A method for solving complex stiffness of floating wind turbine suction anchor-soil system considering long-term cyclic and scouring effects

Abstract

The application discloses a kind of long-term cycle and scouring action considering floating wind turbine suction anchor-soil system complex stiffness solving method, comprising: obtaining suction anchor and seabed soil parameters, calculating the soil volume loss caused by long-term cyclic loading, seabed settlement, and modifying cyclic dense soil parameters;Foundation-soil dynamic interaction model is constructed, and the lateral and rotational soil complex stiffness parameters of the base are solved in frequency domain, and the lateral and rotational complex stiffness parameters of the soil distributed on the side wall are solved;According to the scouring depth, the constraint range of the soil around the suction anchor is corrected, and the lateral and rotational soil complex stiffness matrix under the scouring state is updated;Dynamic equilibrium equation is established, and the lateral, rotational and coupled dynamic complex stiffness of the suction anchor is solved;The obtained dynamic complex stiffness is fitted, and the frequency-independent equivalent dynamic lumped parameter is identified to represent the dynamic characteristics of the foundation.The application can accurately reflect the dynamic response of suction anchor-soil coupling under long-term cyclic sea conditions, and the equivalent parameters can be directly used for time-domain simulation of floating wind turbine.

Description

Technical Field

[0001] This invention relates to the field of deep-sea geotechnical engineering, and in particular to a method for solving the complex stiffness of a floating wind turbine suction anchor-soil system considering long-term circulation and scouring. Background Technology

[0002] With the continuous growth in demand for deep-sea wind power development, floating wind turbines have become an important development direction in the offshore wind power field due to their advantages such as applicability to deep waters, high wind energy resource utilization, and strong adaptability to different sea areas. Compared with near-shore fixed wind turbines, floating wind turbines are usually deployed in deep-sea areas with greater water depth and more complex marine environments, and are subjected to continuous cyclic dynamic loads generated by the coupling effect of environmental loads such as wind, waves, and currents. To ensure the positional stability and operational safety of the overall structure of the floating wind turbine, the dynamic loads on the superstructure need to be transferred to the seabed anchoring foundation through the mooring system, thus forming an overall force transmission system of "floating wind turbine - mooring system - anchoring foundation - seabed soil". Among them, the suction anchor foundation, as an important anchoring structure of the floating wind turbine mooring system, directly bears the alternating dynamic loads from the mooring cable and forms a complex dynamic coupling effect with the surrounding seabed soil. Its dynamic stiffness, damping characteristics, and dynamic response law directly affect the dynamic performance, structural stability, and long-term service safety of the floating wind turbine.

[0003] Currently, research on offshore suction anchor foundations mainly focuses on static bearing characteristics, ultimate bearing capacity, and installation construction, with a particular emphasis on analyzing the influence of foundation dimensions, embedment depth, and soil parameters on compressive, tensile, and shear bearing capacity. In recent years, some scholars have begun to focus on the dynamic characteristics of marine foundations and have conducted experimental and theoretical research on pile foundations and composite cylindrical foundations. For example, cyclic excitation model tests have been used to obtain the dynamic complex stiffness parameters at the top of the foundation, characterizing the dynamic stiffness and damping characteristics of the foundation and providing a reference for wind turbine dynamic analysis. However, existing research primarily focuses on fixed foundations, where the dynamic load is directly transferred from the superstructure to the top of the foundation. In contrast, for floating wind turbine suction anchor foundations, the dynamic load is mainly transferred through the mooring system to the anchor chain connection point, and then diffuses outward through the interaction between the foundation and the surrounding seabed soil. The load transfer paths of the two types of foundations differ significantly.

[0004] Furthermore, suction anchor foundations are subjected to high-cycle cyclic loading from environmental loads such as wind, waves, and currents over long periods, leading to continuous plastic cumulative deformation and structural reorganization of the surrounding seabed soil. Extensive model tests and field observations indicate that under long-term cyclic loading, the soil around the foundation is prone to forming local settlement zones and densification areas, resulting in changes in soil density, shear modulus, and damping characteristics, thereby altering the dynamic stiffness and energy dissipation capacity of the foundation-soil system. This effect accumulates gradually with increasing cycle count and persists throughout the wind turbine's lifespan. Simultaneously, wave and current action may cause continuous scouring of the seabed soil around the suction anchor foundation, reducing the effective embedment depth of the foundation sidewalls and altering the contact and constraint conditions between the foundation and the surrounding soil. This weakens the lateral and rotational constraints provided by the sidewall soil and changes the lateral, rotational, and coupled dynamic complex stiffness of the foundation-soil system. These effects accumulate gradually with increasing cycle count and scouring depth and persist throughout the wind turbine's lifespan. However, most current dynamic analysis methods for suction anchors are based on initial site soil parameters and unscoured terrain. They typically assume that soil properties and foundation placement conditions remain constant throughout the service life, failing to consider the evolution of soil parameters caused by long-term cyclic loading, changes in soil constraints due to scouring, and their combined impact on the foundation's dynamic characteristics. While this assumption may meet short-term dynamic analysis requirements, it struggles to accurately reflect the dynamic response characteristics of suction anchor foundations under long-term service conditions, potentially leading to discrepancies between predicted foundation dynamic stiffness, damping, and overall dynamic response and actual conditions.

