Offshore wind turbine refined overall coupling calculation method under wind-ice combined action

Abstract

The invention discloses an offshore wind turbine refined integral coupling calculation method under the wind-ice combined effect, and belongs to the technical field of offshore wind turbine structure calculation. According to the method, based on structural dynamic nonlinearity, pile-soil interaction, aerodynamic load and aerodynamic damping effect, fluid-solid coupling and sea ice breaking failure modes, wind-water-ice-soil-fan structure integrated coupling reaction analysis is realized; fAST and ANSYS / LS-DYNA are used as platforms, overall refined coupling calculation of ice-induced vibration of the offshore wind turbine is achieved, and dynamic ice force load and structural dynamic response time history are obtained. According to the method, the ice-induced vibration response of the overall structure of the offshore wind turbine and the dynamic ice force load borne by the ice-induced vibration response can be accurately and perfectly estimated, and a basis is provided for refined coupling dynamic analysis.

Description

Technical Field

[0001] This invention belongs to the field of offshore wind turbine structural calculation and analysis, and relates to a refined overall coupling analysis method for offshore wind turbines under the combined effects of wind and ice. Background Technology

[0002] With the vigorous development of offshore wind energy, the problem of ice-induced vibration in flexible offshore wind turbines has become serious, threatening the safe operation of the structure and the physical and mental health of workers. However, the offshore wind turbine system is a strongly coupled system, subjected to loads from aerodynamics, hydrodynamics, and dynamic ice forces. Aerodynamic-hydraulic-elastic coupling modeling of this system structure is fundamental and crucial for studying the dynamic characteristics of offshore wind turbine systems. Currently, the standards lack detailed definitions for the combined wind-ice action condition, and the interaction and coupling effects between ice loads, wind loads, pile-soil interaction, and structural response are quite complex. Current research can only effectively investigate the impact of individual ice loads on the dynamic characteristics of offshore wind turbines; an integrated calculation method for wind-water-ice-soil-structure coupling in offshore wind turbines is still lacking. Summary of the Invention

[0003] To address the aforementioned problems in marine engineering, this invention provides a refined overall coupled calculation method for offshore wind turbines under the combined effects of wind and ice. This method considers structural dynamic nonlinearity, pile-soil interaction, aerodynamic loads and aerodynamic damping effects, fluid-structure interaction, and sea ice breakage failure modes, realizing integrated coupled response analysis of wind-water-ice-soil-wind turbine structures. The method of this invention is easy to master, has extremely high calculation accuracy, and the dynamic ice load and wind turbine ice-induced vibration response obtained by this method can well reflect the structural stress characteristics.

[0004] The technical solution adopted in this invention is:

[0005] A refined overall coupled calculation method for offshore wind turbines under the combined effects of wind and ice includes the following steps:

[0006] S1: Establish the coupled motion control equations for offshore wind turbines under the combined action of wind and ice loads;

[0007] S2: Establish an overall model of the offshore wind turbine in FAST, including the aeroelastic model of the turbine blades and the offshore wind turbine tower-foundation structure model; develop a dynamic icing force module in FAST to input dynamic icing force time history curves, apply dynamic icing force loads to the structural nodes of the offshore wind turbine, and analyze the response of the structural nodes of the offshore wind turbine based on the coupled motion control equations of the offshore wind turbine described in S1, including acceleration, velocity and displacement.

[0008] S3: Based on the Finite Element Method-Cohesive Element Method (FEM-CEM), a three-dimensional refined interaction model of sea ice and offshore wind turbines was built in LS-DYNA;

[0009] S4: Based on the three-dimensional refined interaction model of sea ice and offshore wind turbine established in S3, soil parameters are set in LS-DYNA, and a nonlinear spring-damping theoretical model of soil layer is established on pile foundation to obtain a three-dimensional refined interaction model of sea ice and offshore wind turbine considering pile-soil interaction.

[0010] S5: Based on S4, a three-dimensional refined interaction model of sea ice-offshore wind turbine considering pile-soil interaction is established. The flow field including air domain and sea water domain is constructed in LS-DYNA. The offshore wind turbine structure-sea ice-seawater-air are coupled to obtain a three-dimensional refined interaction model of sea ice-offshore wind turbine considering fluid-structure interaction effect.

[0011] S6: Based on the three-dimensional refined interaction model of sea ice and offshore wind turbine obtained in S5, calculate the dynamic ice force time history at the current time step and input it into the dynamic ice force module of FAST to obtain the structural node response of the offshore wind turbine.

