A floating multi-vertical-axis wind turbine and a fully coupled simulation method and device using MOST-DMS

Abstract

This invention discloses a floating multi-vertical-axis wind turbine and a fully coupled simulation method and apparatus using MOST-DMS. It belongs to the field of offshore floating wind power technology. The turbine includes a floating foundation system, five sets of vertically stacked, counter-rotating dual-rotor vertical-axis wind turbines, and a 5×2 catenary mooring system. Each turbine has a coaxial counter-rotating structure with upper and lower H-shaped rotors, with an initial phase angle difference of 90° between the upper and lower rotors to suppress torque pulsation. The five turbines are arranged in a ring array, with the bottom rotors of adjacent columns rotating in opposite directions to counteract the overall aerodynamic torque. The generator is positioned low inside the columns to lower the center of gravity. The simulation method integrates a dual-disk multi-flow pipe (DMS) aerodynamic module developed based on Fortran into the open-source MOST framework. Through a multi-rotor coupling interface, it achieves time-domain collaborative solving of multiple fields including aerodynamics, hydrodynamics, structure, and mooring, realizing efficient fully coupled time-domain simulation of the floating multi-counterrotating dual-rotor vertical-axis wind turbine. This invention has high wind resistance and is suitable for wind power development in nearshore and deep-sea areas.

Description

Technical Field

[0001] This invention relates to the field of offshore floating wind power generation technology, specifically to a floating multi-vertical-axis wind turbine suitable for nearshore and deep-sea areas, and a fully coupled simulation method and device based on the MOST framework integrated dual-disk multi-stream tube (DMS) method. Background Technology

[0002] With near-shore wind power resources nearing saturation, deep-sea wind power has become an important direction for global new energy development. However, deep-sea areas frequently experience extreme sea conditions such as typhoons and giant waves, placing extremely high demands on the structural strength, anti-overturning capability, and operational safety of floating wind turbines. Existing mainstream floating horizontal axis wind turbines, due to their long blades, high center of gravity, and complex yaw systems, are prone to major accidents such as blade breakage and tower overturning under typhoon conditions, resulting in high operation and maintenance costs and making it difficult to meet the engineering application needs of typhoon-prone sea areas.

[0003] Vertical axis wind turbines (VAWTs) possess natural potential in typhoon-resistant scenarios due to their advantages such as eliminating the need for a yaw system, fixed blade ends, robust structure, and low center of gravity. However, traditional single-rotor VAWTs suffer from large aerodynamic torque pulsation and poor operational stability. Existing multi-vertical axis wind turbines often employ simple parallel arrangements, failing to fully utilize the aerodynamic coupling and load cancellation effects between rotors, resulting in insufficient overall anti-overturning and anti-torsional capabilities. While counter-rotating dual-rotor VAWTs (CR-VAWTs) can partially offset the aerodynamic torque of a single rotor, existing designs often suffer from unreasonable rotor phase matching and low aerodynamic efficiency.

[0004] Floating multi-vertical-axis wind turbines are strongly coupled dynamic systems integrating aerodynamics, hydrodynamics, structure, and mooring. Their simulation analysis relies on high-precision, fully coupled numerical tools. Currently, mature software such as OpenFAST and OrcaFlex are available for floating horizontal-axis wind turbines, but simulation tools for floating multi-rotor dual-rotor vertical-axis wind turbines are extremely scarce. While the open-source tool MOST (Matlab for Offshore Simulation Tool) offers advantages such as high efficiency and ease of secondary development, its built-in aerodynamic model only supports simplified lookup table methods and cannot accurately simulate the complex aerodynamic characteristics and inter-rotor interference effects of multi-rotor dual-rotor systems. Traditional CFD methods, although highly accurate, have extremely low computational efficiency, making it difficult to support batch simulations of parametric sweeps and extreme conditions.

[0005] In terms of mooring systems, traditional 3-point or 4-point catenary mooring arrangements have problems such as insufficient torsional stiffness and uneven distribution of mooring cable tension under extreme loads for multi-rotor array floating foundations, and cannot effectively resist the combined loads of strong winds and giant waves brought by typhoons.

[0006] In summary, improving the typhoon resistance and operational safety of floating wind turbines in extreme sea conditions, while developing a highly efficient, fully coupled simulation tool suitable for floating multi-rotor dual-axis wind turbines, are key technical issues that urgently need to be addressed in this field. Summary of the Invention

[0007] The purpose of this invention is to address the aforementioned deficiencies in the prior art by providing a floating multi-vertical-axis wind turbine and a fully coupled simulation method and device using MOST-DMS. Through structural innovation and breakthroughs in simulation technology, this invention provides support for the engineering application of deep-sea wind power equipment.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A floating multi-vertical-axis wind turbine unit includes a floating foundation system, five sets of vertically stacked counter-rotating dual-rotor vertical-axis wind turbine systems, and a 5×2 catenary mooring system;

[0010] The floating foundation system adopts a five-column symmetrical star-shaped layout, including one pontoon and five independent cylindrical columns evenly distributed around the pontoon. The bottom of each column is rigidly connected to the central pontoon, and the pontoon is equipped with an adjustable ballast water tank.

[0011] The five sets of vertically stacked counter-rotating dual-rotor vertical axis wind turbine systems are respectively installed on the top of five independent columns. Each set includes an upper H-shaped vertical axis rotor and a lower H-shaped vertical axis rotor stacked vertically. The two rotors share the same vertical main shaft and rotate in opposite directions. The initial phase angle difference between the upper and lower rotors is set to 90°. The five sets of wind turbines are evenly arranged in a ring array. The bottom rotors on adjacent columns adopt a counter-rotating design. The generators of each wind turbine are arranged inside the corresponding column near the water surface.