[0005] In summary, research on the dynamic interaction between suction anchor foundation and soil system and the dynamic characteristics of anchor chain connection position under long-term circulation and scouring is still lacking, and existing dynamic parameters are difficult to directly apply to the dynamic analysis of floating wind turbines. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a method for solving the complex stiffness of a floating wind turbine suction anchor-soil system that considers long-term circulation and scouring effects, so as to solve the problems mentioned in the background art.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A method for solving the complex stiffness of a floating wind turbine suction anchor-soil system considering long-term circulation and scouring effects includes the following steps: S1. Determine the physical and mechanical parameters of the suction anchor foundation and the in-situ seabed soil, calculate the soil volume loss and seabed surface settlement depth caused by long-term cyclic loading, and correct the soil parameters after cyclic compaction. S2. Establish a numerical analysis model of the dynamic interaction between suction anchor foundation and soil. Use the soil multidimensional complex stiffness parameter to replace the constraint effect of soil on foundation. Solve the lateral complex stiffness parameter of soil at the bottom of suction anchor foundation, the rotational complex stiffness parameter of soil at the bottom of foundation, the lateral complex stiffness parameter of soil distributed along the sidewall and the rotational complex stiffness parameter of soil distributed along the sidewall through frequency domain analysis. S3. Introduce the scour depth parameter to characterize the scour evolution process of the soil around the suction anchor foundation under the action of water flow. Correct the effective constraint range of the soil around the foundation according to the scour depth and update the complex stiffness matrix of the soil in the lateral direction and rotation of the suction anchor foundation sidewall. S4. Combining the inertial characteristics of the suction anchor foundation itself and the multidimensional complex stiffness parameters of the soil, construct the dynamic equilibrium equation of the foundation-soil system, and solve for the lateral dynamic complex stiffness, rotational dynamic complex stiffness and lateral-rotational coupled dynamic complex stiffness of the suction anchor foundation. S5. Select the main frequency range of environmental load during the normal service period of the floating wind turbine. Based on the solved dynamic complex stiffness, use the least squares method to fit the multidimensional dynamic complex stiffness and identify the dynamic lumped parameters that are suitable for the whole simulation of the floating wind turbine and are independent of the load frequency. Use this set of frequency-independent dynamic lumped parameters to characterize the foundation dynamic complex stiffness.

[0008] Preferably, in step S1, determining the physical and mechanical parameters of the suction anchor foundation and the in-situ seabed soil includes the diameter of the suction anchor foundation. D ,high H Wall thickness (t), density r p soil shear modulus G Soil density r 0 and Poisson's ratio n .

[0009] Preferably, in step S1, calculating the soil volume loss caused by long-term cyclic loading includes: ; In the formula, Δ V LT This refers to the volume loss of soil caused by long-term cyclic loading. r 0 represents the initial soil density; r max This indicates the maximum density of the soil, determined through a laboratory test for relative density.

[0010] Preferably, in step S1, the formula for calculating the seabed surface subsidence depth is as follows: ; In the formula, N Indicates the number of cyclic load applications.

[0011] Preferably, in step S1, the process of correcting the soil parameters after cyclic compaction is as follows: ; ; In the formula, H d Indicates the embedment depth of the suction anchor foundation. G d This represents the long-term cyclic corrected shear modulus of the soil.

[0012] Preferably, in step S2, the lateral complex stiffness parameter of the soil at the bottom of the suction anchor foundation is calculated. as follows: ; ; ; In the formula, k h Indicates the lateral dynamic stiffness coefficient of the exposed foundation; K h Indicates the lateral static stiffness of an exposed foundation; represents an imaginary number; oh Indicates angular frequency; C h Indicates the lateral damping coefficient of the exposed foundation; G d This represents the long-term cyclic corrected shear modulus of the soil. D Indicates the diameter of the suction anchor foundation; A b The area of ​​the foundation bottom surface is represented by the formula. A b = π D 2 / 4 calculation; n Poisson's ratio; V s Represents the soil shear wave velocity, derived from the formula calculate; β Indicates hysteresis damping; r max This indicates the maximum density of the soil.

[0013] Preferably, in step S2, the rotational stiffness parameters of the soil at the bottom of the foundation are calculated. as follows: , ; , ; ; In the formula, kr This indicates the rotational dynamic stiffness coefficient of the exposed foundation. K r Indicates the rotational static stiffness of the exposed foundation. C r Indicates the rotational damping coefficient of the exposed foundation. Indicates the radiation damping calculation coefficient; I b The moment of inertia of the foundation base is expressed by the formula. calculate; V La The Lysmer equivalent wave velocity is expressed by the equation. calculate.

