Offshore floating fan liquid tank structure optimization method and system based on numerical simulation

Abstract

The invention relates to the technical field of ocean energy development, in particular to an offshore floating fan liquid tank structure optimization method and system based on numerical simulation, and the method comprises the steps: obtaining design parameters of a floating fan and a liquid tank, and obtaining a three-dimensional geometric model of the floating fan through geometric modeling according to the design parameters; acquiring marine environment data of the target sea area, and setting an overall computational domain of the fan based on the marine environment data and the overall size of the fan; according to the motion relation among all the components in the three-dimensional geometric model of the floating fan, grid division is conducted on a computational domain and an internal area of a liquid tank of the computational domain; establishing numerical models of the floating fan and the liquid tank of the floating fan in the divided grids; setting and verifying numerical simulation control conditions of the floating fan and the liquid tank of the floating fan; performing numerical simulation on the floating fan by using the established numerical model and set control conditions; and optimizing the structural design of the floating fan based on a numerical simulation analysis result.

Description

Technical Field

[0001] The present invention relates to the technical field of marine energy development, and in particular to a method and system for optimizing the structure of an offshore floating wind turbine tank based on numerical simulation. Background Art

[0002] Under the current technological development, offshore floating wind turbines, as a key technology for deep-sea wind power development, are receiving more and more attention. Floating wind turbines can be built in deeper waters, utilize more abundant wind energy resources, and have flexible deployment and less environmental impact. However, as floating wind turbines develop towards larger sizes, the design and optimization of their tank structures has become an important technical challenge. The tank structure not only affects the stability and safety of floating wind turbines, but is also directly related to their economy and operation and maintenance efficiency.

[0003] At present, the key technologies used for the design and optimization of the tank structure of floating wind turbines include: 1) Finite element analysis: This is a widely used numerical simulation method that can accurately calculate the stress, strain and deformation of the tank structure under static and dynamic loads; 2) Fluid dynamics analysis: Floating wind turbines are subject to complex hydrodynamic effects in deep-sea environments, including waves, currents and wind. Therefore, fluid dynamics analysis is crucial to understanding how the tank structure interacts with the surrounding fluid. This analysis helps designers optimize the shape, size and layout of the tank to improve the overall performance of the floating wind turbine; 3) Model testing and verification: By building a physical model of the tank structure and simulating the deep-sea environment in a laboratory environment, valuable data can be collected to evaluate and optimize the design. Although these technologies can provide relatively accurate numerical predictions and experimental results, the lack of effective data integration and collaborative optimization between different technologies leads to poor data transmission, which affects the accuracy and efficiency of the design. In addition, the existing tank structure design often does not fully consider the impact of the floating body stiffness and modal changes on the performance of the whole machine, especially under extreme survival conditions, the viscosity and nonlinear components of the hydrodynamic load increase significantly, making the traditional design methods and assumptions no longer applicable. Summary of the invention

[0004] In order to comprehensively consider the interaction of multiple disciplines such as aerodynamics, hydrodynamics, and structural mechanics, and realize the accurate analysis and optimal design of the floating wind turbine tank structure, the purpose of the present invention is to provide an offshore floating wind turbine tank structure optimization method and system based on numerical simulation. The technical solutions adopted are as follows:

[0005] In a first aspect, the present application discloses a method for optimizing the structure of an offshore floating wind turbine tank based on numerical simulation, the method comprising:

[0006] S1, obtaining design parameters of a floating wind turbine and a liquid tank, and obtaining a three-dimensional geometric model of the floating wind turbine through geometric modeling according to the design parameters;

[0007] S2, obtaining the marine environment data of the target sea area, and setting the overall calculation domain of the wind turbine based on the marine environment data and the overall size of the wind turbine;

[0008] S3, meshing the computational domain and the internal area of ​​the liquid tank thereof according to the motion relationship between the components in the three-dimensional geometric model of the floating wind turbine;

[0009] S4. Establishing a numerical model of the floating wind turbine and its liquid tank in the divided grid, wherein the numerical model includes a simulation model of the marine environment and liquid tank fluid flow, a simulation model of the hydrodynamic performance, a simulation model of the aerodynamic performance, and a simulation model of the motion characteristics of the anchor chain;

[0010] S5. Set and verify the numerical simulation control conditions of the floating wind turbine and its tank to ensure the accuracy and reliability of the simulation environment;

[0011] S6. Use the established numerical model and set control conditions to carry out numerical simulation of the floating wind turbine and analyze the movement of the floating wind turbine and the flow characteristics of the fluid in its liquid tank;

[0012] S7. Based on the results of numerical simulation analysis, the structural design of the floating wind turbine is optimized to ensure the stable operation of the wind turbine by improving the liquid tank's ability to absorb external impact forces.

[0013] In one embodiment, in step S4, the marine environment and tank fluid flow simulation model is determined based on the fluid motion conservation equation, and its calculation formula includes:

[0014]

[0015] Among them, α represents the volume fraction, and its value range is between 0 and 1. + represents the instantaneous rate of change of volume fraction, (U represents the absolute velocity of the mixed fluid in the gas-liquid two-phase flow, represents the convective transport term with volume fraction α, which describes the volume fraction change caused by fluid motion, U r represents the relative velocity of the mixed fluid in the gas-liquid two-phase flow, It represents the interfacial mixing term due to velocity difference, which describes the mixing effect caused by the velocity difference between the gas and liquid phases.

[0016] In one embodiment, in step S4, when a fixed coordinate system and a body coordinate system are defined, the hydrodynamic performance simulation model is determined based on the motion response of the floating wind turbine in waves, and its calculation formula includes:

[0017]

[0018] Where M represents the mass matrix of the floating body, which includes the mass or moment of inertia of the floating body in different degrees of freedom, x a (t) represents the acceleration of the floating body, x v (t) represents the velocity of the floating body, C represents the damping matrix, which describes the damping effect of the floating body during its motion, K represents the stiffness matrix, which describes the structural stiffness of the floating body, x(t) represents the displacement or rotation angle of the floating body, h(t-τ) represents the impulse response function, which reflects the interaction between the wave and the floating body, and F w (t) represents the excitation force of the wave on the floating body, which depends on the characteristics of the wave and the shape and size of the floating body.

[0019] In one embodiment, in step S4, the aerodynamic performance simulation model is determined based on the viscous force and pressure on the surface unit of the fan blade structure, and its calculation formula includes:

[0020] dF e =τ·d|S e |+pdS e ;

[0021]

[0022] The subscript e indicates that the current solution process is performed in geodetic coordinates. e represents the force acting on the surface of the fan blade structure, S e represents the normal vector of the surface unit pointing to the inside of the structure, p represents pressure, τ represents shear force, ρ represents density, and v eff represents the viscosity coefficient, represents the velocity vector gradient.

[0023] In one embodiment, the mooring system of the floating wind turbine system is composed of three catenary mooring lines. The anchor chain motion characteristic simulation model in step S4 is constructed based on the piecewise extrapolation method, and is obtained by calculating the force and deformation of the mooring line under different conditions, wherein the chain element force balance equations established in the horizontal and vertical directions include:

[0024]

[0025] Among them, T xi+1 is the horizontal force of the anchor chain i+1 segment, T xi is the horizontal force of the i-th segment of the anchor chain, T zi+1 is the vertical force of the anchor chain i+1 segment, T zi is the vertical force of the i-th segment of the anchor chain, F i is the tangential component of the anchor chain unit, ds is the tensile length of the anchor chain unit, D i is the normal component of the anchor chain unit, is the horizontal direction cosine function of the i+1 segment of the anchor chain, is the horizontal sine function of the i+1 segment of the anchor chain, ρ is the fluid density, g is the gravitational acceleration, A is the cross-sectional area of ​​the chain, Δz p is the vertical distance between the two end nodes, and the normal component D of the flow field force on the unit length chain element i With the tangential component F i , calculated by the following formula:

[0026]

[0027] Among them, C DN and C DT are the normal and tangential resistance coefficients of the chain, D is the chain element diameter, U N and U T are the normal and tangential components of the flow velocity, respectively.