[0012] The 5×2 catenary mooring system comprises 5 sets of double catenary mooring units with a total of 10 mooring cables. Each post has a cable guide installed on the lower part of its outer wall. One end of each mooring cable is connected to the corresponding post through the cable guide, and the other end is fixed to the seabed by a high holding power anchor. The 10 mooring cables are evenly radially distributed in the horizontal projection plane.

[0013] Preferably, the five independent columns are evenly distributed around the perimeter of the floating box at equal angular intervals of 72°, forming a regular pentagonal symmetrical array; each column independently supports a set of counter-rotating dual-rotor vertical axis fans, and the axes of each column are parallel to each other and consistent with the vertical direction.

[0014] Preferably, the upper H-shaped vertical shaft rotor and the lower H-shaped vertical shaft rotor are stacked in the vertical direction and share the same vertical main shaft. When the upper rotor rotates clockwise, the lower rotor rotates counterclockwise. The 90° initial phase angle difference causes the blades of the two rotors to be staggered in the azimuth direction, so as to balance the aerodynamic torque output in each azimuth angle and reduce the amplitude of the combined torque pulsation.

[0015] Preferably, in the five sets of vertically stacked counter-rotating dual-rotor vertical axis fans, the rotation directions of the bottom rotors on adjacent columns are opposite to each other, so as to counteract the overall aerodynamic torque and overturning moment of the unit and achieve a symmetrical and balanced distribution of aerodynamic loads in the horizontal plane of the unit.

[0016] Preferably, in the 5×2 catenary mooring system, the 5 sets of double catenary mooring units correspond to 5 independent columns, and the 2 mooring cables of each set of double catenary mooring units are symmetrically arranged with the column axis as the axis of symmetry; the 10 mooring cables are evenly distributed in the horizontal projection plane, with the angle between adjacent mooring cables being 20°. The mooring cables are composed of chain segments, polyester ropes and high holding power anchors, and the nonlinear dynamic characteristics of the catenary are simulated by the lumped mass method.

[0017] Preferably, the ballast tank is equipped with a real-time water volume adjustment and control system, which can adjust the ballast water volume of each column in real time according to the wind and wave load and the attitude of the unit, so as to actively compensate for the longitudinal and transverse tilt of the floating foundation under extreme sea conditions.

[0018] A fully coupled MOST-DMS simulation method for floating multi-vertical-axis wind turbines, wherein the floating multi-vertical-axis wind turbine includes a floating foundation system, multiple sets of counter-rotating dual-rotor vertical-axis wind turbine systems and a catenary mooring system, the method includes the following steps: based on the open-source MOST framework, a dual-disk multi-flow tube method is integrated to construct a time-domain simulation program that realizes the coordination of aerodynamics, hydrodynamics, structure and mooring multi-fields, the program includes a MOST basic framework module, a DMS dual-disk multi-flow tube aerodynamic module and a multi-rotor coupling interface module;

[0019] The MOST basic framework module retains the original core functions of MOST, including hydrodynamic calculation, mooring system simulation and time-domain solution. It supports frequency-domain to time-domain hydrodynamic load calculation through Cummins equations and uses the lumped mass method to simulate the nonlinear dynamics of catenary mooring.

[0020] The DMS dual-disc multi-flow tube aerodynamic module is developed based on the Fortran language and integrated into the MOST framework. It adopts the dual-disc multi-flow tube theory, iteratively solves the axial induction factor for the upstream and downstream disks of each flow tube unit, calculates the instantaneous aerodynamic forces and torques of multiple sets of counter-rotating dual rotors, and supports the simulation of wake interference effects between adjacent rotors.

[0021] The multi-rotor coupling interface module is developed based on MATLAB / Simulink and realizes real-time bidirectional data interaction and multi-threaded parallel calculation of the instantaneous motion state of the floating foundation and the aerodynamic loads of the five sets of wind turbines between the DMS aerodynamic module and the MOST basic frame.

[0022] Preferably, the DMS dual-disc multi-flow tube pneumatic module performs aerodynamic calculations according to the following steps:

[0023] The flow field of the vertical axis wind turbine is divided into several independent flow tube units along the azimuth angle θ, and the wind turbine is divided into upstream disk and downstream disk with the geometric center of the wind turbine as the boundary.

[0024] Initialize the axial induction factor on the upstream and downstream disks of each flow tube unit. and ;

[0025] Calculate the effective inflow velocity of the upstream plate. Calculate the effective inflow velocity at the downstream plate. ,in For free flow velocity;

[0026] Calculate the blade tangential velocity based on the azimuth angle θ, the rotor radius R, and the rotational angular velocity ω. The relative velocity was obtained by synthesis. , and airflow deflection angle , ;

[0027] From local angle of attack Determine the lift coefficient and drag coefficient Then the normal force coefficient can be obtained. and tangential force coefficient ;

[0028] The upstream and downstream axial induction factors are iteratively updated until the iterative change is less than the allowable deviation, thus obtaining the converged aerodynamic load parameters.

[0029] Preferably, the fully coupled simulation is performed according to the following procedure:

[0030] Preprocessing stage: Use hydrodynamic analysis software to calculate the hydrodynamic coefficients of the floating foundation, generate MOST-compatible input files, and input the wind turbine geometric parameters, mooring system parameters and environmental condition parameters;

[0031] Initialization phase: The MOST frame loads hydrodynamic coefficients and mooring model, and the DMS module initializes the multi-rotor aerodynamic parameters;

[0032] Temporal coupling solution stage: Within each time step, the MOST module calculates the floating foundation motion and hydrodynamic and mooring loads, while the DMS module calculates the multi-rotor aerodynamic loads. Data interaction and load superposition are completed through the multi-rotor coupling interface, and the floating foundation motion state is updated.