[0012] S7: Calculate the aerodynamic load and aerodynamic damping at the current time step based on the aeroelastic model of the wind turbine blades in FAST, and input them into the three-dimensional refined interaction model of sea ice-offshore wind turbine obtained in S5. Calculate the dynamic ice force time history, pile foundation nodal force, nodal response of the offshore wind turbine tower structure, and nodal response of the offshore wind turbine foundation structure at the current time step. Based on the nodal responses of the offshore wind turbine tower structure and the offshore wind turbine foundation structure, update the nodal response of the overall wind turbine structure at the next time step.

[0013] S8: Input the dynamic ice force time history calculated in S7 into the dynamic ice force module of FAST, and execute S6~S7 in a loop. Through iteration, complete the dynamic response analysis of the entire wind turbine structure nodes for all time steps, and obtain the final ice-induced vibration response results of the offshore wind turbine (including acceleration, displacement, torque, stress and strain) and the full-time-domain dynamic ice force calculation results.

[0014] Furthermore, in step S1, the coupled motion control equation for the offshore wind turbine under the combined action of wind and ice loads is:

[0015] (1)

[0016] In the formula, [M] is the mass matrix of the wind turbine foundation structure; [C] is the damping matrix of the wind turbine foundation structure; and [K] is the stiffness matrix of the wind turbine foundation structure. , , These are the acceleration, velocity, and displacement vectors of the nodes in the wind turbine foundation structure, respectively; {f ice} represents the dynamic ice force load vector; {f elastodyn} and {f G} are the dynamic and gravitational load vectors acting on the wind turbine foundation structure, respectively;

[0017] When considering the hourglass energy effect, the hourglass resistance vector needs to be added to counteract the hourglass energy generated by ice breaking. The motion control equation shown in formula (1) is transformed into:

[0018] (2)

[0019] in, For wind load, For ice load, This is the internal force vector;

[0020] By solving formula (2) using the central difference method, we can obtain:

[0021] (3)

[0022] (4)

[0023] (5)

[0024] in, For external force vectors, for Acceleration at all times for Speed ​​at any moment for Displacement at any given moment.

[0025] Furthermore, in step S2, establishing the overall model of the offshore wind turbine in FAST includes:

[0026] Set the aerodynamic parameters of the wind turbine blade airfoil and establish the aeroelastic model of the wind turbine blade;

[0027] A model of the offshore wind turbine tower-foundation structure is established based on the geometric parameters of the wind turbine tower-foundation structure.

[0028] Furthermore, in step S3, building a detailed three-dimensional interaction model between sea ice and offshore wind turbines specifically includes:

[0029] Preprocess the sea ice parameters to determine the global coordinate system and the local coordinate system of the sea ice-offshore wind turbine interaction model, and set the action points of the sea ice and the wind turbine foundation structure;

[0030] The constitutive model, yield failure criterion, and physical and mechanical parameters of sea ice were determined; finite element and cohesive element models of sea ice were established respectively, and the two were coupled to build a three-dimensional refined interaction model of sea ice and offshore wind turbine.

[0031] A specific computational grid is defined for the sea ice and offshore wind turbine structures, and the grid is refined at the interaction points between the sea ice and the wind turbine foundation structure.

[0032] Furthermore, in step S4, the method for constructing the three-dimensional refined interaction model of sea ice and offshore wind turbine considering pile-soil interaction includes:

[0033] Using the py curve method, a nonlinear spring-damped theoretical model of the soil layer is established at the nodes in the x and y directions of the pile foundation. The spring damping employs frequency-independent radiation damping per unit length.

[0034] (6)

[0035] In the formula, For spring damping; Soil density; This refers to the shear wave velocity of the soil layer. The diameter of the pile foundation;

[0036] To account for the dynamic effect of the spring, we assume that the dynamic effect of the spring can be expressed by the amplification factor and static force:

[0037] (7)

[0038] In the formula, Powered by springs; The magnification factor is set to 0.5. The absolute value of the relative velocity between the two ends of the spring; The dynamic test speed is the initial drift speed of the sea ice. It is static.

