Floating fan-culture net cage coupling simulation method based on computational fluid mechanics

Abstract

The invention provides a floating fan-culture net cage coupling simulation method based on computational fluid mechanics, and belongs to the technical field of offshore wind power and mariculture. The method comprises the steps that a pneumatic module and a net cage module are simulated on the basis of a computational fluid mechanics method, the net cage module adopts a Darcy-Forchheimer equation, the influence of the movement speed of a floating type draught fan platform on a relative speed item in the Darcy-Forchheimer equation of a culture net cage is considered, a net cage load is applied to the floating type draught fan platform, and the floating type draught fan platform and the net cage module are connected in sequence. And bidirectional coupling simulation of the aquaculture net cage and the floating fan platform is realized. According to the invention, the influence of the net cage on the flow field characteristics of the floating fan platform is considered, and the dynamic response characteristics of the floating fan and the aquaculture net cage under the coupling action of wind, wave and flow can be accurately simulated by coupling the pneumatic thrust of the fan, the hydrodynamic load of the net cage and the motion response of mooring.

Description

Technical Field

[0001] The present invention belongs to the technical field of offshore wind power and seawater aquaculture, and relates to a floating wind turbine-aquaculture cage fusion structure coupling simulation method based on a computational fluid dynamics method. Background Art

[0002] As the global demand for clean energy grows, floating offshore wind turbines (FOWT) have become an important option for solving energy crises and environmental problems. However, the environmental load of floating platforms is complex, and the investment cost is higher than that of onshore wind turbines. Compared with offshore wind turbines, fish farming has a shorter payback period and higher economic benefits. It 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, initial progress has been made in the study of the fusion structure combining floating wind turbines and aquaculture cages. The research methods include model experiments and numerical simulations based on simplified theories, such as the Morrison equation and the screen element method. However, the numerical simulation methods of these simplified theories are limited in calculation accuracy under complex environmental conditions, and it is difficult to fully consider the influence of the structure on the flow field, so there are limitations. Based on this, the present invention provides an effective coupling simulation method of the fusion structure of floating wind turbines and aquaculture cages based on computational fluid dynamics methods. Summary of the invention

[0004] The present invention proposes a coupling simulation method of a floating wind turbine-aquaculture cage fusion structure based on a computational fluid dynamics method. Based on the coupling simulation method of a floating wind turbine-aquaculture cage fusion structure proposed by the invention, the load and motion response characteristics of the floating wind turbine and aquaculture cage fusion structure under the coupling of wind, wave and flow can be accurately simulated by coupling 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, and the influence of the cage structure on the motion response of the overall structure can be analyzed.

[0005] The technical solution adopted by the present invention is:

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

[0007] A floating wind turbine-aquaculture cage coupling simulation model was established based on the actual parameters of the floating wind turbine platform and aquaculture cages;

[0008] Based on the computational fluid dynamics method, the aerodynamic module simulation of the floating wind turbine-aquaculture cage fusion structure is carried out to obtain the total aerodynamic load on the floating wind turbine platform at the current time step;

[0009] Based on the computational fluid dynamics method, the cage module of the floating wind turbine-aquaculture cage fusion structure is simulated to obtain the cage load on the floating wind turbine platform at the current time step;

[0010] The mooring dynamic module is simulated 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, cage load and mooring load on the floating wind turbine platform at the current time step, the six-degree-of-freedom motion calculation of the floating wind turbine platform is performed to obtain motion information such as the speed, displacement and acceleration of the floating wind turbine platform; based on the motion information, the relative motion of the wind turbine blades, the relative motion of the aquaculture cages and the relative motion information at the fairlead holes are updated;

[0012] Based on the relative motion of the wind turbine blades, the relative motion of the aquaculture cages and the relative motion information at the fairlead holes at the current time step, the total aerodynamic load, cage load and mooring load on the floating wind turbine platform at the next time step are iteratively updated, and the relative motion of the wind turbine blades, the relative motion of the aquaculture cages and the relative motion at the fairlead holes at the next time step are further obtained.

