Method and system for analyzing fluid-structure interaction energy dissipation of multi-body floating structure

Abstract

The invention relates to a method and a system for analyzing fluid-structure interaction energy dissipation of a multi-body floating structure. The system comprises a synchronizer which is connected with a data processing and analyzing device and is used for synchronizing a high-speed camera, a PIV laser transmitter, a wave maker controller and a wave height acquisition instrument; the analysis method comprises the following steps: under the condition of synchronization, acquiring a set average velocity field corresponding to each frame of PIV image in multiple frames of PIV images; wherein the multiple frames of PIV images are PIV images at different moments in a wave period; the set average velocity field corresponding to each frame of PIV image is obtained by averaging instantaneous velocity fields of a plurality of regular waves selected in B repeated tests under the same working condition at corresponding moments; each frame of PIV image comprises a viscous dissipation area in a surface boundary layer of the multi-body floating structure and an energy dissipation area used for representing an area of energy dissipation caused by flow separation, so that the test cost is effectively reduced, and the analysis efficiency is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of marine engineering technology, and in particular to an analysis method and system for energy dissipation in fluid-structure interaction of multibody floating structures. Background Technology

[0002] To study the flow field distribution around marine structures under wave action, continuous laser light sources are often used to irradiate tracer particles. However, the problem of strong nonlinear water resonance in the gaps of moving multi-body floating structures under wave action faces challenges such as large velocity changes in narrow gaps, abnormally complex flow field due to fluid-structure interaction between the structure and the fluid, and difficulty in capturing local details.

[0003] Furthermore, when using PIV technology for precise measurements of such complex high-speed flow fields, a very short interval between two particle images is required. Given a fixed channel bandwidth of the camera's CMOS (Complementary Metal Oxide Semiconductor) image sensor, in typical CMOS readout methods, different resolutions correspond to different frame rates due to variations in pixel readout scale. Increasing the camera's resolution and widening the field of view to capture fine local flow field details inevitably necessitates reducing the camera's frame rate, impacting the acquisition of quantitative parameters such as the spatial structure and vortex structure characteristics of the flow field, as well as the subsequent calculation and analysis of experimental data. Dividing the flow field into multiple fields of view (FOVs) and using multiple cameras to form multiple FOVs for observation, or using a single camera to conduct multiple observations in the observation area, presents two challenges. The former is more costly, while the latter requires more experiments. Both require processing images from multiple FOVs, and the velocity field images need to be stitched together with time continuity. This necessitates synchronization of the wave generator controller, wave height acquisition device, and PIV experimental device during observation, increasing the experimental difficulty. Furthermore, due to the asynchrony between the various experimental equipment systems, to ensure the reliability of the experimental results, multiple repeated observations of the same operating condition are required during the experiment. Generally, the same operating condition needs to be observed repeatedly up to 25 times, further increasing the experimental difficulty and resource investment, and severely impacting analysis efficiency. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides an analysis method and system for energy dissipation of multi-body floating structures in fluid-structure interaction, which avoids the problems of high experimental difficulty, high cost and low analysis efficiency caused by the large number of repeated observations in the prior art.

[0006] (II) Technical Solution

[0007] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0008] In a first aspect, embodiments of the present invention provide an analysis method for energy dissipation in fluid-structure interaction of a multi-body floating structure. The analysis method is applied to a data processing and analysis device within an analysis system for energy dissipation in fluid-structure interaction of a multi-body floating structure. The analysis system further includes a synchronizer connected to the data processing and analysis device and used to synchronize a high-speed camera, a PIV laser emitter, a wave generator controller, and a wave height acquisition instrument. The analysis method includes:

[0009] Under synchronous conditions, the ensemble mean velocity field corresponding to each PIV image in the multi-frame PIV image is acquired; wherein, the multi-frame PIV image is a PIV image at different times within one wave cycle; the ensemble mean velocity field corresponding to each PIV image is obtained by averaging the instantaneous velocity fields of multiple regular waves selected in B repeated experiments under the same working condition at the corresponding times, where B is a positive integer less than 25; each PIV image includes a viscous dissipation region within the surface boundary layer of the multibody floating structure and an energy dissipation region used to represent the energy dissipation caused by flow separation;

[0010] Calculate the first instantaneous viscous dissipation rate of the viscous dissipation region and the second instantaneous viscous dissipation rate of the energy dissipation region in each frame of PIV image;

[0011] The first and second instantaneous viscous dissipation rates corresponding to different frames of PIV images are compared to analyze the energy evolution process within a wave cycle.

[0012] In one possible embodiment, the thickness of the viscous dissipation region is a preset multiple of the pixel length of the PIV image.

