Method for calculating wave-current coupling force borne by offshore wind power pile foundation

Abstract

The invention discloses a method for calculating wave-current coupling force borne by an offshore wind power pile foundation. The method comprises the following steps that S1, environmental parameters and a structural state are monitored in real time through a sensor installed on the surface of the offshore wind power pile foundation; s2, constructing a wave calculation module; s3, constructing a stream calculation module; s4, wave pressure and fluid pressure borne by the offshore wind power pile foundation are calculated through a wave calculation module and a flow calculation module, and hydrodynamic pressure distribution under the wave-flow coupling effect is obtained; and S5, the obtained hydrodynamic pressure distribution is integrated, and the wave flow force borne by the offshore wind power pile foundation is obtained. According to the method, the calculation efficiency can be greatly improved while high precision is kept, the method is suitable for offshore buildings of various complex geometrical shapes, including but not limited to offshore wind power pile foundations, floating platforms and other ocean engineering structures, and reliable basis is provided for design and safety evaluation of the offshore wind power pile foundations.

Description

Technical Field

[0001] The present invention belongs to the field of wave-current force calculation, and particularly relates to a method for calculating the wave-current coupling force borne by an offshore wind power pile foundation. Background Art

[0002] With the increasing global demand for renewable energy, offshore wind power, as a clean and sustainable energy form, has developed rapidly. As an important structure for supporting the wind turbine tower and the unit, the safety and reliability of the offshore wind power pile foundation are directly related to the operation life and economic benefits of the entire wind farm.

[0003] The offshore wind power pile foundation is long-term in a complex marine environment and bears the combined action of various environmental loads such as wind, wave, and current. Among them, waves and ocean currents are the main environmental factors leading to fatigue damage and ultimate failure of the pile foundation structure, and the actions of waves and ocean currents on the pile foundation do not exist independently, but are coupled and interact with each other. This wave-current coupling effect will significantly change the stress state of the pile foundation structure, and thus affect its safety and reliability.

[0004] Traditional wave-current force calculation methods mainly rely on linear theories or semi-empirical formulas, such as the Morison equation, which is a classical formula for estimating the wave-current force on a structure and is known for its wide application range and simplicity and intuitiveness. However, it assumes that the flow is two-dimensional and uniform, which may not hold in complex environments, and its prediction accuracy under extreme conditions is insufficient (see the literature Chen Yan, Cai Anmin, Ye Zhiquan, etc. Preliminary calculation and analysis of an offshore wind turbine under extreme waves [J]. Acta Energiae Solaris Sinica, 2008, (02): 180-187.); the boundary element method is a numerical calculation technique that simulates the force under wave-current action by solving the basic equations of fluid dynamics and is particularly suitable for dealing with problems of complex geometries. Although it provides high-precision results, its calculation cost and technical threshold are relatively high (see the literature Shan P, Wang Y, Wang F, et al. Froude-Krylov nonlinear computations of three dimensional wave loads by a hybrid time domain boundary element method [J]. Ocean Engineering, 2020, 195: 106763-106763.). Summary of the Invention

[0005] To solve the above problems, the present invention proposes a method for calculating the wave-current coupling force borne by an offshore wind power pile foundation. The method of the present invention can significantly improve the calculation efficiency while maintaining high accuracy, and is applicable to offshore buildings with various complex geometries, including but not limited to offshore wind power pile foundations, floating platforms, and other ocean engineering structures, providing a reliable basis for the design and safety assessment of offshore wind power pile foundations.

[0006] The method for calculating the wave-current coupling force borne by an offshore wind power pile foundation of the present invention includes the following steps:

[0007] S1. Real-time monitor environmental parameters and structural states, such as incident wave angle, wave speed, temperature, and pressure, etc., through sensors installed on the surface of the offshore wind power pile foundation;

[0008] S2. Construct a wave calculation module to accurately simulate the propagation and interaction of water waves, and then calculate the wave force velocity potential;

[0009] S3. Construct a flow calculation module to calculate the velocity potential of the flow-around force and obtain the velocity and pressure changes of the fluid flowing around the offshore wind power pile foundation;

[0010] S4. Substitute the wave parameters affected by ocean currents into the wave calculation module to calculate the wave pressure borne by the offshore wind power pile foundation; use the flow calculation module to calculate the fluid pressure borne by the offshore wind power pile foundation; obtain the hydrodynamic pressure distribution under the wave-current coupling action by superimposing the wave pressure and the fluid pressure;

[0011] S5. Integrate the obtained hydrodynamic pressure distribution to obtain the wave-current force borne by the offshore wind power pile foundation.

