Method for identifying wave load of fixed structure in any shape based on field wave elevation

Abstract

The invention discloses an arbitrary-shape fixed structure wave load identification method based on field wave elevation, relates to the field of ocean engineering structure health monitoring, and aims to solve the problem that a traditional method depends on incident wave information and is only suitable for a simple structure. The method comprises the following steps: averaging M surface elements on a wet surface of a discrete structure; pre-calculating and storing a transfer matrix which only depends on the structure geometry, the measuring point position and the wave frequency; wave elevation time history data of W measuring points are collected in real time, and main frequency components are reserved through fast Fourier transform; calling a corresponding transfer matrix, and obtaining a surface element pressure Fourier component through matrix multiplication; and performing inverse transformation to synthesize a pressure time history and integrating to obtain a total wave load. The invention also discloses a system for realizing the method, electronic equipment, a computer program product and a storage medium. The method is high in universality, does not need incident wave information, is efficient in calculation, and is suitable for various fixed ocean structures.

Description

Technical Field

[0001] This invention belongs to the field of marine engineering structural health monitoring technology, specifically relating to a method for identifying wave loads on fixed structures of arbitrary shapes based on on-site wave elevation. Background Technology

[0002] Fixed structures such as offshore platforms and offshore wind turbine foundations are critical infrastructure for marine resource development. Accurately obtaining the real-time wave loads they bear is crucial during the design, operation, and maintenance of these structures. Traditional wave load calculation methods, such as the Morrison equation (applicable to small-scale structures) and diffraction theory (applicable to large-scale structures), while theoretically mature, suffer from a fundamental limitation in practical applications: they all require detailed information about the incident wave field undisturbed by the structure, such as wave height, period, and wave direction. However, in real marine environments, due to complex wave reflection and diffraction interference caused by wind, seabed topography, and the structure itself, accurately measuring the pure incident wave parameters is extremely difficult, severely restricting the accuracy of traditional methods in field applications.

[0003] As an alternative, a large number of pressure sensors can be directly installed on the underwater surface of the structure to measure the hydrodynamic pressure, and then integrated to obtain the total load. However, this direct measurement method is generally not practically feasible. The main reason is that deploying and maintaining a large number of pressure sensors in an underwater environment is technically difficult and extremely costly, and inferring the global total load from a limited number of local measurement points also involves additional complexity.

[0004] To overcome these difficulties, researchers have begun exploring the use of more easily measurable physical quantities around structures to invert wave loads. Among these, utilizing wave elevation data near the structure has emerged as a promising direction, given the strong physical correlation between the wave free surface and the underwater pressure field. Chinese Patent Publication No. CN 106777784A discloses a direct mathematical relationship between wave elevation and wave force around a geometrically regular fixed cylinder, validating the feasibility of identifying loads using only local wave elevation data. However, the core drawback of this technique lies in its heavy reliance on the simple geometry of the cylinder, employing specific mathematical methods that can only analytically solve cylindrical problems. This makes it unsuitable for generalization to structures with arbitrarily complex shapes (such as jacket platforms and gravity foundations) more prevalent in marine engineering. Therefore, extending this wave elevation-based load identification approach from simple cylinders to structures of arbitrary shapes is a key technological challenge currently facing this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the limitations of the prior art and provide a wave load identification method for fixed structures of arbitrary shapes based on on-site wave elevation. This method only requires the use of easily measurable on-site wave elevation data around the structure, without any information about the incident wave field, and is applicable to fixed marine structures such as offshore platforms, monopile wind turbine foundations, and cross-sea bridge piers.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for identifying wave loads on a fixed structure of arbitrary shape based on on-site wave elevation, comprising the following steps:

[0007] S1: Discretize the average wetted surface of the fixed structure into... A planar element;

[0008] S2: Establish a direct mapping relationship between the Fourier component vector of the measured wave elevation and the Fourier component vector of the pressure on the structural surface to obtain the transfer matrix. The transfer matrix depends only on the structural geometry, the location of the measuring point and the wave frequency. The transfer matrix corresponding to different wave frequencies is pre-calculated and stored.

[0009] S3: Real-time data acquisition Wave elevation time history data from each wave height monitoring point were processed using a Fast Fourier Transform, retaining the previous values. The main frequency components are used to obtain the Fourier components of the measured wave elevation.

[0010] S4: Retrieve the pre-stored transfer matrix of the corresponding frequency and calculate the pressure Fourier components of each surface element of the structure through matrix multiplication.

