Computational fluid dynamics based coupled simulation method of floating cage-fan system

Abstract

The application provides a floating wind turbine-culture net cage coupling simulation method based on computational fluid dynamics, and belongs to the technical field of offshore wind power and mariculture. The method comprises simulating an aerodynamic module and a net cage module based on a computational fluid dynamics method, wherein the net cage module adopts a Darcy-Forchheimer equation, the influence of a floating wind turbine platform movement speed on a relative speed term in the Darcy-Forchheimer equation of the culture net cage is considered, and the net cage load is applied to the floating wind turbine platform, so that two-way coupling simulation of the culture net cage and the floating wind turbine platform is realized. The application considers the influence of the net cage on the flow field characteristics of the floating wind turbine platform, and can accurately simulate the dynamic response characteristics of the floating wind turbine and the culture net cage under the coupling action of wind, wave and flow by coupling the aerodynamic thrust of the wind turbine, the hydrodynamic load of the net cage and the movement response of the mooring.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of offshore wind power and mariculture, and relates to a floating wind turbine-cage integrated structure coupling simulation method based on a computational fluid dynamics method. BACKGROUND

[0002] With the increasing demand for clean energy worldwide, floating offshore wind turbines (FOWT) have become an important choice to solve energy crisis and environmental problems. However, the environmental load of the floating platform is complex, and the investment cost is higher than that of onshore wind turbines. Fish farming, as an industry with a shorter recovery period and higher economic benefits than offshore wind turbines, can be combined with offshore wind turbines to reduce costs and increase profits, which is of great significance for the sustainable development of energy and marine resources.

[0003] In recent years, research on the integrated structure of floating wind turbines and cage culture has made preliminary progress. Research methods include model experiments and numerical simulations based on simplified theories such as the Morison equation and the net screen element method. However, the numerical simulation methods based on these simplified theories have limited calculation accuracy under complex environmental conditions, and it is difficult to fully consider the influence of the structure on the flow field, thus there are limitations. Therefore, the application provides an effective coupling simulation method for the integrated structure of floating wind turbines and cage culture based on computational fluid dynamics. SUMMARY

[0004] The application provides a floating wind turbine-cage integrated structure coupling simulation method based on computational fluid dynamics. Based on the floating wind turbine-cage integrated structure coupling simulation method provided by the application, the aerodynamic thrust of the wind turbine, the hydrodynamic load of the cage, the mooring load, and the motion response of the floating wind turbine can be coupled to accurately simulate the load and motion response characteristics of the floating wind turbine-cage integrated structure under the coupling action of wind, wave, and current, and analyze the influence of the cage structure on the overall structure motion response.

[0005] The technical scheme adopted by the application is as follows:

[0006] A floating wind turbine-cage coupling simulation method based on computational fluid dynamics, comprising:

[0007] Establishing a floating wind turbine-cage coupling simulation model based on the actual parameters of the floating wind turbine platform and the cage culture;

[0008] Simulating the aerodynamic module of the floating wind turbine-cage integrated structure based on the computational fluid dynamics method to obtain the total aerodynamic load received by the floating wind turbine platform at the current time step;

[0009] simulate the net cage module of the floating wind turbine-cage integrated structure based on the computational fluid dynamics method to obtain the net cage load on the floating wind turbine platform at the current time step;

[0010] simulate the mooring dynamic module based on the lumped mass method to obtain the mooring load on the floating wind turbine platform at the current time step;

[0011] based on the total aerodynamic load, the net cage load and the mooring load on the floating wind turbine platform at the current time step, perform six-degree-of-freedom motion calculation of the floating wind turbine platform to obtain motion information such as speed, displacement and acceleration of the floating wind turbine platform; update the relative motion of the wind turbine blade, the relative motion of the net cage and the relative motion information at the fairlead based on the motion information;

[0012] based on the relative motion of the wind turbine blade, the relative motion of the net cage and the relative motion information at the fairlead at the current time step, iteratively update the total aerodynamic load, the net cage load and the mooring load on the floating wind turbine platform at the next time step, and further obtain the relative motion of the wind turbine blade, the relative motion of the net cage and the relative motion at the fairlead at the next time step.