[0013] Furthermore, the establishment of a floating wind turbine-aquaculture cage coupling simulation model includes:

[0014] Based on the actual shape and size of the floating wind turbine platform and the aquaculture cage, create the geometry file required to generate the mesh based on the simulated floating wind turbine platform and the aquaculture cage;

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

[0016] Pre-process the floating wind turbine platform, determine the grid motion setting file, establish the wind turbine rotor aerodynamic load constraints and cage load constraints, and set the aerodynamic load and cage load action points;

[0017] Pre-process the fan rotor, establish its fan load calculation source item file, and determine the calculation parameters such as blade speed, tip speed ratio, airfoil, and size;

[0018] Pre-process the aquaculture cages, establish the calculation source term file of the aquaculture cages, and determine the coefficients of the Darcy-Forchheimer equation of the aquaculture cages and the local coordinate system of the cages;

[0019] Carry out pre-processing on 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] Furthermore, the aerodynamic module simulation of the floating fan-aquaculture cage fusion structure is performed based on the computational fluid dynamics method to obtain the total aerodynamic load of the floating fan on the floating fan platform at the current time step. The specific process is as follows:

[0021] Calculate the aerodynamic load of the blade element under the influence of the floating wind turbine platform movement. Calculate the lift F on the blade element based on the blade parameter information and the floating wind turbine platform movement information. l_aero and resistance F d_aero :

[0022]

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

[0024] The lift force F based on the blade element l_aero and resistance F d_aero , calculate the total aerodynamic thrust and power of the fan blades and rotor.

[0025] Furthermore, the cage module simulation of the floating wind turbine-aquaculture cage fusion structure is performed based on the computational fluid dynamics method to obtain the cage load on the floating wind turbine platform at the current time step, that is, the lift and resistance on the cage grid unit. The specific method is as follows:

[0026] In order to consider the relative speed of cage movement, the 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 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 unit, respectively; u rel_net It means that the relative speed of the cage translation and rotation is considered, and the relative speed obtained by the translation and rotation is directly added; among them, the translation speed of the grid unit in the cage is directly obtained by the translation speed of the floating wind turbine platform; the relative speed of the cage caused by the rotation of the floating wind turbine platform is calculated by the following formula:

[0029]

[0030] in, represents the relative velocity vector of the grid cell 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;

[0031] As the cage moves continuously, the Darcy-Forchheimer coefficient matrices D and C change in the global coordinate system. The six-degree-of-freedom motion information of the floating wind turbine platform is used to update the Darcy-Forchheimer coefficient in the global coordinate system according to the rotation matrix R:

[0032]

[0033] Among them, R T is the transposed matrix of matrix R;

[0034] According to the updated coefficient matrix, the lift F on the cage grid unit is calculated. d and resistance F t :

[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] Furthermore, the mooring power module simulation based on the lumped mass method is performed to obtain the mooring load on the floating wind turbine platform at the current time step, including:

[0038] Divide the anchor chain into k+1 concentrated mass points according to the user-defined number of segments;

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

[0040]

[0041] Among them, m i represents the mass of the i-th mass point; I is the unit matrix; a i is the additional mass of the ith mass point; is the acceleration of the ith mass point; T and C are the anchor chain tension and internal damping force, respectively, and the subscript ±1 / 2 indicates adjacent mass points; W i Indicates buoyancy; B i is the seabed contact force; D ni and D ti are the normal and tangential drag forces, respectively;

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

[0043] Furthermore, based on the total aerodynamic load, cage load and mooring load received 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 performed to obtain motion information such as the speed, displacement and acceleration of the floating wind turbine platform; the relative motion of the wind turbine blades, the relative motion of the aquaculture cages and the relative motion of the fairlead holes are updated based on the motion information; the specific process is:

[0044] According to the total aerodynamic thrust, cage lift and drag, and anchor chain tension on the floating wind turbine platform at the current time step, the velocity, displacement, acceleration and other motion information of the floating wind turbine platform are calculated and saved in the corresponding dictionary file of the motion information;

[0045] Use the mesh solver to solve the displacements of all mesh nodes in the computational domain;

[0046] The speed, displacement and acceleration information of the floating wind turbine platform are read in the pneumatic module, and the position and relative motion of each blade segment are calculated. The speed, displacement, acceleration and orientation information of the floating wind turbine platform are read in the cage module, and the relative motion of the grid points at the cage is calculated. The speed, displacement and acceleration information of the floating wind turbine platform are read in the mooring power module, and the relative motion at the fairlead hole is calculated.

