A flow field measurement system and method for an oscillating water column wave energy conversion device based on TR-PIV method

Abstract

The present invention discloses a flow field measurement system and method for an oscillating water column wave energy conversion device based on the TR-PIV method, which provides experimental conditions for analyzing the energy capture and wave elimination mechanism and flow field evolution law of the oscillating water column wave energy conversion device. The system comprises three subsystems: a wave making and monitoring subsystem, an image shooting subsystem and a data control and processing system. Among them, the wave making and monitoring subsystem is used to realize the monitoring of macroscopic hydrodynamic phenomena of the simulated oscillating water column wave energy conversion device under the required wave conditions; the image shooting subsystem is used to realize the visualization and image capture of the flow field; the data control and processing system is responsible for coordinating and controlling the work between the wave making and monitoring subsystem and the image shooting subsystem, and performing data processing. The measurement system of the present invention improves the research capabilities of the flow field characteristics and hydrodynamic performance of the oscillating water column wave energy conversion device, and is used by the academic community to conduct mechanism analysis and product performance optimization for the oscillating water column wave energy conversion device.

Description

Technical Field

[0001] The present invention belongs to the field of PIV technology flow field measurement, relates to a wave energy utilization device, and in particular to a flow field measurement system and method of an oscillating water column type wave energy conversion device based on a TR-PIV method. Background Art

[0002] Energy is an important material basis for human survival and development. Among various renewable energy technologies, renewable energy systems such as solar energy systems, wind energy, geothermal energy, biomass energy and hydropower have received good attention and promising investments. Among them, hydropower or hydroelectric power, tidal energy, wave energy and ocean thermal energy conversion (OTEC) are all considered water-based energy systems. In terms of installed capacity and power generation, hydropower is considered the main type. Wave energy is the general term for the kinetic energy and potential energy stored in the waves generated by the seawater on the ocean surface after absorbing wind energy. It not only has a high energy density, but also has advantages such as a wide distribution area compared to tidal energy. It has been widely studied in recent years.

[0003] A comprehensive understanding of the flow field characteristics around an oscillating water column wave energy converter is of great significance for improving its energy extraction. In the study of oscillating water column wave energy converters, converting sufficient kinetic energy into the vertical motion of the water column is a key consideration in the design of OWC converters. However, the interaction mechanism between waves and oscillating water column wave energy converters is still unclear. Most studies regard the flow field of oscillating water column wave energy converters as a black box, and only study macroscopic physical phenomena such as wave reflection and energy extraction characteristics, lacking an investigation of its internal mechanism. However, turbulence and vortex formation in the flow field are one of the main energy loss mechanisms of kinetic energy. Its generation, development, evolution, and interaction with objects will affect and determine the momentum exchange and energy transfer of the flow field, which has an impact on the energy extraction of oscillating water column wave energy converters.

[0004] The measurement system of the present invention improves the research capabilities for flow field measurement and hydrodynamic performance of oscillating water column wave energy conversion devices, and can provide experimental conditions for the academic community to conduct mechanism analysis and product performance optimization for oscillating water column wave energy conversion devices. Summary of the invention

[0005] The present invention discloses a flow field measurement system for an oscillating water column type wave energy conversion device based on the TR-PIV method, which provides experimental conditions for analyzing the energy-capturing and wave-dissipating mechanism and flow field evolution law of the oscillating water column type wave energy conversion device, improves the research capabilities on the flow field measurement and hydrodynamic performance of the oscillating water column type wave energy conversion device, and can provide experimental conditions for the academic community to conduct mechanism analysis and product performance optimization on the oscillating water column type wave energy conversion device.

