A high-precision sand wave form capturing device for offshore sand wave migration experiment and an experimental method

Abstract

The present application relates to the technical field of ocean engineering experiment, and discloses a high-precision sand wave form capturing device for offshore sand wave migration experiment, which comprises a wave flume, a sand wave form high-precision monitoring system, a flow field synchronous measurement system and a data acquisition and processing system. The wave flume is internally provided with a sand bed. The sand wave form high-precision monitoring system comprises a terrain scanning subsystem and an image acquisition subsystem. The data acquisition and processing system is used for synchronously collecting, processing and fusion analyzing the terrain scanning data, the image data and the flow field data, and generating sand wave form parameters and the quantitative results of the interaction between the flow field and the sand wave. The sand wave form high-precision monitoring system, the flow field synchronous measurement system and the data acquisition and processing system are used for accurately capturing the sand wave form, synchronously monitoring the flow field and the sand wave evolution, and revealing the coupling mechanism of the two through data fusion analysis. The experiment design is rigorous and controllable, and can systematically study the influence of multiple factors, thereby providing reliable basis for the anti-scour design of ocean engineering.

Description

Technical Field

[0001] This invention relates to the field of marine engineering experimental technology, specifically a high-precision sand wave morphology capture device for nearshore sand wave migration experiments. Background Technology

[0002] Sand waves refer to the periodic spatial undulations of seabed sediment in nearshore and coastal areas, formed by the transport and deposition of sediment under the continuous action of waves, currents, and other hydrodynamic forces. They are a typical product of the interaction between sediment movement and the hydrodynamic environment, and their morphological parameters (such as wavelength and wave height) and migration characteristics directly reflect the coupling relationship between the sediment movement and the hydrodynamic environment. In nearshore engineering, sand wave migration not only alters seabed topography but also significantly impacts the local scour and dynamic response of marine engineering structures such as pile foundations, subsea pipelines, and offshore wind turbine foundations. Sand wave migration can exacerbate sediment transport around pile foundations, alter the local flow field structure, and thus affect the depth and extent of scour, threatening the stability of the engineering structure.

[0003] However, existing experimental devices and methods for studying nearshore sand wave migration have many limitations: on the one hand, the accuracy of sand wave morphology capture is insufficient. Traditional topographic surveying methods are difficult to achieve high-precision, high-frequency monitoring of the three-dimensional morphology of sand waves (especially small-scale sand waves or sand waves in the process of rapid migration), and cannot accurately obtain the dynamic changes of key parameters such as sand wave wavelength, wave height, and migration speed; on the other hand, the ability to simultaneously measure the flow field and sand wave morphology is lacking. Sand wave migration is the result of the interaction between hydrodynamics and bed sediment. Existing devices often cannot simultaneously obtain the fine features of the flow field (such as vertical velocity distribution, vortex structure, etc.) near the sand wave while capturing the sand wave morphology with high precision, which makes it impossible to deeply analyze the coupling mechanism between the flow field and the evolution of sand wave morphology.

[0004] Therefore, we propose a high-precision sand wave morphology capture device and experimental method for nearshore sand wave migration experiments. Summary of the Invention

[0005] The purpose of this invention is to provide a high-precision sand wave morphology capture device and experimental method for nearshore sand wave migration experiments, thereby solving or at least alleviating one or more of the above-mentioned problems and other problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a high-precision sand wave morphology capture device for nearshore sand wave migration experiments, comprising a wave tank, a high-precision sand wave morphology monitoring system, a flow field synchronous measurement system, and a data acquisition and processing system; The wave tank is equipped with a sand bed at the bottom to simulate the surface environment of nearshore sand waves. Piles are installed on the sand bed to simulate nearshore pile foundations. The high-precision monitoring system for sand wave morphology includes a terrain scanning subsystem and an image acquisition subsystem. The terrain scanning subsystem is used to perform high-precision three-dimensional scanning of the sand bed surface topography and acquire sand bed topography scanning data in real time. The image acquisition subsystem is used to acquire high-frequency images of the sand bed surface and obtain image data. The flow field synchronous measurement system is used to perform multi-dimensional synchronous measurement of the flow field near the sand wave and acquire flow field data. The data acquisition and processing system is used to simultaneously acquire, process, and fuse terrain scanning data, image data, and flow field data to generate sand wave morphology parameters and quantitative results of the interaction between the flow field and sand waves.

[0007] In a high-precision sand wave morphology capture device for nearshore sand wave migration experiments according to the present invention, the terrain scanning subsystem is optionally a multi-phase laser scanner array for achieving full-area coverage scanning of the sand bed, and the multi-phase laser scanner array is arranged above the wave tank.

[0008] In a high-precision sand wave morphology capture device for nearshore sand wave migration experiments according to the present invention, the image acquisition subsystem optionally includes multiple sets of second high-speed cameras for synchronously capturing different areas of the sand bed surface. The multiple sets of second high-speed cameras are arranged on one side of the wave tank and are centrally symmetrical about the center of the sand bed.