[0012] S1. Basic information input module: Real-time monitor environmental parameters and structural states, such as incident wave angle, wave speed, temperature, and pressure, etc., through sensors installed on the surface of the offshore wind power pile foundation. The sensors convert physical quantities into electrical signals, which are then preliminarily processed by a data collector and finally transmitted to a data processing unit for further analysis and storage.

[0013] S2. Construct a wave calculation module to accurately simulate the propagation and interaction of water waves, and then calculate the wave force velocity potential; the calculation process of constructing the wave calculation module is as follows:

[0014] S201. Model assumptions;

[0015] S202. Define the total velocity potential function;

[0016] S203. Set boundary conditions for the scattered wave function, including the water surface, the bottom of the water, and infinity;

[0017] S204. Select the Green's function that satisfies the boundary conditions as the basis function;

[0018] S205. Determine the source points and boundary node sets for calculation;

[0019] S206. Solve for the unknown coefficients according to the interpolation formula, source point strength factor calculation formula, and gradient;

[0020] S207. Solve the scattering wave potential function.

[0021] S201. Model assumptions: Consider an offshore wind power pile foundation perpendicular to the seabed. Assume that the fluid is incompressible and irrotational, the water depth is constant, and the surfaces of the seabed and the offshore wind power pile foundation are impermeable boundaries.

[0022] S202. Define the total velocity potential function. The total velocity potential includes the incident wave velocity potential and the scattering wave velocity potential, and the total velocity potential satisfies the Laplace equation.

[0023]

[0024] Among them, Φ(x, y, z, t) = [φ i (x, y, z) + φ s (x, y, z)]e -iωt (2)

[0025]

[0026] φ i and φ s are the incident wave potential function and the scattering wave potential function respectively. H and d are the wave height and water depth respectively, ω is the wave frequency, the radius of the cylindrical wind power pile foundation is a, θ represents the direction of the incident wave, i usually represents the imaginary unit, satisfying i 2 = -1. In physics, especially in wave and quantum mechanics, the imaginary unit is used to represent the change of phase. t represents the time variable. In the wave equation, the time variable is used to describe the evolution of the wave over time. The exponential term e -iωt represents the periodic time variation of the wave.

[0027] S203. Set the boundary conditions for the scattering wave potential function, including the water surface, the seabed, and infinity.

[0028]

[0029] S204. Use the series form Green's function that satisfies the boundary conditions of the scattering wave water surface, the seabed, and infinity as the basis function.

[0030]

[0031] Among them, and v = ω 2 / g, μ m is ω2 = μ m g tan μ m is the root of d, H0(kr) is the Hankel function of the zero - order and the first kind, K0(μ m r) is the modified Bessel function of the zero - order and the second kind, G(x,y,z,ξ,η,ζ) is the Green's function at the positions (x,y,z) and (ξ,η,ζ) in space, k is the wave number, determined by the equation ω 2 = kg tan kd, g is the acceleration due to gravity, r represents the horizontal distance from the point (x,y) to the point (ξ,η), v is the phase velocity, H and d are the wave height and water depth respectively, (x,y,z) are the coordinates of the collocation points, and (ξ,η,ζ) are the coordinates of the source points.

[0032] S205. Due to the application of the series form of the Green's function, the present invention only needs to place source points on the wet surface of the offshore wind power pile foundation. As Figure 2 shown, by adopting the same - position source - collocation point arrangement strategy, the single - layer boundary discretization is realized through the adaptive characteristics of the Green's function, thus avoiding the computational redundancy of arranging source points throughout the field in the traditional calculation method.

[0033] S206. Solve the unknown coefficients according to the interpolation formula, the calculation formula of the source - point strength factor, and the normal gradient; this method uses the same boundary node set as the source points and the collocation points.

[0034] The interpolation formula for calculating the wave force is:

[0035]

[0036] where the gradient of the source - point strength factor along the normal direction is 0, that is n is the upper limit of the summation, representing the total number of points, G ij (x i ,s j ) is the Green's function, usually used to describe the interaction between the points x i and s j , x i , s j are points in space, β j is the unknown coefficient, and Γ is the boundary.