[0006] In order to realize the above technical functions, the present invention adopts the following technical solutions:

[0007] The present invention firstly discloses a flow field measurement system of an oscillating water column type wave energy conversion device based on the TR-PIV method, wherein the system comprises three subsystems, namely: a wave making and monitoring subsystem, an image shooting subsystem and a data control and processing system;

[0008] The wave-making and monitoring subsystem comprises a wave tank, a wave maker and a wave height meter; the wave maker is arranged at one end of the wave tank, and is used to create the required wave conditions; an oscillating water column type wave energy conversion device is fixed at a middle position in the wave tank far from the end where the wave maker is located, so as to ensure that there are sufficient data that are not affected by secondary reflected waves during the flow field measurement process; the wave height meter is arranged inside each air chamber of the oscillating water column type wave energy conversion device, and is located on a side away from the laser light page and the high-speed camera, and is used to detect the water level inside the oscillating water column type wave energy conversion device in real time;

[0009] The image capture subsystem includes a continuous laser, a CMOS high-speed camera, a first control track, and a second control track; the first control track is placed on the side of the wave tank, and the second control track is placed below the wave tank. Both the first control track and the second control track are horizontal to the wave propagation direction. The length of the first control track and the second control track should exceed the width of the oscillating water column wave energy conversion device, and the full flow field can be captured through multiple windows; the continuous laser is installed on the second control track through a sliding base, below the center line of the tank, to avoid the side wall effect of the wave tank from interfering with the measurement result, and can emit linear continuous laser. A Powell lens is installed on the optical axis of the continuous laser, and the Powell lens refracts the laser light emitted by the continuous laser into a laser light page, and the laser light page is parallel to the wave propagation direction; the CMOS high-speed camera is installed on the first control track through another sliding base, and is used to collect full flow field image data;

[0010] The data control and processing system comprises a data collector, a synchronizer and a control computer. The data collector is connected to the wave height meter and the control computer, collects the data measured by the wave height meter into the control computer, and obtains the velocity field around the oscillating water column type wave energy conversion device by performing data processing through the control computer, and obtains the flow field Q value and vortex pseudo-energy of the flow field around the oscillating water column type wave energy conversion device based on the velocity field calculation; the synchronizer is connected to the data collector, the control computer and the CMOS high-speed camera, and is used for synchronously triggering the wave height meter and the CMOS high-speed camera.

[0011] Furthermore, the wave-making and monitoring subsystem also includes a wave-breaking beach, which is fixed at the end of the wave tank opposite to the wave maker and is used to reduce the wave energy projected to the end of the wave tank. The wave-breaking beach should be made of porous medium material and meet the requirement that the height of the reflected wave is lower than 5% of the incident wave height reaching the corresponding wave-breaking beach.

[0012] Furthermore, the wave maker adopts a push-plate wave maker, which can produce a variety of regular waves and irregular waves required for the experiment.

[0013] Furthermore, the wave maker can create wave conditions similar to those in my country's coastal waters based on the Froude number.

[0014] Furthermore, in the image capturing subsystem, three laser calibration devices are arranged on the first control track and the second control track, and the three laser calibration devices are respectively used to calibrate the vertical position, lateral position of the corresponding control track and the position of the sliding base on the corresponding control track; the image capturing subsystem also includes marker particles to realize flow visualization in the complex flow field of energy capture and wave elimination.

[0015] Furthermore, the marker particles are made of silver-plated glass beads or polystyrene particles, and the density of the marker particles is close to that of water, and the marker particles have good followability when moving with water.

[0016] Furthermore, the synchronizer can trigger the CMOS high-speed camera and the wave height meter to start data recording at the same time, and ensure that each frame of image data and the wave height meter monitoring data are synchronized in time.

[0017] Furthermore, the CMOS high-speed camera keeps the camera shooting direction facing the wave tank when it moves on the moving slide; the continuous laser and the CMOS high-speed camera installed on the moving slide move synchronously to ensure that the shooting area is illuminated by the continuous laser. The distance and vertical height between the moving slide where the continuous laser and the CMOS high-speed camera are installed and the wave tank are adjustable to meet the requirements of covering the entire flow field in the shooting area, and the track direction is always parallel to the axis direction of the wave tank during the adjustment process.

[0018] Furthermore, the control computer can realize image data stitching function, image enhancement function and data pre-processing function.