[0033] Post-processing stage: Output the six-degree-of-freedom motion response of the floating foundation, the tension of the mooring cables, the aerodynamic load of the wind turbine, and the power generation, and complete the load statistics and risk assessment under extreme conditions.

[0034] An apparatus for implementing the MOST-DMS fully coupled simulation method includes a processor and a memory, wherein the memory stores a computer program, and the computer program, when executed by the processor, implements the following functional modules:

[0035] Hydrodynamic calculation module: Based on the Cummins equation, the imported frequency domain potential hydrodynamic coefficients are converted from frequency domain to time domain. At the same time, the Morison equation is used to calculate the viscous forces of small-scale components such as columns and struts.

[0036] DMS aerodynamic calculation module: Based on the Fortran language, the dual-disc multi-flow tube algorithm is implemented to perform multi-threaded parallel aerodynamic load calculations on five sets of counter-rotating dual-rotor vertical axis fans.

[0037] Mooring Dynamics Module: Employs the lumped mass method to simulate the nonlinear dynamic characteristics of 10 catenary mooring cables and supports parallel computation of multiple mooring cables;

[0038] Coupled solution module: Based on the Simulink / Simscape Multibody platform, it realizes the time-domain coupled solution of rigid body six-degree-of-freedom motion and multi-field loads; the coupled solution module realizes real-time bidirectional data interaction with the DMS aerodynamic calculation module through the multi-rotor coupling interface. In each time step, it receives hydrodynamic loads, aerodynamic loads, and mooring loads and completes the load superposition. At the same time, it feeds back the instantaneous displacement, velocity and acceleration of the floating foundation to the DMS aerodynamic calculation module and outputs the fully coupled dynamic response of the unit.

[0039] The beneficial effects of this invention are:

[0040] (1) Significantly improved wind resistance. The combination of the five-column symmetrical layout and the 5×2 catenary mooring system significantly improves the overall torsional stiffness and overturning stiffness, effectively avoiding mooring failure under extreme loads; the low-positioned generator and the robust structural characteristics of the vertical axis wind turbine lower the overall center of gravity of the unit, significantly improving the wind resistance level.

[0041] (2) Operational stability is significantly improved. The 90° initial phase difference design between the upper and lower rotors reduces aerodynamic torque pulsation and significantly reduces unit vibration and fatigue load; the counter-rotating dual rotor structure cancels out the single rotor reverse torque and reduces the torsional requirements on the floating foundation.

[0042] (3) Breakthrough in simulation technology. The MOST-DMS program fills the technical gap in efficient and fully coupled simulation of floating multi-rotor dual-axis wind turbines. Its computational efficiency is significantly better than that of the CFD method. It can support parameterized sweep and batch simulation under extreme conditions, providing an efficient tool for the engineering design of the unit.

[0043] (4) Excellent economic efficiency. The shared floating foundation and mooring system effectively reduces the cost per kilowatt, and the excellent typhoon resistance greatly reduces operation and maintenance costs and downtime losses, thereby improving the power generation revenue throughout the entire life cycle. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the overall layout of the floating multi-vertical-axis wind turbine in this invention;

[0045] Figure 2 This is a schematic diagram of the structure of a single-unit vertically stacked counter-rotating dual-rotor vertical axis fan in this invention;

[0046] Figure 3 This is a block diagram of the MOST-DMS fully coupled simulation program architecture;

[0047] In the diagram: 1—Floating box; 2—Dual rotor vertical axis fan; 3—Column; 4—Mooring cable; 5—Main shaft; 6—Blade; 7—Support; 8—Upper H-type vertical axis rotor; 9—Lower H-type vertical axis rotor. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0049] The first aspect of the present invention provides a floating multi-vertical-axis wind turbine, including a floating foundation system, five sets of vertically stacked counter-rotating dual-rotor vertical-axis wind turbine systems and a 5×2 catenary mooring system.

[0050] The floating foundation system adopts a five-column symmetrical star-shaped layout, comprising one pontoon and five independent cylindrical columns evenly distributed around the pontoon. The five columns are evenly distributed around the pontoon at 72° angular intervals, forming a regular pentagonal symmetrical array. The bottom of each column is rigidly connected to the pontoon, which can effectively distribute the load and lower the overall center of gravity of the unit. The pontoon is equipped with a ballast water tank with real-time adjustable water volume and a real-time water volume adjustment control system, which can adjust the ballast water volume in real time according to wind and wave loads and unit attitude to actively compensate for the longitudinal and transverse tilt of the floating foundation under extreme sea conditions, further improving the stability of the unit under extreme operating conditions.

[0051] The five sets of vertically stacked counter-rotating dual-rotor vertical axis wind turbine systems are each vertically stacked counter-rotating dual-rotor structures (CR-VAWTs), including an upper H-type vertical axis rotor and a lower H-type vertical axis rotor. The two rotors share the same vertical main shaft, are arranged in an axially staggered manner and rotate in opposite directions, with the upper rotor rotating clockwise and the lower rotor rotating counterclockwise. The initial phase angle difference between the upper and lower rotors is set to 90°, so that the blades of the two rotors are staggered in the azimuth direction, thereby balancing the aerodynamic torque output in each azimuth angle and significantly reducing the amplitude of the combined torque pulsation. The five sets of wind turbines are evenly arranged in a ring array on the top of five independent columns. The bottom rotors on adjacent columns adopt a counter-rotating design to counteract the overall aerodynamic torque and overturning moment of the unit. The generators of all wind turbines are arranged inside the corresponding columns near the water surface, which lowers the center of gravity of the whole unit, improves the operational stability, and facilitates operation and maintenance.