[0011] S5: Perform inverse fast Fourier transform on the pressure Fourier components to synthesize the pressure time history. The total wave load is obtained by integrating the pressure on each surface element.

[0012] Furthermore, in step S1, the... The value range is 100-2000. The wave height monitoring points are evenly arranged around the structure.

[0013] Furthermore, in step S2, the expression for the transfer matrix is:

[0014]

[0015] In the formula, The density of the water body; It is the acceleration due to gravity;

[0016]

[0017] In the formula, The area of ​​the face unit; The coordinates of the wave height monitoring point; As the source point;

[0018]

[0019] In the formula, for Bessel function of order 1;

[0020] Let the wave number be and satisfy the linear dispersion relation. ;

[0021] To truncate the order, it must satisfy the following condition. ;

[0022] The radial distance of the wave height monitoring point; The circumferential angle of the wave height monitoring point;

[0023]

[0024] In the formula, As the venue, , All are located at the center coordinates of the surface element, corresponding to the cylindrical coordinate system. ;

[0025] The symbol for Kronecker; For the first The normal vector of each face element;

[0026]

[0027]

[0028] In the formula, The vertical coordinates of the center of the element; The radial distance from the center of the surface element; The circumferential angle of the center of the surface element; This is the vertical distribution function;

[0029]

[0030] In the formula, for The derivative; for Derivative; The normal vectors of the surface elements are respectively in Component of direction;

[0031]

[0032] in, The Green's function has the following form:

[0033] in , It is the angular frequency; For water depth;

[0034] The distance term in the Green's function is defined as:

[0035]

[0036] In the formula, The coordinates of the reference point;

[0037] Furthermore, when the ratio of water depth to wavelength is ≥0.5, the Green's function is calculated using the following formula to simplify the calculation:

[0038]

[0039] Furthermore, in step S5, the calculation expression for the total wave load is:

[0040] In the formula, For the first Each element in the first Pressure Fourier components at the main frequency components For the first The area of ​​each face element; This is the unit vector for the load calculation direction.

[0041] This invention also provides a wave load identification system for arbitrary-shaped fixed structures based on on-site wave elevation, implementing the above-described method for wave load identification of arbitrary-shaped fixed structures based on on-site wave elevation, including:

[0042] The discretization module is configured to discretize the average wetted surface of a fixed structure into... A planar element;

[0043] The transfer matrix pre-calculation module is configured to establish the mapping relationship between the Fourier component vector of the measured wave elevation and the Fourier component vector of the pressure on the structural surface, calculate and store the transfer matrix corresponding to different wave frequencies.

[0044] The data acquisition and frequency domain analysis module is configured to acquire data in real time via sensors. Wave elevation time history data from each wave height monitoring point were processed using a Fast Fourier Transform and the previous data was retained. One main frequency component;

[0045] The pressure calculation module is configured to retrieve a pre-stored transfer matrix and calculate the pressure Fourier components of each surface element through matrix multiplication.

[0046] The load integration module is configured to perform inverse fast Fourier transform on the pressure Fourier components and perform area integration on the pressure of each surface element to obtain the total wave load.

[0047] The present invention also provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the wave load identification method for an arbitrary-shaped fixed structure based on the on-site wave elevation as described above.

[0048] The present invention also provides a computer program product, which, when executed by a processor, implements the wave load identification method for an arbitrary-shaped fixed structure based on the on-site wave elevation as described above.

[0049] The present invention also provides a computer-readable storage medium having a computer program stored thereon, which is executed by a processor to implement a wave load identification method for an arbitrary-shaped fixed structure based on the on-site wave elevation as described above.

[0050] Compared with existing technologies, the advantages of this invention are as follows: It has the advantage of high versatility: by employing the boundary element method, the wave elevation-based load identification method is extended from simple cylindrical structures to fixed structures of arbitrarily complex shapes. It requires no incident wave information: through mathematical derivation, the dependence on unknown incident wave parameters is theoretically eliminated, solving the core problem of on-site measurement. It has the advantage of high computational efficiency: by pre-calculating the transfer matrix, the online computation is minimized, enabling real-time identification and monitoring of wave loads. It has the advantage of good practicality: the method only relies on wave elevation data that is easily measured by sensors deployed near the structure, providing convenience for practical engineering applications. Attached Figure Description

[0051] Figure 1 The flowchart of the wave load identification method of the present invention includes key steps such as data acquisition, transfer matrix calculation, load identification, and integration.