[0014] Preferably, in step S2, the transverse complex stiffness parameters of the soil distributed along the sidewall are calculated. as follows: ; ; ; ; ; ; ; In the formula, For the lateral stiffness of the embedded foundation. H d Indicates the embedment depth of the suction anchor foundation. K hh This indicates the lateral static stiffness of the embedded foundation. K h Indicates the lateral static stiffness of an exposed foundation. Indicates the lateral complex stiffness of the exposed foundation. C hh This represents the lateral damping coefficient of the embedded foundation. I tw ξ represents the lateral embedment coefficient, and ξ represents the lateral dynamic stiffness coefficient of the embedded foundation. a 0 represents the angular frequency. Dimensionless form; effective projected area of ​​the foundation sidewall along the load direction A ws and the effective projected area of ​​the foundation sidewall in the vertical load direction A wce Calculated using the following formula: .

[0015] Preferably, in step S2, the rotational complex stiffness parameters of the soil distributed along the sidewall are calculated. for: ; ; ; ; ; ; In the formula, For the rotational stiffness of the embedded foundation, K rr This indicates the rotational static stiffness of the embedded foundation. K r Indicates the rotational static stiffness of the exposed foundation. Indicates the rotational complex stiffness of the exposed foundation. or c1 represents the rotational embedment coefficient, and c2 represents the sidewall rotational radiation damping correction coefficient. C rr The damping coefficient of the embedded foundation; the area moment of inertia of the sidewall projected perpendicular to the load direction. I wce The polar moment of inertia of the effective projection plane of the sidewall along the load direction J ws And the correction amount of the rotational equivalent force arm Calculated using the following formula: ; ; .

[0016] Preferably, step S3 specifically includes the following process: (1) Introduce scour depth parameter S d It characterizes the degree of scouring of the seabed soil around the suction anchor foundation under the action of water flow; (2) Adjust the effective contact height between the suction anchor foundation sidewall and the surrounding soil according to the scour depth, and the effective embedment depth after scour. H e Calculate using the following formula: ; (3) Using the aforementioned effective burial depth H e The embedment depth in the formula for calculating the complex stiffness of the sidewall soil in step S2 is replaced. H d Recalculate the effective projected area, area moment of inertia, polar moment of inertia, and rotational equivalent force arm correction of the foundation sidewalls. (4) Update the complex stiffness matrix of the soil in the lateral direction and rotation of the suction anchor foundation based on the recalculated sidewall geometric parameters and effective constraint range.

[0017] Preferably, step S4 specifically includes the following process: (1) Calculate the dynamic complex stiffness of the suction anchor foundation relative to the reference point at the bottom of the foundation by combining the inertial characteristics of the suction anchor foundation itself and the multidimensional complex stiffness parameters of the soil after long-term cyclic action and scouring. : ; ; ; ; In the formula, The lateral dynamic complex stiffness is relative to the base position. The rotational dynamic stiffness relative to the base position. The lateral-rotational coupled dynamic complex stiffness relative to the base position. m This represents the sum of the mass of the foundation and the internal soil. J c The moment of inertia of the foundation and the internal soil relative to the center of mass is calculated using the following formula: ; ; in, H d This indicates the effective embedment depth of the suction anchor foundation after considering long-term cyclic action. When scour occurs in the foundation, the effective embedment depth is corrected to... H e ,Right now H e = H d S d and with H e Replace the above formula H d Perform calculations; (2) Based on the principles of rigid body kinematics and dynamic equilibrium, the dynamic complex stiffness of the suction anchor foundation is determined. The dynamic complex stiffness of the anchor chain connection at the foundation bottom is obtained as a function of frequency by transforming the reference point to the critical point of the anchor chain connection. : ; In the formula, z 0 is the base vertical coordinate.z 1 represents the vertical coordinate of the anchor chain connection. This refers to the lateral dynamic complex stiffness relative to the anchor chain connection. The rotational dynamic stiffness relative to the anchor chain connection is... The lateral-rotational coupled dynamic complex stiffness is relative to the anchor chain connection.

[0018] Preferably, S5 specifically includes: Obtaining the lumped dynamic parameters of the suction anchor foundation directly serves the integrated numerical simulation analysis of the floating wind turbine, including the lateral spring stiffness. k 1. Stiffness of the rotating spring k 2 and lateral-rotational coupling spring stiffness k 3. Lateral damping c 1. Rotational damping c 2 and lateral-rotational coupling damping c 3. Top mass block mass m 1 and the mass of the bottom mass block m 2. Length of rigid rod h Based on the frequency-dependent dynamic complex stiffness of the suction anchor foundation anchor chain connection obtained from the solution, the dominant frequency range of environmental loads during the normal service period of the floating wind turbine is selected. The least squares method is used to fit the multidimensional dynamic complex stiffness, and dynamic lumped parameters that are suitable for the whole-machine simulation of the floating wind turbine and independent of the load frequency are identified. This set of frequency-independent dynamic lumped parameters is used to characterize the dynamic complex stiffness of the foundation, including the lateral direction. Rotation direction and the lateral rotational coupling direction .