[0052] The 5×2 catenary mooring system comprises five sets of double catenary mooring units, each corresponding to an independent column, with a total of 10 mooring cables. A guide is installed on the lower middle part of the outer wall of each column. One end of the mooring cable is connected to the column via the guide, and the other end is fixed to the seabed by a high-holding-power anchor. The 10 mooring cables are radially and evenly distributed around the floating foundation, with adjacent mooring cables forming an angle of 20°. The mooring cables are composed of chain segments, polyester ropes, and high-holding-power anchors. Compared with traditional 3-point or 4-point mooring schemes, the 5×2 mooring scheme significantly improves the overall torsional stiffness and anti-overturning capacity of the system, while ensuring uniform tension distribution among the mooring cables under extreme loads.

[0053] The second aspect of this invention provides a MOST-DMS fully coupled simulation method for floating multi-vertical-axis wind turbines, wherein the floating multi-vertical-axis wind turbine includes a floating foundation system, multiple sets of counter-rotating dual-rotor vertical-axis wind turbine systems, and a catenary mooring system. The method includes the following steps: based on the open-source MOST framework, an integrated dual-disk multi-flow tube method (DMS) is used to construct an efficient time-domain simulation program that realizes multi-field coordination of "aerodynamics-hydraulics-structure-mooring". The program includes a MOST basic framework module, a DMS dual-disk multi-flow tube aerodynamic module, and a multi-rotor coupling interface module.

[0054] The MOST basic framework module retains the core functions of MOST's original hydrodynamic calculation, mooring system simulation, and time-domain solution: the hydrodynamic module supports importing frequency domain potential flow results from software such as AQWA and WAMIT, and realizes frequency-domain to time-domain hydrodynamic load calculation through the Cummins equation, while also supporting the calculation of viscous forces of small-scale components such as columns and struts using the Morison equation; the mooring module uses the lumped mass method to simulate the nonlinear dynamic characteristics of catenary mooring and supports parallel calculation of multiple mooring cables; the time-domain solver is based on Simulink / Simscape Multibody to realize the coupled solution of rigid body six-degree-of-freedom motion and multiple loads.

[0055] The DMS dual-disc multi-flow tube aerodynamic module is developed based on the Fortran language and integrated into the MOST framework. It adopts the dual-disc multi-flow tube theory, considers the aerodynamic interference and wake effect between the upper and lower rotors, and accurately calculates the instantaneous aerodynamic force and torque of a single counter-rotating dual rotor. It supports aerodynamic coupling calculation of multi-rotor arrays and can simulate the wake interference effect between adjacent rotors. It has a built-in phase angle adjustable module to support aerodynamic performance simulation under different initial phase differences.

[0056] The multi-rotor coupling interface module is developed based on MATLAB / Simulink and realizes real-time data interaction between the DMS aerodynamic module and the MOST basic framework: the interface transmits the instantaneous displacement, velocity and acceleration information of the floating foundation to the DMS aerodynamic module in real time; the instantaneous aerodynamic forces and torques of the five sets of wind turbines calculated by the DMS module are fed back to the time domain solver of MOST through the interface; it supports multi-threaded parallel computing and can process the aerodynamic loads of five sets of counter-rotating dual rotors simultaneously.

[0057] The fully coupled simulation process includes four stages: preprocessing, initialization, temporal coupled solution, and postprocessing.

[0058] A third aspect of the present invention provides an apparatus for implementing the above-described MOST-DMS fully coupled simulation method, comprising a processor and a memory, wherein the memory stores a computer program, which, when executed by the processor, implements all the functions of the hydrodynamic calculation module, the DMS aerodynamic calculation module, the mooring dynamics module, and the coupled solution module.

[0059] The following examples are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0060] Example 1: Floating Multi-Vertical Axis Wind Turbine

[0061] like Figure 1 As shown, the floating multi-vertical-axis wind turbine in this embodiment includes a floating foundation system, five sets of vertically stacked counter-rotating dual-rotor vertical-axis wind turbine systems, and a 5×2 catenary mooring system.

[0062] The specific structure of the floating foundation system is as follows:

[0063] The floating foundation system adopts a five-column symmetrical star-shaped layout, and the pontoons are large, sealed steel pontoons (preferred options are shown in the attached document). Figure 1 The pentagonal ring structure shown provides the main buoyancy. Five independent cylindrical columns are evenly distributed at 72° angular intervals around the central pontoon, forming a symmetrical pentagonal array. The bottom of each column is rigidly connected to the central pontoon via a high-strength connecting flange. The column diameter is designed to meet buoyancy and strength requirements, and the column height is determined based on the wave height conditions of the sea area to ensure sufficient safety margin between the bottom of the wind turbine rotor blades and the still water surface.

[0064] The floating foundation is internally divided into several watertight ballast tanks, each equipped with independent injection and drainage pipelines and electric valves. A unified intelligent ballast control system manages these tanks, adjusting the water volume in each tank in real time based on wind and wave loads and turbine attitude monitoring data. This proactively compensates for pitch and roll under extreme sea conditions, ensuring the stability of the floating foundation. The five-column symmetrical star-shaped layout ensures a balanced hydrodynamic response to incoming winds and waves from all directions, effectively reducing the average tilt and movement of the turbine in complex sea conditions.

[0065] The specific structure of the five sets of vertically stacked, counter-rotating dual-rotor vertical axis fan systems is as follows:

[0066] like Figure 2 As shown, each CR-VAWTs (counter-rotor vertical axis fans) consists of an upper H-type vertical axis rotor and a lower H-type vertical axis rotor stacked vertically. The two rotors share the same vertical main shaft, are arranged in an axially staggered manner, and rotate in opposite directions.