[0037] Use the source - point strength factor calculation module, which effectively avoids the time - consuming and complex singular integral process in the traditional method. The calculation formula of the source - point strength factor is:

[0038]

[0039] where γ = 0.57721566490153286…, s jis the j-th source point. When i = j, the singularity will occur due to the coincidence of the source point and the collocation point. At this time, the source point strength factor G ii (x i , s i ) is used to replace G ij (x i , s j ). The surface S of the structure is divided into n micro-elements Δs, where n is the total number of micro-elements. h i and h j are the heights of the collocation point and the source point in the z direction, k is the wave number, v is the phase velocity, l i is the characteristic length of the collocation point, and ζ is the coordinate of the source point in the z direction.

[0040] And n z = 0. Obviously, the gradient of the source point strength factor along the normal direction is 0, that is Substitute formula (7) into formula (6) to obtain the unknown coefficient β j .

[0041] S207. The formula for the scattered wave potential function is:

[0042]

[0043] where Γ is the boundary, and G ij is the Green's function, representing the interaction between the source point s j and the collocation point x i . The source point s j is distributed on the boundary. When , the collocation point and the source point do not coincide, and the scattered potential is obtained by weighted averaging the contributions of all points. When x i ∈Γ and i = j, the source point and the collocation point coincide, and the calculation of the scattered potential also includes the contribution of self-action. At this time, this point should use the source point strength factor G ii (x i , s i ) to replace G ij (x i , s j ).

[0044] S3. Build a flow calculation module to calculate the flow force velocity potential and obtain the velocity and pressure changes of the fluid flowing around the offshore wind power pile foundation; the calculation process of the flow calculation module is as follows:

[0045] S301. Model assumption;

[0046] S302. Define the flow force velocity potential function;

[0047] S303. Select and apply the Green's function that satisfies the boundary conditions of the flow field velocity potential;

[0048] S304. Solve for the unknown coefficients according to the difference formula for calculating the flow-around force, the calculation formula for the source point strength factor, and the gradient.

[0049] S305. Handle the singularity and solve.

[0050] S301. Assume that the uniform oncoming flow velocity along the x direction is u c . The flow-around force velocity potential function φ c satisfies the following boundary value problem:

[0051]

[0052] S302. The flow-around force velocity potential function φ c is:

[0053]

[0054] where χ j is the unknown coefficient, (x, y, z) are the collocation point coordinates, u c is the flow velocity, x i is a point in space, s j is the j-th source point.

[0055] S303. represents the Green's function that satisfies the boundary condition of the flow field velocity potential:

[0056]

[0057] In the formula, R is the direct distance between the collocation point P(x, y, z) and the source point Q(ζ, η, ξ), R1 is the distance between this collocation point P and the first image point of the source point Q, R 2n 、R 3n 、R 4n 、R 5n are the distances between this collocation point P and the other image points of the source point Q, where n is the order of the mirror image, r is the projected distance between the collocation point P and the source point Q in the xy plane, and (ζ, η, ξ) are the source point coordinates.

[0058] The Green's function is constructed using the method of images, and the schematic diagram of each image point is as shown in Figure 3 .

[0059] S304. Solve for the unknown coefficients according to the interpolation formula for calculating the flow-around force, the calculation formula for the source point strength factor, and the normal gradient;

[0060] The interpolation formula for calculating the flow-around force is:

[0061]

[0062] In the formula, and are the source strength factor and its normal gradient of the flow calculation module.

[0063] S305. It has the same singularity as the fundamental solution of the three-dimensional Laplace equation. However, the first term of this fundamental solution will generate a singularity at the coincidence of the source point and the collocation point. This singular term has the same singularity as the fundamental solution of the three-dimensional Laplace equation. Therefore, this method uses the source strength factor to replace the singular term in the fundamental solution to solve the singularity problem. It can be expressed as:

[0064]

[0065] where S is the wet surface area of the offshore wind power pile foundation, represents the characteristic radius of the i-th source point, A i is the influence range of the i-th source point, as Figure 2 shown.

[0066] Since and n z = 0, thus, combining formulas (13) and (14) to calculate the unknown coefficient χ j , and finally combining formula (10) to obtain the flow force velocity potential function Φ c .