[0019] The present invention also discloses a flow field measurement method based on the flow field measurement system of the oscillating water column type wave energy conversion device, the method comprising:

[0020] 1) The CMOS high-speed camera and the continuous laser are synchronously moved so that the CMOS high-speed camera faces the wave tank and can capture the entire flow field around the oscillating water column wave energy conversion device at several positions, and the several positions are determined as the window positions for subsequent shooting;

[0021] 2) The control computer controls the wave maker to start wave making, and the wave height meter detects wave propagation. When a stable incident wave is detected to reach the oscillating water column wave energy conversion device, the control computer issues a command to control the CMOS high-speed camera and the wave height meter to start data collection through the synchronizer. Before the reflected wave reaches the oscillating water column wave energy conversion device or the CMOS high-speed camera reaches the storage capacity, the wave height meter data collection and the wave maker wave making are stopped;

[0022] 3) Repeat step 2) multiple times until 40-100 wave cycles are captured so that the collected image data meets the convergence conditions for subsequent phase averaging;

[0023] 4) Move the CMOS high-speed camera and continuous laser to the next window position and shoot again until all window positions are shot to obtain full flow field image data;

[0024] 5) The images in the flow field image sequence are enhanced by high-pass filtering, the enhanced images are processed by calculation, the calculated results are phase averaged to remove noise data, and the phase averaged images of all window positions are stitched to obtain the velocity field around the oscillating water column wave energy conversion device.

[0025] Furthermore, the computational processing of the enhanced image is specifically as follows:

[0026] (a) Each adjacent frame of the enhanced image is evenly divided into several query windows. The size of the query window for the first division is 32*32pix 2 ;

[0027] (b) Taking the query window as the analysis unit, the adjacent images in the flow field image sequence are cross-correlated. The velocity of the water body at the position corresponding to the query window can be calculated by finding the position where the peak of the cross-correlation function appears:

[0028]

[0029]

[0030] In the formula, u and v represent the horizontal and vertical speeds of the water body at the position corresponding to the query window, respectively; w is the number of calculation time intervals, which is 1; Δt represents the time interval between two frames of images taken by the CMOS high-speed camera; Δx and Δy represent the displacement of the water body at the position corresponding to the query window in the two frames obtained by cross-correlation calculation;

[0031] (c) The enhanced image is re-divided into smaller query windows, and the smaller query windows divided this time are translated according to the displacement of the water body obtained by the larger query window divided last time, and the calculation of step (b) is repeated;

[0032] (d) Repeat step (c) 3 times or more to obtain the velocity field at all window positions;

[0033] (e) selecting every two frames of enhanced images at time intervals of 2Δt, 8Δt, and 20Δt, repeating the steps, and calculating the velocity of the water body, wherein the number of calculation time intervals w is 2, 8, and 20 respectively when selecting the enhanced images at time intervals of 2Δt, 8Δt, and 20Δt, and obtaining the velocity fields of all window positions at different time intervals;

[0034] (d) Compare the values ​​of the cross-correlation function calculated at different time intervals, select the water velocity corresponding to the cross-correlation function value greater than 0.95, and select the water velocity calculated at the minimum time interval for each position as the flow velocity measurement result at that position. The flow velocity measurement results obtained after screening are recombined to form the final result flow field.

[0035] Furthermore, when stitching images, the width of the overlapping area should be greater than twice the width of the PIV cross-correlation window error edge of the two windows, and the images are stitched by taking a weighted average of the overlapping areas of adjacent windows according to the distance from the edge.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) The present invention adopts a combination of a CMOS high-speed camera and a continuous laser, and is equipped with a high-pass filter image enhancement technology to achieve high-time resolution photography of the flow field, overcoming the problem of insufficient time resolution of flow field analysis due to low photography frequency in the traditional PIV method, providing more detailed flow field evolution process data, and improving the analysis capability of the flow field of the rapidly evolving oscillating water column wave energy conversion device;

[0038] (2) The present invention adopts a multi-step solution method and uses different query windows from large to small for cross-correlation analysis, which overcomes the problem of low spatial resolution of the result caused by the traditional PIV method using a larger query window to increase the maximum velocity measurement range. While achieving a larger velocity measurement range in the oscillating flow field, it ensures that the flow field measurement results have a higher spatial resolution;

[0039] (3) The present invention adopts a multi-time interval algorithm to overcome the problem that it is difficult to accurately solve all flow velocities with large differences in the flow field when a single time interval is used to solve the flow field. It has higher accuracy when solving complex flow fields with large velocity gradients involving phenomena such as reciprocating flow of water and vortex motion, and improves the ability to analyze complex flow phenomena in the flow field around an oscillating water column wave energy conversion device. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1It is a schematic diagram of the present invention.