[0009] In a high-precision sand wave morphology capture device for nearshore sand wave migration experiments according to the present invention, the flow field synchronous measurement system optionally includes a PIV particle image velocimetry system and an ADCP acoustic Doppler current profiler. The PIV particle image velocimetry system is used to measure the planar velocity field of the flow field above the sand wave and capture the instantaneous vortex structure. The PIV particle image velocimetry system includes a laser emitter and a first high-speed camera. The laser emitter is located directly above the wave tank, and the first high-speed camera is located on one side of the wave tank. The ADCP acoustic Doppler current profiler is used to obtain the current velocity profile distribution along the water depth direction, and is also used to calibrate the measurement error of the PIV particle image velocimetry system. The ADCP acoustic Doppler current profiler is installed on the wave tank.

[0010] In a high-precision sand wave morphology capture device for nearshore sand wave migration experiments according to the present invention, the flow field synchronous measurement system may optionally include an ADV current meter, wherein four sets of ADV current meters are provided, and the four sets of ADV current meters are respectively used to perform high-frequency single-point flow velocity monitoring of the crest, trough, upstream face and downstream face of the sand wave.

[0011] In a high-precision sand wave morphology capture device for nearshore sand wave migration experiments according to the present invention, the flow field synchronous measurement system may optionally include a wave measurement component, the wave measurement component including a wave height meter, four of which are arranged, two of which are arranged at the front end of the pile and the remaining two of which are arranged at the rear end of the pile.

[0012] In a high-precision sand wave morphology capturing device for nearshore sand wave migration experiments according to the present invention, optionally, the distance between the two wave height meters located at the front end of the pile and the distance between the two wave height meters located at the rear end of the pile are both ΔL, where ΔL is less than the wavelength of the wave and not equal to 1 / 2 of the wavelength of the wave.

[0013] In a high-precision sand wave morphology capture device for nearshore sand wave migration experiments according to the present invention, the data acquisition and processing system may optionally include a multi-channel synchronous acquisition module, a raw data processing module, a parameter extraction module, and an intelligent analysis module. The multi-channel synchronous acquisition module is used to align the sand bed topography scanning data of the topography scanning subsystem, the image data of the image acquisition subsystem, and the flow field data of the flow field synchronous measurement system according to timestamps; the raw data processing module is used to preprocess the timestamp-aligned multi-source data. The parameter extraction module is used to extract feature parameters from the preprocessed data; The intelligent analysis module is used to receive the feature parameters output by the parameter extraction module and analyze the coupling mechanism between the flow field and the evolution of sand wave morphology.