[0067] The upper rotor rotates clockwise (viewed from above) and the lower rotor rotates counterclockwise (viewed from above), forming a counter-rotating configuration. The core advantage of this counter-rotating structure is that the aerodynamic torques generated by the two rotors cancel each other out, greatly reducing the combined torque acting on the main bearing housing of the floating foundation, reducing the rotational tendency of the floating foundation in the horizontal plane, and lowering the torsional design requirements of the mooring system.

[0068] The initial phase angle difference between the upper and lower rotors is set to 90°, meaning that the blades of each rotor are offset by 90° along the azimuth direction during installation. Taking a three-bladed H-type rotor as an example, the three blades of the upper rotor are located at azimuths of 0°, 120°, and 240°, respectively, while the three blades of the lower rotor are located at azimuths of 90°, 210°, and 330°, respectively. This phase difference design ensures that the fluctuations in the output torque of the upper and lower rotors are staggered in the time domain. Through a superposition effect, the pulsation amplitude of the total output torque is significantly reduced, thereby effectively reducing the vibration and fatigue load of the unit and extending its service life.

[0069] The generator for each CR-VAWT is positioned inside the corresponding column, close to the water surface. The rotational kinetic energy of the upper and lower rotors is transferred to the generator inside the column to drive it to generate electricity. The low-positioning of the generator effectively lowers the center of gravity of the entire unit, while avoiding the stability risks associated with placing large-mass electromechanical equipment at a high position. It also facilitates maintenance personnel to enter the column for inspection and maintenance work under normal or even light sea conditions.

[0070] Five sets of CR-VAWTs are evenly arranged in a ring array on top of five columns, with the bottom rotors on adjacent columns rotating in opposite directions. This array design of alternating counter-rotation allows the aerodynamic torques generated by the five wind turbines in the horizontal plane to alternately cancel each other out, further optimizing the distribution of the overall aerodynamic load acting on the floating foundation.

[0071] The specific structure of the 5×2 catenary mooring system is as follows:

[0072] The 5×2 catenary mooring system comprises five sets of double catenary mooring units, each corresponding to an independent post, with a total of 10 mooring cables. A guide is welded and installed near the waterline on the lower middle part of the outer wall of each post. The upper end of the mooring cable is connected to the post via the guide, and the lower end is fixed to the seabed rock or soil layer by a high-holding-force anchor. The two mooring cables in each double catenary mooring unit are symmetrically arranged about the post axis, with an angle of approximately 40° between the two cables in the horizontal projection plane (i.e., the angle between adjacent cables in the five sets of 10 cables is 20°). The 10 mooring cables are evenly radially distributed in the horizontal projection plane, providing effective positioning restraint under wind and wave conditions from all directions, achieving a balance of restraint stiffness in all directions.

[0073] The mooring cable is composed of a steel chain, polyester rope, and a high-holding-force anchor: the steel chain segment near the anchor post provides the cable's own weight and catenary effect; the middle section is the polyester rope segment, providing some elasticity to buffer extreme wave impacts; and the end is the high-holding-force anchor, ensuring the mooring cable does not drift under high wind conditions. Compared to traditional 3-point or 4-point catenary mooring, the 5×2 configuration increases the number of mooring cables to 10, significantly improving the overall torsional stiffness and anti-overturning capacity of the system. Furthermore, by increasing the number of mooring points, it ensures a more uniform tension distribution among the mooring cables under extreme loads, effectively preventing overload failure of single or localized mooring cables.

[0074] Example 2: MOST-DMS Fully Coupled Simulation Method and Device

[0075] This embodiment provides a fully coupled MOST-DMS simulation method for floating multi-vertical-axis wind turbines. Based on the open-source MOST framework (Matlab for Offshore Simulation Tool), this method integrates a dual-disk multi-flow pipe (DMS) aerodynamic module developed in Fortran to construct an efficient time-domain simulation program that achieves multi-field coordination across aerodynamics, hydrodynamics, structure, and mooring. Figure 3 As shown.

[0076] The MOST basic framework module retains the core functions of MOST's original hydrodynamic calculations, mooring system simulations, and time-domain solutions. Hydrodynamic calculations use the Cummins equations to transform frequency-domain potential flow hydrodynamic results to the time domain. By importing frequency-domain calculation results from software such as AQWA or WAMIT, time-domain hydrodynamic loads including radiation force memory effects are obtained. It also supports the Morison equations to calculate viscous and inertial forces on small-scale components such as columns and struts. Mooring system simulation employs the lumped mass method, discretizing each mooring cable into several lumped mass elements. Through iterative solutions to the forces and motions of each element, it accurately simulates the nonlinear dynamic characteristics of the catenary and supports parallel calculations for up to 10 mooring cables. The time-domain solver, based on the Simulink / Simscape Multibody platform, achieves coupled time-domain integral solutions of the rigid body's six-degree-of-freedom motion equations and multiple field loads (hydrodynamic, aerodynamic, mooring forces, gravity / buoyancy).

[0077] The DMS dual-disk multi-tube aerodynamic module is developed using the Fortran language and integrated into the MATLAB / Simulink environment via the MEX interface. The core idea of ​​the DMS method is to divide the flow field of the vertical axis wind turbine into several independent tube units along the azimuth direction. Each tube is divided into two independent computational regions, with the rotor geometric center as the boundary: the upstream disk (windward side) and the downstream disk (leeward side). Within each region, momentum theory and blade element theory are applied iteratively to solve for the axial induction factor, ultimately obtaining the convergent aerodynamic load.

