Propeller PIV phase splicing device and method based on time sequence

Abstract

The invention provides a propeller PIV phase splicing device and method based on a time sequence, and belongs to the technical field of flow field measurement, and the device comprises a propeller with a dynamometer, the propeller is located in a test water tank, the propeller is provided with a photosensitive patch sensor, a positioning laser is arranged above the propeller, the positioning laser is located outside the test water tank, and the power meter is connected with the power meter. A particle image acquisition camera and a pulse laser are arranged outside the test water tank; the propeller, the positioning laser, the particle image acquisition camera, the pulse laser and the photosensitive patch sensor are respectively connected with the synchronous signal controller, and the synchronous signal controller is connected with the active control processing system. According to the method, accurate capture and seamless splicing of transient flow fields of the propeller under different rotation phases can be realized, so that a complete periodic three-dimensional flow field structure with high temporal-spatial resolution is reconstructed, and reliable data support is provided for propeller hydrodynamic performance optimization, eddy mechanism and noise characteristic research.

Description

Technical Field

[0001] This invention belongs to the field of flow field measurement technology, specifically relating to a propeller PIV phase splicing device and method based on time series. Background Technology

[0002] When particle image velocimetry (PIV) is applied to the phase analysis of periodic rotating flow fields such as propeller wakes, although flow field data at different phases can be calibrated using the propeller's initial phase and rotation period, reconstructing a complete cycle requires numerous repeated experiments and manual phase adjustments. This process is cumbersome, inefficient, and cannot guarantee strict repeatability of experimental conditions, making it difficult to capture transient flow details between adjacent phases. Given the limitations of the propeller rotation period and camera image acquisition, as well as the difficulty in controlling the propeller's initial phase, a device capable of stably acquiring specific propeller phases is urgently needed. Furthermore, based on the characteristics of PIV, the periodic flow field of the propeller wake can be captured in three dimensions and stitched together using algorithms. However, time-based stitching based solely on the propeller period cannot effectively achieve phase and spatial stitching. Therefore, an intelligent algorithm is also needed to achieve spatial stitching of flow fields with the same phase in different regions. Summary of the Invention

[0003] The purpose of this invention is to provide a propeller PIV phase stitching device and method based on time series, so as to solve the problems of phase asynchrony, discontinuity of flow field information and limited measurement accuracy in traditional PIV technology when measuring unsteady flow fields of rotating propellers.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] A time-series-based propeller PIV phase stitching device includes: a propeller with a power unit located inside the test tank, a photosensitive patch sensor mounted on the propeller, a positioning laser located above the propeller outside the test tank, the laser emitted by the positioning laser illuminating the hub of the propeller, and a particle image acquisition camera and a pulsed laser located outside the test tank.

[0006] The propeller, the positioning laser, the particle image acquisition camera, the pulse laser, and the photosensitive patch sensor are each connected to a synchronization signal controller, which is connected to an active control processing system.

[0007] Furthermore, the test tank is equipped with windows made of light-transmitting material on all four sides for optical observation and measurement.

[0008] Furthermore, the active control processing system controls the synchronous triggering of the positioning laser, propeller, particle image acquisition camera and pulse laser through the synchronization signal controller, and records the acquired data; after receiving the laser emitted by the positioning laser, the photosensitive patch sensor outputs an excitation signal and excites the pulse laser through the synchronization signal controller and the active control processing system. At this time, the active control processing system synchronously starts recording the acquired image.

[0009] Furthermore, the propeller has periodic rotational characteristics and phase characteristics.

[0010] The present invention may also include:

[0011] A time-series-based propeller PIV phase stitching method, employing the apparatus described in any one of claims 1-4, the method comprising:

[0012] First, the experimental platform is set up, the phase condition to be measured is selected, and the positioning laser is fixed to maintain that phase until the measurement is completed. The particle image acquisition camera and the pulse laser are installed, and the positioning laser, particle image acquisition camera and pulse laser are all connected to the synchronous signal processor to ensure unified control. The active control processing system is responsible for issuing commands, processing data and subsequent flow field splicing.

