

[0061] Open the top cover of the cavitation water cylinder and fix the calibration plate into the slot of the calibration plate fixing device using the positioning pin. The size parameters of the calibration plate must match the target measurement area. Taking a three-dimensional cube area with X-axis 80mm, Y-axis 80mm and Z-axis 30mm as an example, select a calibration plate with a specification of 80mm×80mm×6mm (the surface of the calibration plate is printed with a high-precision checkerboard pattern, and the checkerboard unit size is 5mm×5mm).

[0062] The fixing device equipped with the calibration plate is placed inside the cavitation water cylinder and fastened to the bearing platform of the ball screw slide with bolts; according to the spatial position parameters of the target flow field, the height of the calibration plate is adjusted by the drive system of the ball screw slide so that the center plane of the calibration plate coincides with the Z-direction center plane of the flow field.

[0063] Adjust the height of the vertical lifting device so that the center of the lenses of the four cameras is at the same horizontal level as the center of the calibration plate; then focus on the four cameras respectively until the edges of the checkerboard lines are sharp and without blur; for high-speed camera 2 and high-speed camera 4, precisely adjust the Schlieren angle through their attitude adjustment mechanism to ensure that the four corners and the center area of ​​the calibration plate can be clearly imaged in the imaging windows of the four cameras, and that the imaging area is free of distortion.

[0064] After completing the initial positioning and debugging, start the calibration software to perform the first calibration operation, collect imaging data from the four cameras and generate a calibration file, which is saved to the system storage directory with the file name "Calibration_01".

[0065] The control system of the ball screw slide drives the carrier platform to move along the Y direction, with the moving distance set to 6mm (displacement accuracy controlled to ±0.05mm). After moving into position, the calibration plate is kept in a stable posture. The above focusing and Sham angle fine-tuning process is repeated. After ensuring that the image quality meets the requirements, the second calibration is performed, and the calibration file "Calibration_02" is generated and saved.

[0066] Repeat the calibration process as described above. After each calibration, move the calibration plate 6mm along the Y direction. Move the plate 6mm along the Y direction for a total of five times, and complete six calibration operations. The center position of the calibration plate is evenly distributed along the Y direction, completely covering the target measurement area of ​​80mm x 80mm x 30mm.

[0067] After all calibrations are completed, the six sets of calibration files are checked for consistency using calibration software to ensure that the deviation of each set of calibration parameters is within ±0.5 pixels. Once the check is passed, the entire calibration process is complete.

[0068] After the calibration process is completed, remove the calibration plate fixing device inside the cavitation water cylinder and take it out to ensure that there are no foreign objects left inside the cavitation water cylinder; then put the top cover of the cavitation water cylinder on and seal it with the sealing device to prevent water leakage during the experiment.

[0069] Clean water is added to the cylinder to the rated level through the liquid injection system of the cavitation water cylinder. During the filling process, the water flow rate is controlled to avoid the generation of air bubbles. After the liquid level reaches the preset value, tracer particles of appropriate particle size are added to the water, and the tracer particles are evenly dispersed in the water by the stirring device.

[0070] Turn on the laser and preheat for 10 minutes. After the laser output stabilizes, start the four cameras and the laser to work synchronously through the synchronizer. Perform the first set of flow field data acquisition according to the preset shooting parameters. The acquisition time is 10 seconds. After the acquisition is completed, save the data with the file name "Measurement_01".

[0071] The imaging component is driven to move along the Y direction by a horizontal moving device, with the moving distance precisely controlled at 6 mm. After moving into position, the system is kept stable for 30 seconds to ensure that the flow field returns to stability. Then, the second set of flow field data is collected and saved as "Measurement_02".

[0072] The above-described moving-acquisition process is repeated until data acquisition is completed at all preset locations within the target measurement area. During the acquisition process, the imaging quality and tracer particle distribution are observed in real time using monitoring software to ensure data validity.

[0073] Example 3:

[0074] The implementation steps of the online self-calibration and pose optimization method according to the experimental method for the device used to capture Tomo-PIV as described in Example 2 are as follows:

[0075] To further improve the long-term stability of the measurement system and its adaptability to complex environments, based on the above calibration and measurement procedures, this invention also implements an online self-calibration and pose optimization method. This method runs synchronously during flow field data acquisition and specifically includes the following steps:

[0076] S1. Initial reference establishment: Before starting the formal flow field measurement, strictly follow the steps mentioned above to complete the multi-position calibration and obtain a set of high-precision initial camera parameters. This includes the intrinsic parameter matrix, distortion coefficients, and extrinsic parameter rotation matrix and translation vector for each camera, and... Stored as a baseline reference value for parameter optimization.