[0067] S4. Substitute the wave parameters affected by ocean currents into the wave calculation module to calculate the wave pressure on the offshore wind power pile foundation; use the flow calculation module to calculate the fluid pressure on the offshore wind power pile foundation; by superimposing the wave pressure and the fluid pressure, obtain the hydrodynamic pressure distribution under the combined action of waves and currents.

[0068] The dynamic pressure caused by waves is:

[0069]

[0070] where P i f is the dynamic pressure caused by waves, ρ is the density of the fluid, and Re represents taking the real part (Realpart) of a complex number.

[0071] At the same time, to consider the influence of ocean currents, it is necessary to use the wave parameters affected by ocean currents to calculate the wave force. The relative velocity C r of waves to ocean currents and the wave velocity C affected by ocean currents can be expressed as:

[0072]

[0073] C = u c + C r (17)

[0074]

[0075] Among them, L r = L is the wavelength affected by ocean currents, and T w is the wave period not affected by ocean currents, and T r is the wave period relative to ocean currents. From equations (16)-(18), we get:

[0076]

[0077] Among them, is the wave velocity not affected by ocean currents, is the wave number not affected by ocean currents, and L w is the wavelength not affected by ocean currents, and k is the wave number affected by the flow velocity.

[0078] The wave height H caused by the flow velocity is:

[0079]

[0080] Among them,

[0081] Substitute the H and L affected by ocean currents into the wave calculation module for recalculation, and finally obtain the changes in wave parameters under the combined action of waves and currents. The H and L affected by ocean currents can be calculated from equations (19) and (20), and then substituted back into equation (3). Since the change in L will cause the change in k in equation (3).

[0082] The dynamic pressure generated by the flow is:

[0083]

[0084] Among them, n = (n x , n y , n z ) and the gradient is not equal to τ = (τ x , τ y , τ z ) is calculated by the following formula:

[0085]

[0086] Among them

[0087]

[0088] In the formula, ρ is the density of the fluid, and uc is the flow velocity, u τ is the tangential velocity on the surface of the structure, τ = (τ x , τ y , τ z ), τ x , τ y , τ z is the tangential velocity component, representing the component of the fluid velocity in the tangential direction. is the gradient of the velocity potential function, representing the rate of change of the velocity field, C x , C y , C z is the component of the vector .

[0089] Add the wave dynamic pressure and the circumferential flow pressure to obtain the total dynamic pressure.

[0090] S5. Integrate the obtained hydrodynamic pressure distribution to obtain the wave-current force on the offshore wind power pile foundation.

[0091] The calculation formula for the wave-current force on the offshore wind power pile foundation is F = -∫ S p·nds.

[0092] The new method for calculating the wave-current coupling force borne by the offshore wind power pile foundation of the present invention includes a basic information input module, a wave calculation module, a flow calculation module, a hydrodynamic pressure calculation module, and a wave-current force calculation module.

[0093] The basic information input module is used to monitor and input the specific parameters of the offshore wind power pile foundation and its surrounding environment, such as the incident wave angle, wave speed, geometric dimensions of the pile foundation, etc., so as to achieve an accurate simulation of the wave-current force it bears, and can more accurately predict and analyze the dynamic loads it receives in the marine environment.

[0094] The wave calculation module is used to calculate the velocity potential of the flow field under the action of waves on the offshore wind power pile foundation.

[0095] The flow calculation module is used to calculate the velocity potential field when the fluid bypasses the offshore wind power pile foundation.

[0096] The hydrodynamic pressure calculation module is used to calculate the wave pressure and fluid pressure borne by the offshore wind power pile foundation by combining the wave force velocity potential and the circumferential flow force velocity potential, and obtain the hydrodynamic pressure distribution under the combined action of waves and fluids through superposition.

[0097] The wave-current force calculation module is used to calculate the magnitude of the wave-current force borne by the offshore wind power pile foundation based on the hydrodynamic pressure under the combined action of waves and fluids.

[0098] The present invention also discloses an electronic device, including a memory and a processor. A computer program is stored on the memory. When the processor executes the computer program, any step in the method for calculating the wave-current coupling force borne by an offshore wind power pile foundation as described above in the present application is implemented.

[0099] The present invention also discloses a computer-readable storage medium. A computer program is stored on the computer-readable storage medium. When the computer program is executed by a computer processor, any step in the method for calculating the wave-current coupling force borne by an offshore wind power pile foundation as described above in the present application is implemented.

[0100] The beneficial effects of the present invention are as follows.