[0013] In one possible embodiment, the energy dissipation region comprises a rectangular region below the slit entrance of the multibody floating structure, and the rectangular region is the smallest circumscribed rectangular region surrounding the largest vortex generated within a wave cycle.

[0014] In one possible embodiment, both the first instantaneous viscous dissipation rate and the second instantaneous viscous dissipation rate are calculated using the following formula:

[0015] ;

[0016] ;

[0017] ;

[0018] In the formula, Indicates the instantaneous viscous dissipation rate; Represents viscous shear stress; Indicates the average linear deformation rate; Indicates fluid density; Indicates the dynamic viscosity coefficient; and These represent the velocity components of the fluid in the i-direction and the j-direction, respectively; and These represent the directional components in the i-direction and j-direction, respectively.

[0019] In one possible embodiment, the analysis method further includes: calculating the overall viscous dissipation integral value corresponding to the target slit of the multi-body floating structure within one wave cycle; calculating the first viscous dissipation integral value of the viscous dissipation region corresponding to the target slit per unit time based on the first instantaneous viscous dissipation rate, and calculating the first ratio of the first viscous dissipation integral value to the overall viscous dissipation integral value; wherein the first ratio is used to represent the contribution ratio of the viscous dissipation of the viscous dissipation region to the overall viscous dissipation; calculating the second viscous dissipation integral value of the energy dissipation region corresponding to the target slit per unit time based on the second instantaneous viscous dissipation rate, and calculating the second ratio of the second viscous dissipation integral value to the overall viscous dissipation integral value; wherein the second ratio is used to represent the contribution ratio of the viscous dissipation of the energy dissipation region to the overall viscous dissipation.

[0020] In one possible embodiment, the total viscous dissipation integral, the first viscous dissipation integral, and the second viscous dissipation integral are all calculated using the following formula:

[0021] ;

[0022] In the formula, denoted by viscous dissipation integral; p represents the number of time intervals, which is determined by the wave period and the frame rate of the high-speed camera; P represents the total number of time intervals within one wave period; m represents the number of grid points corresponding to each PIV pixel in the x-direction within the target slit; M represents the total number of grid points in the x-direction within the target slit; n represents the number of grid points corresponding to each PIV pixel in the y-direction within the target slit; N represents the total number of grid points in the y-direction within the target slit. Indicates and The corresponding instantaneous viscous dissipation rate; x represents the horizontal position coordinate; y represents the vertical position coordinate; t represents the time coordinate.

[0023] In a second aspect, embodiments of the present invention provide an analysis system for the energy dissipation of fluid-structure interaction in multi-body floating structures, including a data processing and analysis device for performing the analysis method for the energy dissipation of fluid-structure interaction in multi-body floating structures as described in any one aspect.

[0024] Thirdly, embodiments of this application provide a storage medium storing a computer program, which, when executed by a processor, performs the method described in the first aspect or any optional implementation thereof.

[0025] Fourthly, embodiments of this application provide an electronic device, including: a processor, a memory, and a bus. The memory stores machine-readable instructions executable by the processor. When the electronic device is running, the processor communicates with the memory via the bus. When the machine-readable instructions are executed by the processor, they perform the method described in the first aspect or any optional implementation of the first aspect.

[0026] Fifthly, this application provides a computer program product that, when run on a computer, causes the computer to perform the method in the first aspect or any possible implementation thereof.

[0027] (III) Beneficial Effects

[0028] The beneficial effects of this invention are:

[0029] This application provides an analysis method and system for energy dissipation in fluid-structure interaction of a multi-body floating structure. A synchronizer integrates a high-speed camera, a PIV laser emitter, a wave generator controller, and a wave height acquisition instrument, ensuring repeatability of experimental operations on the millisecond scale, simplifying experimental procedures, and reducing experimental complexity. Furthermore, based on this synchronization system, the analysis method provided in this application reduces the number of repeated observations, thereby improving experimental efficiency, reducing experimental costs, and enabling quantitative analysis of flow field energy dissipation, thus studying the energy dissipation mechanism under fluid-structure interaction in a moving multi-body floating structure.

[0030] To make the above-mentioned objectives, features and advantages to be achieved by the embodiments of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This paper shows a structural block diagram of an analysis system for energy dissipation in a multi-body floating structure fluid-structure interaction according to an embodiment of this application.

[0033] Figure 2 This illustration shows a schematic diagram of the cross-frame synchronization relationship between a pulsed laser and a camera, provided in an embodiment of this application.