[0047] Furthermore, based on the relative motion of the wind turbine blades, the relative motion of the aquaculture cages, and the relative motion information at the fairlead holes at the current time step, the total aerodynamic load, cage load, and mooring load on the floating wind turbine platform at the next time step are iteratively updated, and the relative motion of the wind turbine blades, the relative motion of the aquaculture cages, and the relative motion at the fairlead holes at the next time step are further obtained, specifically:

[0048] Based on the relative motion of the wind turbine blades, the relative motion of the aquaculture cages and the relative motion at the fairlead hole at the current time step, the relative speed of the wind turbine blades, the relative speed of the aquaculture cages and the relative speed at the fairlead hole are substituted into the pneumatic module, the cage module and the mooring power module respectively, and the total aerodynamic load, the cage load and the mooring load on the floating wind turbine platform are iteratively updated to obtain the motion information such as the speed, displacement and acceleration of the floating wind turbine platform, and then the relative motion of the wind turbine blades, the relative motion of the aquaculture cages and the relative motion at the fairlead hole are further obtained based on the motion information.

[0049] Beneficial effects of the present invention:

[0050] (1) The present invention is based on computational fluid dynamics methods, takes into account the viscosity of the fluid to accurately analyze the flow field changes, and fully considers the coupling effects between the wind turbine aerodynamic load, cage load, mooring load and platform hydrodynamic load through the solver to establish an accurate overall coupling model of floating wind turbines and aquaculture cages.

[0051] (2) The present invention uses the Darcy-Forchheimer equation to accurately calculate the load changes of the cage structure under complex environmental loads, and can fully consider the impact of the cage structure on the flow field, thereby further affecting the dynamic response changes of the overall structure.

[0052] (3) The present invention can be used to simulate floating wind turbine-aquaculture cage fusion structures of different wind turbine forms, cage forms, and mooring forms according to the initial geometric shape. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is a simulation process of the floating wind turbine-aquaculture cage fusion structure.

[0054] Figure 2 This is a sketch of the floating wind turbine-aquaculture cage fusion structure.

[0055] Figure 3 It is a schematic diagram of the longitudinal response of the fusion structure.

[0056] Figure 4 It is a schematic diagram of the heave response of the fusion structure.

[0057] Figure 5 It is a schematic diagram of the pitch response of the fusion structure.

[0058] Figure 6 It is a schematic diagram of the horizontal load on the aquaculture cage.

[0059] Figure 7 It is a schematic diagram of the vertical load on the aquaculture cage.

[0060] Figure 8 This is a diagram showing the effect of the cage structure on the flow field, where (a) is without the cage and (b) is with the cage. DETAILED DESCRIPTION

[0061] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. The embodiments of the present invention are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0062] like Figure 1 As shown, an embodiment of the present invention provides a coupling simulation method of a floating fan-aquaculture cage fusion structure based on a computational fluid dynamics method, comprising the following steps:

[0063] S1. Taking the IEA15MW floating wind turbine as an example, establish Figure 2The floating wind turbine-aquaculture cage coupling simulation model shown in the figure (①~④ represent the four nets of the cage), the calculation conditions are wind speed 11.4m / s, regular wave height 7.58m, wave period 12.1s; the specific process is as follows:

[0064] S1.1. Based on the actual shape and size of the floating wind turbine platform and the aquaculture cage, create the geometry files required to generate the mesh of the IEA15MW floating wind turbine platform and the aquaculture cage;

[0065] S1.2. Determine the computational domain in the OpenFOAM environment, divide the specific computational grid using the geometry file in S1.1, and generate specific refined grids for the floating wind turbine platform, wind turbine rotor, and aquaculture cages according to the computational requirements;