[0013] After preparation, the propeller equipped with the photosensitive patch sensor will be turned on. Once its rotation speed stabilizes, the positioning laser will be turned on, and the signal output of the device will be observed to ensure it meets expectations. Next, the particle image acquisition camera will be turned on, and the pulsed laser will be kept in a ready-to-excite state. When the active control system issues a command, the pulsed laser will be activated to illuminate the area under test when the photosensitive patch sensor receives a light signal for the first time, and the saving of data from the particle image acquisition camera will begin. The above operation will be performed automatically every time a light signal is received thereafter, until the data volume reaches the required level or the process is stopped manually.

[0014] After data acquisition, a seamless 3D flow field stitching algorithm based on SSIM optimization and Poisson fusion was used to stitch the flow field together.

[0015] Furthermore, the seamless stitching algorithm for three-dimensional flow fields based on SSIM optimization and Poisson fusion first divides each three-dimensional flow field region into 10 parts along the stitching direction in the in-phase flow fields of two adjacent blocks obtained from the image. Then, iterates through each pair of flow field slices and identifies the pair with the highest structural similarity coefficient (SSIM), namely slice A and slice A'. The SSIM value is greater than 0.95. A region with a thickness of 0.5%λ is created between the two slices as the stitching region, where λ is selected as the larger of the length and width of the three-dimensional slice.

[0016]

[0017] in, This is the brightness contrast function. For contrast function, For structural comparison functions, and The average gray level, , Using standard deviation and Perform contrast estimation. , , , , , All are constants;

[0018] For the three-dimensional velocity field in the flow field, the components are spliced ​​one by one, and the Poisson fusion method is used to keep the physical divergence continuous.

[0019] Furthermore, the Poisson-based fusion method involves first defining new velocity components within the fusion region. The velocity component The following Poisson equation applies within the overlapping region:

[0020]

[0021] Simultaneously satisfying the Dirichlet boundary conditions:

[0022]

[0023] in, It is the Laplace operator, representing the divergence gradient; It is a guiding field. It is the gradient of the source field; Represents the boundary of the overlapping region. It is the value of the target on the boundary;

[0024] The Dirichlet boundary condition requires the solution to be completely consistent with the target field at the boundary of the overlapping region, thereby ensuring the absolute continuity of the entire flow field at the splicing boundary and avoiding step jumps.

[0025] Within the overlapping region, its physical meaning is: to find a smooth function within the overlapping region. ,function Laplace's theorem divergence field of the source field The final solution is the optimal compromise under these gradient and boundary constraints, achieving a smooth transition.

[0026] After obtaining a preliminary velocity field Then, the divergence of the preliminary splicing field is calculated. Then, a potential function ϕ is introduced to correct the spliced ​​velocity field, ensuring that it is free of divergence: that is... ,in, For the final velocity field, solve... After this, the final velocity field is obtained:

[0027] .

[0028] The beneficial effects of this invention are as follows:

[0029] The apparatus and method provided by this invention significantly improve the accuracy and efficiency of propeller PIV measurement. The real-time triggering mechanism of the positioning laser and photosensitive patch sensor ensures high precision and stability of phase synchronization, solving the problems of cumbersome manual adjustments and inconsistent experimental conditions in traditional methods. Secondly, the intelligent stitching algorithm based on SSIM optimization and Poisson fusion can achieve a discrepancy-free continuous transition of the velocity field within the overlapping region, effectively eliminating step jumps in flow field stitching, thereby capturing transient flow details between adjacent phases. Finally, the reconstructed three-dimensional flow field has high spatiotemporal resolution, providing highly reliable data for propeller vortex evolution, hydrodynamic noise prediction, and performance optimization, greatly improving experimental efficiency and measurement repeatability.

