A Method and System for Predicting Near-Field Underwater Noise from Single Pile Driving Based on Finite Element Modeling

Abstract

The present invention discloses a method and system for predicting the near-field underwater noise of a single pile driving based on finite element modeling, which belongs to the field of underwater noise prediction of offshore wind turbine single pile foundation sinking, comprising: by performing finite element modeling on the seawater layer, the single pile, the seabed layer, and the two-way coupling of the acoustic-structural boundary and the porous elastic coupling, the transient response of the seawater, the pile and the seabed in the time domain under the transient impact load is calculated, thereby realizing the prediction of the near-field distribution of underwater noise around the pile, and then analyzing the influence of different permeability coefficients and saturations of the porous medium seabed on the underwater noise, providing effective support for the determination of the permeability coefficient and saturation of the seabed in the process of underwater noise prediction when the seabed is a porous medium in the project.

Description

Technical Field

[0001] The present invention relates to the field of offshore wind turbine single pile foundation underwater noise prediction, and in particular to a single pile near-field underwater noise prediction method and system based on finite element modeling. Background Art

[0002] As a key clean energy field, offshore wind power is developing rapidly on a large scale due to its huge offshore wind energy resources, high power generation efficiency, and no soil resource occupation. In the pile sinking process of offshore wind turbine pile foundation installation, it is necessary to use a pile hammer or a vibrating hydraulic hammer to drive the pile to a predetermined depth; during the pile driving process, the transient shock wave generated from the top of the pile will cause the pile wall to vibrate strongly, radiating high-intensity underwater noise to the nearby sea area, which will cause damage to the hearing system of marine animals in the construction sea area; therefore, the study of underwater noise caused by pile driving is of great significance to the protection of marine biodiversity and marine ecological environment.

[0003] The single pile foundation has a simple structure, mature manufacturing technology, fast installation and construction speed, and high applicability to various seabeds, making it the most widely used. For the underwater noise generated by single pile driving, it is necessary to study the system composed of three interrelated domains: single pile, seawater and seabed. The interaction between them determines the generation mechanism of the sound source noise. The research on the underwater noise of single pile driving is divided into two categories, namely near-field research and far-field research. The near-field research refers to the research on the noise within a few tens of meters around the pile, and the far-field research refers to the research on the noise within a few hundred meters to a few thousand meters from the pile. The near-field noise is studied, and the noise value calculated by the near-field research is used as the noise source of the far field, and then the far-field noise value is calculated according to the parabola equation method, wave number integral method, simple normal wave method and other methods; in addition, noise control near the noise source can more effectively achieve noise reduction, and the current noise reduction of single pile driving is achieved by arranging a noise reduction system around the pile; therefore, the accurate understanding of the near-field noise generation mechanism and the accurate prediction of the noise size can provide an important basis for the prediction of far-field noise and the subsequent research on noise reduction around the pile.

[0004] Compared with the deep sea, sound waves in shallow water will be reflected, refracted and diffracted multiple times on the sea surface and seabed, making the noise propagation in shallow water more complicated. The characteristics of the seabed, as the biggest uncertainty, play a key role in this. The numerical model for studying the underwater noise generation mechanism of single pile driving is mainly classified according to the simplified method adopted for the seabed. The current numerical models are divided into two categories. The first category is a single pile driving model that simplifies the seabed into an acoustic medium, and the second category is a single pile driving model that simplifies the seabed into a single-phase elastic medium. The acoustic medium model can only consider the compression waves in the seabed, and the single-phase elastic medium model can consider the compression waves, shear waves and interface waves along the seabed-seawater interface in the seabed. However, in reality, the seabed is often a porous medium with a high degree of saturation. For example, my country's offshore wind power development is mainly concentrated in the eastern coastal areas, and the coastal seabeds in its sea areas are mostly silty clay, silty clay, etc. Under such soil conditions, the previous acoustic medium model or single-phase elastic medium model cannot consider the pore pressure in the soil and the influence of gas in the unsaturated soil. This will not only affect the distribution of the sound field around the pile, the change law of underwater noise and the noise level, but also the reference value of the noise reduction research around the pile based on the previous model will be greatly reduced.