[0014] This invention also provides a method for conducting nearshore sand wave migration experiments, which uses the aforementioned high-precision sand wave morphology capture device for nearshore sand wave migration experiments, and includes the following steps: Step 1: Sandbed Preparation and Environmental Calibration 1.1 Sand Grain Grading Pretreatment: The experimental sand grains were graded and sieved using a standard sand and gravel sieve. The experimental sand grains were from near-shore sand beds. The gradation curve was controlled by weight ratio to ensure that the proportion of each particle size deviated from the preset value by ≤5%. The density of the sand grains was measured using the specific gravity bottle method to ensure that the density fluctuation of the same batch of sand grains was ≤0.02g / cm³, and abnormal particles with a particle size deviation >±0.01mm were removed. 1.2 Initial sand bed laying: The pretreated sand is evenly laid on the sand bed at the bottom of the wave channel, with a thickness of 0.3m-0.5m, and leveled using a level. 1.3 Water Environment Preparation: Experimental water that has undergone sedimentation and deaeration treatment was injected into the wave tank, with the injection rate controlled at 0.05 m / s. 3 / h-0.1m 3 / h to avoid disturbing the sand bed, let it stand for 24 hours after reaching the preset water depth; 1.4 Initial equipment calibration: Start the phase laser scanner array to perform a three-dimensional scan of the initial sand bed and obtain the benchmark terrain data; take an image of the initial sand bed through the second high-speed camera and compare it with the scan data to ensure that the spatial positioning deviation is ≤5mm; Step 2: Setting and Dynamic Verification of Dynamic Field Parameters 2.1 Preset dynamic field parameters: The target parameters are input into the control system via the wave generator in the wave tank; 2.2 Step-by-step start-up of the dynamic field: First, start the ocean current generation system in the wave tank. After the flow velocity has stabilized for 10 minutes, start the wave generation system in the wave tank. The reflected waves are absorbed by the wave damping device at the end of the wave tank to avoid secondary interference. 2.3 Multi-dimensional flow field verification: The full-depth current velocity profile was measured using an ADCP acoustic Doppler current profiler, with a velocity value recorded every 0.1m of water depth. The deviation from the preset value must be ≤2%. Wave height data are collected by wave height meters before and after the pile, and the initial wave period is calculated with a deviation from the set value of ≤0.1s. Step 3: Multi-system synchronous monitoring and data acquisition 3.1 Monitoring System Collaborative Start-up: A trigger start command is sent through the multi-channel synchronous acquisition module of the data acquisition and processing system: Terrain scanning subsystem: The phase laser scanner array performs full-area scanning at intervals of 0.5h-1h, with a single scan time of ≤3 minutes to reduce dynamic errors; Image acquisition subsystem: The second high-speed camera captures images of the sand bed surface at a frame rate of 100fps-200fps. Each camera group has a field of view covering a 1m×1m area, with adjacent fields of view overlapping by ≥10%. Flow field synchronous measurement system: The ADV current meter samples simultaneously at four points: wave crest, wave trough, upstream face, and downstream face, generating a set of hourly average velocity data every 5 minutes. The PIV particle image velocimetry system emits a 2mm thick laser beam with a wavelength of 532nm through a laser emitter, and the first high-speed camera captures the motion trajectory of hollow glass microspheres at a frame rate of 500fps. The wave height meter collects wave height data before and after the pile at a frequency of 100Hz and records the wave phase changes. 3.2 Real-time data synchronization: The multi-channel synchronous acquisition module aligns all device data according to timestamps; Step 4: Multi-source data fusion and quantitative analysis 4.1 Raw Data Preprocessing: The raw data processing module processes the timestamp-aligned terrain data, image data, and flow field data separately: Topographic data: Noise points were removed using a Gaussian filtering algorithm, and a digital elevation model with a resolution of 0.01m × 0.01m was generated by Kriging interpolation; Image data: Distortion correction is performed based on camera intrinsic parameters, and panoramic images are stitched together using the SIFT algorithm and spatially registered with terrain data, with a deviation of ≤5mm; Flow field data: The λ² criterion was used to identify vortices in the PIV data, the ADV data was detrended, and the absolute value of the flow velocity was calibrated using ADCP data with an error ≤3%. 4.2 Extraction of sand wave morphology parameters: Static parameters: The sand wave profile is extracted using the Canny operator, and the wavelength, wave height, and slope are calculated. Dynamic parameters: The migration speed is calculated by the difference in wave crest coordinates at different times, and the daily variation rate of wave height and the wavelength spread rate are statistically analyzed; 4.3 Flow Field-Sand Wave Coupling Analysis: A linear regression model of sand wave migration velocity and velocity gradient at wave crest was established using the least squares method, with R² ≥ 0.9. Quantify the positive correlation coefficient between the vortex intensity on the back surface and the sand accumulation rate; The Goda two-point method was used to calculate the reflection wave coefficients before and after the pile, and the influence weight of the reflected waves on the local sand wave deformation was analyzed. In a method for nearshore sand wave migration experiment according to the present invention, optionally, in step 3, the PIV tracer particles of the flow field synchronous measurement system are hollow glass microspheres with a density matching that of the experimental water, to ensure that the particle tracking error is less than 3%.

[0015] Compared with the prior art, the beneficial effects of the present invention are: By using multiple sets of phase-type laser scanner arrays to achieve full-area high-precision three-dimensional scanning of the sand bed, and combining multiple sets of centrally symmetrically set second high-speed cameras for high-frequency image acquisition, the three-dimensional topographic data and two-dimensional dynamic contours of sand waves can be accurately obtained. This solves the problem of insufficient accuracy of traditional measurement methods in capturing small-scale or rapidly migrating sand waves, and provides reliable data for extracting key parameters such as the wavelength, wave height, and migration speed of sand waves. The synchronous flow field measurement system integrates a PIV particle image velocimetry system, an ADCP acoustic Doppler current profiler, four ADV current meters, and a wave height meter. It can acquire the planar flow velocity, vertical profile distribution, high-frequency flow velocity at key points, and wave parameters of the flow field near sand waves in multiple dimensions simultaneously. Among them, the calibration of PIV by ADCP ensures the accuracy of flow field data, and the "point measurement" of ADV and the "area measurement" of PIV complement each other, realizing the coordinated monitoring of flow field and sand wave morphological evolution, filling the gap in the existing technology for simultaneous measurement of both. The data acquisition and processing system achieves timestamp alignment of terrain, image, and flow field data through a multi-channel synchronous acquisition module. After preprocessing by the raw data processing module, feature parameters are extracted by the parameter extraction module. Finally, a coupled model of flow field and sand wave morphology is established through the intelligent analysis module. This system can quantify the correlation between sand wave migration velocity and flow velocity gradient and vortex intensity, analyze the influence of reflected waves on sand wave deformation, and deeply reveal the intrinsic mechanism of flow field-driven sand wave evolution. Attached Figure Description

[0016] Figure 1 This is a partial cross-sectional structural diagram of a high-precision sand wave morphology capture device for nearshore sand wave migration experiments according to the present invention. Figure 2 This is a top view schematic diagram of a high-precision sand wave morphology capture device for nearshore sand wave migration experiments according to the present invention.