[0052] Figure 2 The following is an example diagram of grid division, using a runway cross-section column and a cylinder with a cantilever slab as examples.

[0053] Figure 3 The diagram shows the locations of wave elevation measurement points evenly distributed around the structure, taking a runway cross-section column as an example (W=12).

[0054] Figure 4 This is a verification diagram of the recognition results of the present invention on two different shape structures. Detailed Implementation

[0055] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments, so as to better understand the present invention.

[0056] Example 1

[0057] The core idea of ​​this method lies in constructing a direct mathematical mapping from "input" (measured wave elevation) to "output" (hydrodynamic pressure on the structural surface). This mapping is achieved through a "transfer matrix," which encapsulates the complex physical processes of wave-structure interaction. This invention, through theoretical construction, completely eliminates the incident wave field parameters, which are unknowns, algebraically during the derivation of this transfer matrix. Thus, the final transfer matrix depends only on the geometry of the structure and the wave frequency, and is independent of specific, unknown incident wave conditions, fundamentally avoiding the need for incident wave information in traditional methods. This method first decomposes the total velocity potential into incident potential and diffraction potential within the framework of linear potential flow theory. The incident potential is represented by a series expansion with undetermined coefficients, representing unknown incident wave information. The diffraction potential is represented by a boundary integral equation based on Green's function, with the key unknown being the source intensity distribution on the structural surface. Subsequently, using linearized free surface conditions and Bernoulli's equation, the relationships between wave elevation and hydrodynamic pressure and these two velocity potentials are established. This results in a system of linear equations containing three core equations and two sets of unknowns (undetermined coefficients of the incident potential and the source strength). Through algebraic operations, these two sets of unknowns can be eliminated from the system of equations, ultimately yielding a transfer matrix directly related to wave elevation and hydrodynamic pressure. To apply this method to structures of arbitrary geometries, this embodiment discretizes the wetted surface of the arbitrary-shaped structure into a series of small surface elements, transforming the complex boundary integral equations into numerically solvable matrix equations. This numerical approach allows the method to overcome its dependence on specific geometries (such as cylinders) and is applicable to various complex configurations, such as jacket structures, gravity foundations, or any irregularly shaped bridge piers. Transfer Matrix The specific form is as follows:

[0058]

[0059] in, For water density, It is the acceleration due to gravity;

[0060] The remaining matrices are defined as follows:

[0061]

[0062] In the formula, The area of ​​the face unit; The coordinates of the wave height monitoring point; As the source point;

[0063]

[0064] In the formula, for Bessel function of order 1;

[0065] Let be the wave number, satisfying the linear dispersion relation: ;

[0066] To truncate the order, it must satisfy the following condition. ;

[0067] The radial distance of the wave height monitoring point; The circumferential angle of the wave height monitoring point;

[0068]

[0069] In the formula, As the venue, , All are located at the center coordinates of the surface element, corresponding to the cylindrical coordinate system. ; The symbol for Kronecker; For the first The normal vector of each face element;

[0070]

[0071]

[0072] In the formula, The vertical coordinates of the center of the element; The radial distance from the center of the surface element; The circumferential angle of the center of the surface element; This is the vertical distribution function;

[0073]

[0074] In the formula, for The derivative; for Derivative; The normal vectors of the surface elements are respectively in Component of direction;

[0075]

[0076] in, The Green's function has the following form:

[0077] in , It is the angular frequency; For water depth;

[0078] The distance term in the Green's function is defined as:

[0079]

[0080] In the formula, The coordinates are for the reference point.

[0081] When the water depth is greater than or equal to the wavelength by 0.5, the Green's function is calculated using the following formula to simplify the calculation:

[0082]

[0083] Specifically, the present invention is achieved through the following steps:

[0084] Step S1 (Discretization): The average wetted surface of the structure Discretized Planar element ,in, The recommended value range is 100-2000.

[0085] Step S2 (Transfer Matrix Construction): Establish the Fourier component vector of the measured wave elevation. Fourier component vector of pressure on structural surface Direct mapping relationship between them:

[0086]

[0087] In the formula, The desired transfer matrix depends only on the structural geometry, measurement point locations, and wave frequency. This matrix can be applied to different frequencies. Calculate and store in advance, the specific form of which is determined by the expression provided above.