[0005] Therefore, when simulating the underwater noise of a single pile driving in a porous medium with a high saturation of the seabed, the pore pressure in the soil and the influence of gas in the unsaturated soil can be considered, and the distribution of the sound field around the pile, the change law of underwater noise and the noise level can be more accurately predicted. By simulating the seabed with different permeability coefficients and different saturations, the influence of permeability coefficient and saturation on underwater noise is studied, which can provide simplified support for the determination of permeability coefficient and saturation when predicting underwater noise in actual engineering. Summary of the invention

[0006] In order to solve the above problems, the purpose of the present invention is to provide a single pile driving near-field underwater noise prediction technology based on finite element modeling, which is suitable for the prediction of near-field underwater noise during the piling process when the single pile foundation of an offshore wind turbine is installed in a highly saturated porous seabed. At the same time, it can also provide simplified support for the determination of seabed permeability coefficient and saturation when predicting underwater noise in engineering.

[0007] In order to achieve the above technical objectives, the present application provides a method for predicting near-field underwater noise of single pile driving based on finite element modeling, comprising the following steps:

[0008] Establish the first finite element model consisting of a two-dimensional axisymmetric seawater layer, a single pile and a seabed layer;

[0009] Based on the first finite element model, perfectly matched layers are respectively set at the outermost boundary of the seawater layer, the outermost boundary of the seabed layer, and the bottommost boundary to avoid wave reflection at the boundary, and a second finite element model is constructed;

[0010] Based on the second finite element model, by establishing the acoustic-structure boundary bidirectional coupling multi-physics interface and the poroelastic multi-physics interface between the model components, the acoustic field distribution around the pile, the change law of underwater noise and the noise level are obtained after the transient impact load acts on the top of the single pile.

[0011] Based on the variation of underwater noise with seabed permeability and saturation, the near-field underwater noise of single pile driving under different seabed conditions is predicted.

[0012] Preferably, in the process of constructing the first finite element model, a seawater layer is established according to the pressure acoustic transient, wherein the fluid model is set to linear elasticity;

[0013] The monopile and seabed layer are established according to solid mechanics, wherein the monopile and seabed layer are set as linear elastic materials, the solid model is isotropic, and the contact surface between the monopile and the seabed is set as a continuous boundary;

[0014] The porous media properties of the seabed soil are established according to Darcy's law.

[0015] Preferably, in the process of constructing the acoustic-structure boundary bidirectional coupling multi-physics field interface, an acoustic-structure boundary coupling is established in the multi-physics field of the second finite element model, and the coupled boundaries are selected as the contact boundary between the single pile and the seawater and the contact boundary between the seabed and the seawater. The acoustics of the coupling interface are pressure acoustic transient, and the structure is solid mechanics.

[0016] Preferably, in the process of constructing the poroelastic multi-physics field interface, poroelastic coupling is established in the multi-physics field of the second finite element model, the coupling domain selects the entire seabed layer, the coupling interface selects solid mechanics, the porous medium flow selects Darcy's law, and the Biot-Wills coefficient value is input.

[0017] Preferably, in the process of obtaining the Biot-Wills coefficient value, the Biot-Wills coefficient value is expressed as:

[0018]

[0019] Among them, K b and K s are the shear moduli of soil skeleton and soil particles, respectively.

[0020] Preferably, in the coupling of poroelasticity, the coupling of poroelasticity is performed by combining the transient formula of Darcy's law with the linear elastic material model of the porous matrix.

[0021] Preferably, in the process of constructing the second finite element model, the external boundary conditions of the second finite element model are set, including: setting a sufficiently large seawater layer and seabed layer outside the single pile, and setting the outer boundary of the seawater layer to a pressure of 0, and setting the outer boundary of the seabed layer to a displacement of 0, so that the wave will not be reflected at the boundary.

[0022] Preferably, in the process of predicting the near-field underwater noise of single pile driving, the permeability coefficient and saturation of the seabed are changed respectively through the control variable method, the influence of different permeability coefficients and saturations of the seabed on the underwater noise is obtained, and the change law of underwater noise with the permeability coefficient and saturation of the seabed is obtained, so as to predict the near-field underwater noise of single pile driving under different seabed conditions.