[0078] The specific calculation steps for the DMS pneumatic module are as follows:

[0079] Step 1: Divide the flow field of the vertical axis wind turbine into several independent flow tube units along the azimuth angle θ, and divide it into two calculation regions, the upstream disk surface and the downstream disk surface, with the geometric center of the wind turbine as the boundary.

[0080] Step 2: Initialize the axial induction factor for the upstream and downstream disk surfaces of each flow tube unit. and Typically, an initial value is taken. .

[0081] Step 3: Calculate the effective inflow velocity at the upstream and downstream pans. The effective inflow velocity at the upstream pan is... The effective inflow velocity of the downstream plate is ,in For the free flow velocity, the coefficient is... This reflects the axial velocity decay of the airflow after it passes through the upstream disk.

[0082] Step 4: Calculate the tangential velocity of the blades at the current flow tube position based on the azimuth angle θ, rotor radius R, and rotational angular velocity ω of the flow tube unit. This velocity is then combined with the effective incoming flow velocity to obtain the relative velocity of the airflow on the upstream and downstream surfaces. , Then, the airflow deflection angle is determined by the following formula. , : .

[0083] Step 5: According to the formula Determine the local angle of attack for each flow tube unit. , This refers to the geometric pitch angle (installation angle) of the blade. Based on the local angle of attack. Read the corresponding lift coefficient from airfoil experimental data or numerical database. and drag coefficient Then, the normal force coefficient is calculated using the following formula. and tangential force coefficient : , .

[0084] Step 6: Update the axial induction factors of the upstream and downstream plates respectively using the following formula. and :

[0085] In the formula, σ represents the local realism of the flow tube element.

[0086] Step 7: Examine upstream and downstream axial induction factors , Is the amount of iterative change less than the set allowable deviation (e.g.) If the convergence condition is not met, return to step 3 and recalculate with the updated induction factor until convergence is achieved. Obtain the convergent factor. , Then, the aerodynamic load of each flow tube unit is obtained, and the total aerodynamic force and aerodynamic torque of the rotor are obtained by integrating over all flow tube units.

[0087] For a counter-rotating dual-rotor structure, the DMS module executes the above calculation process independently for the upper and lower rotors, and considers the influence of the upper rotor wake on the lower rotor inflow (i.e., the outflow velocity of the upper rotor is used as the inflow correction for the lower rotor), thereby accurately simulating the aerodynamic interference effect between the upper and lower rotors. For multiple sets of rotors on adjacent columns, the module further supports aerodynamic coupling calculations between adjacent rotors based on the wake model.

[0088] The multi-rotor coupling interface module, developed using MATLAB / Simulink, is responsible for enabling real-time bidirectional data interaction between the DMS aerodynamic module and the MOST basic framework. At each time step: ① The MOST time-domain solver transmits the six-degree-of-freedom instantaneous displacement, velocity, and acceleration information of the floating foundation to the DMS module; ② The DMS module corrects the inflow velocity of each rotor based on this motion state (considering the equivalent additional wind speed caused by platform motion), and calculates the instantaneous aerodynamic forces and moments of the five sets of CR-VAWTs; ③ The DMS module feeds back the aerodynamic loads of the five sets of fans to the MOST time-domain solver through the interface, completing the superposition of multiple loads at the current time step. The multi-rotor coupling interface supports multi-threaded parallel computation, capable of simultaneously processing the aerodynamic loads of five opposing dual rotors, effectively shortening the total simulation time.

[0089] The MOST-DMS fully coupled simulation process specifically includes the following four stages:

[0090] Preprocessing stage: Using commercial hydrodynamic software such as AQWA or WADAM, the hydrodynamic coefficients (added mass, radiation damping, wave excitation force) of the floating foundation (including five columns and a central pontoon) are calculated based on three-dimensional potential flow theory, generating an input file in MOST-compatible format. Simultaneously, the geometric parameters of each wind turbine (rotor radius, blade chord length, airfoil, number of blades, pitch angle, phase difference, etc.), mooring system parameters (mooring cable length, weight, elastic modulus, anchor point coordinates, etc.), and environmental condition parameters (wind speed, wind direction, significant wave height, spectral peak period, ocean current velocity, etc.) are input.

[0091] Initialization phase: The MOST framework loads frequency domain hydrodynamic coefficients, constructs a time-domain model of radiation force using the Cummins integral kernel function, and initializes the mooring lumped mass model; the DMS module reads the wind turbine geometric parameters and airfoil aerodynamic database, initializes the aerodynamic calculation parameters of five sets of counter-rotating dual rotors, and completes the configuration of the multi-threaded parallel computing framework.

[0092] Temporal coupling solution phase: Temporal integration is advanced with a small time step (typically 0.01–0.05 s). Within each time step, the MOST module calculates the hydrodynamic loads (radiation force, diffraction force, wave excitation force) and mooring loads under the current motion state of the floating foundation; the multi-rotor coupling interface transmits the current platform motion state to the DMS module; the DMS module calculates the instantaneous aerodynamic forces and moments of five sets of CR-VAWTs in parallel and feeds them back to MOST; the MOST time-domain solver superimposes the hydrodynamic loads, aerodynamic loads, mooring loads, and gravity / buoyancy to solve the rigid body six-degree-of-freedom motion equations and obtain the platform motion state for the next time step; this process is iterated until the end of the simulation.