[0034] Figure 3 This illustration shows a schematic diagram of the synchronous integration of various instruments according to an embodiment of this application;

[0035] Figure 4 A flowchart is shown below illustrating an analysis method for energy dissipation in a multi-body floating structure fluid-structure interaction according to an embodiment of this application.

[0036] Figure 5 This illustration shows a schematic diagram of a flow field region division provided in an embodiment of this application. Detailed Implementation

[0037] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] To address the high experimental costs caused by numerous repeated observations in existing technologies, this application provides a method and system for analyzing energy dissipation in fluid-structure interaction (FSI) of multi-body floating structures. A synchronizer integrates a high-speed camera, a PIV laser emitter, a wave generator controller, and a wave height acquisition instrument, ensuring repeatability of experimental operations on the millisecond scale, simplifying the experimental process, and reducing experimental complexity. Furthermore, based on this synchronization system, the post-processing method provided in this application is employed to reduce the number of repeated observations, thereby improving experimental efficiency, reducing experimental costs, and enabling quantitative analysis of flow field energy dissipation, thus studying the energy dissipation mechanism under FSI of moving multi-body floating structures.

[0039] To better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present invention can be understood more clearly and thoroughly, and that the scope of the present invention can be fully conveyed to those skilled in the art.

[0040] Please see Figure 1 , Figure 1 This diagram illustrates a structural block diagram of an analysis system for energy dissipation in a multi-body floating structure fluid-structure interaction according to an embodiment of this application. Figure 1 As shown, the analysis system includes a wave generator, a multi-body floating structure, a PIV laser emitter, a high-speed camera, a digital wave height meter, tracer particles, a data acquisition and analysis device, a synchronizer, and wave suppression facilities.

[0041] Among them, the wave generator produces the incident waves required for the experiment;

[0042] Figure 1 The multi-body floating structure in the example uses a three-floating-box structure for fixation, employing adjustable trusses for support. Ball bearings connect the trusses to the structure, enabling three degrees of freedom of movement in a two-dimensional plane. It should be noted that although... Figure 1 The description is based on a three-floating-box structure, but those skilled in the art should understand that the specific structure of the multi-body floating structure can be set according to actual needs, and the embodiments of this application are not limited thereto.

[0043] Translucent materials can also be used to create the terrain beneath multi-body floating structures;

[0044] This PIV laser emitter uses a dual-pulse laser to irradiate the target area. The peak time interval of the dual-pulse laser is very short. Through precise timing control, these modulated laser "pulses" are synchronized with the cross-frame exposure window of the high-speed camera (i.e., the extremely short gap between the end of the previous frame and the start of the next frame), achieving cross-frame cross-correlation, reducing the camera frame rate, and obtaining ultra-high resolution images while capturing high-speed transient flows, as well as extremely high experimental efficiency and data reliability. The relationship between laser pulse time and camera cross-frame is as follows: Figure 2 As shown, in Figure 2 The black dashed line represents the camera exposure time, which is typically tens of milliseconds, and is certainly longer than the laser pulse duration. However, the laser pulse duration used in this experiment was 1000µs. To ensure high-resolution two-frame images, the two laser pulses need to span the inter-frame time (frame span) between the two camera exposures. The interval between the first and second laser pulses; This refers to the camera's exposure interval.

[0045] This experiment ultimately acquired 30 frames of images, with a 1000µs interval between each pair of images. This setup significantly reduces the frame rate while maintaining the measurement range and short intervals between frames, resulting in high-resolution images. The laser beam ultimately reaches the sheet element, which consists of cylindrical and spherical mirrors. The thickness of the sheet element can be adjusted. During the experiment, the sheet element should be continuously adjusted to ensure the observation surface is at the thinnest point of the laser beam, so that the captured particles are on the same plane. It should be noted that the laser pulse duration, the number of image frames acquired, and the interval between each pair of images used in this experiment can all be set according to actual needs; this embodiment is not limited to these settings.

[0046] The PIV laser emitter can emit dual-pulse lasers with a maximum energy of 120 MJ. Placing the laser emitter under a transparent terrain serves as a heat dissipation method, while the laser beam passing through the bottom can illuminate a larger area, revealing more detailed flow field changes. It should be noted that the specific energy of the dual-pulse laser emitted by the PIV laser emitter can be set according to actual needs, and this application's embodiments are not limited to this.

[0047] The flow field in the gaps within a multi-body floating structure (e.g., the flow field in the two gaps of a three-box floating marine structure) requires a high-speed camera to track each target area. Each high-speed camera's field of view covers the entire flow field, capturing changes throughout the flow. Furthermore, the high-speed camera must be able to capture individual image frames for each laser pulse.