[0030] This invention, through high-precision phase synchronization control and time series analysis, can accurately capture and seamlessly stitch together the transient flow field under different rotation phases of the propeller, thereby reconstructing a complete, high spatiotemporal resolution periodic three-dimensional flow field structure, providing reliable data support for the optimization of propeller hydrodynamic performance, eddy current mechanism and noise characteristics research. Attached Figure Description

[0031] Appendix Figure 1 This is an overall schematic diagram of the present invention;

[0032] Appendix Figure 2 This is a schematic diagram of the propeller photosensitive patch of the present invention;

[0033] Appendix Figure 3 This is an application flowchart of the present invention;

[0034] Figure 4(a) is a schematic diagram of the velocity field of the present invention along the direction of the incoming flow;

[0035] Figure 4(b) is a schematic diagram of the velocity field of the present invention spliced ​​along the radial direction;

[0036] Appendix Figure 5 This is a schematic diagram of the test setup for the Tomo-PIV of the present invention.

[0037] In the attached diagram: 1. Positioning laser, 2. Propeller, 3. Particle image acquisition camera, 4. Pulsed laser, 5. Test water tank, 6. Synchronization signal controller, 7. Active control processing system, 8. Photosensitive patch sensor. Detailed Implementation

[0038] The present invention will now be further described with reference to the accompanying drawings.

[0039] This invention provides a time-series-based propeller PIV phase stitching device, as shown in the attached figure. Figure 1 As shown, it includes: a positioning laser 1, a propeller with a power unit 2, a particle image acquisition camera 3, a pulsed laser 4, a test water tank 5, a synchronization signal controller 6, an active control processing system 7, and a photosensitive patch sensor 8.

[0040] The positioning laser 1 can be irradiated onto the propeller hub and its position can be adjusted according to the required phase.

[0041] The propeller 2 equipped with a power unit has periodic rotation characteristics and phase characteristics.

[0042] The test water tank 5 has windows made of light-transmitting materials such as glass on all four sides, which can be used for optical observation and measurement;

[0043] Specifically, the test water tank 5 can be an empty water tank.

[0044] In this embodiment, the synchronization signal controller 6 connects the positioning laser 1, the propeller and power unit 2, the particle image acquisition camera 3, the pulse laser 4, the active control processing system 7 and the photosensitive patch sensor 8, ensuring the consistency of the triggering and acquisition time of the above devices.

[0045] The active control processing system 7 controls the synchronous triggering of the positioning laser 1, propeller, power unit 2, particle image acquisition camera 3 and pulse laser 4 through the synchronization signal controller 6, and records the acquired data.

[0046] After receiving the laser emitted by the positioning laser 1, the photosensitive patch sensor 8 outputs an excitation signal and excites the pulse laser 4 through the synchronization signal controller 6 and the active control processing system 7. At this time, the synchronization control active control processing system 7 starts to record and acquire images synchronously.

[0047] The flow field measurement device can be a flow field morphology or flow field quantitative characteristic measurement device. In the test environment of PIV as an example, it consists of a particle image acquisition camera 3 and a pulsed laser 4. If a 2D3C or even 3D3C PIV test is required, it can be flexibly adjusted according to the test setup. Figures 4(a) and 4(b) show the test setup diagram of Tomo-PIV (a 3D3C flow field measurement method).

[0048] In this embodiment, the test environment uses PIV shooting as an example, and the test flowchart is attached. Figure 3 As shown:

[0049] First, the experimental platform is set up, the phase condition to be measured is selected, and the positioning laser 1 is fixed to maintain that phase until the measurement is completed. The particle image acquisition camera 3 and the pulsed laser 4 are installed in suitable positions, and all the above equipment is connected to the synchronous signal processor 6 to ensure unified control. The active control processing system 7 is responsible for issuing commands, processing data, and subsequent flow field splicing.

[0050] After preparation, the propeller equipped with the photosensitive patch sensor 8 and the power unit 2 will be turned on. Once their rotation speed stabilizes, the positioning laser 1 will be turned on, and the signal output of the device will be observed to ensure it meets expectations. Next, the particle image acquisition camera 3 will be turned on, keeping the pulsed laser in a ready-to-excite state. When the active control system 7 issues a command, the pulsed laser 4 will be activated simultaneously when the photosensitive patch sensor 8 receives a light signal for the first time, illuminating the area under test, and the data saving of the particle image acquisition camera 3 will begin. This process will continue automatically after each received light signal until the required amount of data is reached or the process is stopped manually.