[0023] The present invention discloses a near-field underwater noise prediction system for single pile driving based on finite element modeling, comprising:

[0024] A model building module is used to build a second finite element model by establishing a two-dimensional axisymmetric first finite element model consisting of a seawater layer, a monopile and a seabed layer, and setting perfect matching layers at the outermost boundary of the seawater layer, the outermost boundary of the seabed layer and the bottommost boundary respectively to avoid wave reflection at the boundary;

[0025] The underwater noise analysis module is used to obtain the acoustic field distribution around the pile, the change law of underwater noise and the noise level after the transient impact load acts on the top of the single pile, based on the second finite element model, by establishing the acoustic-structure boundary bidirectional coupling multi-physics field interface and the porous elastic multi-physics field interface between the model components.

[0026] The underwater noise prediction module is used to predict the near-field underwater noise of single pile driving under different seabed conditions based on the change law of underwater noise with seabed permeability coefficient and saturation.

[0027] Preferably, the model building module is further used to establish a seawater layer according to the pressure acoustic transient, wherein the fluid model is set to linear elasticity;

[0028] The model building module is also used to establish a monopile and a seabed layer according to solid mechanics, wherein the monopile and the seabed layer are set as linear elastic materials, the solid model is isotropic, and the contact surface between the monopile and the seabed is set as a continuous boundary;

[0029] The model building module is also used to establish the porous media properties of the seabed layer soil according to Darcy's law.

[0030] The present invention discloses the following technical effects:

[0031] The present invention respectively performs finite element modeling on the seawater layer, single pile, seabed layer, as well as acoustic-structure coupling and porous elastic coupling, so as to calculate the transient response of seawater, pile and seabed in the time domain under transient impact load, thereby realizing the prediction of the near-field distribution of underwater noise around the pile under the condition of porous medium seabed, and then analyzes the influence of different permeability coefficients and saturations of the porous medium seabed on the underwater noise value, providing simplified support for the determination of permeability coefficient and saturation when the seabed is a porous medium in engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 is a flow chart of the method described in the present invention;

[0034] Figure 2 It is a schematic diagram of modeling the two-dimensional axisymmetric seawater layer, single pile, and seabed layer according to the present invention;

[0035] Figure 3 is the underwater noise variation curve with seabed permeability of the present invention;

[0036] Figure 4 This is the underwater noise variation curve with seabed saturation described in the present invention. DETAILED DESCRIPTION

[0037] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0038] like Figure 1-4 As shown, the present invention provides a method for predicting near-field underwater noise of single pile driving based on finite element modeling, comprising the following steps:

[0039] (1) Establish a two-dimensional axisymmetric finite element model of seawater layer, single pile, and seabed layer:

[0040] The seawater layer is established using "pressure acoustic transient", in which the fluid model is set as linear elasticity; the single pile and seabed layer are established using "solid mechanics", in which the single pile and seabed layer are set as linear elastic materials, the solid model is set as isotropic, and the contact surface between the single pile and the seabed is set as a continuous boundary; the porous medium properties of the seabed soil are established using "Darcy's law", in which the fluid properties in the soil and the properties of the soil skeleton are set in "porous elastic storage";

[0041] (2) Establishing the finite element model of the perfectly matched layer (PML)

[0042] Perfect matching layers are set at the outermost boundary of the seawater layer, the outermost boundary of the seabed layer and the bottom boundary to avoid wave reflection at the boundary. In the "imaginary domain", perfect matching layer 1 - seawater layer is added, and the geometry type, coordinate stretching type, typical wavelength, PML scale factor, PML scale curvature parameter are input. The physical field is set to "pressure acoustic transient". In the "imaginary domain", perfect matching layer 2 - seabed layer is added, and the geometry type, coordinate stretching type, typical wavelength, physical field, PML scale factor, PML scale curvature parameter are input. The physical field is set to "solid mechanics".

[0043] (3) Establishing a bidirectional coupling multiphysics interface between acoustic and structural boundaries

[0044] Establish "acoustic-structure boundary" coupling in multi-physics field, select the contact boundary between single pile and seawater and the contact boundary between seabed and seawater as the coupled boundary, select "pressure acoustic transient" for acoustics of coupling interface, and select "solid mechanics" for structure;

[0045] (4) Establishing a multi-physics interface for poroelasticity

[0046] In the multi-physics field, establish the "porous elasticity" coupling, select the entire seabed layer as the coupling domain, select "solid mechanics" as the coupling interface solid mechanics, select "Darcy's law" for porous media flow, and enter the Biot-Wills coefficient value;

[0047] (5) Based on the main action duration of the transient impact load, the solution duration of the transient solver is set and the transient response of the finite element model in the time domain is calculated to obtain the acoustic field distribution around the pile, the change law of underwater noise, and the noise level;

[0048] (6) The noise results of different permeability coefficients and different saturations of the seabed layer are plotted on a graph, and the variation law of underwater noise with the permeability coefficient and saturation of the seabed is summarized, which provides simplified support for the determination of permeability coefficient and saturation when predicting underwater noise under porous media seabed conditions in engineering.