[0013] Further, the floating wind turbine-cage coupling simulation model comprises:

[0014] based on the actual shape and size of the floating wind turbine platform and the net cage, create a geometry file required for generating a grid based on the simulated floating wind turbine platform and the net cage;

[0015] determine the calculation domain in the OpenFOAM environment, divide the specific calculation grid using the geometry file, and generate a specific refined grid for the floating wind turbine platform, the wind turbine rotor and the net cage according to the calculation requirements;

[0016] pre-process the floating wind turbine platform, determine the grid motion setting file and establish the wind turbine rotor aerodynamic load constraint and the net cage load constraint condition, and set the aerodynamic load and net cage load action point;

[0017] pre-process the wind turbine rotor, establish the wind turbine load calculation source item file, and determine the calculation parameters such as blade speed, tip speed ratio, airfoil, size, etc;

[0018] pre-process the net cage, establish the net cage calculation source item file, and determine the coefficients of the Darcy-Forchheimer equation of the net cage and the local coordinate system of the net cage;

[0019] pre-process the mooring system, establish the mooring system calculation input file, and determine the calculation parameters such as anchor chain length, mass, stiffness, coordinates, etc.

[0020] Further, the aerodynamic module simulation of the floating wind turbine-culture net cage integrated structure based on the computational fluid dynamics method obtains the total aerodynamic load of the floating wind turbine acting on the floating wind turbine platform at the current time step, and the specific process is as follows:

[0021] The aerodynamic load of the blade element under the influence of the floating wind turbine platform motion is calculated according to the blade parameter information and the floating wind turbine platform motion information, and the lift F l_aero and the drag F d_aero on the blade element are calculated:

[0022]

[0023] Wherein, ρ represents the fluid density, c represents the chord length, dr is the length of the airfoil unit on the blade, U rel_aero is the relative speed of the blade under the influence of the floating wind turbine platform motion and the rotor rotation, C l (α) and C d (α) are the lift coefficient and the drag coefficient corresponding to the airfoil respectively;

[0024] Based on the lift F l_aero and the drag F d_aero of the blade element, the total aerodynamic thrust and power of the wind turbine blade and the rotor are calculated.

[0025] Further, the net cage module simulation of the floating wind turbine-culture net cage integrated structure based on the computational fluid dynamics method obtains the net cage load of the floating wind turbine platform at the current time step, that is, the lift and the drag on the net cage grid element, and the specific method is as follows:

[0026] In order to consider the relative speed in the net cage motion, the net cage load calculation method based on the Darcy-Forchheimer equation is as follows:

[0027]

[0028] In the formula, S i is the source term in the momentum equation; D and C are the viscosity term and the inertia term respectively; μ is the dynamic viscosity; ρ is the fluid density; n and t are the normal and tangential directions of the defined grid element respectively; u rel_net represents the relative speed considering the translation motion and the rotation motion of the net cage, and the relative speeds obtained by the translation motion and the rotation motion are directly added; wherein the translation motion speed of the grid element in the net cage is directly obtained from the translation motion speed of the floating wind turbine platform; the relative speed of the net cage caused by the rotation motion of the floating wind turbine platform is calculated by the following formula:

[0029]

[0030] Wherein, represents the relative velocity vector of the mesh element in the net cage due to the rotational motion, ω is the angular velocity vector, n is the rotation axis, and r is the rotation radius vector;

[0031] With the continuous movement of the net cage, the Darcy-Forchheimer coefficient matrix D and C change in the global coordinate system. The Darcy-Forchheimer coefficients in the global coordinate system are updated according to the rotation matrix R using the six-degree-of-freedom motion information of the floating wind turbine platform:

[0032]

[0033] where R T is the transpose matrix of the matrix R;

[0034] According to the updated coefficient matrix, the lift F d and the drag F t on the mesh element of the net cage are calculated:

[0035]

[0036] where V is the volume of the mesh element, and the subscripts n and t represent the normal and tangential components of the mesh plane, respectively.