[0017] In the figure: 1. Wave tank; 2. Sand bed; 3. ADV current meter; 4. PIV particle image velocimetry system; 401. Laser emitter; 402. First high-speed camera; 5. Wave height meter; 6. ADCP acoustic Doppler current profiler; 7. Phase laser scanner array; 8. Second high-speed camera. Detailed Implementation

[0018] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0019] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual images. They should not be construed as limiting the scope of this patent. To better illustrate the embodiments of the present invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0020] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present patent. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0021] In the description of this invention, unless otherwise explicitly specified and limited, the term "connection" or similar designation indicating a connection between components should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral part; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] Example 1 Please see Figures 1 to 2 This embodiment provides a high-precision sand wave morphology capture device for nearshore sand wave migration experiments, including a wave tank 1, a high-precision sand wave morphology monitoring system, a flow field synchronous measurement system, and a data acquisition and processing system; The wave tank is equipped with a sand bed 2, which is laid at the bottom of the wave tank to simulate the bed environment of nearshore sand waves. Piles are installed on the sand bed 2 to simulate nearshore pile foundations. The high-precision monitoring system for sand wave morphology includes a terrain scanning subsystem and an image acquisition subsystem; The terrain scanning subsystem is used to perform high-precision three-dimensional scanning of the sand bed surface topography and acquire sand bed topography scanning data in real time. The image acquisition subsystem is used to acquire high-frequency images of the sand bed surface and obtain image data; The synchronous flow field measurement system is used to perform multi-dimensional synchronous measurement of the flow field near the sandstorm and acquire flow field data. The data acquisition and processing system is used to simultaneously acquire, process, and fuse terrain scanning data, image data, and flow field data to generate sand wave morphology parameters and quantitative results of the interaction between the flow field and sand waves.

[0023] In this embodiment, the terrain scanning subsystem is a multi-phase laser scanner array 7, which is used to achieve full-area coverage scanning of the sand bed 2. The multi-phase laser scanner array 7 is set above the wave tank 1.

[0024] By adopting the above technical solution, the phase laser scanner array 7, arranged in an array above the wave tank 1, uses the laser ranging principle to perform a full-area scan of the sand bed 2. Through the collaborative work of multiple scanners, measurement blind spots are eliminated, and high-precision three-dimensional reconstruction of the sand bed topography is achieved, providing basic data for the extraction of sand wave wavelength and wave height parameters.

[0025] In this embodiment, the image acquisition subsystem includes multiple sets of second high-speed cameras 8 for synchronously capturing images of different areas on the sand bed surface. The multiple sets of second high-speed cameras 8 are arranged on one side of the wave tank 1 and are centrally symmetrical about the center of the sand bed 2.

[0026] By adopting the above technical solution, the second high-speed camera 8 is centrally symmetrically arranged with the center of the sand bed 2 as the symmetrical point, which can cover different areas of the sand bed surface and record the dynamic changes of the sand waves through high-frequency shooting; the symmetrical setting ensures the consistency of image acquisition in the left and right areas, reduces the viewing angle deviation, and combined with the image recognition algorithm, the two-dimensional contour and migration trajectory of the sand waves can be extracted, forming a complementary verification with the terrain scanning data.

[0027] In this embodiment, the flow field synchronous measurement system includes a PIV particle image velocimetry system 4 and an ADCP acoustic Doppler velocity profiler 6. The PIV particle image velocimetry system 4 is used to measure the planar velocity field of the flow field above the sand wave and capture the instantaneous vortex structure. The PIV particle image velocimetry system 4 includes a laser emitter 401 and a first high-speed camera 402. The laser emitter 401 is set directly above the wave tank 1, and the first high-speed camera 402 is set on one side of the wave tank 1. The ADCP acoustic Doppler current profiler 6 is used to obtain the velocity profile distribution along the water depth direction and is also used to calibrate the measurement error of the PIV particle image velocimetry system 4. The ADCP acoustic Doppler current profiler 6 is installed on the wave tank 1.

[0028] By adopting the above technical solution, in the PIV particle image velocimetry system 4, the laser emitter 401 emits a laser beam from directly above the wave tank 1 to illuminate the tracer particles in the flow field, and the first high-speed camera 402 captures the particle motion trajectory from the side. The planar flow velocity field and vortex structure are calculated through particle displacement. The ADCP acoustic Doppler current profiler 6 measures the full-depth flow velocity profile through the acoustic Doppler principle. Its data is used to calibrate the measurement error of the PIV system and ensure the accuracy of the flow field data.

[0029] In this embodiment, the flow field synchronous measurement system also includes an ADV velocity meter 3. The ADV velocity meter 3 is provided in four sets. The four sets of ADV velocity meters 3 are used to perform high-frequency single-point flow velocity monitoring on the crests, troughs, upstream and downstream surfaces of the sand waves.