[0028] In one embodiment, in step S4, after the numerical model of the floating wind turbine and its liquid tank is established, the method further comprises using the SIMPLEC algorithm to perform iterative solution to obtain the pressure and velocity distribution of the fluid flow, and the specific steps are as follows:

[0029] S41, setting the initial pressure field and velocity field;

[0030] S42, based on the currently set initial pressure field, obtain a predicted velocity field by solving the momentum equation;

[0031] S43, calculating a pressure correction amount according to the predicted velocity field and continuity equation;

[0032] S44, using the calculated pressure correction to update the velocity field;

[0033] S45, checking whether the new pressure field and velocity field meet the preset convergence criteria, wherein, if they do, the iteration process is terminated, and if not, steps S42 to S44 are repeated until convergence is reached.

[0034] In one embodiment, in step S5, setting and verifying the numerical simulation control conditions of the floating wind turbine and its liquid tank includes:

[0035] S51, determining the time interval of each step in the simulation according to the physical characteristics and stability conditions of the fluid flow, and setting the number of iterations of the solver in each time step according to the convergence speed and stability requirements of the simulation;

[0036] S52, setting boundary conditions according to the interaction between the liquid tank and the external environment and the physical limitations inside the liquid tank, and setting initial conditions according to the initial state of the simulation and the fluid characteristics, wherein the initial conditions include an initial velocity field and an initial pressure field;

[0037] S53. After setting the numerical simulation control conditions, perform simulation verification, including verifying at least one key parameter among fluid velocity distribution, pressure distribution, and free liquid surface fluctuation.

[0038] In one embodiment, in step S7, optimizing the structural design of the floating wind turbine based on the numerical simulation analysis results includes:

[0039] S71. Analyze fluid flow characteristics based on fluid dynamics simulation technology to obtain fluid dynamics simulation results;

[0040] S72. Optimize the structural design of the floating wind turbine based on the fluid dynamics simulation results.

[0041] In one embodiment, in step S7, the tank structure optimization method adopts a boundary smoothing windowed progressive structural topology optimization method, and achieves flexibility minimization under the condition of satisfying the target volume constraint by stepwise iteration and fine adjustment of the structural layout. Its numerical calculation model is expressed as:

[0042] find:x=[x1,x2,…,x i ,…,x n ] T

[0043]

[0044] F=KU

[0045] 0≤x i ≤1 i=1,2,…,n

[0046] Among them, x represents the variable, n represents the number of variables, and x i represents the i-th variable, u i represents the design variable, k0 represents the stiffness matrix element, v i represents the design factor, V * represents the upper limit of the displacement motion constraint, F represents the constraint condition, K represents the stiffness matrix, and U represents the displacement vector.

[0047] In the second aspect, the present application discloses an offshore floating wind turbine tank structure optimization system based on numerical simulation, the system comprising a floating wind turbine geometric modeling module, a wind turbine calculation domain setting module, a fluid domain meshing module, a numerical model building module, a numerical simulation control condition setting and verification module, a numerical simulation analysis module, and a floating wind turbine structure optimization module, wherein:

[0048] The floating wind turbine geometric modeling module is used to obtain design parameters of the floating wind turbine and the liquid tank, and obtain a three-dimensional geometric model of the floating wind turbine through geometric modeling according to the design parameters;

[0049] The wind turbine calculation domain setting module is used to obtain the marine environment data of the target sea area, and set the overall calculation domain of the wind turbine based on the marine environment data and the overall size of the wind turbine;

[0050] The fluid domain meshing module is used to mesh the computational domain and the internal area of ​​the liquid tank thereof according to the motion relationship between the components in the three-dimensional geometric model of the floating wind turbine;

[0051] The numerical model building module is used to establish a numerical model of the floating wind turbine and its liquid tank within the divided grid, wherein the numerical model includes a marine environment and liquid tank fluid flow simulation model, a hydrodynamic performance simulation model, an aerodynamic performance simulation model, and an anchor chain motion characteristic simulation model;

[0052] The numerical simulation control condition setting and verification module is used to set and verify the numerical simulation control condition settings of the floating wind turbine and its liquid tank to ensure the accuracy and reliability of the simulation environment;

[0053] The numerical simulation analysis module is used to use the established numerical model and the set control conditions to carry out numerical simulation of the floating wind turbine and analyze the movement of the floating wind turbine and the flow characteristics of the fluid in its liquid tank;

[0054] The floating wind turbine structure optimization module is used to optimize the structural design of the floating wind turbine based on the numerical simulation analysis results, and ensure the stable operation of the wind turbine by improving the liquid tank's ability to absorb external impact forces.

[0055] The present invention has the following beneficial effects:

[0056] By accurately obtaining the design parameters and constructing a three-dimensional geometric model, combined with the marine environmental data of the target sea area, setting a reasonable calculation domain and performing detailed grid division, a numerical model containing multiple simulation models was established. The verified numerical simulation control conditions ensure the accuracy and reliability of the simulation environment, and then the movement of the floating wind turbine and the flow characteristics of the fluid in its liquid tank are deeply analyzed through numerical simulation. Finally, based on these analysis results, the structural design of the floating wind turbine is optimized, and the absorption capacity of the liquid tank to external impact force is enhanced, thereby ensuring the stable operation of the wind turbine and improving the overall performance and economy. Compared with traditional technologies, the present invention shows significant beneficial effects in improving the stability of the wind turbine, extending its service life and improving energy conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0058] Figure 1 A method flow chart of a method for optimizing the structure of an offshore floating wind turbine tank based on numerical simulation provided by one embodiment of the present invention;

[0059] Figure 2 This is the stress analysis diagram of anchor chain of offshore floating wind turbine;

[0060] Figure 3 Schematic diagram of the process of boundary smoothing and windowing progressive topology optimization method for tank structure;

[0061] Figure 4 A system structure diagram of an offshore floating wind turbine tank structure optimization system based on numerical simulation provided by one embodiment of the present invention. DETAILED DESCRIPTION

[0062] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description of the specific implementation method, structure, features and effects of a method and system for optimizing the structure of an offshore floating wind turbine tank based on numerical simulation proposed by the present invention in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0063] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0064] The specific scheme of the offshore floating wind turbine tank structure optimization method and system based on numerical simulation provided by the present invention is described in detail below in conjunction with the accompanying drawings.

[0065] See also Figure 1 , which shows a method flow chart of a method for optimizing the structure of an offshore floating wind turbine tank based on numerical simulation according to an embodiment of the present invention, the method comprising:

[0066] Step S1, obtaining design parameters of the floating wind turbine and the liquid tank, and obtaining a three-dimensional geometric model of the floating wind turbine through geometric modeling according to the design parameters.

[0067] Specifically, this application will use 3D modeling software to construct each component of the floating wind turbine one by one according to the acquired design parameters, including wind turbine blades, towers, floating platforms, and mooring chains, and assemble them according to the relative positions and size relationships required by the design to obtain a 3D geometric model of the floating wind turbine.

[0068] In one of the embodiments, in step S1, the design parameters of the floating wind turbine include at least one of the number, size and shape of blades, the shape and size of the tower, the structure and size of the floating platform, and the number, length and weight of mooring chains, and the design parameters of the liquid tank include at least one of the structure of the shell, the number, position and size of internal components, and the layout and thickness of the partition deck.

[0069] Specifically, this application will use 3D modeling software (such as SolidWorks) for geometric modeling. Specifically, in terms of the overall structure of the wind turbine, first, according to the number, size and shape of the blades, an accurate 3D model of the blades will be drawn in the software, and a complete blade entity will be generated through commands such as rotation and stretching. Subsequently, based on the shape and size of the tower, a 3D model of the tower is created in the software, paying attention to maintaining precise alignment of its connection with the blades. Then, based on the structure and size of the floating platform, the main structure of the platform is constructed, including floats, columns, beams and other parts, and necessary detail features are added, such as the connection points of the mooring chains. At the same time, according to the number, length and weight of the mooring chains, corresponding mooring chain entities are created in the model.