[0077] S2. Synchronous Extraction of Flow Field Image Features: After step-by-step acquisition of flow field data using a horizontal moving device, for the synchronized image sequence acquired at each acquisition location from four high-speed cameras, global bundling and optimization are performed using all spatiotemporal data (all locations, all time frames), with the algorithm automatically processing in parallel. Stable natural feature points are extracted in real time from the flow field image containing tracer particles. The feature extraction algorithm combines particle image intensity, local gradient information, and temporal persistence checks to screen out stable feature points.

[0078] S3. Multi-view Feature Matching and Tracking: For the feature points extracted in step S2, a feature description and matching algorithm is used to establish an accurate set of two-dimensional feature point correspondences among the images from the four cameras at the same time. Simultaneously, stable feature points are tracked across frames in the time series.

[0079] S4. Bundling Adjustment and Parameter Fine-tuning: This involves adjusting and optimizing the feature point correspondences obtained in step S3 from multiple perspectives and time points. With the parameters of the currently used camera (Initially) Together with a bundled adjustment and optimization model, the feature points are input. This model uses the three-dimensional spatial coordinates of the feature points. And camera extrinsic parameters (rotation matrix) Translation vector The increment of ) As optimization variables, the objective function is to minimize the sum of squared reprojection errors of all feature points at all camera views and times in which they occur, i.e.:

[0080]

[0081] in, Let be the camera projection function, which includes a lens distortion model. This nonlinear least squares problem is solved using iterative optimization algorithms (such as the Levenberg-Marquardt method).

[0082] S5. Dynamic parameter update and status monitoring: Optimize the camera extrinsic parameters obtained in step S4. Applying the current parameters yields the updated camera parameters. This is used for subsequent tomographic particle field reconstruction. The system monitors the magnitude of parameter updates in real time during the optimization process. The system will also consider the average reprojection error. If any of these values ​​exceeds a preset safety threshold (e.g., a translation change greater than 0.05 mm, or a sudden increase in the average error of 1 pixel), the system is deemed to have experienced a potential abnormal disturbance and will trigger an alarm signal. The system will automatically record the current state and prompt the user whether to continue. If the user chooses to continue, the system can temporarily switch to a degraded mode, such as using only the most recent reliable parameters for reconstruction, and highlighting the data from that period after the experiment. Simultaneously, the system will prompt the user to perform a complete calibration before the next planned experiment.

[0083] S6. Closed-loop application: Camera parameters updated after step S5 This will be immediately applied to 3D tomographic reconstruction calculations at current and subsequent acquisition locations, ensuring that even during long-term experiments, the geometric model upon which the reconstruction depends remains consistent with the actual physical system, which may experience minor drifts.

[0084] Through the above-described online self-calibration process, the method of this invention upgrades the traditional "static calibration-dynamic measurement" mode to an intelligent mode of "static initial calibration-dynamic continuous optimization," effectively suppressing the system error drift introduced by factors such as mechanical vibration and temperature changes, and significantly improving the overall consistency and reliability of large-scale, long-term flow field scanning measurement data.

[0085] 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. A device for filming Tomo-PIV, characterized in that, include: Water prism (5), cavitation water tube (6), laser (7), Tomo-PIV bracket assembly (8), the cavitation water tube (6) is mounted on the Tomo-PIV bracket assembly (8), and the cavitation water tube (6) has multiple high-speed cameras on its exterior; The Tomo-PIV support assembly (8) includes a vertical lifting device (9), a horizontal moving device (10), and a calibration device (11). The calibration device (11) includes two support frames (21), which are connected by a crossbeam (23). A ball screw slide (19) is mounted on the crossbeam (23), a calibration plate fixing device (20) is mounted on the ball screw slide (19), and a calibration plate (22) is mounted on the calibration plate fixing device (20). A water prism bracket (18) is provided on the support frame (21), and a water prism (5) is installed in the water prism bracket (18).

2. The device for shooting Tomo-PIV according to claim 1, characterized in that, The vertical lifting device (9) includes an upper frame (24) and a lower reinforcing frame (13). A lifting support leg (12) is installed between the upper frame (24) and the lower reinforcing frame (13). A slide (15) is installed on the upper frame (24), and a fixed crossbeam (14) is installed on the lower reinforcing frame (13).

3. The device for shooting Tomo-PIV according to claim 1, characterized in that, The horizontal moving device (10) is connected to the slide table (15) of the vertical lifting device (9) via a slider (16), so that the horizontal moving device (10) moves in a direction perpendicular to the water flow of the cavitation water cylinder (6).