[0051] After data acquisition, flow field stitching was performed using an algorithm. The algorithm used was a seamless 3D flow field stitching algorithm based on SSIM optimization and Poisson fusion. Specifically, for the in-phase flow fields of two adjacent blocks captured by the image, each 3D flow field region was first divided into 10 parts along the stitching direction. Each pair of flow field slices was traversed, and the pair with the highest structural similarity coefficient (SSIM) (greater than 0.95) was selected as slice A and slice A'. A region with a thickness of 0.5%λ was created between the two slices as the stitching region, and λ was selected as the larger of the length and width of the 3D slice.

[0052]

[0053] in This is the brightness contrast function. For contrast function, This is a structure comparison function. and The average gray level, , Using standard deviation and Perform contrast estimation. , In particular, . , , All are constants.

[0054] For the three-dimensional velocity field in the flow field, a component-by-component stitching method is used, which, based on the Poisson fusion approach, ensures continuity in physical divergence. The u-component is used as an example below:

[0055] First, define the new velocity components within the fusion region. It satisfies the following Poisson equation within the overlapping region:

[0056]

[0057] The following boundary conditions must be met simultaneously:

[0058]

[0059] in It is the Laplace operator, representing the divergence gradient; This is the guiding field; here we use the gradient of the source field. ; Represents the boundary of the overlapping region. This is the value of the target at the boundary. This Dirichlet boundary condition forces the solution to be completely consistent with the target field at the boundary of the overlapping region, thus ensuring the absolute continuity of the entire flow field at the splicing boundary and avoiding step jumps. Its physical meaning is: within the overlapping region, we search for a smooth function... Its "rate of change of the rate of change" (Laplace) is determined by the divergence field of the source field ( This is guided by gradient and boundary constraints. The final solution is the optimal compromise under these constraints, achieving a smooth transition.

[0060] After obtaining a preliminary velocity field Then, the divergence of the preliminary splicing field is calculated. Then, a potential function ϕ is introduced to correct the spliced ​​velocity field, ensuring that it is free of divergence: that is... ,in, Let's define the final velocity field. Solve for... After this, the final velocity field is obtained: .

[0061] After completing the above work, change the position of positioning laser 1 to collect and stitch other phase data.

[0062] During splicing, in addition to splicing along the flow direction and radial direction, two adjacent three-dimensional flow fields in any direction can be spliced ​​in the same way as described above. It is only necessary to adjust the boundary conditions of the spliced ​​slices to match the splicing direction.

[0063] When stitching together, the experimental setup and stitching algorithm can be used not only along the flow direction and radial direction, but also to stitch together two adjacent three-dimensional flow fields in any direction. The only requirement is to adjust the boundary conditions of the stitched slices to match the stitching direction.

[0064] 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 propeller PIV phase splicing device based on time series, characterized in that, include: A propeller (2) with a power unit is located inside the test tank (5). A photosensitive patch sensor (8) is installed on the propeller (2). A positioning laser (1) is located above the propeller (2) and outside the test tank (5). The laser emitted by the positioning laser (1) illuminates the hub of the propeller (2). A particle image acquisition camera (3) and a pulse laser (4) are also located outside the test tank (5). The propeller (2), the positioning laser (1), the particle image acquisition camera (3), the pulse laser (4), and the photosensitive patch sensor (8) are respectively connected to the synchronization signal controller (6), and the synchronization signal controller (6) is connected to the active control processing system (7).

2. The propeller PIV phase splicing device based on time series according to claim 1, characterized in that, The test tank (5) has windows made of light-transmitting material on all four sides for optical observation and measurement.