[0070] It should be further explained that in terms of the tank structure, first, the outline of the shell will be drawn in the software according to the structure of the shell, and the shell entity will be generated through commands such as stretching and cutting. Then, according to the number, position and size parameters of the internal components, reinforcement materials, partitions and other structures are added inside the tank. Then, according to the layout and thickness of the partition deck, a three-dimensional model of the partition deck is created, and it is accurately assembled with the previously created shell and internal component models to complete the geometric model of the entire tank.

[0071] It should be further noted that this application will integrate various parts such as wind turbine tower, blades, float and liquid tank into a complete floating wind turbine model. During the whole process, all connections and details in the model are checked to ensure that there are no omissions or errors. In this way, through the above-mentioned precise modeling process, a complete and accurate three-dimensional geometric model of the floating wind turbine can be obtained.

[0072] Step S2, obtaining the marine environment data of the target sea area, and setting the overall calculation domain of the wind turbine based on the marine environment data and the overall size of the wind turbine.

[0073] Specifically, this application first calculates the wavelength length based on the marine environment data to determine the horizontal length of the area in front of and behind the wind turbine, and ensures that the wind turbine is located in the center of the calculation domain. Then, considering the influence of waves, currents and wind turbine height, as well as the length of the wind turbine blades and the position of the lower end of the anchor chain fixed to the seabed, the upper and lower boundaries of the calculation domain are set to ensure the accuracy and completeness of the simulated environment.

[0074] In one embodiment, in step S2, the obtaining of marine environment data of the target sea area and setting of the overall calculation domain of the wind turbine based on the marine environment data and the overall size of the wind turbine include:

[0075] Step S21, based on the ocean environment data, the corresponding wavelength length is calculated, and the horizontal length of the front and rear areas of the wind turbine is determined thereby, and it is ensured that the wind turbine is located at the center of the calculation domain.

[0076] The marine environment data includes at least one of wind speed, wind direction, wave height, wave period, water depth, current speed and marine salt spray concentration.

[0077] Specifically, for the determination of the horizontal size of the computational domain, it is taken into account that when floating wind turbines operate in a deep-sea environment, they will be affected by the propagation and reflection of waves from afar. These waves will deform and interact when approaching the wind turbine, forming a complex wave field. In order to accurately simulate this wave field and its impact on the performance and safety of the wind turbine, this application will calculate a length of 10 wavelengths and use it as the horizontal length of the area in front of the wind turbine to ensure that the propagation and deformation process of the waves before approaching the wind turbine can be captured. Similarly, in order to simulate the reflection and dissipation process of the waves behind the wind turbine, this application will calculate a length of 20 wavelengths and use it as the horizontal length of the area behind the wind turbine. It should be further explained that this application will ensure that the wind turbine is located in the center of the computational domain in order to accurately simulate the flow and force conditions around it.

[0078] Step S22, taking into account the influence of waves, currents and wind turbine height, according to the length of the wind turbine blades, the upper boundary of the calculation domain is set to a height above the top of the blade extending by one blade length, and the lower boundary of the calculation domain is set according to the position where the lower end of the anchor chain fixes the seabed.

[0079] Specifically, for the determination of the vertical size of the computational domain, since the fluid environment around the floating wind turbine will be affected by many factors during operation, including the ups and downs of waves, the vertical shear of the current, and the height and shape of the wind turbine itself, it is necessary to consider the influence of waves, currents and wind turbine height. Based on this, this application sets the upper boundary of the computational domain at a height of one blade length above the top of the wind turbine blade, and sets the lower boundary of the computational domain at the depth of the location where the lower end of the anchor chain is fixed to the seabed, to ensure that the flow is fully developed.

[0080] Step S3, meshing the calculation domain and the internal area of ​​the liquid tank thereof according to the motion relationship between the components in the three-dimensional geometric model of the floating wind turbine.

[0081] Specifically, this application will divide the computational domain into the following sub-areas according to the motion relationship between the various components in the floating wind turbine: background grid area, floating support platform and tower body grid area, wind turbine body grid area, etc. These sub-areas each have different grid densities and types to adapt to different fluid dynamics characteristics and computational requirements.

[0082] It should be noted that before meshing, it is also necessary to select the appropriate mesh type based on the geometric characteristics of the structure and the fluid flow characteristics in the computational domain. For example, for areas with complex geometric shapes and flow characteristics, it can be determined to use an unstructured mesh; for areas with regular geometric shapes and stable flow characteristics, it can be determined to use a structured mesh.

[0083] In one of the embodiments, the present application uses mesh generation software (such as ANSYS Mesh, HyperMesh, etc.) to generate meshes. Specifically, for areas with complex flow characteristics or requiring high-precision calculations (such as near wind turbine blades, the surface of floating support platforms, inside liquid tanks, etc.), the present application will also perform mesh encryption to ensure that the flow characteristics of these key areas can be accurately captured and simulated. It should be noted that mesh encryption can improve calculation accuracy, but it will also increase the amount of calculation. Therefore, when implementing it, it is necessary to comprehensively consider computing resources and time costs to determine the appropriate degree and range of encryption. During the mesh generation process, the present application will further check the quality of the generated mesh, including mesh distortion, aspect ratio, volume ratio and other indicators. For meshes that do not meet the quality standards, they will be corrected or re-divided to ensure that the quality of the overall mesh meets the calculation requirements and avoid numerical instability or excessive errors during the calculation process.

[0084] Step S4, establishing a numerical model of the floating wind turbine and its liquid tank within the divided grid, wherein the numerical model includes a marine environment and liquid tank fluid flow simulation model, a hydrodynamic performance simulation model, an aerodynamic performance simulation model, and an anchor chain motion characteristic simulation model.

[0085] Specifically, this application will use the fluid motion conservation equation to establish a simulation model of the marine environment and the fluid flow in the liquid tank to simulate the marine environment and the fluid flow in the liquid tank. In addition, a fixed and body-following coordinate system is defined, and the Cummins equation is used to establish a hydrodynamic performance simulation model to describe the motion response of the floating wind turbine in the waves and calculate the hydrodynamic performance of the floating wind turbine. In addition, an aerodynamic performance simulation model is established based on the viscous force and pressure on the surface unit of the wind turbine blade structure to analyze the aerodynamic performance of the floating wind turbine blade. In addition, a segmented extrapolation method is used to establish a simulation model of the motion characteristics of the anchor chain to analyze the motion characteristics of the anchor chain of the floating wind turbine.

[0086] In one of the embodiments, the present application also uses an improved algorithm of SIMPLE to handle the coupling of pressure and velocity, updates the velocity field by solving the pressure field, and calculates the pressure correction using the continuity equation in each iteration to gradually approach a solution that satisfies all flow equations (including the momentum equation and the continuity equation).

[0087] Step S5, setting and verifying the numerical simulation control conditions of the floating wind turbine and its liquid tank to ensure the accuracy and reliability of the simulation environment.

[0088] Specifically, this application will determine the simulation time step and the number of iterations in each time step based on the physical characteristics and stability conditions of the fluid flow; then, the boundary conditions will be set according to the internal and external interactions and physical limitations of the liquid tank, and the initial conditions will be set in combination with the initial state of the simulation and the fluid characteristics; finally, on the basis of setting the numerical simulation control conditions, simulation verification will be carried out, focusing on verifying key parameters such as fluid velocity distribution, pressure distribution, and free surface fluctuations.

[0089] Step S6, using the established numerical model and the set control conditions, numerical simulation is performed on the floating wind turbine to analyze the movement of the floating wind turbine and the flow characteristics of the fluid in its liquid tank.