[0039] Furthermore, in step S5, the method for a refined three-dimensional interaction model of sea ice and offshore wind turbines considering fluid-structure interaction effects includes:

[0040] Based on the S-ALE method, a flow field including the air domain and the sea area is constructed to model and numerically simulate the coupled interaction between the fluid domain, sea ice, and offshore wind turbine structure. The governing equations based on the S-ALE method are:

[0041] (8)

[0042] In the formula, It is a Jacobian matrix; Let i be the material velocity in the i-direction; Let i be the Euler coordinate in the i-th direction;

[0043] The mass, energy, and momentum conservation equations based on the S-ALE fluid-structure interaction method are as follows:

[0044] (9)

[0045] (10)

[0046] (11)

[0047] In the formula, The flow field density; The material velocity is in the j-direction; Let j be the Euler coordinate in the j-direction; and These are the relative velocities in the i and j directions, respectively; For time; For energy; Force per unit volume; Let be the stress tensor in the j-direction.

[0048] Furthermore, the specific process of step S7 includes:

[0049] S7.1: Set the initial conditions and initial boundary conditions for the overall wind turbine structure dynamic response analysis in FAST, and read in the wind speed time history file; carry out aeroelastic analysis based on the aeroelastic model of the wind turbine blades to obtain the aerodynamic load and aerodynamic damping at the current time step.

[0050] S7.2: Export the aerodynamic load and aerodynamic damping of the current time step to the three-dimensional refined interaction model of sea ice and offshore wind turbine obtained in S5, obtain the dynamic ice force, and calculate the nodal acceleration, displacement and velocity of the offshore wind turbine tower structure in the current time step based on the coupled motion control equation of the offshore wind turbine described in S1; determine whether the dynamic ice force in this time step reaches the sea ice yield and failure criteria, and calculate the effective stress of the sea ice element; if the sea ice element fails and is deleted, import the dynamic ice force load in this time step into the dynamic ice force module of FAST and repeat S6~S7.2 to recalculate the nodal acceleration, displacement and velocity of the offshore wind turbine tower structure.

[0051] The aerodynamic load and aerodynamic damping at the current time step are derived to the three-dimensional refined interaction model of sea ice and offshore wind turbine obtained in S5 to calculate the pile foundation node force. Then, the acceleration, displacement and velocity of the offshore wind turbine foundation structure nodes at the next time step are analyzed and calculated to analyze the influence of the flow field on the wind turbine foundation structure.

[0052] S7.3: Based on the nodal acceleration, displacement, and velocity of the offshore wind turbine tower structure and the nodal acceleration, displacement, and velocity of the offshore wind turbine foundation structure, update the dynamic response of each part of the overall wind turbine structure at the next moment.

[0053] Furthermore, in step S7, the aerodynamic load Including aerodynamic thrust acting on the blades and aerodynamic torque load vector The calculation formula is as follows:

[0054] (12)

[0055] In the formula, air density; This refers to the number of fan blades; For incoming air velocity; The axial induction coefficient; The angle of entry; The length of the chord; Normal force coefficient; This is the tangential force coefficient; The tangential induction coefficient; It is the angular frequency; The relative radius of the blade; The leaf element length.

[0056] Furthermore, in step S7, the calculation formula for the aerodynamic damping is as follows:

[0057] (13)

[0058] In the formula, For aerodynamic damping; For rotor thrust; The wind speed is at the height of the wind turbine hub.

[0059] The beneficial effects of this invention are as follows: By establishing a unified coupled model of offshore wind turbines involving wind, water, ice, soil, and structure, this invention achieves refined simulation of the entire system of offshore wind turbines, from the superstructure to the interaction between the foundation and soil, under extreme wind and ice loads. This method significantly improves the prediction accuracy of the dynamic response and dynamic ice load of offshore wind turbines in complex marine environments, providing key theoretical basis and technical means for wind turbine structural optimization design, safety assessment, and life prediction, effectively supporting the improvement of the economy and safety of offshore wind power projects. Attached Figure Description

[0060] Figure 1 This is a flowchart of the present invention.

[0061] Figure 2 Comparison of dynamic ice force time histories considering fluid-structure interaction effects.

[0062] Figure 3 The image shows a comparison of the structural time history response obtained from the overall coupled model of offshore wind turbines under sea ice load.

[0063] Figure 4 The diagram shows the energy changes in the flow field; where (a) represents the kinetic energy change and (b) represents the energy ratio.

[0064] Figure 5 The diagram shows the velocity distribution in the seawater medium; (a) is the flow field cloud map at 11.9s during the mid-collision period, and (b) is the flow field cloud map at 33.2s during the late-collision period.