[0101] 1. In terms of calculation efficiency. By placing the source point on the wet surface of the offshore wind power pile foundation and introducing the source strength factor and the series expansion form of the Green's function, the present invention effectively avoids the time-consuming and complex singular integral process in the traditional method, thereby avoiding the numerical instability problem caused by the singularity of the Green's function. This method not only simplifies the mathematical processing flow but also significantly reduces the required computing resources. Compared with the traditional wave-current force calculation method, the method of the present invention greatly reduces the calculation complexity while maintaining high accuracy, significantly reducing the amount of calculation in the entire simulation process and significantly improving the calculation efficiency.

[0102] 2. In terms of calculation accuracy. A new method for calculating the wave-current coupling force borne by an offshore wind power pile foundation is provided, and a comprehensive wave calculation module and a current calculation module are established. This module can effectively handle the influence of various design parameters, including geometric shape, size, material properties, and environmental conditions, on the wave-current force. Numerical experiments prove that the present invention shows excellent calculation accuracy and numerical stability in calculating the wave-current force of offshore wind power pile foundations, and its results show a high degree of consistency compared with experimental data and other existing numerical methods. In addition, the present invention has the characteristics of high accuracy, fast calculation, low calculation cost, and easy programming, and is applicable to the analysis of wave-current forces of offshore structures, the optimal design of offshore wind power pile foundations, the formulation of coastal disaster prevention measures, and a wide range of ocean engineering fields, which is of great significance for promoting the development of offshore wind power technology and its application in related engineering and technical fields.

[0103] 3. In terms of economy. From an economic perspective, accurate mechanical analysis optimizes the use of materials and the design of facilities, enhances the safety and reliability of the design of offshore wind power pile foundations, thereby reducing costs and extending the system life, which can greatly save the upfront investment and later maintenance costs of a single project. At the same time, by improving the system performance, additional power generation benefits are increased. In addition, increasing the supply of clean energy and reducing fossil fuel consumption contribute to addressing climate change and improving social well-being, achieving the dual goals of economic benefits and environmental protection.

[0104] 4. Innovation aspect. The present invention is a meshless method, which does not require meshing of the solution domain. Instead, it directly uses discrete points on the boundary for calculation, that is, only source points need to be placed on the wet surface of the offshore wind turbine pile foundation, avoiding the complexity of mesh generation and reconstruction. This method uses the source point strength factor to replace the series form of the Green's function at the source point, effectively avoiding the time-consuming and complex singular integral process in the traditional method, thus avoiding the numerical instability problem caused by the singularity of the Green's function. The traditional method ignores the dynamic correction of ocean currents on wave speed and wave height, resulting in deviation in the prediction of pile foundation forces. However, this method significantly improves the calculation accuracy through a coupling model, especially suitable for strong ocean current areas. Description of the Drawings

[0105] Figure 1 It is a technical flow chart of a new method for calculating the wave-current coupling force borne by an offshore wind turbine pile foundation;

[0106] Figure 2 It is a schematic diagram of the distribution of source points and collocation points of an offshore wind turbine pile foundation;

[0107] Figure 3 It is a schematic diagram of each image point;

[0108] Figure 4 It is a schematic diagram of five evenly distributed offshore wind turbine pile foundations in Embodiment 1;

[0109] Figure 5 It is a schematic diagram of the wave height of an offshore wind turbine pile foundation in Embodiment 1;

[0110] Figure 6 It is a schematic diagram of the structure of a new method system for calculating the wave-current coupling force borne by an offshore wind turbine pile foundation.

[0111] Figure 7 It is a flow chart of the calculation process of the wave calculation module;

[0112] Figure 8 It is a flow chart of the calculation process of the flow calculation module. Detailed Embodiment

[0113] The embodiments of the present invention are described in detail below. The examples of the embodiments are shown in the drawings. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present invention, and should not be construed as limiting the present invention.

[0114] As Figures 1-8 shown, the calculation method for the wave-current coupling force borne by the offshore wind turbine pile foundation of the present invention includes the following steps:

[0115] S1. Basic information input module: The environmental parameters and structural states, such as the incident wave angle, wave speed, temperature, and pressure, are monitored in real time by sensors installed on the surface of the offshore wind power pile foundation. The sensors convert physical quantities into electrical signals, which are then preliminarily processed by a data collector and finally transmitted to a data processing unit for further analysis and storage.

