A hydrodynamic load model for offshore floating platforms considering wave-current coupling

Abstract

The present invention discloses a hydrodynamic load model of an offshore floating platform considering wave-current coupling, comprising the following steps: a) obtaining relevant parameters of the floating platform; b) determining the analysis parameters of the forced vibration of the floating platform and the current velocity of the sea area where the floating platform is located according to the relevant parameters of the floating platform; c) establishing a hydrodynamic load model of the floating platform under the influence of the reduced current velocity and the analysis parameters. The present invention constructs a hydrodynamic load model of a wind turbine considering the current effect, and analyzes the influence of the reduced current velocity and the forced vibration frequency on the hydrodynamic load coefficient, thereby improving the prediction accuracy of the hydrodynamic load and the dynamic response. The overall accuracy of the hydrodynamic load prediction of floating wind turbines under the action of wave-current coupling is improved, the applicability is improved at the source, the accuracy of the wind turbine load evaluation and analysis is improved, and at the same time, the dynamic response of offshore wind turbines can be accurately predicted, thereby increasing the safety performance, economic benefits and energy utilization of wind turbines.

Description

Technical Field

[0001] The present invention relates to the field of offshore wind power equipment, and in particular to a hydrodynamic load model of an offshore floating platform taking wave-current coupling into consideration. Background Art

[0002] With the high development and utilization of traditional energy sources such as coal, oil and natural gas, energy issues will become a serious bottleneck restricting the sustainable development of the economy. As one of the most promising alternative energy sources, the development and utilization of wind energy has received more and more attention from countries around the world. Compared with onshore wind energy, offshore wind energy has more obvious advantages. "From land to sea, from shallow to deep, from fixed foundation to floating platform" has become an inevitable trend in the construction of wind farms in the future. In the marine environment, accurate evaluation of the hydrodynamic loads acting on the floating platform is crucial to predict the dynamic response of floating offshore wind turbines. Potential flow theory and Morrison equation are widely used to evaluate the hydrodynamic loads acting on floating wind turbine platforms. Therefore, the reasonable selection of the hydrodynamic added mass and drag coefficient used in the Morrison equation is crucial to accurately predict the hydrodynamic loads on floating wind turbine platforms under the influence of wave and current coupling.

[0003] The hydrodynamic load coefficients obtained from tank tests are widely used to predict the hydrodynamic loads on offshore wind turbines. These hydrodynamic coefficient models are able to predict the wave loads acting on fixed marine structures with reasonable accuracy, but they have limitations in evaluating the hydrodynamic loads on floating wind turbines under wave-current action. The reasons can be attributed to two issues. One issue is the determination of the frequency-dependent hydrodynamic load coefficients. Studies have shown that the hydrodynamic load coefficients of a smooth cylinder subjected to oscillating flow depend on the Reynolds number and the Keulegan-Carpenter number. This highlights the importance of further studying the effect of oscillation frequency on the hydrodynamic coefficients to accurately predict the hydrodynamic effects on floating wind turbines, as these loads are closely related to the platform motion at various oscillation frequencies. Another issue is the evaluation of the effect of ocean currents on the hydrodynamic load coefficients. Since traditional hydrodynamic load models based on the model without considering the effect of ocean currents show inadequacies in predicting the hydrodynamic loads on floating wind turbines under wave-current action, the effect of ocean currents on the hydrodynamic load coefficients should be considered.

[0004] In the field of structural wind engineering, forced vibration tests are usually carried out on structural models at different wind speeds in wind tunnels to accurately evaluate aerodynamic effects by defining different vibration modes. In addition to the Reynolds number and mass ratio, the reduced wind speed is also one of the most important independent variables for determining the aerodynamic load coefficient of the structure, because the wind speed has a direct impact on the vortex shedding frequency and vortex-induced vibration. However, in the field of marine engineering, most studies on forced vibration tests of marine structures focus on still water conditions, which means that the current velocity below the mean sea level is zero. Research on ocean currents is still limited, but they are often encountered in actual marine environments. Existing studies have shown that the hydrodynamic load coefficient generated by the combined action of oscillating flow and uniform flow on a cylinder is significantly dependent on the reduced ocean current velocity, which indicates that the mechanism of the influence of ocean currents on the hydrodynamic load coefficient of floating wind turbine platforms has not yet been fully clarified.