[0048] The experiment uses a digital wave height meter to accurately measure the free surface within the structural gap, which can effectively solve the problem of free surface identification in PIV test and obtain accurate free surface change data;

[0049] Tracer particles need to be uniformly distributed in the interstitial flow field. The tracer particles will move along with the water body. The flow field is reflected by capturing the trajectory of the tracer particles with a high-speed camera.

[0050] Once two light pulse sequences are recorded, the data acquisition and analysis device divides the image into multiple small blocks called query (IA) regions. Each image frame within the query region undergoes pixel-by-pixel cross-correlation processing. Similar pixels generate a signal peak due to cross-correlation, thus identifying and determining the average flow velocity within the query region. Sub-pixel interpolation allows for precise measurement of the tracer particle displacement, thereby obtaining accurate velocity. By repeatedly performing cross-correlation calculations within the query region across the entire target area, the tracer particle velocity across the entire flow field is obtained. Finally, the images from all high-speed cameras are stitched together to depict the entire velocity field distribution. Figure 3 As shown, the synchronizer in this application can synchronize the high-speed camera, PIV laser emitter, wave generator controller, and wave height acquisition instrument. When the wave generator starts working, the PIV laser emitter and high-speed camera start working simultaneously to acquire data. The synchronizer not only simplifies the operation during the experiment and improves the repeatability of the experiment, but also reduces the workload of data processing after the experiment. Combined with the optimized post-processing method proposed in this invention, the number of experimental observations can be reduced. In the same observation, the data correlation between each wave is good. When the water resonance state in the gap under the structural fluid-structure interaction stabilizes in the experiment, the differences between the data recorded by each wave are small. When performing data post-processing, multiple sets of waves in one observation can be selected as the original data, reducing the number of observations required.

[0051] Based on the above analysis system, such as Figure 4As shown, this application embodiment further proposes a flowchart of an analysis method for energy dissipation in fluid-structure interaction of multi-body floating structures. It should be understood that this analysis method is applied to a data processing and analysis device in an analysis system for energy dissipation in fluid-structure interaction of multi-body floating structures. The analysis system also includes a synchronizer connected to the data processing and analysis device for synchronizing a high-speed camera, a PIV laser emitter, a wave generator controller, and a wave height acquisition instrument. The analysis method includes:

[0052] Step S410: Under synchronization, acquire the ensemble mean velocity field corresponding to each PIV image in the multi-frame PIV image. The multi-frame PIV image consists of PIV images at different times within one wave cycle; the ensemble mean velocity field corresponding to each PIV image is obtained by averaging the instantaneous velocity fields of multiple regular waves selected in B repeated experiments under the same working condition at corresponding times, where B is a positive integer less than 25; each PIV image includes a viscous dissipation region within the surface boundary layer of the multi-body floating structure and an energy dissipation region representing the energy dissipation caused by flow separation.

[0053] Specifically, under the fluid-structure interaction of waves and a moving multibody floating structure, viscous dissipation is calculated using flow field data (i.e., velocity data of water particles within the flow field) collected by PIV (Polymerization in Vibration) to quantitatively analyze the evolution of energy components within the flow field surrounding the structure. For data obtained from repeated measurements in the experiment, the classical ensemble averaging method is applied, and the horizontal and vertical average velocities are calculated as follows:

[0054] (1);

[0055] (2);

[0056] In the formula, Indicates the position at time t Average horizontal velocity at the location; symbol The ensemble mean is represented by N; N represents the total number of repeated trials, for example, N equals 25; n represents the nth trial. Indicates the position at time t in the nth trial. The horizontal velocity at that location; Indicates the position at time t The average vertical velocity at that location; Indicates the position at time t in the nth trial. The vertical velocity at that location.

[0057] Furthermore, the synchronous measurement method proposed in this application ensures the repeatability of the experimental operation on the order of milliseconds. In the same experiment, for multiple stable waves, the flow field velocity and wave surface data corresponding to the same phase are not significantly different. Therefore, for the relevant parameters at multiple important phases recorded within one second, we can calculate and analyze them using multiple regular wave data from B experiments. Thus, the horizontal and vertical average velocities proposed in this application are calculated as follows:

[0058] (3);

[0059] (4);