[0093] Post-processing stage: Statistical analysis is performed on the time-domain simulation results, and the time history curves, power spectrum, and statistical extreme values ​​of the six-degree-of-freedom motion response (sway, roll, heave, tilt, pitch, and yaw) of the floating foundation are output; the time history curves and extreme values ​​of the tension of each mooring cable are also output; the time history and statistics of the aerodynamic loads (thrust, torque, and power) of the five wind turbines are also output; and the load statistics and failure risk assessment under extreme conditions (typhoon conditions, once-in-a-century waves, etc.) are completed, providing quantitative basis for the unit structural design and mooring system selection.

[0094] The MOST-DMS simulation device in this embodiment can be implemented on a general-purpose computer or workstation, including a processor and memory. The memory stores computer programs that implement the above methods. All functional modules are deployed on the same computing node. The DMS pneumatic module is compiled into a high-efficiency executable program using Fortran and communicates with the MATLAB / Simulink environment through the MEX interface, fully leveraging the numerical computation efficiency advantages of Fortran while retaining the system integration flexibility and secondary development convenience of the MATLAB / Simulink platform.

[0095] Example 3: Simulation Verification and Technical Effect Description

[0096] Using a nearshore sea area as a background, the unit of this invention was subjected to MOST-DMS fully coupled simulation verification under typhoon conditions.

[0097] Simulation results show that under typhoon conditions, the floating foundation of the unit of this invention exhibits excellent control over the maximum pitch / roll angle; the tension of the 10 mooring cables is uniform, and the maximum tension does not exceed 60% of the safe breaking load, indicating no risk of mooring failure. Compared with the traditional 3-point mooring scheme, the torsional stiffness of the 5×2 mooring system is significantly improved, and the maximum tension of a single mooring cable is significantly reduced, fully verifying the significant improvement in the typhoon resistance performance of the unit of this invention.

[0098] In terms of aerodynamic performance, after the 5 sets of CR-VAWTs adopt the 90° phase difference design, the total output torque ripple coefficient (the ratio of ripple amplitude to mean) of the unit is significantly reduced compared with the traditional 0° phase difference design, and the vibration level of the unit is significantly reduced; the alternating reverse rotation design of adjacent columns greatly reduces the aerodynamic torque of the whole unit and significantly reduces the yaw motion amplitude of the floating foundation.

[0099] In terms of simulation efficiency, the MOST-DMS program takes about 1 / 3 of the calculation time of OpenFAST for a single working condition (3600s simulation time), which is about two orders of magnitude shorter than the CFD method. It can efficiently support parametric sweep (such as multi-parameter optimization design of blade chord length, phase difference, mooring pretension, etc.) and large-scale extreme working condition simulation, which fully verifies the efficiency and engineering applicability of the MOST-DMS method of this invention.

[0100] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A floating multi-vertical-axis wind turbine generator, characterized in that, Includes a floating foundation system, five sets of vertically stacked counter-rotating dual-rotor vertical axis wind turbine systems, and a 5×2 catenary mooring system; The floating foundation system adopts a five-column symmetrical star-shaped layout, including one pontoon and five independent cylindrical columns evenly distributed around the pontoon. The bottom of each column is rigidly connected to the central pontoon, and the pontoon is equipped with an adjustable ballast water tank. The five sets of vertically stacked counter-rotating dual-rotor vertical axis wind turbine systems are respectively installed on the top of five independent columns. Each set includes an upper H-shaped vertical axis rotor and a lower H-shaped vertical axis rotor stacked vertically. The two rotors share the same vertical main shaft and rotate in opposite directions. The initial phase angle difference between the upper and lower rotors is set to 90°. The five sets of wind turbines are evenly arranged in a ring array. The bottom rotors on adjacent columns adopt a counter-rotating design. The generators of each wind turbine are arranged inside the corresponding column near the water surface. The 5×2 catenary mooring system comprises 5 sets of double catenary mooring units with a total of 10 mooring cables. Each post has a cable guide installed on the lower part of its outer wall. One end of each mooring cable is connected to the corresponding post through the cable guide, and the other end is fixed to the seabed by a high holding power anchor. The 10 mooring cables are evenly radially distributed in the horizontal projection plane.

2. The floating multi-vertical-axis wind turbine generator according to claim 1, characterized in that: The five independent columns are evenly distributed around the perimeter of the floating box at equal angular intervals of 72°, forming a regular pentagonal symmetrical array; each column independently supports a set of counter-rotating dual-rotor vertical axis fans, and the axes of each column are parallel to each other and consistent with the vertical direction.

3. The floating multi-vertical-axis wind turbine generator according to claim 1, characterized in that: The upper H-shaped vertical shaft rotor and the lower H-shaped vertical shaft rotor are stacked vertically and share the same vertical main shaft. When the upper rotor rotates clockwise, the lower rotor rotates counterclockwise. The 90° initial phase angle difference causes the blades of the two rotors to be staggered in the azimuth direction in order to balance the aerodynamic torque output in each azimuth angle and reduce the amplitude of the combined torque pulsation.

4. The floating multi-vertical-axis wind turbine generator according to claim 1, characterized in that: In the five sets of vertically stacked counter-rotating dual-rotor vertical axis fans, the rotation directions of the bottom rotors on adjacent columns are opposite to each other, so as to counteract the overall aerodynamic torque and overturning moment of the unit and achieve a symmetrical and balanced distribution of aerodynamic loads in the horizontal plane of the unit.

5. The floating multi-vertical-axis wind turbine generator according to claim 1, characterized in that: In the 5×2 catenary mooring system, the 5 sets of double catenary mooring units correspond to 5 independent columns. The 2 mooring cables of each set of double catenary mooring units are symmetrically arranged with the column axis as the axis of symmetry. The 10 mooring cables are evenly distributed in the horizontal projection plane, with the angle between adjacent mooring cables being 20°. The mooring cables are composed of chain segments, polyester ropes and high holding power anchors. The nonlinear dynamic characteristics of the catenary are simulated using the lumped mass method.