[0037] Further, the mooring dynamic module simulation based on the lumped mass method is performed to obtain the mooring load received by the floating wind turbine platform at the current time step, including:

[0038] According to the user-defined number of segments, the anchor chain is divided into k+1 lumped mass points;

[0039] The Morison equation is used to calculate the anchor chain load, considering the gravity, buoyancy, seabed contact force, and internal stiffness and damping of the mooring line. The calculation equation is as follows:

[0040]

[0041] where m i represents the mass of the i th mass point; I is the unit matrix; a i is the added mass of the i th mass point; is the acceleration of the i th mass point; T and C are the anchor tension and internal damping force, respectively, and the subscripts ±1 / 2 represent adjacent mass points; W i represents the buoyancy; B i is the seabed contact force; D ni and D ti are the normal and tangential drag forces, respectively;

[0042] The anchor tension T at the fairlead is calculated according to formula (8).

[0043] Further, based on the total aerodynamic load, net cage load and mooring load suffered by the floating wind turbine platform at the current time step, six-degree-of-freedom motion calculation of the floating wind turbine platform is performed to obtain motion information such as speed, displacement and acceleration of the floating wind turbine platform; the relative motion of the wind turbine blade, the relative motion of the net cage and the relative motion at the fairlead are updated based on the motion information; the specific process is as follows:

[0044] According to the total aerodynamic thrust, net cage lift and drag and anchor chain tension suffered by the floating wind turbine platform at the current time step, the motion information such as speed, displacement and acceleration of the floating wind turbine platform is calculated and saved to the corresponding dictionary file of the motion information;

[0045] The displacement of all grid nodes in the calculation domain is solved by using a grid solver;

[0046] The speed, displacement and acceleration information of the floating wind turbine platform is read in the aerodynamic module to calculate the position and relative motion of each section of the blade; the speed, displacement, acceleration and azimuth information of the floating wind turbine platform is read in the net cage module to calculate the relative motion of the grid points at the net cage; the speed, displacement and acceleration information of the floating wind turbine platform is read in the mooring power module to calculate the relative motion at the fairlead.

[0047] Further, based on the relative speed of the wind turbine blade, the relative speed of the net cage and the relative speed at the fairlead in the relative motion information of the wind turbine blade, the relative motion of the net cage and the relative motion at the fairlead at the next time step, the total aerodynamic load, net cage load and mooring load suffered by the floating wind turbine platform are iteratively updated, and further the relative motion of the wind turbine blade, the relative motion of the net cage and the relative motion at the fairlead at the next time step are obtained, and the specific process is as follows:

[0048] Based on the relative speed of the wind turbine blade, the relative speed of the net cage and the relative speed at the fairlead in the relative motion information of the wind turbine blade, the relative motion of the net cage and the relative motion at the fairlead at the current time step, the total aerodynamic load, net cage load and mooring load suffered by the floating wind turbine platform are iteratively updated by being substituted into the aerodynamic module, the net cage module and the mooring power module respectively, and further the motion information such as speed, displacement and acceleration of the floating wind turbine platform is obtained, and further the relative motion of the wind turbine blade, the relative motion of the net cage and the relative motion at the fairlead are obtained based on the motion information.

[0049] The beneficial effects of the present application are as follows:

[0050] (1) The present application is based on the computational fluid dynamics method, accurately analyzes the flow field change by considering the fluid viscosity, and fully considers the coupling effect between the wind turbine aerodynamic load, the net cage load, the mooring load and the platform hydrodynamic load through the solver, and establishes an accurate overall coupling model of the floating wind turbine and the net cage.

[0051] (2) The Darcy-Forchheimer equation is used to accurately calculate the load changes of the net cage structure under complex environmental loads, and the influence of the net cage structure on the flow field is fully considered, thereby further affecting the dynamic response changes of the overall structure.

[0052] (3) The present application can be used for simulation of different fan forms, net cage forms and mooring forms of the floating fan-culture net cage integrated structure according to the initial geometric shape. BRIEF DESCRIPTION OF DRAWINGS

[0053] Figure 1 is a floating fan-culture net cage integrated structure simulation process.