[0116] S2. Build a wave calculation module to accurately simulate the propagation and interaction of water waves, and then calculate the wave force velocity potential, as Figure 7 shown.

[0117] Considering an offshore wind power pile foundation perpendicular to the seabed, it is assumed that the fluid is incompressible and irrotational, the water depth is constant, and the seabed and the surface of the offshore wind power pile foundation are impermeable boundaries. The total velocity potential satisfies the Laplace equation.

[0118]

[0119] where

[0120] Φ(x,y,z,t)=[φ i (x,y,z)+φ s (x,y,z)]e -iωt (2)

[0121]

[0122] φ i and φ s are the incident wave potential function and the scattered wave potential function respectively, H and d are the wave height and water depth respectively, ω is the wave frequency, the radius of the cylindrical wind power pile foundation is a, and θ represents the direction of the incident wave.

[0123] Set boundary conditions for the scattered wave potential function, including the water surface, the seabed, and infinity.

[0124]

[0125] In this method, a series-form Green's function that satisfies the boundary conditions of the scattered wave water surface, seabed, and infinity is used as the basis function.

[0126]

[0127] where and v=ω 2 / g, μ m is the root of ω 2 =μ m g tan μ m d, H0(kr) is the Hankel function of the zero order and the first kind, K0(μ mr) is the zeroth-order and second-kind modified Bessel function. Due to the application of the series form of the Green's function, this method only needs to place source points on the wet surface of the offshore wind power pile foundation. As Figure 2 shown, the same-position source point - collocation point arrangement strategy is adopted, and the single-layer boundary discretization is realized through the adaptive characteristics of the Green's function, thus avoiding the computational redundancy of arranging source points in the whole field in the traditional calculation method.

[0128] The interpolation formula for calculating the wave force is:

[0129]

[0130] where β j is the unknown coefficient. Use the source point strength factor calculation module, which effectively avoids the time-consuming and complex singular integral process in the traditional method. The calculation formula for the source point strength factor is:

[0131]

[0132] where γ = 0.57721566490153286…

[0133] and n z = 0. Obviously, the gradient of the source point strength factor along the normal direction is 0, that is The unknown coefficient β j .

[0134] After obtaining the unknown coefficient β j , the scattered wave potential function is obtained by the following formula:

[0135]

[0136] S3. Construct a flow calculation module to calculate the flow force velocity potential and obtain the velocity and pressure changes of the fluid flowing around the offshore wind power pile foundation, as Figure 8 shown.

[0137] Let the uniform incoming flow velocity along the x direction be u c . The flow force velocity potential function φ c satisfies the following boundary value problem:

[0138]

[0139] In this method, the velocity potential function φ c is:

[0140]

[0141] where χ j is the unknown coefficient. Denote the Green's function that satisfies the boundary conditions of the flow field velocity potential:

[0142]

[0143] The mirror method is used to construct the Green's function. The schematic diagram of each mirror point is as Figure 3 shown.

[0144] The interpolation formula for calculating the flow-around force is:

[0145]

[0146] In the formula and are the source point strength factor and its normal gradient of the flow calculation module, and has the same singularity as the fundamental solution of the three-dimensional Laplace equation. However, the first term of this fundamental solution will produce a singularity at the coincidence of the source point and the collocation point. This singular term has the same singularity as the fundamental solution of the three-dimensional Laplace equation. Therefore, the source point strength factor is used to replace the singular term in the fundamental solution to solve the singularity problem, which can be expressed as:

[0147]

[0148] where S is the wet surface area of the offshore wind power pile foundation, represents the characteristic radius of the i-th source point. A i is the influence range of the i-th source point, as Figure 2 shown.

[0149] Since and n z = 0, thus the unknown coefficient χ j is calculated, and finally the flow-around force velocity potential function Φ c is obtained.

[0150] S4. Hydrodynamic pressure calculation module: Substitute the wave parameters affected by ocean currents into the wave calculation module to calculate the wave pressure on the offshore wind power pile foundation. Use the flow calculation module to calculate the fluid pressure on the offshore wind power pile foundation. By superimposing the wave pressure and the fluid pressure, the hydrodynamic pressure distribution under the wave-current coupling action is obtained.