[0041] Figure 2 It is a partial schematic diagram of the present invention.

[0042] Figure 3 It is a schematic diagram of the velocity field measurement result of the present invention.

[0043] Figure 4 It is a schematic diagram of the image stitching method adopted by the present invention.

[0044] Figure 5 It is a schematic diagram of the Q criterion result of the present invention.

[0045] Figure 6 It is a schematic diagram of the vortex simulation energy result of the present invention.

[0046] In the figure: 1. wave tank, 2. wave maker, 3. wave-breaking beach, 4. oscillating water column wave energy conversion device, 5. wave height meter, 6. CMOS high-speed camera, 7. continuous laser, 8. first control track, 9. second control track, 10. control computer, 11. data acquisition device, 12. laser light page, 13. CMOS high-speed camera shooting angle, 14. sliding base. DETAILED DESCRIPTION

[0047] In order to facilitate the understanding of the present invention, embodiments of the present invention are described below in conjunction with the accompanying drawings. Those skilled in the art should understand that the following description is only for the convenience of explaining the invention and is not intended to be a specific limitation on the scope of the invention.

[0048] The experimental steps of this experimental device are:

[0049] Before the experiment, several wave height meters 5 should be arranged in the wave tank 1, and the wave conditions of the experimental conditions, including water depth, wave height and period, should be calculated by the Froude number similarity principle. The water level in the wave tank 1 should be raised to an appropriate height, and the accuracy of each wave height meter 5 should be calibrated. The required wave parameters should be input into the wave maker 2, and wave making should be started. The generated wave parameters should be monitored to see if they meet the experimental requirements and the parameter settings should be corrected.

[0050] Preliminary experimental equipment installation for this experiment:

[0051] Installation arrangement of the wave-making and monitoring subsystem: The wave tank (1) in the wave-making and monitoring subsystem described in the experiment is a rectangular tank with a length of 25 m, and the side of the wave tank is transparent; the width of the wave tank 1 is greater than or equal to the width of the oscillating water column type wave energy conversion device 4 to be tested, and the oscillating water column type wave energy conversion device can be placed exactly in the wave tank 1, and the experiment satisfies the two-dimensional wave experiment hypothesis. The upper part of the oscillating water column type wave energy conversion device 4 is firmly fixed to the side wall of the wave tank 1 by a clamp so that it cannot translate or rotate in the wave tank 1.

[0052] Installation and arrangement of the image shooting subsystem: After the oscillating water column wave energy conversion device 4 is fixed and installed, the installation and arrangement of the image shooting subsystem begins. First, fix the continuous laser 7 on the base 14 of the second control track 9, and place the second control track 9 below the wave tank 1. Adjust the second control track 9 to be horizontal, and the direction is parallel to the long axis direction of the wave tank 1, that is, the wave propagation direction. At the same time, the second control track 9 should be placed below the oscillating water column wave energy conversion device 4 to be tested, and located in the middle of the width of the wave tank 1. Turn on the power of the continuous laser 7 and adjust the lens of the continuous laser 7 to make the brightness of the laser light page 12 uniform and parallel to the wave propagation direction. After the continuous laser 7 and the second control track 9 are installed, install the first control track 8 on the side of the oscillating water column wave energy conversion device 4 at a certain distance from the wave tank 1, and adjust the track to be horizontal, and the direction is parallel to the wave propagation direction. Install the CMOS high-speed camera 6 on the base 14 of the first control track 8, turn on the power of the CMOS high-speed camera 6 to observe whether the range of the shooting area meets the experimental requirements. If not, adjust the distance between the first control track 8 and the wave tank 1.