[0019] Beneficial effects of this invention: 1. This invention can reasonably characterize the compaction, settlement, and dynamic parameter changes of the soil surrounding the foundation caused by long-term cyclic loading, as well as the reduction in the effective embedment depth of the foundation and the changes in the constraint conditions of the sidewall soil caused by scouring, and further reflect the frequency-dependent dynamic characteristics of the suction anchor foundation-soil system. Based on this, dynamic lumped parameters that can equivalently reproduce the target complex stiffness frequency response are obtained through parameter identification. Compared with the traditional constant stiffness-damping matrix at the mud surface, the dynamic lumped parameters can reflect the characteristics of the dynamic stiffness and damping of the foundation-soil system changing with frequency, thus more accurately reflecting the response mechanism of the suction anchor foundation under frequency-dependent dynamic actions such as earthquakes and wind and wave loads. Furthermore, these parameters can be embedded in the integrated nonlinear time-domain analysis model of the floating wind turbine, providing technical support for the prediction of dynamic response, structural design optimization, and service safety assessment of deep-sea floating wind turbines.

[0020] 2. More reasonable long-term service conditions: It can simultaneously consider the changes in soil density, settlement and dynamic parameters around the suction anchor caused by long-term cyclic loading, as well as the changes in the effective constraint conditions of the foundation sidewall caused by scour evolution, so that the obtained complex stiffness can more realistically reflect the evolution process of the suction anchor foundation's service state.

[0021] 3. Higher load position matching: The basic dynamic complex stiffness relative to the anchor chain connection position can correspond to the actual position of the mooring load, making it more suitable for dynamic analysis of floating wind turbine anchor foundations.

[0022] 4. Higher computational efficiency: By using equivalent dynamic lumped parameters that are independent of frequency, the dynamic interaction between the foundation and the soil can be simulated efficiently, improving computational efficiency while ensuring analysis accuracy.

[0023] 5. Good engineering applicability: The obtained lumped dynamic parameters can be directly embedded into the nonlinear dynamic analysis model of floating wind turbines, providing technical support for the prediction of dynamic response and service safety assessment of deep-sea floating wind turbines. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating a method for solving the complex stiffness of a floating wind turbine suction anchor-soil system that considers long-term circulation and scouring. Figure 2 Schematic diagram of the suction anchor foundation-soil system for a floating wind turbine; Figure 3 A schematic diagram of the relative positions of the basic complex stiffness; Figure 4 The figure shows the fitting diagram of the basic dynamic complex stiffness and the corresponding lumped parameters; In the diagram, 1-suction anchor foundation; 2-lateral complex stiffness of the sidewall soil; 3-rotational complex stiffness of the sidewall soil; 4-lateral complex stiffness of the base soil; 5-rotational complex stiffness of the base soil; 6-center of the base; 7-anchor chain connection. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0026] Example 1: As Figure 1 As shown, a method for solving the complex stiffness of a floating wind turbine suction anchor-soil system considering long-term cycling and scouring effects is presented. The method includes the following steps: S1. Long-term wind, wave, and current loads continuously act on the suction anchor foundation through the mooring system, forming a settlement zone on the seabed surface around the foundation and a dense zone near the foundation sidewalls. The soil density and stiffness gradually evolve with cyclic loading, thus affecting the dynamic stiffness and damping characteristics of the suction anchor foundation. Therefore, before solving for the complex stiffness, the soil parameters around the foundation are subjected to long-term cyclic correction.

[0027] (1) Determine the physical and mechanical parameters of the suction anchor foundation and the in-situ seabed soil, including the diameter of the suction anchor foundation. D (m), height H (m), wall thickness t (m), density r p (kg / m 3 soil shear modulus G (kPa), soil density r 0 (kg / m 3 ) and Poisson's ratio n ; (2) Calculate the volume loss of soil caused by long-term cyclic loading.

[0028] In the formula, Δ V LT This refers to the volume loss of soil caused by long-term circulation and scouring. r 0 (kg / m 3 () represents the initial soil density; r max (kg / m 3 The value of ) indicates the maximum density of the soil, which can be determined through indoor tests for relative density.

[0029] (3) Calculate the depth of seabed surface subsidence

[0030] In the formula, N This indicates the number of cyclic loads. For offshore floating wind turbines, under long-term wind, wave, and current environmental loads, they typically need to withstand a large number of cyclic loads during their service life, with the number of cycles reaching up to 10. 5 10 8 Magnitude.

[0031] (4) Correction of soil parameters after cyclic compaction

[0032]

[0033] In the formula, H d (m) indicates the embedment depth of the suction anchor foundation. G d (kPa) represents the long-term cyclic corrected shear modulus of the soil. The corrected soil parameters will be used to solve for the complex stiffness of the soil below.

[0034] S2. Establish a numerical analysis model of the dynamic interaction between the suction anchor foundation and the soil, and use the multidimensional complex stiffness parameters of the soil to equivalently replace the constraint effect of the soil on the foundation. Solve for the lateral complex stiffness parameters of the soil at the bottom of the suction anchor foundation through frequency domain analysis. Rotational complex stiffness parameters of the soil at the foundation bottom Transverse complex stiffness parameters of soil distributed along the sidewall and the rotational complex stiffness parameters of the soil distributed along the sidewall .

[0035] (1) Calculate the lateral complex stiffness parameters of the soil at the bottom of the suction anchor foundation. :

[0036]

[0037]

[0038] In the formula, k h This represents the lateral dynamic stiffness coefficient of an exposed foundation, which can generally be taken as 1. K h Indicates the lateral static stiffness of an exposed foundation. represents an imaginary number, oh Represents angular frequency. C h Indicates the lateral damping coefficient of the exposed foundation; A b The area of ​​the foundation bottom surface can be represented by the formula. A b = π D 2 / 4 calculation; V s The shear wave velocity of soil can be expressed by the formula: calculate; β This represents hysteresis damping, which is typically taken as 0.03 to 0.06.