[0088] Step S3 (Data Acquisition): Real-time data acquisition Wave elevation time history at each measuring point Perform FFT analysis and retain the previous values. The main frequency components were used to obtain the Fourier components of the measured wave elevation. .

[0089] Step S4 (Load Identification): Retrieve pre-stored data Through matrix multiplication Calculate the pressure components.

[0090] Step S5 (Integration): Synthesize the pressure time history using inverse FFT. and to The total wave load is obtained by integrating the pressure on each surface element. The expression for calculating the total wave load is as follows:

[0091] In the formula, For the first Each element in the first Pressure Fourier components at the main frequency components For the first The area of ​​each face element; This is the unit vector for the load calculation direction.

[0092] This invention offers significant practical advantages, namely, the feasibility of real-time calculation. The most computationally intensive part of the method (calculation of the transfer matrix) depends only on the structural geometry, the arrangement of measuring points, and the frequency. Therefore, for a given structure, a series of frequency-corresponding transfer matrices can be pre-calculated and stored offline. In the online monitoring phase, the actual task is simplified to: collecting wave elevation data, performing a fast Fourier transform, and then executing simple matrix multiplication operations to obtain the pressure. This design, which offlineizes the "heavy computation" and onlineizes the "light computation," makes the entire identification process extremely efficient, fully meeting the needs of real-time monitoring at engineering sites.

[0093] Example 2

[0094] like Figure 1 As shown, the process is divided into two stages: an offline pre-calculation stage and an online real-time identification stage.

[0095] Offline pre-computation phase (steps S1, S2):

[0096] (a) Obtain underwater geometric models of fixed structures (such as offshore wind turbine foundations, platforms, etc.).

[0097] (b) Mesh the average wetted surface of the model, such as... Figure 2 As shown, it is discretized into Each face value.

[0098] (c) Determine Location of each wave height monitoring point ( =12), monitoring points should be evenly distributed around the structure, such as Figure 3 As shown.

[0099] (d) Define a frequency range (e.g., 0.05–5.0 Hz). For each discrete frequency within this range... According to the formula described in Example 1, the transfer matrix is ​​calculated and stored. .

[0100] Online real-time identification stage (steps S3, S4, S5):

[0101] (e) Data acquisition: via installation on Sensors (such as wave height meters, cameras, or wave radars) at individual measurement points collect real-time wave elevation time history data. .

[0102] (f) Fourier transform: for the acquired time history data Perform an FFT to obtain the frequency domain coefficient vector. And cut off, retaining the maximum energy Each frequency component ( =50), that is:

[0103]

[0104] (g) Load calculation: For this Each frequency retrieves a pre-stored transfer matrix from the database. Calculated by matrix multiplication Pressure components on each surface element:

[0105]

[0106] (h) Synthesize and integrate the total pressure: by inverse FFT Transforming back to the time domain, the integral yields the total wave force acting on the structure, i.e.:

[0107]

[0108] Example 3

[0109] This embodiment provides a runway cross-section model to verify the applicability of the method to arbitrary (non-circular) geometries. The model is a runway-shaped cross-section (semicircular ends and rectangular middle). Model parameters: =540, =12, =6, =50. For example... Figure 4 As shown in (a), the identification results are in high agreement with the experimental measurements, and the normalized root mean square error under irregular waves is only 2%. This embodiment demonstrates that the present invention successfully overcomes the limitation of existing methods that are only applicable to cylinders.

[0110] Example 4

[0111] This embodiment provides a complex model with an arc-shaped plate to verify the application of this method in structures with complex auxiliary components. The model is a cylinder with an annular underwater arc-shaped protective plate, a structure that leads to stronger wave interactions. Model parameters: =577, =8, =10, =50. For example... Figure 4 As shown in (b), the identified wave forces agree well with the measured values ​​in terms of phase and overall trend. However, at certain extreme peaks (such as the irregular condition from +6s to +8s), the identified values ​​are lower than the measured peak impact values ​​due to wave breaking and impact. Nevertheless, the overall normalized root mean square error remains at 9%.

[0112] In summary, this invention provides a universal, efficient, and accurate method for wave load identification. Utilizing readily measurable on-site wave elevation data and a pre-calculated, geometry-dependent transfer matrix, it can invert the wave load on fixed structures of arbitrary shapes in real time, solving the technical problems of traditional methods that rely on incident wave parameters and are limited to simple geometric shapes.