[0049] In the simulation of underwater noise from single pile driving, the coupling settings of acoustic-structure boundary and poroelasticity need to be completed. Among them, in the two-way coupling of acoustic-structure boundary, the fluid load on the structure and the structural acceleration experienced by the fluid are included. Predefined multi-physics interfaces can be used or coupling can be added manually. In the coupling of poroelasticity, by combining the transient formulation of Darcy's law with the linear elastic material model of the porous matrix, the fluid flow affects the compressibility of the porous medium, and the change in volume strain affects the mass transfer. Therefore, the multi-physics interface contains a stress tensor expression (as a function of volume strain) and the Biot-Willis coefficient.

[0050] The key mechanism of seabed poroelastic coupling can be explained by the following formula:

[0051]

[0052]

[0053] Among them, K b and K s are the shear moduli of soil skeleton and soil particles, respectively.

[0054] For the simulation of a poroelastic seabed, the equation of motion for a saturated poroelastic seabed is:

[0055]

[0056]

[0057] Where b = ρ f gφ 2 / k represents the damping caused by the relative motion between the solid part and the fluid part in the porous medium, k is the permeability coefficient of the porous medium, and φ is the porosity of the porous medium. mn The density of the solid and liquid parts ρ d =(1-φ)ρ f D s and ρ f Related,D s is the specific gravity of soil particles, λ s and μ s is the Lame constant of the solid part, Q and R are the coupling parameters representing the solid and fluid parts.

[0058] Q=φ(α-φ)M;R=φ 2 M;

[0059] α=1-K b / K s ;

[0060] M=1 / [φβf +(1-α)(α-φ) / K b ];

[0061]

[0062] Among them, K s and K b is the shear modulus of soil particles and soil skeleton, β f is the compressibility of the fluid part, v s is the drainage Poisson's ratio of the soil.

[0063] The effect of saturation on the compressibility modulus of a fluid can be described by the following equation:

[0064] K f =1 / [1 / K w +(1-S r ) / p0]

[0065] Where p0 = p a +ρ w gh w is the absolute confining pressure acting on the fluid, p a is the atmospheric pressure.

[0066] Therefore, it can be seen that saturation affects the compression modulus of the fluid in the porous media seabed. In the model, the compression modulus of the fluid in different porous media is set to simulate the seabed with different saturations.

[0067] In addition, the finite element simulation model needs to set external boundary conditions. The present invention stipulates that a sufficiently large seawater layer and seabed layer are set outside the single pile, and the outer boundary of the seawater layer is set to a pressure of 0, and the outer boundary of the seabed layer is set to a displacement of 0, so that the wave will not be reflected at the boundary, thereby ensuring that the finite element simulation can be realized and has a solution.

[0068] The present invention is combined with Figure 1 The prediction process of the near-field underwater noise of a single pile driving proposed by the present invention is described in detail, which specifically includes the following steps:

[0069] S1. Establish a 2D axisymmetric finite element model of seawater layer, single pile and seabed layer:

[0070] The seawater layer is established using "pressure acoustic transient"; the single pile and seabed layer are established using "solid mechanics"; and the porous medium properties of the seabed layer are established using "Darcy's law". Figure 2 shown.

[0071] According to the size of large-diameter monopiles of offshore wind turbines currently widely used in engineering, the seawater layer, monopiles and seabed layer are respectively established according to the description in the present invention.

[0072] Physical field settings for seawater layer: Figure 2 As shown, the fluid model is set to linear elastic, the density and speed of sound are specified, and the water surface pressure is set to 0.

[0073] Single pile and seabed physics settings: Figure 2 As shown in the figure, the monopile and seabed layer are set as linear elastic materials, the solid model is set to be isotropic, and Young's modulus and Poisson's ratio are specified; the contact surface between the monopile and the seabed is set to a continuous boundary; and a transient impact pile driving load is specified on the top of the monopile.