[0054] Figure 2 is a floating fan-culture net cage integrated structure sketch.

[0055] Figure 3 is an integrated structure surge response schematic diagram.

[0056] Figure 4 is an integrated structure heave response schematic diagram.

[0057] Figure 5 is an integrated structure pitch response schematic diagram.

[0058] Figure 6 is a culture net cage horizontal direction load schematic diagram.

[0059] Figure 7 is a culture net cage vertical direction load schematic diagram.

[0060] Figure 8 is a net cage structure influence on the flow field diagram, wherein (a) is without a net cage, and (b) is with a net cage. DETAILED DESCRIPTION

[0061] The specific embodiments of the present application will be further described in detail below in combination with the drawings and examples. The embodiments of the present application are implemented on the premise of the technical solution of the present application, and detailed implementation modes and specific operation processes are given, but the protection scope of the present application is not limited to the following examples.

[0062] As shown in Figure 1 , the embodiment of the present application provides a floating fan-culture net cage integrated structure coupling simulation method based on a computational fluid dynamics method, comprising the following steps:

[0063] S1, taking IEA15MW floating fan as an example, establishing as Figure 2The shown floating wind turbine-cage coupling simulation model (1-4 represent the four pieces of netting of the cage), the calculation condition is wind speed 11.4 m / s, regular wave height 7.58 m, wave period 12.1 s; the specific process is as follows:

[0064] S1.1, based on the actual shape and size of the floating wind turbine platform and the cage, create the geometric file required for generating the grid of the IEA15MW floating wind turbine platform and the cage;

[0065] S1.2, determine the calculation domain in the OpenFOAM environment, use the geometric file in S1.1 to divide the specific calculation grid, generate the specific refined grid for the floating wind turbine platform, the wind turbine rotor and the cage according to the calculation requirements;

[0066] S1.3, preprocess the floating wind turbine platform, determine the grid motion setting file and establish the wind turbine rotor aerodynamic load constraint and cage load constraint condition, set the aerodynamic load and cage load action point;

[0067] S1.4, preprocess the wind turbine rotor, establish its wind turbine load calculation source item file, determine the calculation parameters such as blade speed, tip speed ratio, airfoil, size, etc;

[0068] S1.5, preprocess the cage, establish the cage calculation source item file, determine the coefficients of the Darcy-Forchheimer equation of the cage and the local coordinate system of the cage;

[0069] S1.6, preprocess the mooring system, establish the mooring system calculation input file, determine the calculation parameters such as anchor chain length, mass, stiffness, coordinates, etc.

[0070] S2, based on the computational fluid dynamics method, simulate the aerodynamic module of the floating wind turbine-cage integrated structure, obtain the total aerodynamic load of the floating wind turbine acting on the floating wind turbine platform at the current time step; the specific process is as follows:

[0071] S2.1, calculate the aerodynamic load of the blade element under the influence of the floating wind turbine platform motion, according to the blade parameter information and the floating wind turbine platform motion information, calculate the lift F l_aero and the drag F d_aero on the blade element:

[0072]

[0073] Where, ρ represents the fluid density, c represents the chord length, dr is the length of the airfoil element on the blade, U rel_aero is the relative speed of the blade under the influence of the floating wind turbine platform motion and the rotor rotation, C l (α) and C d(α) are lift coefficient and drag coefficient of the corresponding airfoil, respectively;

[0074] S2.2, lift F of the blade element unit based on S2.1 l_aero and drag F d_aero , the total aerodynamic thrust and power of the wind turbine blade and rotor are calculated.