[0005] Through physical tank tests, the dependence of the current velocity, KC number and Reynolds number on the hydrodynamic load coefficient of marine structures can be established. Compared with physical model tests, numerical forced vibration tests are more cost-effective. In addition, the limitations of experimental equipment can be overcome by accurate and effective numerical methods, making it easier to conduct forced vibration tests in uniform flow. One of the most widely used numerical methods is computational fluid dynamics (CFD), which can accurately evaluate motion-induced and current-induced hydrodynamic effects through the finite volume method and various turbulence models. Although numerical forced vibration tests of simple marine structures considering uniform flow have been studied using CFD methods, the research on the hydrodynamic load coefficient of floating wind platforms is still limited. Given the complexity of the structure of semi-submersible wind platforms, such as the OC4 DeepCwind platform, their hydrodynamic load coefficients may be more sensitive to the current velocity, KC number and Reynolds number, and therefore require further attention. Summary of the invention

[0006] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a hydrodynamic load model for an offshore floating platform taking into account wave-current coupling, so as to solve the problem of distortion in motion response assessment caused by insufficient accuracy of traditional hydrodynamic load models used in existing wind turbine hydrodynamic load assessment and dynamic response prediction technologies.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0008] A hydrodynamic load model for an offshore floating platform considering wave-current coupling includes the following steps:

[0009] a) Obtain relevant parameters of the floating platform;

[0010] b) Determine the analysis parameters of the forced vibration of the floating platform and the current velocity of the sea area where the floating platform is located according to the relevant parameters of the floating platform;

[0011] c) Establishing a hydrodynamic load model of a floating platform under the influence of reduced current velocity and the analysis parameters.

[0012] As an optimization, the floating platform includes a plurality of buoys in a cylindrical structure, and the buoys are interconnected and fixed by connecting rods; the relevant parameters include the diameter of the buoy and the natural frequency of the floating platform in six degrees of freedom directions.

[0013] As an optimization, the buoy includes a central buoy and three combined buoys, the three combined buoys are located at three vertices of an equilateral triangle centered on the central buoy, and a wind turbine is installed on the central buoy.

[0014] As an optimization, in step b, the analysis parameters are determined by establishing a viscous numerical wave pool through a CFD numerical simulation tool and performing a forced vibration test on the floating platform. The analysis parameters include:

[0015] The vibration equation is expressed as follows:

[0016] x(t)=asin(ωt) (1)

[0017] Keulegan-Carpenter number, or KC number, is expressed as follows:

[0018]

[0019] The Reynolds number is expressed as follows:

[0020]

[0021] The frequency parameter is expressed as follows:

[0022]

[0023] Where a is the forced vibration amplitude, T is the vibration period, ω is the vibration frequency, v is the fluid kinematic viscosity, D is the diameter of the float, and u is the flow rate of the fluid.

[0024] As an optimization, in step b, the reduced ocean current velocity is expressed by the following formula:

[0025]

[0026] Where T is the vibration period, U0 is the current velocity, and D is the diameter of the buoy.

[0027] As an optimization, step c includes:

[0028] c1) Determine the hydrodynamic loads on the floating platform taking into account the effects of ocean currents,

[0029]

[0030] In the formula, ρ w is the fluid density, A is the characteristic area, V is the characteristic volume, C dc is the hydrodynamic resistance coefficient considering the effect of ocean current, U0 is the ocean current velocity, C mc The hydrodynamic added mass coefficient considering the effect of ocean current;

[0031] c2) Determine the hydrodynamic load coefficient of the floating platform at different oscillation frequencies and current velocities, i.e.,

[0032]

[0033]

[0034] In the formula, T is the vibration period, ω is the vibration frequency, and U m is the maximum forced vibration velocity.

[0035] c3) Establish a hydrodynamic load model for floating platforms that takes into account the effects of reduced current velocity, KC number and frequency parameters.