[0066] S1.3. Pre-process the floating wind turbine platform, determine the grid motion setting file, establish the wind turbine rotor aerodynamic load constraints and cage load constraints, and set the aerodynamic load and cage load action points;

[0067] S1.4. Pre-process the fan rotor, establish its fan load calculation source item file, and determine the calculation parameters such as blade speed, tip speed ratio, airfoil, and size;

[0068] S1.5. Pre-process the aquaculture cages, establish the calculation source term file of the aquaculture cages, and determine the coefficients of the Darcy-Forchheimer equation of the aquaculture cages and the local coordinate system of the cages;

[0069] S1.6. 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.

[0070] S2. Based on the computational fluid dynamics method, the aerodynamic module simulation of the floating fan-aquaculture cage fusion structure is carried out to obtain the total aerodynamic load of the floating fan on the floating fan platform at the current time step; the specific process is:

[0071] S2.1. Calculate the aerodynamic load of the blade element under the influence of the floating wind turbine platform movement. Calculate the lift F on the blade element based on the blade parameter information and the floating wind turbine platform movement information. l_aero and resistance F d_aero :

[0072]

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

[0074] S2.2. Lift F of blade element obtained based on S2.1 l_aero and resistance F d_aero , calculate the total aerodynamic thrust and power of the fan blades and rotor.

[0075] S3. Based on the computational fluid dynamics method, the cage module of the floating wind turbine-aquaculture cage fusion structure is simulated to obtain the cage load on the floating wind turbine platform at the current time step. The specific process is as follows:

[0076] S3.1. In order to consider the relative speed of cage movement, the cage load calculation method based on the 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 unit, respectively; u rel_net It indicates the relative speed of the cage's translational and rotational motions, which is obtained by directly adding the relative speeds obtained by the translational and rotational motions. The translational speed of the grid unit in the cage is directly obtained by the translational speed of the floating wind turbine platform, and the relative speed of the cage caused by the rotational motion of the floating wind turbine platform is calculated using the following formula:

[0079]

[0080] in, represents the relative velocity vector of the grid cell 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. As the cage moves continuously, the Darcy-Forchheimer coefficient matrices D and C change in the global coordinate system. Using the six-degree-of-freedom motion information of the floating wind turbine platform, the Darcy-Forchheimer coefficients in the global coordinate system are updated according to the rotation matrix R:

[0082]

[0083] Among them, R T is the transposed matrix of matrix R;

[0084] S3.3, based on the updated coefficient matrix calculated in S3.2, the lift F on the cage grid unit d and resistance F tCalculate according to the following formula:

[0085]

[0086] Here, V is the volume of the unit cell on the mesh, and the subscripts n and t denote the normal and tangential components of the mesh plane, respectively.

[0087] The cage load calculation results in this embodiment are as follows: Figures 6-7 The calculation results of the influence of the cage structure on the flow field are shown in Figure 8 As shown, the presence of the cage significantly reduced the flow rate.

[0088] S4. Based on the lumped mass method, the mooring dynamic module is simulated to obtain the mooring load on the floating wind turbine platform at the current time step, which is:

[0089] S4.1. Divide the anchor chain into k+1 concentrated mass points according to the user-defined number of segments;

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

[0091]

[0092] Among them, m i represents the mass of the i-th mass point; I is the unit matrix; a i is the additional mass of the ith mass point; is the acceleration of the ith mass point; T and C are the anchor chain tension and internal damping force, respectively, and the subscript ±1 / 2 indicates the adjacent mass point; W i Indicates 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 hole is calculated according to formula (8), which is the mooring load on the floating wind turbine platform.

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

[0095] S5.1. Calculate the velocity, displacement, acceleration and other motion information of the floating wind turbine according to the total aerodynamic thrust, cage lift and drag, and anchor chain tension of the floating wind turbine platform calculated in S2, S3, and S4, and save them in the corresponding dictionary file of motion information. In this embodiment, the motion response result of the floating wind turbine is calculated as follows: Figures 3 to 5 As shown in the figure, the existence of the cage structure increases the mean longitudinal motion of the floating wind turbine, reduces the mean pitch motion, and has almost no effect on the heave motion.