[0065] Figure 6 This is a schematic diagram of a nonlinear spring-damped pile-soil interaction model. Detailed Implementation

[0066] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. The embodiments of the present invention are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operating procedures are given. However, the scope of protection of the present invention is not limited to the following embodiments.

[0067] Please see Figure 1 This invention provides a refined calculation method for the overall offshore wind turbine involving wind, water, ice, soil, and structure coupling, comprising the following steps:

[0068] Step 1: Establish the coupled motion control equations for offshore wind turbines under the combined action of sea ice and wind loads:

[0069] (1)

[0070] In the formula, [M] is the mass matrix of the wind turbine foundation structure; [C] is the damping matrix of the wind turbine foundation structure; and [K] is the stiffness matrix of the wind turbine foundation structure. , , These are the acceleration, velocity, and displacement vectors of the nodes in the wind turbine foundation structure, respectively; {f ice} represents the dynamic ice force load vector; {f elastodyn} and {f G} are the dynamic and gravitational load vectors acting on the wind turbine foundation structure, respectively.

[0071] When considering the hourglass energy effect, the hourglass resistance vector needs to be added to counteract the hourglass energy generated by ice breaking. Then the motion control equation shown in equation (1) can be transformed into:

[0072] (2)

[0073] in, For wind load, For ice load, This is the internal force vector.

[0074] By solving formula (2) using the central difference method, we can obtain:

[0075] (3)

[0076] (4)

[0077] (5)

[0078] in, For external force vectors, for Acceleration at all times for Speed ​​at any moment for Displacement at any given moment.

[0079] Step 2: Build an overall model of the offshore wind turbine in FAST, including:

[0080] Set the aerodynamic parameters of the wind turbine blade airfoil and establish the aeroelastic model of the blade;

[0081] A model of offshore wind turbine tower-foundation structure is established based on the geometric parameters of the wind turbine tower-foundation structure.

[0082] Compile the main program module and various calculation modules in FAST, including the structural elasticity ElastoDyn module, the basic structure SubDyn module, and the aerodynamics AeroDyn module, etc.

[0083] Develop the IceDyn module for dynamic ice loads in FAST, and write the data interface for the module, including data transmission, data processing, and data output. Set the time step and develop the data interaction interface between FAST and LS-DYNA.

[0084] The IceDyn module is used to input the ice force time history curve and apply ice force loads to the offshore wind turbine structural nodes based on the ice force time history curve. The response of the offshore wind turbine structural nodes, including acceleration, velocity and displacement, is analyzed based on the coupled motion control equation of the offshore wind turbine described in S1.

[0085] The dynamic ice force module is an independent module that can calculate the ice-induced vibration response of offshore wind turbines independently, and can also be combined with LS-DYNA to conduct a holistic analysis of offshore wind turbines involving wind, water, ice, soil, and structure coupling.

[0086] Step 3: Based on the FEM-CEM method, build a three-dimensional refined interaction model of sea ice and offshore wind turbine in LS-DYNA to determine the ice constitutive model, yield failure criterion and physical and mechanical parameters.

[0087] Step 4: Based on the refined three-dimensional interaction model of sea ice and offshore wind turbine established in S3, soil parameters are set in LS-DYNA, and a nonlinear spring-damping theoretical model of the soil layers is built on the pile foundation to obtain a refined three-dimensional interaction model of sea ice and offshore wind turbine considering pile-soil interaction. The specific process is as follows:

[0088] Using the Python curve method, such as Figure 6 As shown, a nonlinear spring-damped theoretical model of the soil layer is established at the nodes in the x and y directions of the pile foundation, where the spring damping... Using frequency-independent radiation damping per unit length:

[0089] (6)

[0090] In the formula, Soil density; This refers to the shear wave velocity of the soil layer. This refers to the diameter of the pile foundation.

[0091] To account for the dynamic effect of the spring, we assume that the dynamic effect of the spring can be expressed by the amplification factor and static force:

[0092] (7)

[0093] In the formula, Powered by springs; The magnification factor is set to 0.5. The absolute value of the relative velocity between the two ends of the spring; The dynamic test speed is the initial drift speed of the sea ice. It is static.