[0090] Specifically, when analyzing the movement of floating wind turbines and the flow characteristics of the fluid in their liquid tanks, the following aspects are mainly included:

[0091] 1) Analysis of free surface fluctuation characteristics: Specifically, this application uses wave generation technology to simulate waves in actual marine environments. During the analysis, the wave parameters are adjusted to match the marine environment characteristics of the expected operating area to accurately simulate the impact of waves on the free surface of the liquid tank. In addition, due to the action of external waves, the free surface in the liquid tank will fluctuate. This fluctuation not only affects the stability of the liquid tank, but may also be transmitted to other parts of the floating wind turbine through the tank wall, affecting the overall stability of the wind turbine. Therefore, an in-depth analysis of the free surface fluctuation characteristics is crucial to evaluating the performance of floating wind turbines in complex marine environments.

[0092] 2) Analysis of internal vortex and turbulence effects: Inside the tank, vortices and turbulence may occur due to the viscosity and inertia of the fluid. These complex flow phenomena will increase the energy dissipation of the fluid and reduce the stability of the tank. Through numerical simulation, the formation mechanism, distribution characteristics of vortices and turbulence and their impact on the flow characteristics of the tank fluid will be further analyzed in detail, thereby providing a basis for optimizing the tank design.

[0093] 3) Analysis of the interaction mechanism between fluid and bulkhead: During the flow process, the fluid will interact with the tank wall, generating friction and pressure. These forces will affect the flow state of the fluid and may also cause scouring and corrosion to the tank wall. Based on this, this application analyzes the flow characteristics of the fluid inside the tank under different sea conditions, including fluid velocity distribution, pressure changes, vortex generation and dissipation, etc., to evaluate the response of the existing tank design to external impact forces.

[0094] Step S7, based on the numerical simulation analysis results, the structural design of the floating wind turbine is optimized to ensure the stable operation of the wind turbine by improving the absorption capacity of the liquid tank to the external impact force.

[0095] Specifically, this application precisely simulates and analyzes the flow behavior of the fluid in the tank, and based on the results of fluid dynamics analysis, finely optimizes the shape, size and internal layout of the tank. In addition, streamlined design is used to reduce fluid resistance, reasonable internal baffles are set to guide fluid flow, and internal damping mechanisms are added to improve the tank's ability to absorb external impact forces, so that the tank can provide effective shock absorption in multiple directions such as horizontal, vertical and inclined. Through the above designs, a tank structure that can efficiently absorb and disperse external impact forces is constructed to ensure that the wind turbine can maintain stable operation under various sea conditions.

[0096] As can be seen from the above, the present application discloses a method for optimizing the structure of an offshore floating wind turbine tank based on numerical simulation. By accurately obtaining design parameters and constructing a three-dimensional geometric model, combined with the marine environmental data of the target sea area, a reasonable calculation domain is set and detailed grid division is performed, and a numerical model containing multiple simulation models is established. The verified numerical simulation control conditions ensure the accuracy and reliability of the simulation environment, and then the movement of the floating wind turbine and the flow characteristics of the fluid in its tank are deeply analyzed through numerical simulation. Finally, based on these analysis results, the structural design of the floating wind turbine is optimized, and the absorption capacity of the tank to external impact force is enhanced, thereby ensuring the stable operation of the wind turbine and improving the overall performance and economy. Compared with traditional technologies, the present invention shows significant beneficial effects in improving the stability of the wind turbine, extending the service life and improving the energy conversion efficiency.

[0097] In one embodiment, in step S4, the marine environment and tank fluid flow simulation model is determined based on the fluid motion conservation equation, and its calculation formula includes:

[0098]

[0099] Among them, α represents the volume fraction, and its value range is between 0 and 1. + represents the instantaneous rate of change of volume fraction, (U represents the absolute velocity of the mixed fluid in the gas-liquid two-phase flow, represents the convective transport term with volume fraction α, which describes the volume fraction change caused by fluid motion, U r α represents the relative velocity of the mixed fluid in the gas-liquid two-phase flow, It represents the interfacial mixing term due to velocity difference, which describes the mixing effect caused by the velocity difference between the gas and liquid phases.

[0100] Specifically, the present application uses the fluid motion conservation equations to establish a numerical simulation model of the marine environment and the flow of liquid tank fluids. The fluid motion conservation equations are basic equations that describe fluid motion. They are based on the conservation principles in physics, including mass conservation and momentum conservation. The following is the basic form of these equations:

[0101]

[0102] in, It represents the rate of change of the mass of the fluid per unit volume of space over time. It represents the net mass flow out of unit volume space caused by velocity transport, It represents the rate of change of the momentum of the fluid per unit volume with time. represents the net momentum flow out of a unit volume space caused by velocity transport, It represents the viscous stress per unit volume of fluid. Indicates the pressure per unit volume of fluid, f v It represents the source term of the body force acting on the unit volume of fluid.

[0103] Furthermore, the present application considers using the VOF method at the interface between fluid and gas to solve the gas-liquid two-phase flow problem, wherein the VOF method is a commonly used numerical technique for tracking the fluid interface and calculating the flow field. This method describes the distribution of the fluid in the grid unit by introducing the concept of volume fraction. In the current embodiment, the present application calculates the values ​​of parameters such as the density ρ and the dynamic viscosity coefficient μ of the mixed fluid by introducing the volume fraction α, and specifically refers to the following formula:

[0104]

[0105] Among them, ρ l and ρ g Denote the density of liquid and gas, μ l and μ g Represent the dynamic viscosity coefficients of liquid and gas respectively. The value range of α is between 0 and 1. When α is 0, it means that the fluid is gas. When α is 1, it means that the fluid is water. When α is between 0 and 1, it represents the interface of the two-phase fluid (i.e., the free surface position). For details, please refer to the following formula:

[0106]

[0107] Furthermore, based on the formula form of the density ρ and dynamic viscosity coefficient μ of the mixed fluid, the transport equation of water and air can be further derived. This equation is mainly used to describe the transmission process of the mass, momentum or other physical quantities of water and air in the gas-liquid two-phase flow. It describes the calculation method of the mixing velocity U at a certain position in the gas-liquid two-phase flow (i.e., water and air). The specific calculation formula is:

[0108] U=αU l +(1-α)U g ;

[0109] Among them, (1-α) represents the volume fraction of air, and α represents the volume fraction of water, which is a value between 0 and 1. When αU is 1, it means that the position is completely occupied by water; when α is 0, it means that the position does not contain water; when αU is between 0 and 1, it means that the position is the interface between water and air. The subscripts l and g represent the water and air terms respectively, and U l represents the velocity vector of water, U g Represents the velocity vector of the air.

[0110] In one embodiment, in step S4, when a fixed coordinate system and a body coordinate system are defined, the hydrodynamic performance simulation model is determined based on the motion response of the floating wind turbine in waves, and its calculation formula includes:

[0111]

[0112] Where M represents the mass matrix of the floating body, which includes the mass or moment of inertia of the floating body in different degrees of freedom, x a (t) represents the acceleration of the floating body, x v (t) represents the velocity of the floating body, C represents the damping matrix, which describes the damping effect of the floating body during its motion, K represents the stiffness matrix, which describes the structural stiffness of the floating body, x(t) represents the displacement or rotation angle of the floating body, h(t-μ) represents the impulse response function, which reflects the interaction between the wave and the floating body, and F w(t) represents the excitation force of the wave on the floating body, which depends on the characteristics of the wave and the shape and size of the floating body.

[0113] It should be noted that the floating wind turbine system consists of a generator system, a floating foundation system and a mooring system. This application uses the Cummins equation to describe the motion response of the floating wind turbine in waves. Its expression can refer to the above formula. Specifically, the application of the Cummins equation in the floating wind turbine system is mainly reflected in describing the six-degree-of-freedom motion response of the floating foundation in waves. The equation solves the motion response of the floating body by decomposing the motion of the floating body into the radiation potential caused by its own motion and the diffraction potential caused by the incident waves. In the floating wind turbine system, the Cummins equation can take into account factors such as the shape, size, mass distribution of the floating foundation and the constraints of the mooring system, and more accurately predict the dynamic behavior of the floating wind turbine in waves, including motion parameters such as displacement, velocity, and acceleration, providing an important basis for the design and optimization of floating wind turbines.