6. The floating multi-vertical-axis wind turbine generator according to claim 1, characterized in that: The ballast tank is equipped with a real-time water volume adjustment and control system, which can adjust the ballast water volume of each column in real time according to the wind and wave load and the attitude of the unit, so as to actively compensate for the longitudinal and transverse tilt of the floating foundation under extreme sea conditions.

7. A MOST-DMS fully coupled simulation method for floating multi-vertical-axis wind turbine units, wherein the floating multi-vertical-axis wind turbine unit includes a floating foundation system, multiple sets of counter-rotating dual-rotor vertical-axis wind turbine systems, and a catenary mooring system, characterized in that, The method includes the following steps: based on the open-source MOST framework, a dual-disk multi-flow tube method is integrated to construct a time-domain simulation program that realizes the coordination of multiple fields such as aerodynamics, hydrodynamics, structure, and mooring. The program includes a MOST basic framework module, a DMS dual-disk multi-flow tube aerodynamic module, and a multi-rotor coupling interface module. The MOST basic framework module retains the original core functions of MOST, including hydrodynamic calculation, mooring system simulation and time-domain solution. It supports frequency-domain to time-domain hydrodynamic load calculation through Cummins equations and uses the lumped mass method to simulate the nonlinear dynamics of catenary mooring. The DMS dual-disc multi-flow tube aerodynamic module is developed based on the Fortran language and integrated into the MOST framework. It adopts the dual-disc multi-flow tube theory, iteratively solves the axial induction factor for the upstream and downstream disks of each flow tube unit, calculates the instantaneous aerodynamic forces and torques of multiple sets of counter-rotating dual rotors, and supports the simulation of wake interference effects between adjacent rotors. The multi-rotor coupling interface module is developed based on MATLAB / Simulink and realizes real-time bidirectional data interaction and multi-threaded parallel calculation of the instantaneous motion state of the floating foundation and the aerodynamic loads of the five sets of wind turbines between the DMS aerodynamic module and the MOST basic frame.

8. The MOST-DMS fully coupled simulation method according to claim 7, characterized in that: The DMS dual-disc multi-flow tube pneumatic module performs pneumatic calculations according to the following steps: The flow field of the vertical axis wind turbine is divided into several independent flow tube units along the azimuth angle θ, and the wind turbine is divided into upstream disk and downstream disk with the geometric center of the wind turbine as the boundary. Initialize the axial induction factor on the upstream and downstream disks of each flow tube unit. and ; Calculate the effective inflow velocity of the upstream plate. Calculate the effective inflow velocity at the downstream plate. ,in For free flow velocity; Calculate the blade tangential velocity based on the azimuth angle θ, the rotor radius R, and the rotational angular velocity ω. The relative velocity was obtained by synthesis. , and airflow deflection angle , ; From local angle of attack Determine the lift coefficient and drag coefficient Then the normal force coefficient can be obtained. and tangential force coefficient ; The upstream and downstream axial induction factors are iteratively updated until the iterative change is less than the allowable deviation, thus obtaining the converged aerodynamic load parameters.

9. The MOST-DMS fully coupled simulation method according to claim 7, characterized in that: The fully coupled simulation is performed according to the following procedure: Preprocessing stage: Use hydrodynamic analysis software to calculate the hydrodynamic coefficients of the floating foundation, generate MOST-compatible input files, and input the wind turbine geometric parameters, mooring system parameters and environmental condition parameters; Initialization phase: The MOST frame loads hydrodynamic coefficients and mooring model, and the DMS module initializes the multi-rotor aerodynamic parameters; Temporal coupling solution stage: Within each time step, the MOST module calculates the floating foundation motion and hydrodynamic and mooring loads, while the DMS module calculates the multi-rotor aerodynamic loads. Data interaction and load superposition are completed through the multi-rotor coupling interface, and the floating foundation motion state is updated. Post-processing stage: Output the six-degree-of-freedom motion response of the floating foundation, the tension of the mooring cables, the aerodynamic load of the wind turbine, and the power generation, and complete the load statistics and risk assessment under extreme conditions.

10. An apparatus for implementing the MOST-DMS fully coupled simulation method according to any one of claims 7 to 9, characterized in that: It includes a processor and a memory, the memory storing a computer program, which, when executed by the processor, implements the following functional modules: Hydrodynamic calculation module: Based on the Cummins equation, the imported frequency domain potential hydrodynamic coefficients are converted from frequency domain to time domain. At the same time, the Morison equation is used to calculate the viscous forces of small-scale components such as columns and struts. DMS aerodynamic calculation module: Based on the Fortran language, the dual-disc multi-flow tube algorithm is implemented to perform multi-threaded parallel aerodynamic load calculations on five sets of counter-rotating dual-rotor vertical axis fans. Mooring Dynamics Module: Employs the lumped mass method to simulate the nonlinear dynamic characteristics of 10 catenary mooring cables and supports parallel computation of multiple mooring cables; Coupled solution module: Based on the Simulink / Simscape Multibody platform, it realizes the time-domain coupled solution of rigid body six-degree-of-freedom motion and multi-field loads; the coupled solution module realizes real-time bidirectional data interaction with the DMS aerodynamic calculation module through the multi-rotor coupling interface. In each time step, it receives hydrodynamic loads, aerodynamic loads, and mooring loads and completes the load superposition. At the same time, it feeds back the instantaneous displacement, velocity and acceleration of the floating foundation to the DMS aerodynamic calculation module and outputs the fully coupled dynamic response of the unit.

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