[0030] By adopting the above technical solution, four ADV flow meters 3 are strategically placed at key locations on the sand wave. Through high-frequency sampling, they capture instantaneous flow velocity changes and accurately obtain the flow velocity characteristics of different parts of the sand wave. This provides high-precision single-point data for analyzing the influence of the flow field on sand wave erosion / deposition, forming a "point-to-surface" complementarity with the planar flow field data of PIV.

[0031] In this embodiment, the flow field synchronous measurement system also includes a wave measurement component, which includes a wave height meter 5. Four wave height meters 5 are provided, with two wave height meters 5 located at the front end of the pile and the remaining two wave height meters 5 located at the rear end of the pile.

[0032] By adopting the above technical solution, four wave height meters 5 are respectively arranged at the front and rear ends of the pile. The wave height data is collected in real time through non-contact measurement such as laser ranging. The data at the front end of the pile reflects the characteristics of the incident wave, and the data at the rear end reflects the characteristics of the wave after reflection by the pile body. By combining the two sets of data, the incident wave and the reflected wave can be separated, providing a basis for assessing the interference of the pile foundation on the wave field.

[0033] In this embodiment, the distance between the two wave height meters 5 located at the front end of the pile and the distance between the two wave height meters 5 located at the rear end of the pile are both ΔL. ΔL is less than the wavelength of the wave and not equal to 1 / 2 of the wavelength of the wave.

[0034] By adopting the above technical solution, the setting of ΔL must meet the condition of "less than the wavelength and not equal to 1 / 2 wavelength", which can avoid interference of measurement signals caused by path difference. By calculating the phase difference of wave height data at two points, combined with Goda's two-point method, the wave heights of incident waves and reflected waves can be accurately separated, improving the accuracy of wave reflection coefficient calculation and providing reliable parameters for analyzing the reflection effect of pile foundation on wave energy.

[0035] In this embodiment, the data acquisition and processing system includes a multi-channel synchronous acquisition module, a raw data processing module, a parameter extraction module, and an intelligent analysis module; The multi-channel synchronous acquisition module is used to align the sand bed topography scanning data of the topography scanning subsystem, the image data of the image acquisition subsystem, and the flow field data of the flow field synchronous measurement system according to the timestamp. The raw data processing module is used to preprocess multi-source data after timestamp alignment; The parameter extraction module is used to extract feature parameters from the preprocessed data; The intelligent analysis module is used to receive the feature parameters output by the parameter extraction module and analyze the coupling mechanism between the flow field and the sand wave morphology evolution.

[0036] By adopting the above technical solutions, the multi-channel synchronous acquisition module ensures the spatiotemporal consistency of multi-source data through timestamp alignment; the raw data processing module performs preprocessing such as noise reduction and correction on the data to eliminate interference; the parameter extraction module extracts sand wave morphology parameters and flow field parameters from the processed data; and the intelligent analysis module establishes a correlation model between the two through algorithms, ultimately analyzing the intrinsic mechanism of flow field-driven sand wave evolution.