[0151] First, the dynamic pressure caused by the wave is:

[0152]

[0153] At the same time, considering the influence of ocean currents, it is necessary to use the wave parameters affected by ocean currents to calculate the wave force. The relative velocity C r of the wave with respect to the ocean current and the wave velocity C affected by the ocean current can be expressed as:

[0154]

[0155] C = u c + C r (17)

[0156]

[0157] wherein, L r = L is the wavelength affected by ocean currents, T w is the wave period not affected by ocean currents, T r is the wave period relative to the ocean current. From equations (16) - (18), we get

[0158]

[0159] wherein, is the wave velocity not affected by ocean currents, is the wave number not affected by ocean currents, L w is the wavelength not affected by ocean currents, k is the wave number affected by the flow velocity, P i f is the dynamic pressure caused by the wave, ρ is the density of the fluid, and Re represents taking the real part (Realpart) of the complex number.

[0160] The wave height H caused by the flow velocity is:

[0161]

[0162] wherein,

[0163] Substitute the H and L affected by the ocean current into the wave calculation module for recalculation, and finally obtain the change of wave parameters under the wave - current coupling effect.

[0164] Secondly, the dynamic pressure generated by the flow is:

[0165]

[0166] where n = (n x , n y , n z ) and τ = (τ x , τ y , τ z ) are calculated by the following formula:

[0167]

[0168] where

[0169]

[0170] The wave-flow dynamic pressure and the circumferential flow dynamic pressure are added together to obtain the total dynamic pressure

[0171] S5. Wave-current force calculation module: By integrating the hydrodynamic pressure on the wet surface of the offshore wind power pile foundation, the wave-current force on the offshore wind power pile foundation is obtained, that is, F = -∫ S p·nds.

[0172] Embodiment 1

[0173] Consider five evenly distributed offshore wind power pile foundations as shown in Figure 4 . Among them, the radius a of the cylindrical offshore wind power pile foundation is 0.5, the incident wave angle The wave speed ka = 2, the wave height H = 2, and the water depth d = 2.5. Calculate the wave-current force on each offshore wind power pile foundation.

[0174] By applying the method of the present invention, the problem of the wave-current force on five evenly distributed offshore wind power pile foundations is successfully solved, and the wave-current force on each pile foundation is accurately calculated. Specifically, the following calculation results are obtained:

[0175] FP1 = 0.0441;

[0176] FP2 = 0.0468;

[0177] FP3 = 0.0579;

[0178] FP4 = 0.0607;

[0179] FP5 = 0.

[0180] The wave height diagram is as shown in Figure 5 .

[0181] Embodiment 2

[0182] Table 1 compares the differences between the wave-current forces calculated by using this method and the reference results in the literature. It should be noted that due to the lack of an analytical solution, the data in the reference is also an approximate result. Therefore, it is considered that an error within 3% is acceptable. It can be seen that the calculation results of this method are basically consistent with the results in the literature. This proves the correctness of the calculation model proposed in this paper. (Reference: J.H. Tao, Numerical simulation of water waves, Tianjin university press, Tianjin, 2021.)

[0183] Table 1 Calculation results of this method and reference results

[0184] Serial number <![CDATA[u c / c]]> ka Reference data RSBM Error 1 0.10 1.37 4.34 4.43 2.1％ 2 0.05 1.48 4.17 4.13 0.96％ 3 0 1.57 3.91 3.90 0.26％ 4 -0.05 1.68 3.71 3.68 0.81％ 5 -0.10 1.78 3.56 3.52 1.1％

[0185] In the present invention, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations 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 one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0186] Although the above embodiments have been shown and described, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions, and variations made by those of ordinary skill in the art to the above embodiments are within the protection scope of the present invention.

Claims

1. A calculation method for the wave-current coupled force borne by an offshore wind power pile foundation, characterized in that It includes the following steps: S1. Real-time monitor the environmental parameters and structural status through sensors installed on the surface of the offshore wind power pile foundation; S2. Construct a wave calculation module; S3. Construct a flow calculation module; S4. Calculate the wave pressure and fluid pressure on the offshore wind power pile foundation through the wave calculation module and the flow calculation module, and obtain the hydrodynamic pressure distribution under the combined action of waves and currents; S5. Integrate the obtained hydrodynamic pressure distribution to obtain the wave-current force on the offshore wind power pile foundation.