[0060] In the formula, in formula (3) This represents the average horizontal velocity obtained by averaging the instantaneous velocity fields of J regular waves selected from B repeated tests under the same working condition at corresponding times (i.e., using it as instantaneous horizontal velocity data), and the specific value of B can be set according to actual needs, for example, B can be 3, etc. Similarly, J represents the ensemble mean; J represents the total number of regular waves selected in B repeated trials, and the specific value of J can be set according to actual needs, for example, J can be 25, etc.; j represents the data of the j-th regular wave. Indicates the position of the j-th regular wave at time t. The horizontal velocity at the location; in formula (4) This represents the average vertical velocity obtained by averaging the instantaneous velocity fields of J regular waves selected from B repeated tests under the same working condition at corresponding times (i.e., using it as instantaneous vertical velocity data). Indicates the position of the j-th regular wave at time t. The vertical velocity at the location. Among them, regular wave is a term specific to marine engineering, which means that the wave's period, wave height, and wavelength remain constant, and it is a type of wave. The wave type can be selected when the wave generator generates waves. This application studies the interaction between regular waves and multi-body floating structures, so all experiments used regular waves rather than irregular waves, and all the images obtained from the experiments are the results of regular wave action.

[0061] It should be noted that this application is available. This represents the ensemble average velocity calculated above. Wherein, and These are the first and second components of the vector u, respectively, with the first component representing the average velocity in the horizontal direction and the second component representing the average velocity in the vertical direction. Unless otherwise specified, superscript tildes will be omitted in the following descriptions for simplicity. After obtaining the average horizontal and vertical velocities, the energy dissipation near the structure can be calculated.

[0062] In other words, the proposed solution is to select multiple images from the wave images taken during the B test to form an image of a wave cycle, and finally to perform a quantitative analysis of the fluid-structure interaction energy dissipation within a cycle.

[0063] It's important to clarify that a single experiment typically records multiple waves. "Regular wave" is a term specific to marine engineering, indicating that the wave's period, wave height, and wavelength remain constant. For example, if the wave period is set to 1.2 seconds during wave generation, a single experiment would generally record data for about 30 seconds (this invention primarily records velocity field data), meaning this experiment records over 20 regular wave data points. However, to avoid random errors, an experiment with the same parameters usually needs to be repeated 25 times. Then, one regular wave data point is selected from each of the 20+ recorded data points to form 25 regular wave data points for the next step of ensemble averaging. This method results in a significant amount of experimental data being wasted. This application, however, utilizes a synchronizer to achieve millisecond-level repeatability. Therefore, only a small number (B times) of repeated experiments are needed, and 25 regular wave data points are selected from the data recorded in these few repeated experiments for calculation (generally 10+10+5), greatly reducing the experimental cost.

[0064] Furthermore, the application proposes a method for quantitatively analyzing energy dissipation during fluid-structure interaction in a moving multibody floating structure. First, the dissipation rate at each point within the entire flow field is calculated. Then, the distribution of the dissipation rate is observed, revealing two main distribution patterns: energy dissipation consists of two main components. Further detailed regional calculations are then performed. These components are: one part is viscous dissipation within the boundary layer of the structure surface (i.e., the viscous dissipation region); the other part is energy dissipation caused by flow separation (the energy dissipation region). To quantitatively analyze these two dissipation components, such as... Figure 5 As shown, different control volumes (e.g., regions V1, V2, and V3) are used for computational analysis near the structure. Region V1, enclosed by the blue line, includes the laser-illuminated inverted triangular measurement area and the narrow-slit water body, minus the area occupied by the structural wall thickness. The viscous dissipation region V2, corresponding to the red line, is a thin layer surrounding the two rectangular structures. The thickness of this viscous dissipation region V2 is a preset multiple of the pixel length of the PIV image, and this preset multiple can be set according to actual needs. For example, the thickness of the viscous dissipation region V2... The energy dissipation region V3, enclosed by the green line, can include a portion of the narrow slit water area and a rectangular region below the slit entrance. This rectangular region is the smallest circumscribed rectangular region surrounding the largest vortex generated within one wave cycle. For example, the energy dissipation region V3 can include a range covering 30 PIV pixels above and below the slit entrance and 29 PIV pixels to the left and right of the center line. This region is the main area for vortex generation and dissipation, centered at the entrance and extending outwards to the furthest point that the vortex evolution can reach.

[0065] Step S420: Calculate the first instantaneous viscous dissipation rate of the viscous dissipation region and the second instantaneous viscous dissipation rate of the energy dissipation region in each frame of the PIV image.