[0053] Calibration of the image capture subsystem: Move the CMOS high-speed camera 6 and the continuous laser 7 so that the CMOS high-speed camera 6 faces the wave tank 1 and can capture the entire flow field around the oscillating water column wave energy conversion device 4 at several positions. Place markers in the adjacent and overlapping areas of several windows and capture them to guide the subsequent image stitching. At the same time, determine the ratio coefficient between the pixel points of the captured image and the actual length (cm) according to the size of the marker. After completing the calibration capture of all positions, remove the markers in the flow field.

[0054] Installation and setting of data control and processing system: In the experiment, the wave height meter 5 is connected to the data collector 11, and the signal of the data collector 11 is transmitted to the control computer 10. The synchronizer is connected to the data collector 11, the CMOS high-speed camera 6 and the control computer 10. After the control computer 10 issues an instruction, the data collector 11 can start recording the wave height meter 5 data, and the CMOS high-speed camera 6 starts to shoot the flow field. The control computer 10 is connected to the wave maker 2 to control the start and stop of the wave maker 2.

[0055] The installed flow field measurement system of the oscillating water column wave energy conversion device based on the TR-PIV method is as follows Figure 1 As shown, Figure 2 The positional relationship of each subsystem in the system except the wave tank 1, the wave maker 2 and the wave-breaking beach 3 is shown.

[0056] Experimental conduct: add marker particles into the wave tank 1, mix the components around the oscillating water column wave energy conversion device 4, control the wave maker 2 through the control computer 10 to start wave making, detect wave propagation through the wave height meter 5, when the stable incident wave reaches the oscillating water column wave energy conversion device 4, the control computer 10 issues a command to control the CMOS high-speed camera 6 and the data acquisition device 11 through the synchronizer to start data collection, before the reflected wave reaches the oscillating water column wave energy conversion device 4 or after a batch of data is shot by the CMOS high-speed camera 6, stop the wave height meter 5 data acquisition and the wave maker 2 wave making. Repeat several times so that the collected image data meets the analysis standard. Move the CMOS high-speed camera 6 and the continuous laser 7 to the next shooting position, shoot again, until all window positions are shot.

[0057] Data processing: The captured image is enhanced by high-pass filtering. The specific method of high-pass filtering is: the image of the grayscale distribution in the spatial domain is converted to the frequency domain through two-dimensional Fourier transform, and multiplied with the high-pass filter function in the frequency domain to enhance the high-frequency information in the image and filter the low-frequency information. Finally, the result is converted back to the spatial domain through the Fourier inverse transform function to realize the high-pass filtering process and highlight the marker particles. The calculation method is as follows:

[0058] F(U,V)=ζ[f(x,y)]

[0059] G(U,V)=F(U,V)·H(U,V)

[0060] g(x,y)=ζ -1 [G(U,V)]

[0061] Where f(x,y) represents the grayscale matrix of the original image, ζ[.] represents the two-dimensional Fourier transform operation, F(.) represents the frequency domain matrix obtained after the original image is transformed by two-dimensional Fourier transform, H(.) represents the high-pass filter function, G(.) represents the enhanced frequency domain matrix, ζ -1 [.] represents the two-dimensional Fourier inverse transform operation, and g(.) represents the grayscale matrix of the enhanced image.

[0062] The enhanced image is processed by cross-correlation calculation. The basic principle is:

[0063] First, except for the first and last 10 frames, every two adjacent frames of the enhanced image are evenly divided into several query windows. The size of the query window for the first division is 32*32pix 2 , taking the query window as the analysis unit, the cross-correlation calculation is performed on the adjacent images in the flow field image sequence, which can be realized by the function normxcorr2 in the MATLAB software. The velocity of the water body represented by the query window can be calculated by finding the position where the peak of the cross-correlation function appears:

[0064]

[0065]

[0066] Where u and v represent the velocities in the horizontal and vertical directions, respectively; w is the number of calculation time intervals, which is 1; Δt represents the time interval between two frames of images taken by the CMOS high-speed camera; Δx and Δy represent the displacement of the water body at the position corresponding to the query window obtained by cross-correlation calculation in the two frames.