[0094] Step 5: Based on the refined three-dimensional interaction model of sea ice and offshore wind turbine considering pile-soil interaction established in S4, construct the flow field including the air domain and seawater domain in LS-DYNA, and couple the offshore wind turbine structure-sea ice-seawater-air to obtain a refined three-dimensional interaction model of sea ice and offshore wind turbine considering fluid-structure interaction effects. Specifically, this includes:

[0095] Based on the S-ALE method, the coupled interaction between the fluid domain, sea ice, and wind turbine structure is modeled and numerically simulated. The governing equations based on the S-ALE method are:

[0096] (8)

[0097] In the formula, For Jacobian matrices, Let i be the material velocity in the i-direction; Let i be the Euler coordinate in the i-th direction.

[0098] The mass, energy, and momentum conservation equations based on the S-ALE fluid-structure interaction method are:

[0099] (9)

[0100] (10)

[0101] (11)

[0102] In the formula, The flow field density; The material velocity is in the j-direction; Let j be the Euler coordinate in the j-direction; and These are the relative velocities in the i and j directions, respectively; For time; For energy; Force per unit volume; Let be the stress tensor in the j-direction.

[0103] Step 6: Based on the three-dimensional refined interaction model of sea ice and offshore wind turbine considering the fluid-structure interaction effect obtained in S5, calculate the dynamic ice force time history at the current time step and input it into the dynamic ice force module of FAST to obtain the structural node response of the offshore wind turbine.

[0104] Step 7: Set initial conditions and initial boundary conditions in FAST, read in the wind speed time history file, and perform aeroelastic analysis based on the aeroelastic model of the wind turbine blades to obtain the aerodynamic load at the current time step. and aerodynamic damping :

[0105] (12)

[0106] In the formula, and These are the aerodynamic thrust and aerodynamic torque load vectors acting on the blades, respectively.

[0107] (13)

[0108] In the formula, For rotor thrust; The wind speed is at the height of the wind turbine hub.

[0109] Step 8: Import the aerodynamic load and aerodynamic damping of the current time step into the three-dimensional refined interaction model of sea ice and offshore wind turbine obtained in Step 5 to obtain the dynamic ice force. Based on the coupled motion control equation of the offshore wind turbine in Step 1, calculate the nodal acceleration, displacement and velocity of the offshore wind turbine tower structure at each time step. Determine whether the dynamic ice force at this time step reaches the sea ice yield and failure criteria, and calculate the effective stress of the sea ice element. If the sea ice element fails and is deleted, import the dynamic ice force load at this time step into the dynamic ice force module of FAST. Repeat Steps 6 to 8 to recalculate the nodal acceleration, displacement and velocity of the offshore wind turbine tower structure.

[0110] In this embodiment, time-domain numerical collision analysis is performed in LS-DYNA. An aerodynamic load interface between FAST and LS-DYNA is built using FORTRAN, and a custom load subroutine, LOADSETUD, is used to couple the main program with the aerodynamic model. This subroutine provides a means to apply nodal loads as a function of velocity. First, the aerodynamic damping coefficients for turbulent wind loads and mean wind speeds are pre-calculated using FAST and HAWC2 programs. Aerodynamic damping includes the effect of wind shear on the rotor plane and is calculated using a constant power-law exponent, establishing an aerodynamic damping calculation framework. Second, at each FAST calculation time step, LS-DYNA transmits the dynamic icing load information for each time step to the dynamic icing force module of FAST. Finally, the coupled aerodynamic load results (including shear force and bending moment data) calculated in FAST are input into LS-DYNA.

[0111] Step 9: Import the aerodynamic load and aerodynamic damping of the current time step into the three-dimensional refined interaction model of sea ice-offshore wind turbine obtained in Step 5 to calculate the pile foundation nodal forces, and carry out the dynamic response analysis of the offshore wind turbine foundation structure at the next time step; based on the nodal acceleration, displacement and velocity of the offshore wind turbine tower structure, and the nodal acceleration, displacement and velocity of the offshore wind turbine foundation structure, obtain the dynamic response parameters of each part of the overall wind turbine structure at the next time step.

[0112] Step 10: Repeat steps 6 to 9 to carry out the next coupled loop calculation until the boundary condition calculation and structural dynamic response analysis of all time steps are completed, and output the ice-induced vibration response results of the offshore wind turbine (including acceleration, displacement, torque, stress and strain) and the full-time domain dynamic ice force calculation results.

[0113] The aforementioned development, combining multibody dynamics and finite element methods, enables FAST and ANSYS / LS-DYNA to perform coupled calculations of sea ice-wind loads and to perform coupled response analysis and calculations of the overall structure of offshore wind turbines under fluid-structure interaction.