[0039] (2) Calculate the rotational complex stiffness parameters of the soil at the bottom of the foundation. : ,

[0040] ,

[0041]

[0042] In the formula, k r This indicates the rotational stiffness coefficient of the exposed foundation. Kr Indicates the rotational static stiffness of the exposed foundation. C r Indicates the rotational damping coefficient of the exposed foundation. Indicates the radiation damping calculation coefficient; I b The moment of inertia of the foundation base can be expressed by the formula: calculate.

[0043] (3) Calculate the transverse complex stiffness parameters of the soil distributed along the sidewall. :

[0044]

[0045]

[0046]

[0047]

[0048]

[0049]

[0050] In the formula, For the lateral stiffness of the embedded foundation. K hh This indicates the lateral static stiffness of the embedded foundation. C hh This represents the lateral damping coefficient of the embedded foundation. I tw ξ represents the lateral embedment coefficient, and ξ represents the lateral dynamic stiffness coefficient of the embedded foundation. a 0 represents the angular frequency. Dimensionless form; A ws , A wce ,as well as V La It can be calculated using the following formula:

[0051]

[0052] (4) Calculate the rotational complex stiffness parameters of the soil distributed along the sidewall. :

[0053]

[0054]

[0055]

[0056]

[0057]

[0058] In the formula, For the rotational stiffness of the embedded foundation, K rr This indicates the rotational static stiffness of the embedded foundation. or Indicates the rotational embedment coefficient. C rr Indicates the rotational damping coefficient of the embedded foundation; I wce , J ws ,as well as It can be calculated using the following formula:

[0059]

[0060]

[0061] S3. Introduce the scour depth parameter to characterize the scour evolution process of the soil around the suction anchor foundation under the action of water flow. Correct the effective constraint range of the soil around the foundation according to the scour depth and update the complex stiffness matrix of the soil in the lateral direction and rotation of the suction anchor foundation sidewall. (1) Introduce scour depth parameter S d It characterizes the degree of scouring of the seabed soil around the suction anchor foundation under the action of water flow; (2) Calculate the effective burial depth after scour. H e : .

[0062] (3) Using the aforementioned effective burial depth H e The embedment depth in the formula for calculating the complex stiffness of the sidewall soil in step S2 is replaced. H d Recalculate the relevant parameters; (4) Update the lateral complex stiffness matrix of the suction anchor foundation sidewall and the complex stiffness matrix of the rotating soil sidewall.

[0063] S4. Combining the inherent inertial characteristics of the suction anchor foundation with the multidimensional complex stiffness parameters of the soil after long-term cyclic action and scouring, the dynamic equilibrium equations of the foundation-soil system are constructed, and the lateral dynamic complex stiffness of the suction anchor foundation is obtained by solving the equations. Rotational dynamic stiffness and lateral-rotational coupled dynamic complex stiffness .

[0064] (1) Calculate the dynamic complex stiffness of the suction anchor foundation relative to the base position. :

[0065]

[0066]

[0067]

[0068] In the formula, The lateral dynamic complex stiffness is relative to the base position. The rotational dynamic stiffness relative to the base position. The lateral-rotational coupled dynamic complex stiffness relative to the base position. m This represents the sum of the mass of the foundation and the internal soil. J c The moment of inertia of the foundation and the internal soil relative to the center of mass can be calculated using the following formula:

[0069]

[0070] It should be pointed out that, H d This indicates the effective embedment depth of the suction anchor foundation after considering long-term cyclic action. When scour occurs in the foundation, the effective embedment depth is corrected to... H e ( H e = H d S d ), and H e Replace the above formula H d Perform the calculation.

[0071] (2) Based on the principles of rigid body kinematics and dynamic equilibrium, the dynamic complex stiffness of the suction anchor foundation is determined. The dynamic complex stiffness of the anchor chain connection at the foundation bottom is obtained as a function of frequency by transforming the reference point to the critical point of the anchor chain connection. :

[0072] In the formula,z 0 is the base vertical coordinate. z 1 represents the vertical coordinate of the anchor chain connection. This refers to the lateral dynamic complex stiffness relative to the anchor chain connection. The rotational dynamic stiffness relative to the anchor chain connection is... The lateral-rotational coupled dynamic complex stiffness is relative to the anchor chain connection.

[0073] S5. Obtain the lumped dynamic parameters of the suction anchor foundation, which can be directly used for integrated numerical simulation analysis of floating wind turbines, including lateral spring stiffness. k 1. Stiffness of the rotating spring k 2 and lateral-rotational coupling spring stiffness k 3. Lateral damping c 1. Rotational damping c 2 and lateral-rotational coupling damping c 3. Top mass block mass m 1 and the mass of the bottom mass block m 2. Length of rigid rod h This step, based on the frequency-dependent dynamic complex stiffness of the suction anchor foundation anchor chain connection obtained from the solution, selects the dominant frequency range of environmental loads (0~10Hz) during the normal service of the floating wind turbine. The least squares method is used to fit the multidimensional dynamic complex stiffness, identifying dynamic lumped parameters suitable for the overall simulation of the floating wind turbine and independent of the load frequency. Using this set of frequency-independent dynamic lumped parameters, the dynamic complex stiffness of the foundation, including the lateral direction, can be accurately characterized. Rotation direction and the lateral rotational coupling direction It can be directly applied to the overall time-domain nonlinear dynamic analysis of floating wind turbines, effectively improving the computational efficiency of whole-machine numerical simulation while ensuring simulation accuracy.