[0067] The enhanced image is re-divided evenly into query windows smaller than the last query window. The smaller query window is first translated according to the displacement of the water body obtained by the last query window. The above calculation is repeated for 3 times or more to obtain the velocity field of all window positions.

[0068] Then, except for the first and last 10 frames, select every two frames of enhanced images with 2 times, 8 times, and 20 times the time interval, repeat the above operation, and calculate the speed of the water body. During the calculation process, the number of time intervals w is equal to 2, 8, and 20 when selecting enhanced images with 2 times, 8 times, and 20 times the time interval, respectively, to obtain the velocity field of all window positions under different time intervals.

[0069] Finally, the water velocity solution results obtained at each time interval are screened in order from small to large. In the velocity screening process, the peak value of the cross-correlation function obtained in the cross-correlation calculation process is used as the judgment basis. Specifically, the water velocity corresponding to the cross-correlation function value exceeding 0.95 is screened, and the water velocity calculated at the minimum time interval at each position is selected as the flow velocity measurement result at that position. Finally, the screened flow velocity measurement results are recombined to form the final result flow field.

[0070] Due to the strong turbulence in the oscillating flow field, the phase of the flow field needs to be averaged to obtain regular flow field results. In the experiment, the wave height meter and the CMOS high-speed camera were triggered simultaneously. The water level signal captured by the wave height meter can be used to determine the phase information corresponding to each frame of the picture. The velocity field with the same phase is averaged to eliminate the influence of error vectors and outliers in the instantaneous flow field solution, and improve the reliability and data accuracy of the flow velocity solution in the flow field. The calculation results are shown in Figure 2. Figure 3 As shown, each sub-figure represents the flow field velocity distribution at 1 / 6 wave period, 1 / 3 wave period, 1 / 2 wave period, 2 / 3 wave period, 5 / 6 wave period and 1 wave period respectively.

[0071] After the above calculations are completed, all phase-averaged images are stitched together to obtain the velocity field around the oscillating water column wave energy conversion device 4. The image stitching method used in this embodiment is as follows: Figure 4 As shown in the figure, the Q criterion and vortex pseudo-energy are calculated based on the velocity field, highlighting the characteristics of vortex and energy dissipation in the flow field. The calculation method of the Q criterion is as follows:

[0072]

[0073] Where Q is the Q criterion around the oscillating water column wave energy conversion device, ||.|| represents the modulus of the matrix, Ω is the velocity antisymmetric tensor, and E is the velocity symmetric tensor. The calculation formulas are:

[0074]

[0075]

[0076] in, represents the velocity gradient in the horizontal direction, represents the velocity gradient in the vertical direction. The calculation results of the Q criterion are as follows Figure 5 As shown, each sub-figure represents the Q-criterion distribution of the flow field at 1 / 6 wave period, 1 / 3 wave period, 1 / 2 wave period, 2 / 3 wave period, 5 / 6 wave period and 1 wave period respectively.

[0077] The calculation method of the vortex pseudo-energy is as follows:

[0078]

[0079] Among them, ε represents the vortex pseudo-energy around the oscillating water column wave energy conversion device, s represents the area of ​​the integration region, ω represents the vorticity, and the calculation formula of the vorticity is:

[0080]

[0081] The vortex energy calculation results are as follows Figure 6 As shown, each sub-figure represents the vortex pseudo-energy distribution of the flow field at 1 / 6 wave period, 1 / 3 wave period, 1 / 2 wave period, 2 / 3 wave period, 5 / 6 wave period and 1 wave period respectively.