3. The propeller PIV phase splicing device based on time series according to claim 2, characterized in that, The active control processing system (7) controls the synchronous triggering of the positioning laser (1), propeller (2), particle image acquisition camera (3) and pulse laser (4) through the synchronization signal controller (6), and records the acquired data; the photosensitive patch sensor (8) outputs an excitation signal after receiving the laser emitted by the positioning laser (1), and excites the pulse laser (4) through the synchronization signal controller (6) and the active control processing system (7). At this time, the active control processing system (7) synchronously starts recording the acquired image.

4. The propeller PIV phase splicing device based on time series according to claim 3, characterized in that, The propeller (2) has periodic rotation characteristics and phase characteristics.

5. A propeller PIV phase stitching method based on time series, characterized in that, Using the apparatus according to any one of claims 1-4, the method comprises: First, the experimental platform is set up, the phase condition to be measured is selected, the positioning laser (1) is fixed to maintain the phase until the measurement is completed; the particle image acquisition camera (3) and the pulse laser (4) are installed, and the positioning laser (1), the particle image acquisition camera (3) and the pulse laser (4) are all connected to the synchronous signal processor (6) to ensure unified control. The active control processing system (7) is responsible for issuing commands, data processing and subsequent flow field splicing. After the preparation work is completed, the propeller (2) with the photosensitive patch sensor (8) installed will be turned on. After its rotation speed is stable, the positioning laser (1) will be turned on. The signal output of the device will be observed to see if it meets the expectations. Then the particle image acquisition camera (3) will be turned on. The pulse laser will be kept in the state of being ready to be excited. The active control system (7) will issue a command. When the photosensitive patch sensor (8) receives the light signal for the first time from this moment, the pulse laser (4) will be excited to illuminate the area to be tested, and the data of the particle image acquisition camera (3) will be saved. After that, the above operation will be performed automatically every time a light signal is received until the amount of data reaches the requirement or the operation is stopped actively. After data acquisition, a seamless 3D flow field stitching algorithm based on SSIM optimization and Poisson fusion was used to stitch the flow field together.

6. The propeller PIV phase stitching method based on time series according to claim 5, characterized in that, The aforementioned seamless stitching algorithm for 3D flow fields based on SSIM optimization and Poisson fusion first divides each 3D flow field region into 10 parts along the stitching direction in the in-phase flow fields of two adjacent blocks captured by imaging. It then iterates through each pair of flow field slices, identifying the pair with the highest SSIM structural similarity coefficient (SSIM) as slice A and slice A' (SSIM greater than 0.95). A region with a thickness of 0.5%λ is created between the two slices as the stitching region, where λ is the larger of the length and width of the 3D slice. in, This is the brightness contrast function. For contrast function, For structural comparison functions, and The average gray level, , Using standard deviation and Perform contrast estimation. , , , , , All are constants; For the three-dimensional velocity field in the flow field, the components are spliced ​​one by one, and the Poisson fusion method is used to keep the physical divergence continuous.

7. The propeller PIV phase stitching method based on time series according to claim 6, characterized in that, The Poisson-based fusion method is as follows: First, define a new velocity component within the fusion region. The velocity component The following Poisson equation applies within the overlapping region: Simultaneously satisfying the Dirichlet boundary conditions: in, It is the Laplace operator, representing the divergence gradient; It is a guiding field. It is the gradient of the source field; Represents the boundary of the overlapping region. It is the value of the target on the boundary; The Dirichlet boundary condition forces the solution to be completely consistent with the target field at the boundary of the overlapping region, thereby ensuring the absolute continuity of the entire flow field at the splicing boundary and avoiding step jumps. Within the overlapping region, its physical meaning is: to find a smooth function within the overlapping region. ,function Laplace's theorem divergence field of the source field The final solution is the optimal compromise under these gradient and boundary constraints, achieving a smooth transition. After obtaining a preliminary velocity field Then, the divergence of the preliminary splicing field is calculated. Then, a potential function ϕ is introduced to correct the spliced ​​velocity field, ensuring that it is free of divergence. ,in, For the final velocity field, solve... After this, the final velocity field is obtained: 。

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