[0074] Example 2: Taking the suction anchor foundation of a floating wind turbine in Timor Sea (Randolph and Gourvenec, 2011) as an example, the specific implementation of the present invention is described. The foundation has a diameter of 5m, a height of 12m, a wall thickness of 0.02m, and a material density of 7850kg / m³. 3 The soil shear modulus is 5000 kPa, and the initial soil density is 2040 kg / m³. 3 The maximum density is 2300 kg / m³. 3 The Poisson's ratio is 0.33, the hysteretic damping is 0.05, the scour depth is 0.5m, the soil layer is uniformly distributed, and the site geological conditions are stable.

[0075] (1) Based on the suction anchor foundation and the site physical and mechanical parameters, calculate the soil compaction and settlement around the foundation caused by long-term cyclic action, and correct parameters such as soil density and shear modulus to obtain the soil physical and mechanical parameters under long-term service conditions.

[0076] (2) Construct a multidimensional constraint numerical analysis model of suction anchor foundation-soil, such as Figure 2 As shown, the lateral complex stiffness parameters of the soil at the bottom of the suction anchor foundation are solved by frequency domain analysis. Rotational complex stiffness parameters of the soil at the foundation bottom Transverse complex stiffness parameters of soil distributed along the sidewall and the rotational complex stiffness parameters of the soil distributed along the sidewall .

[0077] (3) Correct the effective contact range between the foundation sidewall and the surrounding soil according to the scour depth, and update the transverse soil complex stiffness matrix and the rotational soil complex stiffness matrix distributed along the sidewall accordingly.

[0078] (4) Combining the inertial characteristics of the suction anchor foundation itself and the multidimensional complex stiffness of the soil after long-term cycling and scouring, the dynamic equilibrium equation of the foundation-soil system is constructed, and the dynamic complex stiffness of the suction anchor foundation relative to the base position is obtained by solving it. This includes lateral dynamic complex stiffness, rotational dynamic complex stiffness, and lateral-rotational coupled dynamic complex stiffness. Subsequently, based on the principles of rigid body kinematics and dynamic equilibrium, the dynamic complex stiffness of the suction anchor foundation is... The dynamic complex stiffness of the anchor chain connection at the foundation bottom is obtained as a function of frequency by transforming the reference point to the critical point of the anchor chain connection. In this example, the distance from the critical point of the anchor chain connection to the bottom of the foundation is 0.5. H ,Right now( z 0 z 1) = 0.5 H Substituting into the calculation formula in step S3, the lateral dynamic complex stiffness relative to the anchor chain connection can be obtained. Rotational dynamic stiffness and lateral-rotational coupled dynamic complex stiffness .

[0079] (5) Based on the fundamental frequency domain dynamic complex stiffness obtained by the solution, 0~10Hz is selected as the main frequency range of the load during the normal service of the floating wind turbine. The least squares method is used to fit the complex stiffness to obtain the dynamic lumped parameters of the anchor chain connection that are suitable for the whole-machine simulation of the wind turbine and are independent of the load frequency, including the lateral spring stiffness. k 1 = 254416 kN / m, rotational spring stiffness k2 = 7580476 kN / m and lateral-rotational coupling spring stiffness k 3 = 22657 kN / m, lateral damping c 1 = 34879 kN / m·s -1 Rotational damping c 2 = 723344 kN / m·s -1 and lateral-rotational coupling damping c 3 = 798 kN / m·s -1 Top mass block mass m 1 = 532 t and the mass of the bottom mass block m 2 = 0 t, length of rigid rod h = 16 m. For example... Figure 4 As shown, the thick solid line represents the theoretical calculation value, and the thin dashed line represents the fitted value of the lumped dynamic parameters. It can be seen that the two results are similar, indicating that the calculated lumped dynamic parameters can accurately reproduce the dynamic characteristics of the floating wind turbine suction anchor foundation-soil system. Furthermore, the obtained lumped dynamic parameters are frequency-independent and can be directly applied to the nonlinear time-domain analysis of the entire floating wind turbine system. This provides an efficient and reliable analytical method for predicting the dynamic response and assessing the service safety of deep-sea floating wind turbines, demonstrating significant engineering application value and promising prospects for wider application.