[0114] Specifically, in the hydrodynamic analysis of the floating platform, the model defines two sets of coordinate systems, of which the first set is based on the numerical wave pool, which is a global coordinate system specifically used to describe and simulate various movements in the wave pool; the second set of coordinate systems with the center of mass of the floating wind turbine as the coordinate origin is specifically used to define the rotation and translation process of the floating wind turbine. It should be noted that the origin of the global coordinate system here is defined at the free liquid surface of the numerical wave pool, the Z axis is perpendicular to the still water surface, the XOY plane is used as the still water surface, and the positive X direction is defined as the direction of wave movement.

[0115] In one of the embodiments, the present application defines the floating wind turbine as a rigid structure, and defines the origin of the platform motion coordinate system at the center of mass of the platform. The six directions of motion in this coordinate system are defined separately, including linear motion along the three coordinate axes of X, Y, and Z, and rotation around the three coordinate axes of X, Y, and Z, wherein: the reciprocating linear motion in the X-axis direction is defined as longitudinal swing; the reciprocating linear motion in the Y-axis direction is defined as transverse swing; the reciprocating linear motion in the Z-axis direction is defined as vertical swing; the rotation around the X-axis is defined as roll; the rotation around the Y-axis is defined as pitch; the rotation around the Z-axis is defined as bow swing.

[0116] In one embodiment, in step S4, the aerodynamic performance simulation model is determined based on the viscous force and pressure on the surface unit of the fan blade structure, and its calculation formula includes:

[0117] dF e =τ·d|S e |+pdS e ;

[0118]

[0119] The subscript e indicates that the current solution process is performed in geodetic coordinates. e represents the force acting on the surface of the fan blade structure, S e represents the normal vector of the surface unit pointing to the inside of the structure, p represents pressure, τ represents shear force, ρ represents density, and v eff represents the viscosity coefficient, represents the velocity vector gradient.

[0120] It should be noted that the force acting on the surface unit of the fan blade structure is composed of viscous force and pressure. The shear stress tensor can be solved through the fluid velocity field: It should be further explained that in the formula of the shear stress tensor τ, dev represents the partial component of the second-order tensor. For any tensor T, we have:

[0121]

[0122] Therefore, after transforming the calculation formula of τ by the above two formulas, the expression of shear stress τ can be obtained as follows:

[0123] It is further necessary to explain that by integrating the viscous force and pressure on the surface unit of the fan blade structure, the aerodynamic load of the flow field on the entire blade can be calculated. This integration process takes into account every tiny unit on the blade surface, thereby ensuring the accuracy of the calculation. Based on these calculated aerodynamic loads, aerodynamic performance simulation can be performed to evaluate the operating efficiency and stability of the fan.

[0124] In one embodiment, the mooring system of the floating wind turbine system is composed of three catenary mooring lines. The anchor chain motion characteristic simulation model in step S4 is constructed based on the piecewise extrapolation method, and is obtained by calculating the force and deformation of the mooring line under different conditions, wherein the chain element force balance equations established in the horizontal and vertical directions include:

[0125]

[0126] Where, T xi+1 is the horizontal force of the anchor chain i+1 segment, T xi is the horizontal force of the i-th segment of the anchor chain, T zi+1 is the vertical force of the anchor chain i+1 segment, T zi is the vertical force of the i-th segment of the anchor chain, F i is the tangential component of the anchor chain unit, d s is the tensile length of the anchor chain unit, D i is the normal component of the anchor chain unit, is the horizontal direction cosine function of the i+1 segment of the anchor chain, is the horizontal sine function of the i+1 segment of the anchor chain, ρ is the fluid density, g is the gravitational acceleration, A is the cross-sectional area of ​​the chain, Δz p is the vertical distance between the two end nodes, and the normal component D of the flow field force on the unit length chain element i With the tangential component F i , calculated by the following formula:

[0127]

[0128] In the formula, C DN and C DT are the normal and tangential resistance coefficients of the chain, D is the chain element diameter, U N and U T are the normal and tangential components of the flow velocity, respectively.

[0129] It should be noted that the present application divides the mooring chain into chain elements, selects the chain element numbered i for force analysis, and numbers the node near the mooring end as i+1, and the node near the anchor end as i. Figure 2 As shown. x , T z and They represent the horizontal component, vertical component and the angle between the tension and its horizontal component at each node in the mooring chain coordinate system. The direction of attention is as agreed in the figure and has nothing to do with the positive and negative directions of the coordinate axes of the chain coordinate system. l and d s Denote the length of the chain element before and after stretching, ω denotes the weight of the unit length chain element in water, D and F denote the normal and tangential components of the flow force on the unit length chain element, respectively (both in N / m), U denotes the velocity vector of the flow field near the chain element. The chain element is decomposed into the normal component U N and the tangential component U T .

[0130] In one embodiment, in addition to the force balance equation, the chain element also has a geometric relationship between the node coordinates and the stretch length, as shown in the following formula:

[0131]

[0132] Where Δx p and Δz p Respectively represent the horizontal and vertical distances between the two end nodes, x i and x i+1 Respectively represent the horizontal distance between the i-th section and the i+1-th section of the anchor chain, z i and z i+1They represent the vertical distances between the i-th and i+1-th sections of the anchor chain respectively.

[0133] In addition, the relationship between the chain element tension and tensile deformation can also be obtained:

[0134]

[0135] Among them, T i+1 represents the force on the i+1th segment of the anchor chain, EA represents the tensile stiffness, d s Indicates the horizontal extension distance, d l Indicates vertical extension distance.

[0136] In one embodiment, in step S4, after the numerical model of the floating wind turbine and its liquid tank is established, the method further comprises using the SIMPLEC algorithm to perform iterative solution to obtain the pressure and velocity distribution of the fluid flow, and the specific steps are as follows:

[0137] Step S41, setting the initial pressure field and velocity field.

[0138] Specifically, this is the starting point of the iterative process, and the initial values ​​of these settings can be derived based on experience, boundary conditions, or approximate solutions calculated previously.

[0139] Step S42, based on the currently set initial pressure field, obtain the predicted velocity field by solving the momentum equation.

[0140] Specifically, the momentum equation is solved by explicitly or implicitly processing other terms (such as viscosity, gravity, etc.) while keeping the pressure term at its current value. The purpose of this step is to obtain a predicted velocity field, which will serve as the basis for calculating the pressure correction in the subsequent steps.

[0141] Step S43, calculating the pressure correction amount according to the predicted velocity field and the continuity equation.

[0142] Specifically, the improvement of the SIMPLEC algorithm in this step is that it calculates the pressure correction more accurately. By considering the continuity equation, a new velocity field can be calculated that makes the pressure correction that satisfies the continuity equation more closely as a whole.

[0143] Step S44: Use the calculated pressure correction value to update the velocity field.

[0144] Specifically, in this step, the velocity field is corrected to satisfy both the momentum equation and the continuity equation. The SIMPLEC algorithm enhances the consistency of the algorithm by considering all terms in the velocity correction equation (including the product terms with the velocity differences of adjacent cells), thereby improving the convergence speed and accuracy.

[0145] Step S45, checking whether the new pressure field and velocity field meet the preset convergence criteria, wherein, if they do, the iteration process is terminated, and if not, steps S42 to S44 are repeated until convergence is reached.

[0146] Specifically, after each iteration, it is checked whether the new pressure field and velocity field meet the preset convergence criteria. If the convergence criteria are met, the iteration process ends; if not, steps S42 to S44 are repeated until convergence is reached. The convergence criteria are usually set based on the relative changes in the velocity field and the pressure field.

[0147] In one embodiment, in step S5, setting and verifying the numerical simulation control conditions of the floating wind turbine and its liquid tank includes:

[0148] Step S51, determining the time interval of each step in the simulation according to the physical characteristics of the fluid flow and the stability condition, and setting the number of iterations of the solver in each time step according to the convergence speed and stability requirements of the simulation.