[0037] This invention also provides a method for conducting nearshore sand wave migration experiments, using the aforementioned high-precision sand wave morphology capture device for nearshore sand wave migration experiments, specifically including the following steps: Step 1: Sandbed Preparation and Environmental Calibration 1.1 Sand Grain Grading Pretreatment: The experimental sand grains were graded and sieved using a standard sand and gravel sieve. The experimental sand grains were from near-shore sand beds. The gradation curve was controlled by weight ratio to ensure that the proportion of each particle size deviated from the preset value by ≤5%. The density of the sand grains was measured using the specific gravity bottle method to ensure that the density fluctuation of the same batch of sand grains was ≤0.02g / cm³, and abnormal particles with a particle size deviation >±0.01mm were removed. 1.2 Initial sand bed laying: The pretreated sand is evenly laid on the sand bed 2 at the bottom of the wave channel 1, with a thickness of 0.3m-0.5m, and leveled using a level. 1.3 Water environment preparation: Inject experimental water that has been treated by sedimentation and degassing into wave tank 1. The water injection rate is controlled at 0.05 m³ / h-0.1 m³ / h to avoid disturbing the sand bed. After reaching the preset water depth, let it stand for 24 hours. 1.4 Initial equipment calibration: The phase-type laser scanner array 7 is activated to perform a three-dimensional scan of the initial sand bed to obtain benchmark terrain data; the initial sand bed image is captured by the second high-speed camera 8 and compared with the scan data to ensure that the spatial positioning deviation is ≤5mm; Step 2: Setting and Dynamic Verification of Dynamic Field Parameters 2.1 Preset dynamic field parameters: Input the target parameters through the wave generator control system in wave tank 1; 2.2 Step-by-step start-up of the dynamic field: First, start the ocean current generation system in wave tank 1. After the flow velocity stabilizes for 10 minutes, start the wave generation system in wave tank 1. The reflected waves are absorbed by the wave damping device at the end of wave tank 1 to avoid secondary interference. 2.3 Multi-dimensional flow field verification: The full-depth current velocity profile was measured using an ADCP acoustic Doppler current profiler 6, with a velocity value recorded every 0.1m of water depth. The deviation from the preset value must be ≤2%. Wave height data were collected by wave height meters 5 before and after the pile, and the initial wave period was calculated. The deviation from the set value was ≤0.1s. Step 3: Multi-system synchronous monitoring and data acquisition 3.1 Monitoring System Collaborative Start-up: A trigger start command is sent through the multi-channel synchronous acquisition module of the data acquisition and processing system: Terrain scanning subsystem: Phase laser scanner array 7 performs full-area scanning at intervals of 0.5h-1h, with a single group scanning time of ≤3 minutes to reduce dynamic errors; Image acquisition subsystem: The second high-speed camera 8 captures images of the sand bed surface at a frame rate of 100fps-200fps. Each camera group's field of view covers an area of ​​1m×1m, with adjacent fields of view overlapping by ≥10%. Flow field synchronous measurement system: The ADV flow meter 3 samples simultaneously at four points: wave crest, wave trough, upstream face, and downstream face, generating a set of hourly average flow velocity data every 5 minutes. The PIV particle image velocimetry system 4 emits a 2mm thick laser beam with a wavelength of 532nm through a laser emitter 401, and the first high-speed camera 402 captures the motion trajectory of the hollow glass microspheres at a frame rate of 500fps. Wave height meter 5 collects wave height data before and after the pile at a frequency of 100Hz and records wave phase changes; 3.2 Real-time data synchronization: The multi-channel synchronous acquisition module aligns all device data according to timestamps; Step 4: Multi-source data fusion and quantitative analysis 4.1 Raw Data Preprocessing: The raw data processing module processes the timestamp-aligned terrain data, image data, and flow field data separately: Topographic data: Noise points were removed using a Gaussian filtering algorithm, and a digital elevation model with a resolution of 0.01m × 0.01m was generated by Kriging interpolation; Image data: Distortion correction is performed based on camera intrinsic parameters, and panoramic images are stitched together using the SIFT algorithm and spatially registered with terrain data, with a deviation of ≤5mm; Flow field data: The λ2 criterion was used to identify vortices in the PIV data, the ADV data was detrended, and the absolute value of the flow velocity was calibrated using ADCP data with an error ≤3%. 4.2 Extraction of sand wave morphology parameters: Static parameters: The sand wave profile is extracted using the Canny operator, and the wavelength, wave height, and slope are calculated. Dynamic parameters: The migration speed is calculated by the difference in wave crest coordinates at different times, and the daily variation rate of wave height and the wavelength spread rate are statistically analyzed; 4.3 Flow Field-Sand Wave Coupling Analysis: A linear regression model of sand wave migration velocity and velocity gradient at wave crest was established using the least squares method, with R² ≥ 0.9. Quantify the positive correlation coefficient between the vortex intensity on the back surface and the sand accumulation rate; The Goda two-point method was used to calculate the reflection wave coefficients before and after the pile, and the influence weight of the reflected wave on the local sand wave deformation was analyzed.

[0038] In this embodiment, in step 3, the PIV tracer particles of the flow field synchronous measurement system are hollow glass microspheres with a density matching that of the experimental water, ensuring that the particle tracking error is less than 3%.

[0039] By adopting the above technical solution, the density difference between the PIV tracer particles and the experimental water is ≤0.01g / cm³, which can ensure the following of the particles with the flow field and reduce the measurement deviation caused by particle settling or floating. The following error <3% ensures that the flow field information captured by the PIV system can truly reflect the actual flow field characteristics near the sand wave, providing a reliable flow field data basis for flow field-sand wave coupling analysis.

[0040] Specifically, in this embodiment, in step 4.3, the following sand wave migration rate prediction model is used to quantify the sand wave migration velocity V. b Relationship with flow field characteristic parameters: in: V b Sand wave migration rate (m / s); Horizontal velocity gradient at wave crest (s) -1 ); Γ: Backflow surface vortex intensity (m² / s); ρ: Water density (kg / m³); ν: Kinematic viscosity of water (m² / s); H: Shapobo height (m); λ: Wavelength of the sand wave (m); k, α, β, γ: Fitting coefficients, determined from experimental data using the least squares method, typically satisfying α≈0.8–1.2, β≈0.5–0.7, γ≈-0.3–0.3.

[0041] I. Derivation Process This equation is derived based on the following physical mechanism: 1. Velocity gradient driven: Sand wave migration is mainly driven by shear force caused by the velocity gradient at the wave crest, therefore, the following is introduced: item; 2. Eddy-enhanced transport: Eddies on the back surface promote sediment resuspension and transport, introducing... Item, of which The vortex intensity is a dimensionless value. 3. Influence of Sand Wave Geometry: The shape of sand waves (wave height to wavelength ratio H / λ) affects flow field separation and sediment transport efficiency. item; 4. Coefficient Fitting: Using multiple sets of experimental data, the nonlinear least squares method was employed to fit k, α, β, and γ, making them consistent with the measured V. b The coefficient of determination R² ≥ 0.9.