[0080] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A method for solving the complex stiffness of a floating wind turbine suction anchor-soil system considering long-term circulation and scouring, characterized in that: Includes the following steps: S1. Determine the physical and mechanical parameters of the suction anchor foundation and the in-situ seabed soil, calculate the soil volume loss and seabed surface settlement depth caused by long-term cyclic loading, and correct the soil parameters after cyclic compaction. S2. Establish a numerical analysis model of the dynamic interaction between suction anchor foundation and soil. Use the soil multidimensional complex stiffness parameter to replace the constraint effect of soil on foundation. Solve the lateral complex stiffness parameter of soil at the bottom of suction anchor foundation, the rotational complex stiffness parameter of soil at the bottom of foundation, the lateral complex stiffness parameter of soil distributed along the sidewall and the rotational complex stiffness parameter of soil distributed along the sidewall through frequency domain analysis. S3. Introduce the scour depth parameter to characterize the scour evolution process of the soil around the suction anchor foundation under the action of water flow. Correct the effective constraint range of the soil around the foundation according to the scour depth and update the complex stiffness matrix of the soil in the lateral direction and rotation of the suction anchor foundation sidewall. S4. Combining the inertial characteristics of the suction anchor foundation itself and the multidimensional complex stiffness parameters of the soil, construct the dynamic equilibrium equation of the foundation-soil system, and solve for the lateral dynamic complex stiffness, rotational dynamic complex stiffness and lateral-rotational coupled dynamic complex stiffness of the suction anchor foundation. S5. Select the main frequency range of environmental load during the normal service period of the floating wind turbine. Based on the solved dynamic complex stiffness, use the least squares method to fit the multidimensional dynamic complex stiffness and identify the dynamic lumped parameters that are suitable for the whole simulation of the floating wind turbine and are independent of the load frequency. Use this set of frequency-independent dynamic lumped parameters to characterize the foundation dynamic complex stiffness.

2. The method for solving the complex stiffness of a floating wind turbine suction anchor-soil system considering long-term circulation and scouring as described in claim 1, characterized in that: In step S1, determining the physical and mechanical parameters of the suction anchor foundation and the in-situ seabed soil includes the diameter of the suction anchor foundation. D ,high H Wall thickness (t), density ρ p soil shear modulus G Soil density ρ 0 and Poisson's ratio ν .

3. The method for solving the complex stiffness of a floating wind turbine suction anchor-soil system considering long-term circulation and scouring, as described in claim 2, is characterized in that: In S1, the calculation of soil volume loss caused by long-term cyclic loading includes: ； In the formula, Δ V LT This refers to the volume loss of soil caused by long-term cyclic loading. ρ 0 represents the initial soil density; ρ max This indicates the maximum density of the soil, determined through a laboratory test for relative density.

4. The method for solving the complex stiffness of a floating wind turbine suction anchor-soil system considering long-term circulation and scouring as described in claim 3, characterized in that: In S1, the formula for calculating the seabed surface subsidence depth is as follows: ； In the formula, N Indicates the number of cyclic load applications.

5. The method for solving the complex stiffness of a floating wind turbine suction anchor-soil system considering long-term circulation and scouring as described in claim 4, characterized in that: In step S1, the process of correcting the soil parameters after cyclic compaction is as follows: ； ； In the formula, H d Indicates the embedment depth of the suction anchor foundation. G d This represents the long-term cyclic corrected shear modulus of the soil.

6. The method for solving the complex stiffness of a floating wind turbine suction anchor-soil system considering long-term circulation and scouring as described in claim 1, characterized in that: In S2, the lateral complex stiffness parameters of the soil at the bottom of the suction anchor foundation are calculated. as follows: ； ； ； In the formula, k h Indicates the lateral dynamic stiffness coefficient of the exposed foundation; K h Indicates the lateral static stiffness of an exposed foundation; represents an imaginary number; ω Indicates angular frequency; C h Indicates the lateral damping coefficient of the exposed foundation; G d This represents the long-term cyclic corrected shear modulus of the soil. D Indicates the diameter of the suction anchor foundation; A b The area of ​​the foundation bottom surface is represented by the formula. A b = π D 2 / 4 calculation; ν Poisson's ratio; V s Represents the soil shear wave velocity, derived from the formula calculate; β Indicates hysteresis damping; ρ max This indicates the maximum density of the soil.

7. The method for solving the complex stiffness of a floating wind turbine suction anchor-soil system considering long-term circulation and scouring as described in claim 6, characterized in that: In step S2, the rotational stiffness parameters of the soil at the bottom of the foundation are calculated. as follows: ， ； ， ； ； In the formula, k r This indicates the rotational dynamic stiffness coefficient of the exposed foundation. K r Indicates the rotational static stiffness of the exposed foundation. C r Indicates the rotational damping coefficient of the exposed foundation. Indicates the radiation damping calculation coefficient; I b The moment of inertia of the foundation base is expressed by the formula. calculate; V La The Lysmer equivalent wave velocity is expressed by the equation. calculate.