[0149] Specifically, this application will determine the time interval of each step in the simulation based on the physical characteristics and stability conditions of the fluid flow. Specifically, this application will use a smaller time step to improve the stability of the simulation, so as to fully capture the high-frequency components and transient effects in the fluid flow, and avoid numerical instability and distortion of simulation results caused by too large a time step. At the same time, according to the convergence speed and stability of the simulation, by monitoring the fluctuations of the physical quantity, the number of iterations of the solver in each time step is dynamically adjusted to ensure that the convergence standard is met.

[0150] Step S52, setting boundary conditions according to the interaction between the liquid tank and the external environment and the physical limitations inside the liquid tank, and setting initial conditions according to the initial state of the simulation and the fluid characteristics, wherein the initial conditions include an initial velocity field and an initial pressure field.

[0151] Specifically, in the numerical simulation of fluid motion in the liquid tank of an offshore floating wind turbine, the setting of boundary conditions is crucial to the accuracy of the simulation results. These boundary conditions usually reflect the interaction between the liquid tank and the external environment, as well as the physical limitations inside the liquid tank. Specifically, this application adopts the VOF method to simulate the free surface boundary conditions by solving the free surface equations in the Navier-Stokes equations. Among them, on the free liquid surface, it is usually assumed that the pressure is equal to the atmospheric pressure. This assumption helps to simplify the calculation process and maintain the rationality of the simulation. On the solid wall of the liquid tank, in order to simulate the interaction between the fluid and the wall, it is usually assumed that there is no relative sliding between the fluid and the wall, that is, the velocity vector of the fluid parallel to the wall is zero. At the same time, according to the actual roughness of the liquid tank wall, this application also introduces an appropriate wall friction coefficient to more accurately simulate the obstruction of the wall to the fluid flow. In addition, the wave incident boundary is a key boundary in the simulation, and its parameters such as waveform, period, height and direction have an important influence on the simulation results. In order to ensure the accuracy and authenticity of the simulation, these parameters will be reasonably set according to the actual marine environment data.

[0152] Furthermore, when setting the initial velocity field, on the one hand, considering that the fluid is in a uniform flow state at the beginning of the simulation, the present application sets the initial velocity field to a uniform distribution. This setting is suitable for scenes with relatively simple flows and relatively regular boundary conditions. On the other hand, for complex flows, such as turbulent flows or flows with complex boundary conditions, the initial velocity field is set to a non-uniform distribution. It should be noted that this non-uniform distribution is specifically determined by experimental data, results of previous simulations, or empirical formulas to ensure the accuracy and authenticity of the simulation. In the simulation, if it is determined that there is a clear inlet boundary, the inlet velocity is set as part of the initial velocity field, and its value is also determined by experimental data, results of previous simulations, or empirical formulas.

[0153] Furthermore, when setting the initial pressure field, at the beginning of the simulation, the present application will set the static pressure distribution according to the actual situation. In order to simplify the calculation process and improve the calculation accuracy, when solving the pressure field, the present application selects a reference pressure point or reference pressure surface and sets its pressure value to a known value. This setting helps to simplify the calculation process and improve the calculation accuracy. Similarly, if it is determined that there are clear pressure boundary conditions in the simulation, these boundary conditions are included in the setting of the initial pressure field to ensure that the simulation can fully consider the impact of these boundary conditions on fluid flow.

[0154] Step S53, after setting the numerical simulation control conditions, perform simulation verification, including verifying at least one key parameter of fluid velocity distribution, pressure distribution, and free liquid surface fluctuation.

[0155] Specifically, the simulation and verification of the movement of offshore floating wind turbines and the movement of fluids in their tanks is a key step to ensure that the established model can accurately simulate the actual fluid behavior. The specific aspects of the model that need to be verified include fluid velocity distribution, pressure distribution, free surface fluctuations, etc. This requires verification of the model calculation accuracy, such as error range, correlation coefficient, etc., based on experimental data, theoretical solutions or industry standards.

[0156] Specifically, in order to verify the calculation accuracy of the model, this application will collect experimental data that matches the model simulation conditions. These data include the measured values ​​of key parameters such as fluid velocity, pressure, and free liquid surface height. Theoretical solutions or analytical solutions can also be used as a reference for verification. In addition, other verified model results can also be used as a basis for comparative verification. Design verification cases based on verification objectives and data availability. The cases need to cover different wind and wave conditions, tank shapes, fluid types, etc. to ensure that the boundary conditions in the simulation are consistent with the verification data or experimental conditions.

[0157] In one of the embodiments, the present application will run the model in CFD software to simulate the set verification scenario. By extracting key parameters in the simulation results, such as fluid velocity field, pressure field, free liquid surface shape, etc., and quantitatively comparing these simulation results with the verification data, such as statistical indicators such as calculation error and correlation coefficient, the accuracy and reliability of the simulation results are evaluated. In addition, in addition to quantitative comparison, the present application also conducts qualitative analysis by observing whether the fluid behavior in the simulation results is consistent with expectations, such as vortex structure, flow pattern, etc., to verify whether the simulation results conform to physical laws and actual phenomena.

[0158] Finally, based on the validation results, the model parameters, mesh settings, or solution strategies can be further adjusted to improve the model performance. The above validation process is repeated until the model performance meets the requirements, that is, the error between the simulation results and the validation data is within an acceptable range, and the simulation results can accurately reflect the physical characteristics and behavior of the actual fluid flow.

[0159] In one embodiment, in step S7, optimizing the structural design of the floating wind turbine based on the numerical simulation analysis results includes:

[0160] Step S71, analyzing the fluid flow characteristics based on fluid dynamics simulation technology to obtain fluid dynamics simulation results.

[0161] Specifically, this application will be based on fluid dynamics simulation technology, by constructing an accurate tank geometry model and setting reasonable fluid parameters to simulate the three-dimensional flow process of the fluid in the tank. By carefully observing the fluid flow state, including its velocity distribution, pressure changes, and the evolution of complex phenomena such as eddies and turbulence, it is possible to fully understand the movement laws of the fluid inside the tank. These fluid dynamics simulation results not only reveal the dynamic behavior of the fluid in the tank, but also help to discover potential design defects and performance bottlenecks, laying a solid foundation for subsequent optimization work.

[0162] Step S72: optimizing the structural design of the floating wind turbine based on the fluid dynamics simulation results.

[0163] Specifically, based on the fluid dynamics simulation results, when determining that the fluid velocity is unevenly distributed, the position of the internal partition is arranged according to the distribution of the fluid velocity vector, and the liquid tank is reasonably divided into multiple small chambers to guide the fluid flow, effectively separate and slow down the fluid movement, and reduce the violent shaking of the fluid in the liquid tank caused by external impact. In view of the influence of pressure distribution on the stability of the liquid tank structure, the pressure bearing capacity of the liquid tank is significantly enhanced by optimizing the support structure and selecting suitable materials (such as high-strength alloy steel or carbon fiber composite materials). In view of dynamic characteristics such as eddy currents and turbulence, damping materials are introduced into the liquid tank or specific damping structures are designed, such as elastic partitions, damping holes, etc. These structures or materials can absorb and dissipate the kinetic energy of the fluid to effectively control adverse phenomena, thereby improving the flow stability and overall performance of the liquid tank and enhancing the buffering capacity of the liquid tank against external impacts.

[0164] In one embodiment, in step S7, the tank structure optimization method adopts a boundary smoothing windowed progressive structural topology optimization method, and achieves flexibility minimization under the condition of satisfying the target volume constraint by stepwise iteration and fine adjustment of the structural layout. Its numerical calculation model is expressed as:

[0165] find:x=[x1,x2,…,x i ,…,x n ] T

[0166]

[0167] F=KU

[0168] 0≤x i ≤1i=1,2,…,n

[0169] Among them, x represents the variable, n represents the number of variables, and x i represents the i-th variable, u i represents the design variable, k0 represents the stiffness matrix element, v i represents the design factor, V* represents the upper limit of the displacement motion constraint, F represents the constraint condition, K represents the stiffness matrix, and U represents the displacement vector.