[0075] S3, floating wind turbine-cage integrated structure cage module simulation based on computational fluid dynamics method, the net cage load received by the floating wind turbine platform at the current time step is obtained, the specific process is as follows:

[0076] S3.1, in order to consider the relative velocity in the cage motion, the cage load calculation method based on Darcy-Forchheimer equation is as follows:

[0077]

[0078] In the formula, S i is the source term in the momentum equation; D and C are the viscous term and the inertial term, respectively; μ is the dynamic viscosity; ρ is the fluid density; n and t are the normal and tangential directions of the defined grid element, respectively; u rel_net represents the relative velocity considering the translational motion and rotational motion of the cage, which is directly added by the relative velocity obtained by the translational motion and the rotational motion, wherein the translational motion velocity of the grid element in the cage is directly obtained from the translational motion velocity of the floating wind turbine platform, and the relative velocity of the cage caused by the rotational motion of the floating wind turbine platform is calculated by the following formula:

[0079]

[0080] wherein, represents the relative velocity vector of the grid element in the cage due to the rotational motion, ω is the angular velocity vector, n is the rotation axis, and r is the rotation radius vector;

[0081] S3.2, with the continuous movement of the cage, the Darcy-Forchheimer coefficient matrix D and C change in the global coordinate system, the Darcy-Forchheimer coefficient in the global coordinate system is updated according to the rotation matrix R by using the six-degree-of-freedom motion information of the floating wind turbine platform:

[0082]

[0083] wherein, R T is the transpose matrix of the matrix R;

[0084] S3.3, according to the updated coefficient matrix calculated by S3.2, the lift F d and drag F tThe calculation is performed according to the following formula:

[0085]

[0086] where V is the volume of the unit cell in the network, and the subscripts n and t represent the normal and tangential components of the net plane, respectively.

[0087] The results of the net cage load calculation in this embodiment are shown in Figures 6-7 The results of the calculation of the influence of the net cage structure on the flow field are shown in Figure 8 The net cage significantly reduces the flow velocity.

[0088] S4, mooring dynamic module simulation is performed based on the lumped mass method to obtain the mooring load on the floating wind turbine platform at the current time step, specifically:

[0089] S4.1, the anchor chain is divided into k+1 lumped mass points according to the number of segments defined;

[0090] S4.2, the Morison equation is used to calculate the anchor chain load, considering gravity, buoyancy, seabed contact force and internal stiffness and damping of the mooring line, and the calculation equation is as follows:

[0091]

[0092] where m i represents the mass of the i-th mass point; I is the unit matrix; a i is the added mass of the i-th mass point; is the acceleration of the i-th mass point; T and C are the anchor chain tension and internal damping force, respectively, and the subscripts ±1 / 2 represent the adjacent mass point; W i represents the buoyancy; B i is the seabed contact force; D ni and D ti are the normal and tangential drag forces, respectively;

[0093] The anchor chain tension T at the fairlead, i.e. the mooring load on the floating wind turbine platform, is calculated according to formula (8).

[0094] S5, based on the total aerodynamic load, net cage load and mooring load on the floating wind turbine platform at the current time step, six-degree-of-freedom motion calculation of the floating wind turbine platform is performed to obtain the motion information such as speed, displacement and acceleration of the floating wind turbine platform; based on the motion information, the relative motion of the wind turbine blade, the relative motion of the net cage and the relative motion at the fairlead are updated; the specific method is:

[0095] S5.1, according to the total aerodynamic thrust, net cage lift and drag, and anchor tension calculated in S2, S3, S4, the speed, displacement, acceleration and other motion information of the floating wind turbine are calculated and saved to the corresponding dictionary file of motion information; in this embodiment, the calculated motion response results of the floating wind turbine are shown in FIG. 8, and the presence of the net cage structure increases the mean value of the surge motion of the floating wind turbine and reduces the mean value of the pitch motion, and has little effect on the heave motion. Figures 3-5

[0096] S5.2, the displacement of all grid nodes in the calculation domain is solved using a grid solver;

[0097] S5.3, the speed, displacement and acceleration information of the floating wind turbine platform is read in the aerodynamic module, the position and relative motion of the blade sections are calculated; the speed, displacement, acceleration and orientation information of the floating wind turbine platform is read in the net cage module, the relative motion of the grid points at the net cage is calculated; the speed, displacement and acceleration information of the floating wind turbine platform is read in the mooring dynamic module, the relative motion at the fairlead is calculated; the relative motion includes displacement, relative velocity and other information.