8. The method for solving the complex stiffness of a floating wind turbine suction anchor-soil system considering long-term circulation and scouring, as described in claim 7, is characterized in that: In step S2, the lateral complex stiffness parameters of the soil distributed along the sidewall are calculated. as follows: ； ； ； ； ； ； ； In the formula, For the lateral stiffness of the embedded foundation. H d Indicates the embedment depth of the suction anchor foundation. K hh This indicates the lateral static stiffness of the embedded foundation. K h Indicates the lateral static stiffness of an exposed foundation. Indicates the lateral complex stiffness of the exposed foundation. C hh This represents the lateral damping coefficient of the embedded foundation. I tw ξ represents the lateral embedment coefficient, and ξ represents the lateral dynamic stiffness coefficient of the embedded foundation. a 0 represents the angular frequency. Dimensionless form; effective projected area of ​​the foundation sidewall along the load direction A ws and the effective projected area of ​​the foundation sidewall in the vertical load direction A wce Calculated using the following formula: 。 9. The method for solving the complex stiffness of a floating wind turbine suction anchor-soil system considering long-term circulation and scouring as described in claim 8, characterized in that: In step S2, the rotational complex stiffness parameters of the soil distributed along the sidewall are calculated. for: ； ； ； ； ； ； In the formula, For the rotational stiffness of the embedded foundation, K rr This indicates the rotational static stiffness of the embedded foundation. K r Indicates the rotational static stiffness of the exposed foundation. Indicates the rotational complex stiffness of the exposed foundation. η c1 represents the rotational embedment coefficient, and c2 represents the sidewall rotational radiation damping correction coefficient. C rr Indicates the rotational damping coefficient of the embedded foundation; The area moment of inertia of the sidewall perpendicular to the effective projection plane of the load direction I wce Polar moment of inertia of the effective projection plane of the sidewall along the load direction J ws and the correction amount of the rotational equivalent force arm Calculated using the following formula: ； ； 。 10. The method for solving the complex stiffness of a floating wind turbine suction anchor-soil system considering long-term circulation and scouring as described in claim 9, characterized in that: S3 specifically includes the following process: (1) Introduce scour depth parameter S d It characterizes the degree of scouring of the seabed soil around the suction anchor foundation under the action of water flow; (2) Adjust the effective contact height between the suction anchor foundation sidewall and the surrounding soil according to the scour depth, and the effective embedment depth after scour. H e Calculate using the following formula: ； (3) Using the aforementioned effective burial depth H e The embedment depth in the formula for calculating the complex stiffness of the sidewall soil in step S2 is replaced. H d Recalculate the effective projected area, area moment of inertia, polar moment of inertia, and rotational equivalent force arm correction of the foundation sidewalls; (4) Update the complex stiffness matrix of the soil in the lateral direction and rotation of the suction anchor foundation based on the recalculated sidewall geometric parameters and effective constraint range.

11. The method for solving the complex stiffness of a floating wind turbine suction anchor-soil system considering long-term circulation and scouring, as described in claim 10, is characterized in that: S4 specifically includes the following process: (1) Calculate the dynamic complex stiffness of the suction anchor foundation relative to the reference point at the bottom of the foundation by combining the inertial characteristics of the suction anchor foundation itself and the multidimensional complex stiffness parameters of the soil after long-term cyclic action and scouring. : ； ； ； ； In the formula, The lateral dynamic complex stiffness is relative to the base position. The rotational dynamic stiffness relative to the base position. The lateral-rotational coupled dynamic complex stiffness relative to the base position. m This represents the sum of the mass of the foundation and the internal soil. J c The moment of inertia of the foundation and the internal soil relative to the center of mass is calculated using the following formula: ； ； in, H d This indicates the effective embedment depth of the suction anchor foundation after considering long-term cyclic action. When scour occurs in the foundation, the effective embedment depth is corrected to... H e ,Right now H e = H d S d and with H e Replace the above formula H d Perform calculations; (2) Based on the principles of rigid body kinematics and dynamic equilibrium, the dynamic complex stiffness of the suction anchor foundation is determined. The dynamic complex stiffness of the anchor chain connection at the foundation bottom is obtained as a function of frequency by transforming the reference point to the critical point of the anchor chain connection. : ； In the formula, z 0 is the base vertical coordinate. z 1 represents the vertical coordinate of the anchor chain connection. This refers to the lateral dynamic complex stiffness relative to the anchor chain connection. The rotational dynamic stiffness relative to the anchor chain connection is... The lateral-rotational coupled dynamic complex stiffness is relative to the anchor chain connection.

12. The method for solving the complex stiffness of a floating wind turbine suction anchor-soil system considering long-term circulation and scouring as described in claim 11, characterized in that: S5 specifically includes: Obtaining the lumped dynamic parameters of the suction anchor foundation directly serves the integrated numerical simulation analysis of the floating wind turbine, including the lateral spring stiffness. k 1. Stiffness of the rotating spring k 2 and lateral-rotational coupling spring stiffness k 3. Lateral damping c 1. Rotational damping c 2 and lateral-rotational coupling damping c 3. Top mass block mass m 1 and the mass of the bottom mass block m 2. Length of rigid rod h Based on the frequency-dependent dynamic complex stiffness of the suction anchor foundation anchor chain connection obtained from the solution, the dominant frequency range of environmental loads during the normal service period of the floating wind turbine is selected. The least squares method is used to fit the multidimensional dynamic complex stiffness, and dynamic lumped parameters that are suitable for the whole-machine simulation of the floating wind turbine and independent of the load frequency are identified. This set of frequency-independent dynamic lumped parameters is used to characterize the dynamic complex stiffness of the foundation, including the lateral direction. Rotation direction and the lateral rotational coupling direction .

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