[0082] Through the above description, those skilled in the art can make various changes and modifications within the scope of the technical concept of the present invention without departing from the scope of the present invention. Matters not covered in the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A flow field measurement system for an oscillating water column wave energy conversion device based on the TR-PIV method, characterized in that: The system comprises three subsystems, namely: wave making and monitoring subsystem, image capturing subsystem and data control and processing system; The wave-making and monitoring subsystem comprises a wave tank (1), a wave maker (2), an oscillating water column type wave energy conversion device (4) and a wave height meter (5); the wave maker (2) is arranged at one end of the wave tank (1) and is used to create required wave conditions; the oscillating water column type wave energy conversion device (4) is fixed at a middle position of the wave tank (1) far from the end where the wave maker is located; the wave height meter (5) is arranged inside the oscillating water column type wave energy conversion device and is used to detect the water level inside the oscillating water column type wave energy conversion device in real time; The image capture subsystem comprises a continuous laser (7), a CMOS high-speed camera (6), a first control track (8), and a second control track (9); the first control track is placed on the side of the wave tank (1), and the second control track is placed below the wave tank (1), and both the first control track and the second control track are horizontal to the wave propagation direction; the continuous laser (7) is mounted on the second control track (9) via a sliding base, and can emit linear continuous laser light; a Powell lens is mounted on the optical axis of the continuous laser (7), and the Powell lens refracts the laser light emitted by the continuous laser into a laser light page, and the laser light page is parallel to the wave propagation direction; the CMOS high-speed camera (6) is mounted on the first control track via another sliding base, and is used to collect full flow field image data; The data control and processing system comprises a data acquisition device (11), a synchronizer and a control computer (10); the data acquisition device (11) is connected to a wave height meter (5) and a control computer (10); the data acquired by the wave height meter (5) is collected into the control computer (10); the control computer (10) performs data processing to obtain a velocity field around an oscillating water column type wave energy conversion device; and the flow field Q value and vortex pseudo energy of the flow field around the oscillating water column type wave energy conversion device (4) are calculated based on the velocity field; the synchronizer is connected to the data acquisition device (11), the control computer (10) and a CMOS high-speed camera (6) and is used for synchronously triggering the wave height meter and the CMOS high-speed camera.

2. The flow field measurement system of the oscillating water column type wave energy conversion device based on the TR-PIV method as claimed in claim 1, characterized in that: The wave-making and monitoring subsystem further comprises a wave-breaking beach (3), which is fixed to the end of the wave tank (1) opposite to the wave generator and is used to reduce the wave energy projected to the end of the wave tank (1).

3. The flow field measurement system of the oscillating water column type wave energy conversion device based on the TR-PIV method as claimed in claim 1, characterized in that: The wave maker (2) is a push-plate type wave maker, which can produce a variety of regular waves and irregular waves required for the experiment.

4. The flow field measurement system of the oscillating water column type wave energy conversion device based on the TR-PIV method as claimed in claim 1, characterized in that: In the image capturing subsystem, three laser calibration devices are arranged on the first control track and the second control track, and the three laser calibration devices are respectively used to calibrate the vertical position, the lateral position and the position of the sliding base on the corresponding control track; the image capturing subsystem also includes marker particles to realize flow visualization in the complex flow field of energy capture and wave elimination.

5. The flow field measurement system of the oscillating water column type wave energy conversion device based on the TR-PIV method as claimed in claim 4, characterized in that: The marker particles are silver-plated glass beads or polystyrene particles. The density of the marker particles is close to that of water, and the marker particles have good followability when moving with water.

6. The flow field measurement system of the oscillating water column type wave energy conversion device based on the TR-PIV method as claimed in claim 1, characterized in that: The synchronizer can trigger the CMOS high-speed camera (6) and the wave height meter (5) to start data recording at the same time, and ensure that each frame of image data and the monitoring data of the wave height meter (5) are synchronized in time.

7. The flow field measurement system of the oscillating water column type wave energy conversion device based on the TR-PIV method as claimed in claim 1, characterized in that: When the CMOS high-speed camera (6) moves on the moving slide rail, the camera shooting direction is kept facing the wave tank (1); the continuous laser (7) and the CMOS high-speed camera (6) installed on the moving slide rail move synchronously to ensure that the shooting area is illuminated by the continuous laser (7); the distance and vertical height between the moving slide rail on which the continuous laser (7) and the CMOS high-speed camera (6) are installed and the wave tank (1) are adjustable to ensure that the shooting area covers the entire flow field, and during the adjustment process, the track direction is always parallel to the axial direction of the wave tank (1).