4. The device for filming Tomo-PIV according to claim 3, characterized in that, The horizontal moving device (10) includes a camera base (25) and a laser base (17), on which a laser (7) is mounted.

5. The device for shooting Tomo-PIV according to claim 4, characterized in that, The laser base (17) has a three-dimensional adjustment mechanism.

6. The device for filming Tomo-PIV according to claim 1, characterized in that, Multiple high-speed cameras, including high-speed camera one (1), high-speed camera two (2), high-speed camera three (3), and high-speed camera four (4), are respectively installed and fixed on the camera base (25) of the horizontal moving device (10), so that they are located on the left, left rear, right, and right rear sides of the cavitation water cylinder, respectively. The high-speed camera two (2) and the high-speed camera four (4) are perpendicular to the water prism (5).

7. An experimental method for using the device for filming Tomo-PIV as described in any one of claims 1-6, characterized in that, The method includes the following steps: Perform initial positioning and debugging of the equipment. After the initial positioning and debugging are completed, start the calibration software to perform the first calibration operation, collect the imaging data of the four cameras and generate a calibration file, which is then saved to the system storage directory. The control system of the ball screw slide (19) drives the carrier platform to move along the Y direction by a set distance; after moving to the position, the calibration plate is kept stable and the above focusing and Sham angle fine-tuning process is repeated. After ensuring that the imaging quality meets the requirements, the second calibration is performed, and the calibration file is generated and saved. Repeat the calibration process as described above. After each calibration, move the calibration plate a set distance along the Y direction. Move the plate five times in total to complete six calibration operations. The center positions of the calibration plate in the six calibrations are evenly distributed along the Y direction, completely covering the target measurement area. After all calibrations are completed, the six sets of calibration files are checked for consistency using calibration software to ensure that the deviation of each set of calibration parameters is within ±0.5 pixels. Once the check is passed, the entire calibration process is complete. After the calibration process is completed, remove the calibration plate fixing device inside the cavitation water cylinder and take it out to ensure that there are no foreign objects left inside the cavitation water cylinder; then put the top cover of the cavitation water cylinder on and seal it with the sealing device to prevent water leakage during the experiment. Clean water is added to the cylinder to the rated level through the liquid injection system of the cavitation water cylinder. During the filling process, the water flow rate is controlled to avoid the generation of air bubbles. After the liquid level reaches the preset value, tracer particles of appropriate particle size are added to the water, and the tracer particles are evenly dispersed in the water by the stirring device. Turn on the laser and preheat for 10 minutes. After the laser output stabilizes, start the four cameras to work synchronously with the laser through the synchronizer. Perform the first set of flow field data acquisition according to the preset shooting parameters. The acquisition time is 10 seconds. After the acquisition is completed, save the data to the folder. The imaging component is driven to move along the Y direction by a horizontal moving device, and the moving distance is precisely controlled to a set distance. After moving into position, the system is kept stable for a period of time to ensure that the flow field returns to stability. Then, the second set of flow field data is collected and saved. Repeat the above-described movement and acquisition process until data acquisition is completed at all preset locations within the target measurement area. During the acquisition process, monitor the imaging quality and tracer particle distribution in real time using monitoring software to ensure data validity.

8. The experimental method for using the device for photographing Tomo-PIV according to claim 7, characterized in that, The initial positioning and debugging of the equipment includes: Perform the pre-experiment preparation procedure and assemble the water prism and high-speed camera into the preset installation positions; Connect the signal output terminals of multiple high-speed cameras to the signal input terminal of the synchronizer and the network port of the switch, respectively. The laser is positioned and its emission angle is adjusted by the three-dimensional adjustment mechanism of the laser base (17) according to the spatial coordinate range of the target flow field, so that the laser beam can completely cover the flow field area to be measured; after the laser beam is positioned, the control signal terminal of the laser is connected to the signal output terminal of the synchronizer. Open the top cover of the cavitation water cylinder (6), install the calibration plate (22) on the calibration plate fixing device (20), place the fixing device with the calibration plate inside the cavitation water cylinder (6), and adjust the height of the calibration plate through the drive system of the ball screw slide (19) according to the spatial position parameters of the target flow field, so that the center plane of the calibration plate (22) coincides with the Z-direction center plane of the flow field; Adjust the height of the vertical lifting device so that the center of the lenses of the four cameras is at the same horizontal level as the center of the calibration plate; then focus the four cameras separately.

Images