[0114] To verify the effectiveness of the method of this invention, corresponding numerical simulations were conducted on the above process. To explore the refined overall coupling response of offshore wind turbines under combined wind and ice effects, as well as the influence of flow field and pile-soil interaction on structural ice-induced vibration, three sets of comparative working conditions were set up for the NREL 5MW offshore wind turbine: 1) considering fluid-structure interaction and pile-soil interaction; 2) not considering fluid-structure interaction but considering pile-soil interaction; 3) considering fluid-structure interaction but not considering pile-soil interaction. Through the comparison of these working conditions, the key contributions of the refined overall coupling calculation method for offshore wind turbines under combined wind and ice effects can be clearly revealed.

[0115] Taking the DUT10 MW offshore wind turbine as an example, Figure 2 The collision force time history curves with and without fluid-structure interaction (FSI) are shown, specifically for conditions 1 and 2, with an initial interaction velocity of 1.2 m / s. The overall trends in both cases are largely consistent, while the collision force with FSI (condition 1) exhibits a significant lag. Since a large portion of the damage in sea ice is caused by FSI, ice force fluctuations with FSI (condition 1) are more frequent than those without FSI (condition 2). The maximum ice forces with and without FSI are 0.458 MN and 0.569 MN, respectively, indicating that the influence of the fluid on the load is within the allowable error range. The ice force reaches its maximum value between 0.8 s and 1.2 s, corresponding to a significant increase and fluctuation in sea ice erosion energy. Figure 3 The comparison of tower top displacement under operating conditions 1 and 3 is shown. The presence of pile-soil interaction has a significant impact on the response amplitude at the tower top. Compared to the FA-direction displacement of the wind turbine without considering pile-soil interaction, the displacement amplitude tends to increase due to pile-soil interaction.

[0116] Taking the DUT10 MW offshore wind turbine as an example, the calculation conditions are a wind speed of 11.4 m / s and an ice thickness of 0.3 m; for Figure 4 The flow field energy change results are given, with ice velocity ranging from 0.1 to 0.6 m / s. Figure 4 The flow field kinetic energy and energy ratio are shown. It can be seen that throughout the ice-structure interaction process, the flow field kinetic energy increases significantly with increasing ice velocity. However, in the initial stage of the interaction, the internal energy at an ice velocity of 0.1 m / s is slightly higher than that at 0.2 m / s. Ice has a stochastic negative feedback effect on the water body, especially under low ice velocity conditions, which may lead to ice-induced resonance in offshore wind turbine structures. Furthermore, the energy ratio increases significantly with increasing ice velocity, proving that at high ice velocities, the change in flow field kinetic energy is greater than the change in internal energy, exceeding 0.8. When the ice velocity increases from 0.2 m / s to 0.4 m / s, the maximum energy ratio increases by 68.4%. This value is most significant in the initial stage of the interaction and decreases rapidly after 3 s, indicating that in the initial stage of the interaction, sea ice has the greatest influence on the flow field kinetic energy and internal energy difference. Figure 5 The study demonstrates the significant changes in the water velocity field between the wind turbine structure and the floating ice due to the compression effect of ice on the water body. The velocity is clearly concentrated at the contact point between the ice and the structure, while the velocity variation is more uniform further away from the impact area, indicating that the ice creates a high-pressure field by compressing the water medium and generates instantaneous impact loads.

[0117] In summary, the present invention proposes a refined coupled calculation method for offshore wind turbines under the combined action of wind and ice. This method considers the coupled response of the overall structure and achieves this by simultaneously solving the coupled motion equations of the ice-wind turbine structure interaction model. This enables a refined simulation of the entire offshore wind turbine system, from the superstructure to the foundation-soil interaction, under extreme wind-ice environmental loads.