[0066] Specifically, viscous shear stress is proportional to the deformation rate of a Newtonian fluid. Newton's law of internal friction for compressible fluids involves two proportionality constants, the first being the (dynamic) viscosity coefficient. The second viscosity coefficient characterizes the stress caused by linear deformation. The stress characterizing the volumetric deformation, with respect to the viscosity coefficient. There is not much understanding of it because its practical use is minimal; in engineering, it can be used... For incompressible fluids, the mass conservation equation is: The viscous shear stress is twice the linear deformation rate multiplied by the dynamic viscosity coefficient. According to Newton's law of internal friction, the nine components of viscous shear stress are:

[0067] (5);

[0068] In the formula, Represents viscous shear stress, and The subscripts i and j indicate that the shear stress acts on a plane parallel to the i direction and points in the j direction; and These represent the velocity components of the fluid in the i and j directions, respectively, and i and j can both take values ​​of 1, 2, and 3, respectively, and they represent the x, y, and z directions, respectively. and Let represent the directional components in the i-direction and j-direction, respectively, where i and j can both take values ​​of 1, 2, and 3, and represent the x, y, and z directions, respectively. Also, 6 of these components are independent of each other.

[0069] Furthermore, for isotropic fluids, in the three-dimensional case, the average linear deformation rate... It has 9 components, of which 6 are independent. Furthermore, this... The calculation expression is:

[0070] (6);

[0071] In the formula, The average linear deformation rate is represented by i and j, which can both take values ​​of 1, 2, and 3, respectively, representing the x, y, and z directions. The average linear deformation rate includes 3 tensile deformation components and 6 pure shear deformation components.

[0072] Furthermore, by applying the Newtonian incompressible model of viscous shear stress and eliminating kinetic energy from the energy equation, the internal energy equation can be obtained as follows:

[0073] (7);

[0074] In the formula, t represents internal energy; t represents time. And the kinematic viscosity coefficient ,in The dynamic viscosity coefficient is... The fluid density is given.

[0075] Furthermore, all effects caused by viscous shear stress are defined in the first term on the right-hand side of equation (7) (i.e., the term within the curly braces {} on the right-hand side of equation (7)). After a large number of algebraic operations conforming to Einstein's conventions (Einstein summation convention, Einstein reduction), the first term on the right-hand side of equation (7) can be expressed as a viscous dissipation rate function. Regarding the viscous dissipation rate per unit mass The specific derivation process is as follows:

[0076] (8);

[0077] Substituting equation (5) into equation (8) and performing appropriate algebraic operations, we obtain the instantaneous viscous dissipation rate:

[0078] (9).

[0079] From the mathematical expression of equation (8), it can be seen that the dissipation equation does not contain negative numbers because it only contains square terms and represents the internal energy caused by the deformation effect of fluid particles. From the form of equation (9), it can be seen that dissipation is mainly caused by mechanical motion and gradually converted into internal energy and heat. The dimension of m 2 s -3 Furthermore, it plays an important role in estimating viscous dissipation within different control volumes.

[0080] Furthermore, the instantaneous viscous dissipation rate can be calculated in each region control body by dividing the flow field into regions using the above formula (9). For example, the first instantaneous viscous dissipation rate of the viscous dissipation region and the second instantaneous viscous dissipation rate of the energy dissipation region in each frame of PIV image can be calculated respectively.

[0081] Step S430: Compare the first instantaneous viscous dissipation rate and the second instantaneous viscous dissipation rate corresponding to different frame PIV images to analyze the energy evolution process within a wave cycle.

[0082] Specifically, in the interaction between waves and the solid-state coupling of a moving multibody floating structure, multiple PIV images will be obtained within one wave cycle. By calculating the instantaneous viscous dissipation rate of each frame and comparing the results between different frames, the generation, distribution and evolution of energy dissipation within one cycle can be preliminarily analyzed.

[0083] In other words, the calculated result of the viscous dissipation rate for each frame represents the distribution of the viscous dissipation rate at a certain moment within a cycle. By observing and comparing the distribution of the viscous dissipation rate at different moments within a cycle, the energy evolution of a cycle can be analyzed.

[0084] Furthermore, the analysis method also includes: calculating the overall viscous dissipation integral value corresponding to the target slit of the multi-body floating structure within one wave cycle; calculating the first viscous dissipation integral value of the viscous dissipation region corresponding to the target slit per unit time based on the first instantaneous viscous dissipation rate, and calculating the first ratio of the first viscous dissipation integral value to the overall viscous dissipation integral value; wherein, the first ratio is used to represent the contribution ratio of the viscous dissipation of the viscous dissipation region to the overall viscous dissipation; calculating the second viscous dissipation integral value of the energy dissipation region corresponding to the target slit per unit time based on the second instantaneous viscous dissipation rate, and calculating the second ratio of the second viscous dissipation integral value to the overall viscous dissipation integral value; wherein, the second ratio is used to represent the contribution ratio of the viscous dissipation of the energy dissipation region to the overall viscous dissipation.