[0042] II. Example 1. Extract the peak from PIV data ; 2. Extract the vortex intensity Γ on the back surface from the vortex identification results; 3. Extract H and λ from the terrain data; 4. Substitute into the equation to calculate V b ; 5. Compare the model with the measured migration rate to verify its accuracy.

[0043] III. Technical Effects 1. Quantitative coupling mechanism: Directly correlates flow field characteristics with sand wave migration rate, breaking through the limitations of traditional empirical formulas; 2. Multi-parameter fusion: Integrates multi-dimensional information such as velocity gradient, eddy intensity, and sand wave morphology to improve prediction accuracy; 3. High portability: Applicable to sand wave migration prediction at different scales and under different environments; 4. Supporting engineering applications: Providing a theoretical basis for scour risk assessment of structures such as submarine pipelines and pile foundations.

[0044] IV. Working Principle and Flowchart 1. Data Acquisition: Synchronously acquire terrain, flow field, and image data; 2. Parameter Extraction: Extraction Parameters such as Γ, H, and λ; 3. Model Calculation: Substitute into the equation to calculate V b ; 4. Validation and optimization: Compare with measured values ​​and optimize the fitting coefficients; 5. Mechanism Analysis: The influence weight of each physical process on the migration rate is determined by the magnitude of the coefficients.

[0045] All parts not described in this invention are the same as or can be implemented using existing technology. Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for nearshore sand wave migration experiments, characterized in that, Includes the following steps: Step 1: Sandbed Preparation and Environmental Calibration Step 2: Setting and Dynamic Verification of Dynamic Field Parameters 2.1 Preset dynamic field parameters: Input the target parameters through the wave generator control system in the wave tank (1); 2.2 Step-by-step start-up of the dynamic field: First, start the ocean current generation system in the wave tank (1). After the flow velocity stabilizes for 10 minutes, start the wave generation system in the wave tank (1). The reflected waves are absorbed by the wave damping device at the end of the wave tank (1) to avoid secondary interference. 2.3 Multi-dimensional flow field verification: The full-depth velocity profile was measured using an ADCP acoustic Doppler velocity profiler (6); Wave height data were collected by wave height meters (5) before and after the pile, and the initial wave period was calculated. Step 3: Multi-system synchronous monitoring and data acquisition 3.1 Monitoring System Collaborative Start-up: A trigger start command is sent through the multi-channel synchronous acquisition module of the data acquisition and processing system: Terrain scanning subsystem: Phase-type laser scanner array (7) performs full-area scanning at 0.5h-1h intervals; Image acquisition subsystem: The second high-speed camera (8) captures images of the sand bed surface at a frame rate of 100fps-200fps; Flow field synchronous measurement system: The ADV flow meter (3) simultaneously samples at four points: wave crest, wave trough, upstream face, and downstream face, generating a set of hourly average flow velocity data every 5 minutes. The PIV particle image velocimetry system (4) emits a 2mm thick laser beam with a wavelength of 532nm through a laser emitter (401), and the first high-speed camera (402) captures the motion trajectory of the hollow glass microspheres at a frame rate of 500fps. The wave height meter (5) collects wave height data before and after the pile at a frequency of 100Hz and records the wave phase change; 3.2 Real-time data synchronization: The multi-channel synchronous acquisition module aligns all device data according to timestamps; Step 4: Multi-source data fusion and quantitative analysis 4.1 Raw Data Preprocessing: The raw data processing module processes the timestamp-aligned terrain data, image data, and flow field data separately: Topographic data: Noise points were removed using a Gaussian filtering algorithm, and a digital elevation model with a resolution of 0.01m × 0.01m was generated by Kriging interpolation; Image data: Distortion correction is performed based on camera intrinsic parameters, and panoramic images are stitched together using the SIFT algorithm and spatially registered with terrain data, with a deviation of ≤5mm; Flow field data: The λ² criterion was used to identify vortices in the PIV data, the ADV data was detrended, and the absolute value of the flow velocity was calibrated using ADCP data with an error ≤3%. 4.2 Extraction of sand wave morphology parameters: Static parameters: The sand wave profile is extracted using the Canny operator, and the wavelength, wave height, and slope are calculated. Dynamic parameters: The migration speed is calculated by the difference in wave crest coordinates at different times, and the daily variation rate of wave height and the wavelength spread rate are statistically analyzed; 4.3 Flow Field-Sand Wave Coupling Analysis: By establishing a linear regression model between the sand wave migration velocity and the velocity gradient at the wave crest using the least squares method, R... 2 ≥0.9; Quantify the positive correlation coefficient between the vortex intensity on the back surface and the sand accumulation rate; The Goda two-point method was used to calculate the reflection wave coefficients before and after the pile, and the influence weight of the reflected wave on the local sand wave deformation was analyzed.