[0118] The above description represents a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A refined overall coupled calculation method for offshore wind turbines under the combined effects of wind and ice, characterized in that, include: S1: Establish the coupled motion control equations for offshore wind turbines under the combined action of wind and ice loads; S2: Establish an overall model of the offshore wind turbine in FAST, including the aeroelastic model of the turbine blades and the offshore wind turbine tower-foundation structure model; A dynamic icing force module was developed in FAST to input dynamic icing force time history curves, apply dynamic icing force loads to offshore wind turbine structural nodes, and analyze the response of offshore wind turbine structural nodes, including acceleration, velocity, and displacement, based on the coupled motion control equations of offshore wind turbines described in S1. S3: Based on the finite element method-cohesive element method, a three-dimensional refined interaction model of sea ice and offshore wind turbine was built in LS-DYNA; S4: Based on the three-dimensional refined interaction model of sea ice and offshore wind turbine established in S3, soil parameters are set in LS-DYNA, and a nonlinear spring-damping theoretical model of soil layer is established on pile foundation to obtain a three-dimensional refined interaction model of sea ice and offshore wind turbine considering pile-soil interaction. S5: Based on S4, a three-dimensional refined interaction model of sea ice-offshore wind turbine considering pile-soil interaction is established. The flow field including air domain and sea water domain is constructed in LS-DYNA. The offshore wind turbine structure-sea ice-seawater-air are coupled to obtain a three-dimensional refined interaction model of sea ice-offshore wind turbine considering fluid-structure interaction effect. S6: Based on the three-dimensional refined interaction model of sea ice and offshore wind turbine obtained in S5, calculate the dynamic ice force time history at the current time step and input it into the dynamic ice force module of FAST to obtain the structural node response of the offshore wind turbine. S7: Based on the aeroelastic model of wind turbine blades in FAST, calculate the aerodynamic load and aerodynamic damping at the current time step and input them into the three-dimensional refined interaction model of sea ice-offshore wind turbine obtained in S5. Calculate the dynamic ice force time history, pile foundation nodal force, nodal response of offshore wind turbine tower structure and nodal response of offshore wind turbine foundation structure at the current time step. Based on the nodal responses of the offshore wind turbine tower structure and the offshore wind turbine foundation structure, update the nodal response of the overall wind turbine structure at the next moment. S8: Input the dynamic ice force time history calculated in S7 into the dynamic ice force module of FAST, and execute S6~S7 in a loop. Through iteration, complete the dynamic response analysis of the entire wind turbine structure nodes for all time steps, and obtain the final ice-induced vibration response result of the offshore wind turbine and the full-time-domain dynamic ice force calculation result.

2. The refined overall coupling calculation method for offshore wind turbines under the combined effects of wind and ice, as described in claim 1, is characterized in that... In step S1, the coupled motion control equations for the offshore wind turbine under the combined action of wind and ice loads are as follows: (1) In the formula, [M] is the mass matrix of the wind turbine foundation structure; [C] is the damping matrix of the wind turbine foundation structure; and [K] is the stiffness matrix of the wind turbine foundation structure. , , These are the acceleration, velocity, and displacement vectors of the nodes in the wind turbine foundation structure, respectively; {f ice } represents the dynamic ice force load vector; {f elastodyn } and {f G } are the dynamic and gravitational load vectors acting on the wind turbine foundation structure, respectively; When considering the hourglass energy effect, the hourglass resistance vector needs to be added to counteract the hourglass energy generated by ice breaking. The motion control equation shown in formula (1) is transformed into: (2) in, For wind load, For ice load, This is the internal force vector; Solving formula (2) using the central difference method yields: (3) (4) (5) in, For external force vectors, for Acceleration at all times for Speed ​​at any moment for Displacement at any given moment.

3. The refined overall coupling calculation method for offshore wind turbines under the combined effects of wind and ice, as described in claim 1, is characterized in that... Step S2, establishing the overall model of the offshore wind turbine in FAST, includes: Set the aerodynamic parameters of the wind turbine blade airfoil and establish the aeroelastic model of the wind turbine blade; A model of the offshore wind turbine tower-foundation structure is established based on the geometric parameters of the wind turbine tower-foundation structure.

4. The refined overall coupling calculation method for offshore wind turbines under combined wind and ice effects as described in claim 1, characterized in that, Step S3, which involves building a detailed three-dimensional interaction model between sea ice and offshore wind turbines, specifically includes: Preprocess the sea ice parameters to determine the global coordinate system and the local coordinate system of the sea ice-offshore wind turbine interaction model, and set the action points of the sea ice and the wind turbine foundation structure; The constitutive model, yield failure criterion, and physical and mechanical parameters of sea ice were determined; finite element and cohesive element models of sea ice were established respectively, and the two were coupled to build a three-dimensional refined interaction model of sea ice and offshore wind turbine. A specific computational grid is defined for the sea ice and offshore wind turbine structures, and the grid is refined at the interaction points between the sea ice and the wind turbine foundation structure.