[0096] S5.2. Use the mesh solver to solve the displacements of all mesh nodes in the computational domain;

[0097] S5.3. The speed, displacement and acceleration information of the floating wind turbine platform are read in the pneumatic module, and the position and relative motion of each blade segment are calculated; the speed, displacement, acceleration and orientation information of the floating wind turbine platform are read in the cage module, and the relative motion of the grid points at the cage is calculated; the speed, displacement and acceleration information of the floating wind turbine platform are read in the mooring power module, and the relative motion at the fairlead hole is calculated; the relative motion includes information such as displacement and relative speed.

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

[0099] The above is a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A floating fan-aquaculture cage coupling simulation method based on computational fluid dynamics, characterized in that: include: A floating wind turbine-aquaculture cage coupling simulation model was established based on the actual parameters of the floating wind turbine platform and aquaculture cages; Based on the computational fluid dynamics method, the aerodynamic module simulation of the floating wind turbine-aquaculture cage fusion structure is carried out to obtain the total aerodynamic load on the floating wind turbine platform at the current time step; Based on the computational fluid dynamics method, the cage module of the floating wind turbine-aquaculture cage fusion structure is simulated to obtain the cage load on the floating wind turbine platform at the current time step; The mooring dynamic module is simulated based on the lumped mass method to obtain the mooring load on the floating wind turbine platform at the current time step; Based on the total aerodynamic load, cage load and mooring load on the floating wind turbine platform at the current time step, the six-degree-of-freedom motion calculation of the floating wind turbine platform is performed to obtain the motion information of the floating wind turbine platform including velocity, displacement and acceleration; based on the motion information, the relative motion information of the wind turbine blades, the relative motion of the aquaculture cages and the relative motion information at the fairlead holes are updated; Based on the relative motion of the wind turbine blades, the relative motion of the aquaculture cages and the relative motion information at the fairlead holes at the current time step, the total aerodynamic load, cage load and mooring load on the floating wind turbine platform at the next time step are iteratively updated, and the relative motion of the wind turbine blades, the relative motion of the aquaculture cages and the relative motion at the fairlead holes at the next time step are further obtained.

2. The floating wind turbine-aquaculture cage coupling simulation method based on computational fluid dynamics according to claim 1 is characterized in that: The establishment of the floating fan-aquaculture cage coupling simulation model comprises: Based on the actual shape and size of the floating wind turbine platform and the aquaculture cage, create the geometry file required to generate the mesh based on the simulated floating wind turbine platform and the aquaculture cage; Determine the computational domain in the OpenFOAM environment, divide a specific computational grid using the geometry file, and generate specific refined grids for the floating wind turbine platform, the wind turbine rotor, and the aquaculture cage according to computational requirements; Pre-process the floating wind turbine platform, determine the grid motion setting file, establish the wind turbine rotor aerodynamic load constraints and cage load constraints, and set the aerodynamic load and cage load action points; Pre-process the fan rotor, establish its fan load calculation source item file, and determine the blade calculation parameters; Pre-process the aquaculture cages, establish the calculation source term file of the aquaculture cages, and determine the coefficients of the Darcy-Forchheimer equation of the aquaculture cages and the local coordinate system of the cages; Carry out pre-processing on the mooring system, establish the mooring system calculation input file, and determine the anchor chain calculation parameters.

3. The floating wind turbine-aquaculture cage coupling simulation method based on computational fluid dynamics according to claim 1 or 2, characterized in that: The calculation process of the total aerodynamic load on the floating wind turbine platform at the current time step is as follows: Calculate the aerodynamic load of the blade element under the influence of the floating wind turbine platform movement. Calculate the lift F on the blade element based on the blade parameter information and the floating wind turbine platform movement information. l_aero and resistance F d_aero : Where ρ represents the fluid density, c represents the chord length, dr is the length of the airfoil unit on the blade, and U rel_aero is the relative speed of the blades under the influence of the movement of the floating wind turbine platform and the rotation of the rotor, C l (α) and C d (α) are the lift coefficient and drag coefficient of the corresponding airfoil; The lift force F based on the blade element l_aero and resistance F d_aero , calculate the total aerodynamic thrust and power of the fan blades and rotor.