[0098] S6, enter the next time step, based on the relative motion of the wind turbine blades, the relative motion of the net cage and the relative motion at the fairlead obtained in S5, repeat S2-S5, iteratively update the total aerodynamic load, net cage load and mooring load of the floating wind turbine platform, and further obtain the relative motion of the wind turbine blades, the relative motion of the net cage and the relative motion at the fairlead.

[0099] The above describes the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any skilled person in the art can make equivalent replacement or change according to the technical solution and inventive concept of the present application within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.​

Claims

1. A method for coupled simulation of a floating cage based on computational fluid dynamics, characterized in that, The application relates to a method for simulating the coupling of a floating wind turbine platform and a culture net cage. The method comprises the following steps: Based on the actual parameters of the floating wind turbine platform and the culture net cage, a coupling simulation model of the floating wind turbine platform and the culture net cage is established. Based on the computational fluid dynamics method, the aerodynamic module simulation of the fusion structure of the floating wind turbine platform and the culture net cage is carried out, so as to obtain the total aerodynamic load borne by the floating wind turbine platform at the current time step. Based on the computational fluid dynamics method, the net cage module simulation of the fusion structure of the floating wind turbine platform and the culture net cage is carried out, so as to obtain the net cage load borne by the floating wind turbine platform at the current time step. (1) (2) where is a source term in the momentum equation; D and C are viscous and inertial terms, respectively; is the dynamic viscosity; is the fluid density; n and t are the normal and tangential directions of the defined grid cell, respectively; denotes the relative velocity considering the translational and rotational motion of the cage. With the net cage moving, the Darcy-Forchheimer coefficient matrix D and C Changes in the global coordinate system, using floating fan platform six degrees of freedom motion information, according to the rotation matrix R Update the Darcy-Forchheimer coefficient under the global coordinate system: (3) wherein is the transpose matrix of the matrix R is the transpose matrix of the matrix Calculate the lift force on the mesh cells of the cage based on the updated coefficient matrix. and resistance : (4) wherein, V is the volume of the grid cell, the subscript n and t denote the normal and tangential components of the grid plane, respectively; In order to consider the relative speed in the net cage movement, the net cage load calculation method based on the Darcy-Forchheimer equation is as follows: Based on the lumped mass method, the mooring dynamic module simulation is carried out, so as to obtain the mooring load borne by the floating wind turbine platform at the current time step. Based on the total aerodynamic load, the net cage load and the mooring load borne by the floating wind turbine platform at the current time step, the six-degree-of-freedom motion calculation of the floating wind turbine platform is carried out, so as to obtain the motion information of the floating wind turbine platform, including the speed, the displacement and the acceleration.

2. The computational fluid dynamics based coupled simulation method of a floating wind- farm-seaweed farming net-pen system according to claim 1, wherein, Based on the relative motion of the wind turbine blade, the relative motion of the culture net cage and the relative motion at the fairlead at the current time step, the total aerodynamic load, the net cage load and the mooring load borne by the floating wind turbine platform at the next time step are iteratively updated, and the relative motion of the wind turbine blade, the relative motion of the culture net cage and the relative motion at the fairlead at the next time step are further obtained. The method for simulating the coupling of the floating wind turbine platform and the culture net cage comprises the following steps: Based on the actual shape and size of the floating wind turbine platform and the culture net cage, a geometry file required for generating the grid based on the simulated floating wind turbine platform and the culture net cage is created. In the OpenFOAM environment, the calculation domain is determined, the specific calculation grid is divided by using the geometry file, and the specific refined grid of the floating wind turbine platform, the wind turbine rotor and the culture net cage is generated according to the calculation requirement. The floating wind turbine platform is preprocessed, the grid motion setting file is determined, the wind turbine rotor aerodynamic load constraint and the net cage load constraint condition are established, and the aerodynamic load and the net cage load action point are set. The wind turbine rotor is preprocessed, the wind turbine load calculation source item file is established, and the blade calculation parameter is determined. The culture net cage is preprocessed, the culture net cage calculation source item file is established, and the Darcy-Forchheimer equation coefficient and the net cage local coordinate system are determined.