2. The method according to claim 1, characterized in that, In step 3, the PIV tracer particles of the flow field synchronous measurement system are hollow glass microspheres with a density that matches the experimental water, ensuring that the particle tracking error is less than 3%.

3. A high-precision sand wave morphology capture device for nearshore sand wave migration experiments, used to implement the method described in any one of claims 1-2, characterized in that, Includes wave flume (1), high-precision monitoring system for sand wave morphology, synchronous flow field measurement system, and data acquisition and processing system; The wave tank is equipped with a sand bed (2) inside. The sand bed (2) is laid at the bottom of the wave tank to simulate the bed environment of nearshore sand waves. The sand bed (2) is equipped with piles to simulate nearshore pile foundations. The high-precision monitoring system for sand wave morphology includes a terrain scanning subsystem and an image acquisition subsystem. The terrain scanning subsystem is used to perform high-precision three-dimensional scanning of the sand bed surface topography and acquire sand bed topography scanning data in real time. The image acquisition subsystem is used to acquire high-frequency images of the sand bed surface and obtain image data. The flow field synchronous measurement system is used to perform multi-dimensional synchronous measurement of the flow field near the sand wave and acquire flow field data. The data acquisition and processing system is used to simultaneously acquire, process, and fuse terrain scanning data, image data, and flow field data to generate sand wave morphology parameters and quantitative results of the interaction between the flow field and sand waves.

4. The high-precision sand wave morphology capture device for nearshore sand wave migration experiments according to claim 3, characterized in that, The terrain scanning subsystem is a multi-phase laser scanner array (7) used to achieve full-area coverage scanning of the sand bed (2), and the multi-phase laser scanner array (7) is set above the wave tank (1).

5. The high-precision sand wave morphology capture device for nearshore sand wave migration experiments according to claim 3, characterized in that, The image acquisition subsystem includes multiple sets of second high-speed cameras (8) for synchronously capturing images of different areas on the sand bed surface. The multiple sets of second high-speed cameras (8) are set on one side of the wave tank (1) and are centrally symmetrical about the center of the sand bed (2).

6. The high-precision sand wave morphology capture device for nearshore sand wave migration experiments according to claim 3, characterized in that, The flow field synchronous measurement system includes a PIV particle image velocimetry system (4) and an ADCP acoustic Doppler velocity profiler (6). The PIV particle image velocimetry system (4) is used to measure the planar velocity field of the flow field above the sand wave and capture the instantaneous vortex structure. The PIV particle image velocimetry system (4) includes a laser emitter (401) and a first high-speed camera (402). The laser emitter (401) is located directly above the wave tank (1), and the first high-speed camera (402) is located on one side of the wave tank (1). The ADCP acoustic Doppler current profiler (6) is used to obtain the velocity profile distribution along the water depth direction and to calibrate the measurement error of the PIV particle image velocimetry system (4). The ADCP acoustic Doppler current profiler (6) is installed on the wave tank (1).

7. A high-precision sand wave morphology capture device for nearshore sand wave migration experiments according to claim 3, characterized in that, The flow field synchronous measurement system also includes an ADV flow meter (3), which is provided in four sets. The four sets of ADV flow meters (3) are used to monitor the high-frequency single-point flow velocity of the sand wave crest, trough, upstream face and downstream face respectively.

8. The high-precision sand wave morphology capture device for nearshore sand wave migration experiments according to claim 3, characterized in that: The flow field synchronous measurement system also includes a wave measurement component, which includes a wave height meter (5). Four wave height meters (5) are provided, two of which are located at the front end of the pile and the remaining two are located at the rear end of the pile.

9. A high-precision sand wave morphology capturing device for nearshore sand wave migration experiments according to claim 8, characterized in that, The distance between the two wave height meters (5) located at the front end of the pile and the distance between the two wave height meters (5) located at the rear end of the pile are both ΔL, where ΔL is less than the wavelength of the wave and not equal to 1 / 2 of the wavelength of the wave.

10. A high-precision sand wave morphology capturing device for nearshore sand wave migration experiments according to claim 3, characterized in that, The data acquisition and processing system includes a multi-channel synchronous acquisition module, a raw data processing module, a parameter extraction module, and an intelligent analysis module; The multi-channel synchronous acquisition module is used to align the sand bed topography scanning data of the topography scanning subsystem, the image data of the image acquisition subsystem, and the flow field data of the flow field synchronous measurement system according to the timestamp. The raw data processing module is used to preprocess the timestamp-aligned multi-source data; The parameter extraction module is used to extract feature parameters from the preprocessed data; The intelligent analysis module is used to receive the feature parameters output by the parameter extraction module and analyze the coupling mechanism between the flow field and the evolution of sand wave morphology.

Images