5. The refined overall coupling calculation method for offshore wind turbines under combined wind and ice effects as described in claim 1, characterized in that, In step S4, the method for constructing the three-dimensional refined interaction model of sea ice and offshore wind turbine considering pile-soil interaction includes: Using the py curve method, a nonlinear spring-damped theoretical model of the soil layer is established at the nodes in the x and y directions of the pile foundation. The spring damping employs frequency-independent radiation damping per unit length. (6) In the formula, For spring damping; Soil density; This refers to the shear wave velocity of the soil layer. The diameter of the pile foundation; To account for the dynamic effect of the spring, we assume that the dynamic effect of the spring is represented by the amplification factor and static force: (7) In the formula, Powered by a spring; Amplification factor; The absolute value of the relative velocity between the two ends of the spring; The dynamic test speed is the initial drift speed of the sea ice. It is static.

6. The refined overall coupling calculation method for offshore wind turbines under combined wind and ice effects as described in claim 1, characterized in that, In step S5, the method for a refined three-dimensional interaction model of sea ice and offshore wind turbines considering fluid-structure interaction effects includes: Based on the S-ALE method, a flow field including the air domain and the sea area is constructed to model and numerically simulate the coupled interaction between the fluid domain, sea ice, and offshore wind turbine structure. The governing equations based on the S-ALE method are: （8） In the formula, It is a Jacobian matrix; Let i be the material velocity in the i-direction; Let i be the Euler coordinate in the i-th direction; The mass, energy, and momentum conservation equations based on the S-ALE fluid-structure interaction method are as follows: （9） （10） （11） In the formula, The flow field density; Let j be the material velocity in the j-direction; Let j be the Euler coordinate in the j-direction; and These are the relative velocities in the i and j directions, respectively; For time; For energy; Force per unit volume; Let be the stress tensor in the j-direction.

7. The refined overall coupling calculation method for offshore wind turbines under combined wind and ice effects as described in claim 1, characterized in that, The specific process of step S7 includes: S7.1: Set the initial conditions and initial boundary conditions for the overall wind turbine structure dynamic response analysis in FAST, and read in the wind speed time history file; carry out aeroelastic analysis based on the aeroelastic model of the wind turbine blades to obtain the aerodynamic load and aerodynamic damping at the current time step. S7.2: Export the aerodynamic load and aerodynamic damping of the current time step to the three-dimensional refined interaction model of sea ice and offshore wind turbine obtained in S5, obtain the dynamic ice force, and calculate the nodal acceleration, displacement and velocity of the offshore wind turbine tower structure in the current time step based on the coupled motion control equation of the offshore wind turbine described in S1; determine whether the dynamic ice force in this time step reaches the sea ice yield and failure criteria, and calculate the effective stress of the sea ice element; if the sea ice element fails and is deleted, import the dynamic ice force load in this time step into the dynamic ice force module of FAST and repeat S6~S7.2 to recalculate the nodal acceleration, displacement and velocity of the offshore wind turbine tower structure. The aerodynamic load and aerodynamic damping at the current time step are derived to the three-dimensional refined interaction model of sea ice and offshore wind turbine obtained in S5 to calculate the pile foundation node force. Then, the acceleration, displacement and velocity of the offshore wind turbine foundation structure nodes at the next time step are analyzed and calculated to analyze the influence of the flow field on the wind turbine foundation structure. S7.3: Based on the nodal acceleration, displacement, and velocity of the offshore wind turbine tower structure and the nodal acceleration, displacement, and velocity of the offshore wind turbine foundation structure, update the dynamic response of each part of the overall wind turbine structure at the next moment.

8. The refined overall coupling calculation method for offshore wind turbines under combined wind and ice effects as described in claim 1, characterized in that, In step S7, the aerodynamic load includes the aerodynamic thrust acting on the blades. and aerodynamic torque load vector The calculation formula is as follows: (12) In the formula, For aerodynamic loads; air density; This refers to the number of fan blades; For incoming air velocity; The axial induction coefficient; The angle of entry; The length of the chord; Normal force coefficient; This is the tangential force coefficient; The tangential induction coefficient; It is the angular frequency; The relative radius of the blade; The leaf element length.

9. The refined overall coupling calculation method for offshore wind turbines under the combined effects of wind and ice, as described in claim 1, is characterized in that... In step S7, the calculation formula for the aerodynamic damping is as follows: (13) In the formula, For aerodynamic damping; For rotor thrust; The wind speed is at the height of the wind turbine hub.

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