[0085] To facilitate understanding of the above contribution ratio process, specific examples are described below.

[0086] Specifically, the viscous dissipation of the control volume per unit time can be obtained by integrating the energy dissipation rate within the control volume using the following formula:

[0087] (10);

[0088] In the formula, E represents the viscous dissipation per unit time; m represents the number of grid points corresponding to each PIV pixel in the x-direction within the target slit; M represents the total number of grid points in the x-direction within the target slit; n represents the number of grid points corresponding to each PIV pixel in the y-direction within the target slit; and N represents the total number of grid points in the y-direction within the target slit. denoted by , x represents the instantaneous viscous dissipation rate; x represents the horizontal position coordinate. y represents the horizontal length of the m-th grid in the horizontal direction; y represents the vertical position coordinate. This represents the vertical length of the nth grid cell.

[0089] Furthermore, to calculate the proportion of viscous dissipation contribution of each control volume within one wave cycle, the integral value of viscous dissipation is defined as:

[0090] (11);

[0091] In the formula, denoted by viscous dissipation integral value; p represents the number of time intervals, which is determined by the wave period and the frame rate of the high-speed camera. For example, if the wave period is 1.2 seconds and the high-speed camera records 15 frames per second, then there are 18 frames of image data in one wave period, and the corresponding number of time intervals is 18; P represents the total number of time intervals in one wave period; t represents time. This represents the length of the p-th time interval.

[0092] In formula (11), by taking the control volume as the entire flow field region, the total viscous dissipation integral value within one wave cycle can be calculated. In the process of calculating the total viscous dissipation integral value, the instantaneous viscous dissipation rate of the entire flow field region is taken as the control volume. Substituting into formula (11), the first viscous dissipation integral value of the viscous dissipation region and the second viscous dissipation integral value of the energy dissipation region can be calculated using formula (11). Thus, the dissipation intensity of different regions of the flow field can be quantitatively described, and the contribution ratio of viscous dissipation in different regions to the total viscous dissipation can be obtained. Furthermore, the main generation regions and mechanisms of viscous dissipation during the flow-solid coupling interaction between waves and multi-body structures can be analyzed.

[0093] In other words, the viscous dissipation integral values ​​of region V2, region V3 and the entire flow field region can be calculated using the above formula (11). Then, the first viscous dissipation integral value of region V2 can be divided by the total viscous dissipation integral value of the entire region to obtain the contribution ratio of the viscous dissipation of region V2 to the total viscous dissipation. The second viscous dissipation integral value of region V3 can be divided by the total viscous dissipation integral value of the entire region to obtain the contribution ratio of the viscous dissipation of region V3 to the total viscous dissipation.

[0094] In summary, by utilizing the above-mentioned technical solutions, compared with the continuous light source in PIV technology, the pulsed laser source can achieve high-resolution images at shorter time intervals through cross-frame synchronization of the pulsed laser and the camera, enabling precise measurements of the flow field over a larger area. The synchronous measurement system of this application allows for rapid comparison of flow field and wave height data at the same phase during post-processing, facilitating the screening and verification of experimental data. Simultaneously, it effectively reduces the number of experiments required, significantly improves experimental repeatability, and saves on experimental costs.

[0095] Furthermore, for the fluid-structure interaction between waves and moving multibody floating structures, the complex flow field structure makes the energy evolution process equally complex. The energy dissipation analysis method of this application can perform quantitative analysis of the flow field in different regions. By calculating the energy dissipation of the flow field at different phases within a wave cycle, the energy evolution process within the flow field can be studied.

[0096] It should be understood that the above-described analysis method for energy dissipation in fluid-structure interaction of multi-body floating structures is merely exemplary. Those skilled in the art can make various modifications based on the above method, and the modified solutions also fall within the protection scope of this application.

[0097] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0098] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, as well as combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions.

[0099] It should be noted that any reference numerals placed between parentheses in the claims should not be construed as limiting the claims. The word "comprising" does not exclude the presence of components or steps not listed in the claims. The word "a" or "an" preceding a component does not exclude the presence of a plurality of such components. The invention can be implemented by means of hardware comprising several different components and by means of a suitably programmed computer. In claims that enumerate several means, several of these means may be embodied by the same hardware. The use of the terms first, second, third, etc., is merely for convenience of expression and does not indicate any order. These terms can be understood as part of the component names.

[0100] Furthermore, it should be noted that in the description of this specification, the terms "one embodiment," "some embodiments," "embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0101] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the claims should be interpreted to include both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0102] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, then this invention should also include these modifications and variations.