2. The calculation method for the wave-current coupling force borne by an offshore wind power pile foundation according to claim 1, wherein Constructing the wave calculation module in S2 requires accurate simulation of water wave propagation and interaction, and then calculating the wave force velocity potential, including the following steps: S201. Model assumption; S202. Define the total velocity potential function; S203. Set boundary conditions for the scattered wave function, including the water surface, the bottom of the water, and infinity; S204. Select the Green's function that satisfies the boundary conditions as the basis function; S205. Determine the source points and boundary node sets for calculation; S206. Solve the unknown coefficients according to the interpolation formula, the source point strength factor calculation formula, and the gradient; S207. Solve the scattered wave potential function.

3. The calculation method of the wave-current coupling force borne by the offshore wind power pile foundation according to claim 2, characterized in that, The total velocity potential includes the incident wave velocity potential and the scattered wave velocity potential. The calculation formula of the total velocity potential function is as follows: Φ(x,y,z,y) = [φ i (x,y,z) + φs(x,y,z)]e -iωt (2) where, φ i and φ s are the incident wave potential function and the scattered wave potential function respectively, ω is the wave frequency, i usually represents the imaginary unit, satisfying i 2 = -1, t represents the time variable, and the exponential term e -iωt represents the periodic time variation of the wave.

4. The calculation method for the wave-current coupled force borne by an offshore wind power pile foundation according to claim 2, wherein The formula of the scattered wave potential function is: Among them, β i is an unknown, Γ is the boundary, and G ij is the Green's function, representing the interaction between the source point s j and the collocation point x i . The source point s j is distributed on the boundary. When , the collocation point and the source point do not coincide, and the scattering potential is obtained by the weighted average of the contributions of all points. When x i ∈Γ and i = j, the source point and the collocation point coincide with each other, and the calculation of the scattering potential also includes the contribution of self-action. At this time, this point should use the source point strength factor G ii (x i , s i ) to replace G ij (x i , s j ); The calculation formula of the source point strength factor is: Among them, γ = 0.57721566490153286…, the surface S of the structure is divided into n micro - surface elements Δs, n being the total number of micro - surface elements, h i and h j are the heights of the collocation point and the source point in the z - direction, d is the water depth, k is the wave number, v is the phase velocity, l i is the characteristic length of the collocation point, and ζ is the coordinate of the source point in the z - direction.

5. The calculation method for the wave-current coupling force borne by an offshore wind power pile foundation according to claim 1, characterized in that, The calculation process of the flow calculation module in S3 is as follows: S301. Model assumption; S302. Define the flow-around force velocity potential function; S303. Select and apply the Green's function that satisfies the boundary conditions of the flow field velocity potential; S304. Solve the unknown coefficients according to the interpolation formula for calculating the flow-around force, the source point strength factor calculation formula, and the gradient; S305. Handle the singularity and solve.

6. The calculation method for the wave-current coupled force borne by an offshore wind power pile foundation according to claim 5, characterized in that, The calculation formula of the flow-around force velocity potential function is: Among them, χ j is an unknown coefficient, which is solved by the interpolation formula, the source point intensity factor calculation formula, and the normal gradient. represents the Green's function that satisfies the boundary condition of the flow field velocity potential, and the source point intensity factor is expressed as: Among them, S is the wet surface area of the offshore wind power pile foundation, represents the characteristic radius of the i-th source point, A i is the influence range of the i-th source point.

7. The calculation method for the wave-current coupled force borne by an offshore wind power pile foundation according to claim 1, characterized in that The formula of the hydrodynamic pressure distribution in S4 is: Where, In the formula, is the dynamic pressure caused by waves, is the dynamic pressure generated by the flow, ρ is the density of the fluid, u c is the flow velocity, u τ is the tangential velocity on the surface of the structure, τ = (τ x , τ y , τ z ), τ x , τ y , τ z are the tangential velocity components, representing the components of the fluid velocity in the tangential direction.

8. The calculation method for the wave-current coupling force borne by an offshore wind power pile foundation according to claim 7, characterized in that, The calculation formula for the wave and current forces on the offshore wind power pile foundation in S5 is F = -∫ S p·nds.

9. An electronic device, comprising a memory and a processor, wherein a computer program is stored on the memory, characterized in that, When the processor executes the computer program, it implements any step in the calculation method for the offshore wind power pile foundation to bear the combined wave-current force as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, A computer program is stored on the computer-readable storage medium. When the computer program is executed by a computer processor, it implements any step in the calculation method for the offshore wind power pile foundation to bear the combined wave-current force as described in any one of claims 1 to 7.

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