8. The flow field measurement system of the oscillating water column type wave energy conversion device based on the TR-PIV method as claimed in claim 1, characterized in that: The control computer (10) can realize image data splicing function, image enhancement function and data pre-processing function.

9. A flow field measurement method using the flow field measurement system of the oscillating water column type wave energy conversion device based on the TR-PIV method according to claim 1, characterized in that: The method comprises: 1) The CMOS high-speed camera (6) and the continuous laser (7) are synchronously moved so that the CMOS high-speed camera (6) faces the wave tank (1) and can capture the entire flow field around the oscillating water column type wave energy conversion device at a plurality of positions, and the plurality of positions are determined as the window positions for subsequent capturing; 2) The control computer (10) controls the wave generator (2) to start wave generation, and the wave height meter (5) detects wave propagation. When a stable incident wave is detected to arrive at the oscillating water column type wave energy conversion device, the control computer (10) issues an instruction to control the CMOS high-speed camera (6) and the wave height meter (5) through a synchronizer to start data collection. Before the reflected wave arrives at the oscillating water column type wave energy conversion device or after the storage capacity of the CMOS high-speed camera (6) is reached, the wave height meter (5) stops data collection and the wave generator (2) stops wave generation; 3) Repeat step 2) multiple times until 40-100 wave cycles are captured so that the collected image data meets the convergence conditions for subsequent phase averaging; 4) moving the CMOS high-speed camera (6) and the continuous laser (7) to the next window position, and taking pictures again, until all window positions are photographed, and obtaining full flow field image data; 5) The images in the flow field image sequence are enhanced by a high-pass filtering method, the enhanced images are processed by calculation to obtain the velocity field of each window, the velocity field of each window is phase averaged to remove noise data, and the phase averaged images of all window positions are stitched to obtain the velocity field around the oscillating water column wave energy conversion device (4).

10. The flow field measurement method according to claim 9, characterized in that: The calculation process of the enhanced image is specifically as follows: (a) Each adjacent frame of the enhanced image is evenly divided into several query windows. The size of the query window for the first division is 32*32pix 2 ; (b) Taking the query window as the analysis unit, the adjacent images in the flow field image sequence are cross-correlated. The velocity of the water body at the position corresponding to the query window can be calculated by finding the position where the peak of the cross-correlation function appears: In the formula, u and v represent the horizontal and vertical speeds of the water body at the position corresponding to the query window, respectively; w is the number of calculation time intervals, which is 1; Δt represents the time interval between two frames of images taken by the CMOS high-speed camera; Δx and Δy represent the displacement of the water body at the position corresponding to the query window in the two frames obtained by cross-correlation calculation; (c) The enhanced image is re-evenly divided into smaller query windows, and the smaller query windows divided this time are translated according to the displacement of the water body obtained by the larger query window divided last time, and the calculation of step (b) is repeated; (d) Repeat step (c) 3 times or more to obtain the velocity field at all window positions; (e) selecting every two frames of enhanced images at time intervals of 2Δt, 8Δt, and 20Δt, repeating steps (a)-(d), and calculating the velocity of the water body, wherein the number of calculation time intervals w is 2, 8, and 20 when selecting enhanced images at time intervals of 2Δt, 8Δt, and 20Δt, respectively, to obtain velocity fields at all window positions calculated at different time intervals; (d) Compare the values ​​of the cross-correlation function calculated at different time intervals, select the water velocity corresponding to the cross-correlation function value exceeding 0.95, and select the water velocity calculated at the minimum time interval for each position as the flow velocity measurement result at that position. If the cross-correlation function values ​​of all calculated results are less than 0.95, take the result with the largest cross-correlation function value, and reorganize the flow velocity measurement results obtained after screening to form the final result flow field.

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