3. The computational fluid dynamics based coupled simulation method of a floating wind- farm-seaweed farming net pen according to claim 1 or 2, characterized in that, The mooring system is preprocessed, the mooring system calculation input file is established, and the anchor chain calculation parameter is determined. The aerodynamic load of the blade element under the influence of the floating wind turbine platform motion is calculated according to the blade parameter information and the floating wind turbine platform motion information, and the lift and drag on the blade element are calculated and resistance : (5) (6) wherein, represents the fluid density, c represents the chord length, dr is the length of this airfoil element on the blade, is the relative velocity of the blade under the influence of the floating wind turbine platform motion and the rotor rotation, and are the lift and drag coefficients, respectively, of the corresponding airfoil. Lift based on the blade element and drag , the total aerodynamic thrust and power of the fan blade and rotor are calculated.

4. The computational fluid dynamics based coupled simulation method of a floating wind- farming cage according to claim 3, wherein, The The relative velocity of the net cage caused by the translational motion and the rotational motion is directly added up; wherein the translational motion velocity of the net cage is directly obtained from the translational motion velocity of the floating wind turbine platform; the relative velocity of the net cage caused by the rotational motion of the floating wind turbine platform is calculated by the following formula: (7) wherein represents the relative velocity vector of the mesh element within the cage due to the rotational motion, is the angular velocity vector, is the rotation axis, and r is the rotation radius vector.

5. The computational fluid dynamics based coupled simulation method of a floating wind- farm-seaweed farming net pen system according to claim 4, wherein, The calculation process of the total aerodynamic load borne by the floating wind turbine platform at the current time step is as follows: The anchor chain is divided into k +1 lumped mass point; The calculation method of the mooring load borne by the floating wind turbine platform at the current time step comprises the following steps: (8) where, M represents the mass of the i I is the identity matrix; i Cm represents the added mass of the i F represents the buoyancy; F represents the seabed contact force; and F and F represent the normal and tangential drag forces, respectively.​​​ 6. The computational fluid dynamics based coupled simulation method of a floating wind- farming cage according to claim 5, wherein, The anchor chain tension T at the fairlead is solved by using the Morison equation, and the equation is as follows: The specific process of updating the relative motion of the wind turbine blade, the relative motion of the culture net cage and the relative motion at the fairlead is as follows: According to the total aerodynamic thrust, the net cage lift and drag, and the anchor tension of the floating wind turbine platform at the current time step, the motion information of the floating wind turbine platform including velocity, displacement, and acceleration is calculated and saved to the corresponding dictionary file of the motion information; The displacement of all grid nodes in the calculation domain is solved using a grid solver; The velocity, displacement, and acceleration information of the floating wind turbine platform is read in the aerodynamic module to calculate the position and relative motion of the blade sections, and the velocity, displacement, acceleration, and orientation information of the floating wind turbine platform is read in the net cage module to calculate the relative motion of the grid points at the net cage; The velocity, displacement, and acceleration information of the floating wind turbine platform is read in the mooring dynamic module to calculate the relative motion at the fairlead.

7. The computational fluid dynamics based coupled simulation method of a floating wind- farm-seaweed farming net pen system according to claim 1, wherein, The total aerodynamic load, net cage load, and mooring load of the floating wind turbine platform at the next time step are iteratively updated based on the relative velocity of the wind turbine blade, the relative velocity of the net cage, and the relative velocity at the fairlead in the relative motion information of the wind turbine blade, the net cage, and the fairlead at the current time step, and the relative motion of the wind turbine blade, the relative motion of the net cage, and the relative motion at the fairlead at the next time step are obtained, specifically as follows: The total aerodynamic load, net cage load, and mooring load of the floating wind turbine platform are iteratively updated based on the relative velocity of the wind turbine blade, the relative velocity of the net cage, and the relative velocity at the fairlead in the relative motion information of the wind turbine blade, the net cage, and the fairlead at the current time step, and the motion information of the floating wind turbine platform is obtained, and the relative motion of the wind turbine blade, the relative motion of the net cage, and the relative motion at the fairlead are further obtained based on the motion information.

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