4. The floating wind turbine-aquaculture cage coupling simulation method based on computational fluid dynamics according to claim 3 is characterized in that: The calculation method of the cage load on the floating wind turbine platform at the current time step is as follows: In order to consider the relative speed of cage movement, the cage load calculation method based on the Darcy-Forchheimer equation is as follows: 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 unit, respectively; u rel_net represents the relative speed considering the translational and rotational motions of the cage; As the cage moves continuously, the Darcy-Forchheimer coefficient matrices D and C change in the global coordinate system. The six-degree-of-freedom motion information of the floating wind turbine platform is used to update the Darcy-Forchheimer coefficient in the global coordinate system according to the rotation matrix R: Among them, R T is the transposed matrix of matrix R; According to the updated coefficient matrix, the lift F on the cage grid unit is calculated. d and resistance F t : 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.

5. The floating wind turbine-aquaculture cage coupling simulation method based on computational fluid dynamics according to claim 4 is characterized in that: The u rel_net The relative speed obtained by the translational motion and the rotational motion is directly added; among them, the translational motion speed of the grid unit in the cage is directly obtained from the translational motion speed of the floating wind turbine platform; the relative speed calculation formula of the cage caused by the rotational motion of the floating wind turbine platform is: in, represents the relative velocity vector of the grid cells 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.

6. The floating wind turbine-aquaculture cage coupling simulation method based on computational fluid dynamics according to claim 5 is characterized in that: The calculation method of the mooring load on the floating wind turbine platform at the current time step includes: Divide the anchor chain into k+1 concentrated mass points according to the user-defined number of segments; The Morison equation is used to solve the anchor chain tension T at the fairlead hole. The equation is as follows: Among them, m i represents the mass of the i-th mass point; I is the unit matrix; a i is the additional mass of the ith mass point; is the acceleration of the ith mass point; T and C are the anchor chain tension and internal damping force, respectively, and the subscript ±1 / 2 indicates adjacent mass points; W i Indicates buoyancy; B i is the seabed contact force; D ni and D ti are the normal and tangential drag forces, respectively.

7. The floating wind turbine-aquaculture cage coupling simulation method based on computational fluid dynamics according to claim 6 is characterized in that: The specific process of updating the relative movement of the fan blades, the relative movement of the aquaculture cages and the relative movement of the cable guide holes is as follows: According to the total aerodynamic thrust, cage lift and drag, and anchor chain 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 in the corresponding dictionary file of the motion information; Use the mesh solver to solve the displacements of all mesh nodes in the computational domain; The speed, displacement and acceleration information of the floating wind turbine platform are read in the pneumatic module to calculate the position and relative motion of each blade segment; the speed, displacement, acceleration and orientation information of the floating wind turbine platform are read in the cage module to calculate the relative motion of the grid points at the cage; The velocity, displacement and acceleration information of the floating wind turbine platform are read in the mooring power module, and the relative motion at the fairlead hole is calculated.

8. The floating wind turbine-aquaculture cage coupling simulation method based on computational fluid dynamics according to claim 1, characterized in that: The iterative update of the total aerodynamic load, cage load and mooring load on the floating wind turbine platform in the next time step, and the relative motion of the wind turbine blades, the relative motion of the aquaculture cages and the relative motion of the fairlead holes in the next time step are specifically as follows: Based on the relative motion of the wind turbine blades, the relative motion of the aquaculture cages and the relative motion at the fairlead hole at the current time step, the relative speed of the wind turbine blades, the relative speed of the aquaculture cages and the relative speed at the fairlead hole are substituted into the pneumatic module, the cage module and the mooring power module respectively, and the total aerodynamic load, the cage load and the mooring load on the floating wind turbine platform are iteratively updated to obtain the motion information of the floating wind turbine platform, and then the relative motion of the wind turbine blades, the relative motion of the aquaculture cages and the relative motion at the fairlead hole are further obtained based on the motion information.

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