[0170] Specifically, this application adopts a boundary-smoothing windowed progressive structural topology optimization method, aiming to find the best structural layout that meets specific performance requirements through a step-by-step iterative optimization process. During the optimization process, by introducing boundary smoothing technology, the jagged boundaries that may appear in traditional topology optimization can be effectively avoided, making the final structure more practical and easy to manufacture. At the same time, the windowed progressive strategy ensures the stability and convergence of the optimization process, and can gradually approach the global optimal solution.

[0171] Specifically, for the numerical calculation model shown above, this application performs smooth design of topological solution based on the WESO method, and its implementation process is as follows: Figure 3 As shown, the specific implementation steps include:

[0172] 1) The finite element meshing technology is used to discretize the design domain and assign values ​​to the material density of the unit, with its initial value being 1.

[0173] 2) Set volume constraint V*, filter radius r, and number of interpolation nodes n a , sensitivity reduction coefficient RF, sensitivity evolution coefficient ER.

[0174] 3) Set the elastic modulus and Poisson's ratio of the finite element analysis model according to the equation, and apply load and support constraints.

[0175] 4) Solve the constructed finite element model, analyze and extract the result data.

[0176] 5) Obtain the overall strain energy and unit sensitivity of the structure according to the following equation:

[0177]

[0178] Where k0 is the element stiffness matrix with material interpolation density of "1", n is the number of elements, C i is the unit strain energy, x i is the i-th variable, u i is the design variable, A s is the area or volume of the finite element discrete unit. Specifically, this application will calculate the performance index of the optimization result according to the following equation and judge the optimization result:

[0179]

[0180] Where: V0 and V n They represent the x in the design domain during the first and nth iterations. i>0, the sum of the unit areas (volumes); C0 and C n They represent the average strain energy density of the units in the design domain during the first and nth iterations, respectively; PI reflects the volume change and strain energy change level of the design domain. When its value is less than 1, it indicates that the topological solution at the nth iteration is better than the initial design structure. Under the same conditions, the smaller the PI value, the better the topological result. In order to ensure the efficient optimization ability of the WESO method, the PI value is used as the optimal judgment condition in each iterative calculation, and the corresponding test conditions are set.

[0181] 6) The obtained unit sensitivity values ​​are converted into strain energy according to a gridless filtering technology algorithm, and a level set function represented by the unit node sensitivity is established.

[0182] 7) Solve the zero potential surface of the level set function value according to the following equation to achieve smooth design of the topological solution:

[0183]

[0184] Where: To establish the node sensitivity threshold of the level function, N is the number of level set functions, is the sensitivity value of each node.

[0185] 8) Map the topological solution to the finite element analysis grid and complete the material interpolation density x through the following equation i The update calculation equation is as follows:

[0186]

[0187] In the formula, is the sensitivity value of the node with unit number i, n a is the number of interpolation nodes in the element, n s is the number of interpolation points in the boundary unit with Φ ≥ 0. In the current step, the RF value will be updated to determine whether the effective design domain area (volume) in the design domain meets the constraint target. If not, return to step 4) for the next iterative calculation.

[0188] 9) Repeat the calculation process from step 4) to step 8) until the effective design domain area (volume) in the design domain meets the constraint target, stop the iterative calculation, and output the topology optimization results.

[0189] In summary, at the critical stage of liquid tank design, this application introduces advanced topology optimization technology. Through topology optimization, every detail of the liquid tank shape is deeply analyzed and reconstructed. According to the optimization algorithm, unnecessary material areas are eliminated, and key support points and stress-bearing parts are strengthened. After multiple rounds of fine-tuning, numerical simulations are carried out on the adjusted liquid tank, and the performance of the liquid tank in terms of strength, stability and fluid flow efficiency is analyzed to ensure that the design of the liquid tank not only meets the performance requirements, but also takes into account economy and practicality.

[0190] Please refer to Figure 4 The present application discloses an offshore floating wind turbine tank structure optimization system based on numerical simulation, the system comprising a floating wind turbine geometry modeling module, a wind turbine calculation domain setting module, a fluid domain meshing module, a numerical model building module, a numerical simulation control condition setting and verification module, a numerical simulation analysis module, and a floating wind turbine structure optimization module, wherein:

[0191] The floating wind turbine geometric modeling module is used to obtain design parameters of the floating wind turbine and the liquid tank, and obtain a three-dimensional geometric model of the floating wind turbine through geometric modeling based on the design parameters.

[0192] The wind turbine calculation domain setting module is used to obtain the marine environment data of the target sea area, and to set the overall calculation domain of the wind turbine based on the marine environment data and the overall size of the wind turbine.

[0193] The fluid domain meshing module is used to mesh the computational domain and the internal area of ​​the liquid tank thereof according to the motion relationship between the components in the three-dimensional geometric model of the floating wind turbine.

[0194] The numerical model building module is used to establish a numerical model of a floating wind turbine and its liquid tank within the divided grid, wherein the numerical model includes a marine environment and liquid tank fluid flow simulation model, a hydrodynamic performance simulation model, an aerodynamic performance simulation model, and an anchor chain motion characteristic simulation model.

[0195] The numerical simulation control condition setting and verification module is used to set and verify the numerical simulation control condition settings of the floating wind turbine and its liquid tank to ensure the accuracy and reliability of the simulation environment.

[0196] The numerical simulation analysis module is used to use the established numerical model and set control conditions to carry out numerical simulation of the floating wind turbine and analyze the movement of the floating wind turbine and the flow characteristics of the fluid in its liquid tank.

[0197] The floating wind turbine structure optimization module is used to optimize the structural design of the floating wind turbine based on the numerical simulation analysis results, and ensure the stable operation of the wind turbine by improving the liquid tank's ability to absorb external impact forces.

[0198] In one embodiment, the above modules are also used to implement the offshore floating wind turbine tank structure optimization method based on numerical simulation as described in any one of the aforementioned method embodiments, which is not limited in this application.

[0199] As can be seen from the above, the present application discloses an offshore floating wind turbine tank structure optimization system based on numerical simulation. By accurately obtaining design parameters and constructing a three-dimensional geometric model, combined with the marine environmental data of the target sea area, a reasonable calculation domain is set and detailed grid division is performed, and a numerical model containing multiple simulation models is established. The verified numerical simulation control conditions ensure the accuracy and reliability of the simulation environment, and then the movement of the floating wind turbine and the flow characteristics of the fluid in its tank are deeply analyzed through numerical simulation. Finally, based on these analysis results, the structural design of the floating wind turbine is optimized, and the absorption capacity of the tank to external impact force is enhanced, thereby ensuring the stable operation of the wind turbine and improving the overall performance and economy. Compared with traditional technologies, the present invention shows significant beneficial effects in improving the stability of the wind turbine, extending the service life and improving the energy conversion efficiency.

[0200] It should be noted that the sequence of the above embodiments of the present invention is only for description and does not represent the advantages and disadvantages of the embodiments. The processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0201] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

Claims

1. A method for optimizing the structure of an offshore floating wind turbine tank based on numerical simulation, characterized in that: The method comprises: S1, obtaining design parameters of a floating wind turbine and a liquid tank, and obtaining a three-dimensional geometric model of the floating wind turbine through geometric modeling according to the design parameters; S2, obtaining the marine environment data of the target sea area, and setting the overall calculation domain of the wind turbine based on the marine environment data and the overall size of the wind turbine; S3, meshing the computational domain and the internal area of ​​the liquid tank thereof according to the motion relationship between the components in the three-dimensional geometric model of the floating wind turbine; S4. Establishing a numerical model of the floating wind turbine and its liquid tank in the divided grid, wherein the numerical model includes a simulation model of the marine environment and liquid tank fluid flow, a simulation model of the hydrodynamic performance, a simulation model of the aerodynamic performance, and a simulation model of the motion characteristics of the anchor chain; S5. Set and verify the numerical simulation control conditions of the floating wind turbine and its tank to ensure the accuracy and reliability of the simulation environment; S6. Use the established numerical model and set control conditions to carry out numerical simulation of the floating wind turbine and analyze the movement of the floating wind turbine and the flow characteristics of the fluid in its liquid tank; S7. Based on the results of numerical simulation analysis, the structural design of the floating wind turbine is optimized to ensure the stable operation of the wind turbine by improving the liquid tank's ability to absorb external impact forces.