Claims

1. A method for identifying wave loads on a fixed structure of arbitrary shape based on in-situ wave elevation, characterized by, The method comprises the following steps: S1: discretize the average wet surface of the fixed structure into plane facets; S2: establishing a direct mapping relationship between the Fourier component vector of the measured wave height and the Fourier component vector of the structural surface pressure, obtaining a transfer matrix, and the transfer matrix only depends on the structural geometry, the measuring point position and the wave frequency, and the transfer matrix corresponding to different wave frequencies is pre-calculated and stored; S3: Real-time acquisition wave height monitoring points, and the wave height time series data are obtained. Fast Fourier transform is performed on the data, and the first main frequency components are reserved to obtain the Fourier components of the measured wave height. S4: calling the pre-stored transfer matrix corresponding to the frequency, and calculating the pressure Fourier component of each surface element of the structure surface through matrix multiplication; S5: Perform inverse fast Fourier transform on the pressure Fourier components to synthesize the pressure time history, perform area integration on the pressure on the surface element to obtain the total wave load. S5: Perform inverse fast Fourier transform on the pressure Fourier components to synthesize the pressure time history, perform area integration on the pressure on the surface element to obtain the total wave load.

2. The method of claim 1, wherein, In step S1, the ranges from 100 to 2000, wave height monitoring points are uniformly arranged around the structure.

3. The method of claim 1, wherein, In step S2, the expression of the transfer matrix is: wherein is the density of the water body; is the acceleration due to gravity; In the formula, is the area of the facet; is the wave height monitoring point coordinate; is the source point; In the formula, is Bessel function of the first kind For the wave number, the linear dispersion relation is satisfied: ; For the order of truncation, it is necessary to satisfy ; is a radial distance of the wave height monitoring point; is a circumferential angle of the wave height monitoring point; In the formula, is the field point, , are located in the center coordinates of the surface element, and correspond to the column coordinates ; is the Kronecker symbol; is the normal vector of the th surface element; wherein is the vertical coordinate of the bin center; is the radial distance of the bin center; is the circumferential angle of the bin center; is the vertical distribution function; wherein is the derivative of ; is the derivative of ; are the components of the face normal vector in the directions, respectively. wherein G is the Green function, having the form wherein , is the circular frequency; is the water depth; The distance term in the Green function is defined as: In the formula, is the reference point coordinate.

4. The method of claim 3, wherein, When the ratio of water depth to wavelength is greater than or equal to 0.5, the Green function adopts the following formula to simplify the calculation:

5. The in-situ wave elevation based arbitrary shape fixed structure wave load identification method of claim 1, wherein, In step S5, the calculation expression of the total wave load is: wherein is the pressure Fourier component of the th surface element at the th dominant frequency component, is the area of the th surface element; is the unit vector of the load calculation direction.

6. A system for identifying wave loads on a fixed structure of arbitrary shape based on in-situ wave elevation, characterized by, A flow of a wave load identification method for a fixed structure of any shape based on an in-situ wave height according to any one of claims 1-5, comprising: a discretization module configured to discretize the average wet surface of the fixed structure into a plurality of planar facets; A transfer matrix pre-calculation module configured to establish a mapping relationship between the Fourier component vector of the measured wave height and the Fourier component vector of the structural surface pressure, calculate the transfer matrix corresponding to different wave frequencies and store them; The data acquisition and frequency domain analysis module is configured to acquire wave height time history data of a wave height monitoring point in real time through a sensor, perform fast Fourier transform, and retain the first main frequency components.​ A pressure calculation module configured to call the pre-stored transfer matrix and calculate the pressure Fourier component of each surface element through matrix multiplication; A load integration module configured to perform inverse fast Fourier transform on the pressure Fourier component and perform area integration on the pressure of each surface element to obtain the total wave load.

7. An electronic device, comprising: It comprises: A memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor executes the program to implement a wave load identification method for a fixed structure of any shape based on an in-situ wave height according to any one of claims 1-5.

8. A computer program product, characterised in that, The computer program / instructions are executed by the processor to implement a wave load identification method for a fixed structure of any shape based on an in-situ wave height according to any one of claims 1-5.

9. A computer-readable storage medium having stored thereon a computer program, characterized in that, The program is executed by the processor to implement a wave load identification method for a fixed structure of any shape based on an in-situ wave height according to any one of claims 1-5.

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