[0074] Darcy's law physics field settings: Figure 2 As shown, select the seabed layer, set the fluid properties and matrix properties in the soil in "Poroelastic Storage"; specify the density for the fluid properties, and the porosity and permeability for the matrix properties; set the pressure head of the seawater-seabed interface to 0.

[0075] S2. Establish the finite element model of perfectly matched layer (PML):

[0076] like Figure 2 As shown, the seawater perfect matching layer and the seabed perfect matching layer are established in the definition respectively, and the geometry type, coordinate stretching type, physical field, typical wavelength, PML scale factor, and PML scale curvature parameters are specified.

[0077] S3. Establishing the acoustic-structure boundary bidirectional coupling multiphysics interface

[0078] The predefined acoustic-structure boundary bidirectional coupling multiphysics interface is used to specify pressure acoustic transients for acoustics and solid mechanics for structures to achieve bidirectional coupling between acoustic media and structures.

[0079] S4. Establishing the Poroelasticity Multiphysics Interface

[0080] The predefined Poroelasticity multiphysics interface is used, with the seabed layer specified by solid mechanics, the porous media flow specified by Darcy’s law, and the Biot-Willis coefficients input into the poroelasticity coupling properties.

[0081] S5. Calculate the near-field noise around the pile

[0082] The time step and research duration are set according to the main action time of the transient impact load, and transient time-domain finite element simulation is carried out to statistically analyze the sound field distribution at different times after single pile driving, the noise changes at fixed points and fixed sections, and the size of noise values.

[0083] S6. Obtain the influence of seabed permeability and saturation on underwater noise

[0084] The control variable method is used to change the permeability coefficient and saturation of the seabed.

[0085] In this example, the permeability coefficient of the seabed is k = 1×10 -3 m / s, k = 1 × 10 -7 m / s and k = 1 × 10 -10 m / s to simulate three types of seabeds: sand, silt and clay; the saturation of the seabed is S r =100%, S r =99% and S r =95%.

[0086] like Figure 3 As shown, the sound pressure level in sand is lower than the values ​​in silt and clay, while the difference in sound pressure level between silt and clay is negligible, which means that the slower second compression wave in the porous media plays a role in the sandy seabed because the sound pressure level is reduced compared to the case dominated by the faster first compression wave (silt and clay seabed).

[0087] like Figure 4 As shown in the figure, the sound pressure level near the pile is higher when the seabed is fully saturated, while the sound pressure level near the pile is higher when the seabed is partially saturated (S r =99% and S r =95%), which is caused by the small bubbles appearing in the unsaturated seabed which significantly reduce the speed of the first compression wave, but the number of small bubbles has little effect on the highly saturated seabed.

[0088] The discovery of the above rules indicates that in actual engineering, it is not necessary to accurately determine the seabed permeability coefficient and saturation, and they can be selected based on the results measured by indoor models or field tests. Therefore, the method proposed in the present invention has practical engineering application value.

[0089] At the same time, the method for predicting near-field underwater noise of single pile driving based on finite element modeling provided by the present invention also has the following beneficial effects:

[0090] (1) The present invention is simulated strictly according to the prototype size of offshore wind turbine single pile driving, with a single pile radius a=1-5m, an aspect ratio of 10-15, a wall thickness h=(0.01-0.02)a, and a water depth h w =20~30m, which makes it possible to restore the actual project and ensure the accuracy of the simulation results.

[0091] (2) The present invention uses a two-dimensional axisymmetric model to simulate three dimensions, and sets perfect matching layers at the outer boundary of the seawater layer, the outer boundary of the seabed layer, and the bottom boundary, so that waves will not be reflected at the boundary, thereby reducing the time cost of simulation calculation and the equipment hardware requirements.

[0092] (3) The present invention is applicable to the driving of single piles with different burial depths, single piles with different water depths and porous media seabeds with different parameter values, and can be constructed according to different single piles, seawater layers and seabed layers during modeling.