2. The method according to claim 1, characterized in that In step S4, the marine environment and tank fluid flow simulation model is determined based on the fluid motion conservation equation, and its calculation formula includes: Among them, α represents the volume fraction, and its value range is between 0 and 1. represents the instantaneous rate of change of volume fraction, U represents the absolute velocity of the mixed fluid in the gas-liquid two-phase flow, represents the convective transport term with volume fraction α, which describes the volume fraction change caused by fluid motion, U r represents the relative velocity of the mixed fluid in the gas-liquid two-phase flow, It represents the interfacial mixing term due to velocity difference, which describes the mixing effect caused by the velocity difference between the gas and liquid phases.

3. The method according to claim 1, characterized in that In step S4, when a fixed coordinate system and a body coordinate system are defined, the hydrodynamic performance simulation model is determined based on the motion response of the floating wind turbine in waves, and its calculation formula includes: Where M represents the mass matrix of the floating body, which includes the mass or moment of inertia of the floating body in different degrees of freedom, x a (t) represents the acceleration of the floating body, x v (t) represents the velocity of the floating body, C represents the damping matrix, which describes the damping effect of the floating body during its motion, K represents the stiffness matrix, which describes the structural stiffness of the floating body, x(t) represents the displacement or rotation angle of the floating body, h(t-τ) represents the impulse response function, which reflects the interaction between the wave and the floating body, and F w (t) represents the excitation force of the wave on the floating body, which depends on the characteristics of the wave and the shape and size of the floating body.

4. The method according to claim 1, characterized in that In step S4, the aerodynamic performance simulation model is determined based on the viscous force and pressure on the surface unit of the fan blade structure, and its calculation formula includes: dF e =τ·d|S e |+pdS e ; The subscript e indicates that the current solution process is performed in geodetic coordinates. e represents the force acting on the surface of the fan blade structure, S e represents the normal vector of the surface unit pointing to the inside of the structure, p represents pressure, τ represents shear force, ρ represents density, and v eff represents the viscosity coefficient, represents the velocity vector gradient.

5. The method according to claim 1, characterized in that The mooring system of the floating wind turbine system consists of three catenary mooring lines. The anchor chain motion characteristic simulation model in step S4 is constructed based on the piecewise extrapolation method, and is obtained by calculating the force and deformation of the mooring line under different conditions. The force balance equations of the chain element established in the horizontal and vertical directions include: Where, T xi+1 is the horizontal force of the anchor chain i+1 segment, T xi is the horizontal force of the i-th segment of the anchor chain, T zi+1 is the vertical force of the anchor chain i+1 segment, T zi is the vertical force of the anchor chain segment i, F i is the tangential component of the anchor chain unit, d s is the tensile length of the anchor chain unit, D i is the normal component of the anchor chain unit, is the horizontal direction cosine function of the i+1 segment of the anchor chain, is the horizontal sine function of the i+1 segment of the anchor chain, ρ is the fluid density, g is the gravitational acceleration, A is the cross-sectional area of ​​the chain, Δz p is the vertical distance between the two end nodes, and the normal component D of the flow field force on the unit length chain element i With the tangential component F i , calculated by the following formula: Among them, C DN and C DT are the normal and tangential resistance coefficients of the chain, D is the chain element diameter, U N and U T are the normal and tangential components of the flow velocity, respectively.

6. The method according to claim 1, characterized in that In step S4, after the numerical model of the floating wind turbine and its liquid tank is established, the method further includes using the SIMPLEC algorithm to perform iterative solution to obtain the pressure and velocity distribution of the fluid flow. The specific steps are as follows: S41, setting the initial pressure field and velocity field; S42, based on the currently set initial pressure field, obtain a predicted velocity field by solving the momentum equation; S43, calculating a pressure correction amount according to the predicted velocity field and continuity equation; S44, using the calculated pressure correction to update the velocity field; S45, checking whether the new pressure field and velocity field meet the preset convergence criteria, wherein, if they do, the iteration process is terminated, and if not, steps S42 to S44 are repeated until convergence is reached.

7. The method according to claim 1, characterized in that In step S5, the setting and verification of numerical simulation control conditions of the floating wind turbine and its liquid tank include: S51, determining the time interval of each step in the simulation according to the physical characteristics and stability conditions of the fluid flow, and setting the number of iterations of the solver in each time step according to the convergence speed and stability requirements of the simulation; S52, setting boundary conditions according to the interaction between the liquid tank and the external environment and the physical limitations inside the liquid tank, and setting initial conditions according to the initial state of the simulation and the fluid characteristics, wherein the initial conditions include an initial velocity field and an initial pressure field; S53. After setting the numerical simulation control conditions, perform simulation verification, including verifying at least one key parameter among fluid velocity distribution, pressure distribution, and free liquid surface fluctuation.

8. The method according to claim 1, characterized in that In step S7, the structural design of the floating wind turbine is optimized based on the numerical simulation analysis results, including: S71. Analyze fluid flow characteristics based on fluid dynamics simulation technology to obtain fluid dynamics simulation results; S72. Optimize the structural design of the floating wind turbine based on the fluid dynamics simulation results.

9. The method according to claim 1, characterized in that: In step S7, the tank structure optimization method adopts a boundary smoothing windowed progressive structural topology optimization method. By gradually iterating and finely adjusting the structural layout, the flexibility is minimized under the condition of satisfying the target volume constraint. Its numerical calculation model is expressed as: find:x=[x1,x2,…,x i ,…,x n ] T F=KU 0≤x i ≤1i=1,2,…,n Among them, x represents the variable, n represents the number of variables, and x i represents the i-th variable, u i represents the design variable, k0 represents the stiffness matrix element, v i represents the design factor, V * represents the upper limit of the displacement motion constraint, F represents the constraint condition, K represents the stiffness matrix, and U represents the displacement vector.

10. An offshore floating wind turbine tank structure optimization system based on numerical simulation, characterized in that: The system includes a floating wind turbine geometric modeling module, a wind turbine calculation domain setting module, a fluid domain meshing module, a numerical model building module, a numerical simulation control condition setting and verification module, a numerical simulation analysis module, and a floating wind turbine structure optimization module, wherein: The floating wind turbine geometric modeling module is used to obtain design parameters of the floating wind turbine and the liquid tank, and obtain a three-dimensional geometric model of the floating wind turbine through geometric modeling according to the design parameters; The wind turbine calculation domain setting module is used to obtain the marine environment data of the target sea area, and set the overall calculation domain of the wind turbine based on the marine environment data and the overall size of the wind turbine; The fluid domain meshing module is used to mesh the computational domain and the internal area of ​​the liquid tank thereof according to the motion relationship between the components in the three-dimensional geometric model of the floating wind turbine; The numerical model building module is used to establish a numerical model of the floating wind turbine and its liquid tank within the divided grid, wherein the numerical model includes a marine environment and liquid tank fluid flow simulation model, a hydrodynamic performance simulation model, an aerodynamic performance simulation model, and an anchor chain motion characteristic simulation model; The numerical simulation control condition setting and verification module is used to set and verify the numerical simulation control condition settings of the floating wind turbine and its liquid tank to ensure the accuracy and reliability of the simulation environment; The numerical simulation analysis module is used to use the established numerical model and the set control conditions to carry out numerical simulation of the floating wind turbine and analyze the movement of the floating wind turbine and the flow characteristics of the fluid in its liquid tank; The floating wind turbine structure optimization module is used to optimize the structural design of the floating wind turbine based on the numerical simulation analysis results, and ensure the stable operation of the wind turbine by improving the liquid tank's ability to absorb external impact forces.

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