Claims

1. An analytical method for energy dissipation in a multi-body floating structure fluid-structure interaction, characterized in that, The analytical method is applied to a data processing and analysis device in an analysis system for energy dissipation in fluid-structure interaction of multi-body floating structures. The analysis system further includes a synchronizer connected to the data processing and analysis device for synchronizing a high-speed camera, a PIV laser emitter, a wave generator controller, and a wave height acquisition instrument. The analytical method includes: While synchronizing, the ensemble average velocity field corresponding to each PIV image in a multi-frame PIV image is acquired; wherein, the multi-frame PIV images are PIV images at different times within one wave cycle; the ensemble average velocity field corresponding to each PIV image is obtained by averaging the instantaneous velocity fields of multiple regular waves selected in B repeated experiments under the same working condition at corresponding times, where B is a positive integer less than 25; each PIV image includes a viscous dissipation region within the surface boundary layer of the multi-body floating structure and an energy dissipation region representing the energy dissipation caused by flow separation. Calculate the first instantaneous viscous dissipation rate of the viscous dissipation region and the second instantaneous viscous dissipation rate of the energy dissipation region in each frame of the PIV image; The first instantaneous viscous dissipation rate and the second instantaneous viscous dissipation rate corresponding to different frames of PIV images are compared to analyze the energy evolution process within one wave cycle.

2. The analytical method according to claim 1, characterized in that, The thickness of the viscous dissipation region is a preset multiple of the pixel length of the PIV image.

3. The analytical method according to claim 1 or 2, characterized in that, The energy dissipation region includes a rectangular region below the narrow slit entrance of the multibody floating structure, and the rectangular region is the smallest circumscribed rectangular region surrounding the largest vortex generated within one wave cycle.

4. The analytical method according to claim 1, characterized in that, Both the first instantaneous viscous dissipation rate and the second instantaneous viscous dissipation rate are calculated using the following formulas: ； ； ； In the formula, Indicates the instantaneous viscous dissipation rate; Represents viscous shear stress; Indicates the average linear deformation rate; Indicates fluid density; Indicates the dynamic viscosity coefficient; and These represent the velocity components of the fluid in the i-direction and the j-direction, respectively; and These represent the directional components in the i-direction and the j-direction, respectively.

5. The analytical method according to claim 1, characterized in that, The analytical method further includes: Calculate the overall viscous dissipation integral value corresponding to the target narrow slot of the multi-body floating structure within one wave cycle. Based on the first instantaneous viscous dissipation rate, the first viscous dissipation integral value of the viscous dissipation region corresponding to the target slit per unit time is calculated, and the first ratio of the first viscous dissipation integral value to the total viscous dissipation integral value is calculated; wherein, the first ratio is used to represent the contribution ratio of the viscous dissipation of the viscous dissipation region to the total viscous dissipation. Based on the second instantaneous viscous dissipation rate, the second viscous dissipation integral value of the energy dissipation region corresponding to the target slit per unit time is calculated, and the second ratio of the second viscous dissipation integral value to the total viscous dissipation integral value is calculated; wherein, the second ratio is used to represent the contribution ratio of the viscous dissipation of the energy dissipation region to the total viscous dissipation.

6. The analytical method according to claim 5, characterized in that, The total viscous dissipation integral value, the first viscous dissipation integral value, and the second viscous dissipation integral value are all calculated using the following formula: ； In the formula, The integral value represents the viscous dissipation; p represents the number of time intervals, which is determined by the wave period and the frame rate of the high-speed camera; P represents the total number of time intervals within one wave period; m represents the number of grid points corresponding to each PIV pixel in the x-direction within the target slit; M represents the total number of grid points in the x-direction within the target slit; n represents the number of grid points corresponding to each PIV pixel in the y-direction within the target slit; N represents the total number of grid points in the y-direction within the target slit. Indicates the above The corresponding instantaneous viscous dissipation rate; x represents the horizontal position coordinate; y represents the vertical position coordinate; t represents the time coordinate.

7. An analysis system for energy dissipation in fluid-structure interaction of multi-body floating structures, characterized in that, The device includes a data processing and analysis apparatus for performing the analysis method for energy dissipation in fluid-structure interaction of a multibody floating structure as described in any one of claims 1-6.

8. A storage medium having a computer program stored thereon, characterized in that, The computer program is executed by the processor to perform the analysis method for energy dissipation of fluid-structure interaction in multibody floating structures as described in any one of claims 1-6.

9. An electronic device comprising a processor, a memory, and a computer program stored in the memory, characterized in that, The processor executes the computer program to implement the analysis method for energy dissipation in fluid-structure interaction of multibody floating structures as described in any one of claims 1-6.

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