[0093] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0094] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0095] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for predicting near-field underwater noise of single pile driving based on finite element modeling, characterized in that: The following steps are involved: Establish the first finite element model consisting of a two-dimensional axisymmetric seawater layer, a single pile and a seabed layer; Based on the first finite element model, perfectly matched layers are respectively set at the outermost boundary of the seawater layer, the outermost boundary and the bottommost boundary of the seabed layer to avoid wave reflection at the boundary, and a second finite element model is constructed; Based on the second finite element model, by establishing the acoustic-structure boundary bidirectional coupling multi-physics interface and the poroelastic multi-physics interface between the model components, the acoustic field distribution around the pile after the transient impact load acts on the top of the single pile, the change law of the underwater noise and the noise level are obtained; Based on the variation law of underwater noise with seabed permeability coefficient and saturation, the near-field underwater noise of single pile driving under different seabed conditions is predicted; In the process of constructing the first finite element model, the seawater layer under the pressure acoustic transient module is established according to the control equations of the compressible and inviscid fluid time domain, wherein the fluid model is set to linear elasticity; According to the control equation of linear elastic body in time domain, the single pile and seabed layer under the solid mechanics module are established, where the single pile and seabed layer are set as linear elastic materials, the solid model is isotropic, and the contact surface between the single pile and the seabed is set as a continuous boundary; The porous media properties of the seabed soil are established based on the saturated poroelastic motion equation and constitutive equation of Darcy's law seepage; In the process of constructing the acoustic-structure boundary bidirectional coupling multi-physics field interface, the acoustic-structure boundary coupling is established in the multi-physics field of the second finite element model, and the coupled boundaries are selected as the contact boundary between the single pile and the seawater and the contact boundary between the seabed and the seawater. The acoustics of the coupling interface are pressure acoustic transient, and the structure is solid mechanics.

2. The method for predicting near-field underwater noise of single pile driving based on finite element modeling according to claim 1 is characterized in that: In the process of constructing the poroelastic multi-physics field interface, poroelastic coupling is established in the multi-physics field of the second finite element model, the entire seabed layer is selected as the coupling domain, solid mechanics is selected as the coupling interface, Darcy's law is selected as the porous medium flow, and the Biot-Wills coefficient value is input.

3. The method for predicting near-field underwater noise of single pile driving based on finite element modeling according to claim 2 is characterized in that: In the process of obtaining the Biot-Wills coefficient value, the Biot-Wills coefficient value is expressed as: Among them, K b and K s are the shear moduli of soil skeleton and soil particles, respectively.

4. The method for predicting near-field underwater noise of single pile driving based on finite element modeling according to claim 3 is characterized in that: In the coupling of poroelasticity, the transient formulation of Darcy's law is combined with the linear elastic material model of the porous matrix to carry out the coupling of poroelasticity.

5. The method for predicting near-field underwater noise of single pile driving based on finite element modeling according to claim 4 is characterized in that: In the process of constructing the second finite element model, the external boundary conditions of the second finite element model are set, including: setting a seawater layer and a seabed layer outside the single pile, and setting the external boundary of the seawater layer to a pressure of 0, and setting the external boundary of the seabed layer to a displacement of 0, so that the wave will not be reflected at the boundary.

6. The method for predicting near-field underwater noise of single pile driving based on finite element modeling according to claim 5 is characterized in that: In the process of predicting the near-field underwater noise of single pile driving, the permeability coefficient and saturation of the seabed are changed respectively through the control variable method to obtain the influence of different permeability coefficients and saturations of the seabed on the underwater noise, and the change law of underwater noise with the permeability coefficient and saturation of the seabed is obtained, so as to predict the near-field underwater noise of single pile driving under different seabed conditions.

7. A single pile driving near-field underwater noise prediction system based on finite element modeling, used to implement the single pile driving near-field underwater noise prediction method based on finite element modeling as claimed in claim 1, characterized in that: include: A model building module, for building a second finite element model by establishing a two-dimensional axisymmetric first finite element model consisting of a seawater layer, a monopile and a seabed layer, and respectively setting perfect matching layers at the outermost boundary of the seawater layer, the outermost boundary of the seabed layer and the bottommost boundary to avoid wave reflection at the boundary; An underwater noise analysis module is used to obtain the acoustic field distribution around the pile, the change law of underwater noise and the noise level after a transient impact load acts on the top of a single pile, based on the second finite element model, by establishing an acoustic-structure boundary bidirectional coupling multi-physics field interface and a poroelastic multi-physics field interface between the model components; The underwater noise prediction module is used to predict the near-field underwater noise of single pile driving under different seabed conditions based on the change law of the underwater noise with the seabed permeability coefficient and saturation.

Images