[0036]

[0037]

[0038] Where i is the floating platform component, k is the direction of the hydrodynamic added mass and the resistance coefficient, is the hydrodynamic added mass coefficient of platform component i, is the hydrodynamic resistance coefficient of platform component i, is the hydrodynamic added mass coefficient of platform component r, is the hydrodynamic resistance coefficient of platform component r, is the correction factor of the hydrodynamic added mass coefficient considering the interaction between platform components. is the correction factor of the hydrodynamic resistance coefficient considering the interaction between platform components. is the correction factor of the hydrodynamic added mass coefficient considering the influence of vibration frequency, is the correction factor of the hydrodynamic resistance coefficient considering the influence of vibration frequency, is the correction factor of the hydrodynamic added mass coefficient considering the effect of ocean currents, The correction factor of the hydrodynamic resistance coefficient considering the effect of ocean current;

[0039] c4) Determine the global hydrodynamic load coefficient matrix of the floating platform,

[0040]

[0041]

[0042] In the formula, the global hydrodynamic added mass coefficient matrix is ​​calculated using the following formula:

[0043]

[0044]

[0045]

[0046]

[0047]

[0048] The global hydrodynamic resistance coefficient matrix is ​​calculated using the following formula:

[0049]

[0050]

[0051]

[0052]

[0053]

[0054] In the formula, a three-dimensional coordinate system is established with the projection of the center of gravity of the floating platform on the still water surface as the origin. The still water surface is the mutually perpendicular x-axis and y-axis, the vertical plane is the z-axis, and θ x is the angle between the float and the x-axis, θ z is the angle between the buoy and the z-axis, N is the number of buoys of the floating platform in the water, z G is the coordinate of the center of gravity of the floating platform on the z-axis.

[0055] Compared with the prior art, the present invention has the following advantages: the present invention constructs a wind turbine hydrodynamic load model that takes into account the effect of ocean currents, and analyzes the influence of reduced ocean current velocity and forced vibration frequency on the hydrodynamic load coefficient, thereby improving the prediction accuracy of hydrodynamic loads and dynamic responses. The overall accuracy of the prediction of hydrodynamic loads of floating wind turbines under the action of wave-ocean current coupling is improved, the applicability is improved at the source, the accuracy of wind turbine load assessment and analysis is improved, and the dynamic response of offshore wind turbines can be accurately predicted, thereby increasing the safety performance, economic benefits and energy utilization of wind turbine operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 This is a schematic diagram of the main structure of the floating platform of the present invention;

[0057] Figure 2 It is a schematic diagram of the top view of the floating platform of the present invention;

[0058] Figure 3 A viscous numerical wave pool established by the present invention using a CFD numerical simulation tool;

[0059] Figure 4 This is the flow field diagram of the horizontal forced oscillation test of the present invention;

[0060] Figure 5 This is the flow field diagram of the vertical forced oscillation test of the present invention;

[0061] Figure 6 is the resistance coefficient of the lower buoy II in the forced vibration test result of the present invention;

[0062] Figure 7 is the resistance coefficient of the lower buoy III in the forced vibration test result of the present invention;

[0063] Figure 8 is the resistance coefficient of the upper buoy II in the forced vibration test result of the present invention;

[0064] Fig. 9 is the resistance coefficient of the upper buoy III in the forced vibration test result of the present invention;

[0065] Fig.10 The relationship between the resistance coefficient and the reduced flow velocity of the upper buoy II in the forced vibration test results of the present invention;

[0066] Fig.11 The relationship between the central buoy resistance and the additional mass coefficient and the reduced flow velocity in the forced vibration test results of the present invention;

[0067] Fig.12 The longitudinal surge response of the wind turbine dynamic response comparison diagram under the action of regular waves of the present invention;

[0068] Fig.13 The pitch response of the wind turbine dynamic response comparison diagram under the action of regular waves of the present invention;

[0069] Fig.14 It is the heave response of the comparison diagram of the wind turbine dynamic response under the action of regular waves of the present invention;

[0070] Fig.15 This is a comparison diagram of the wind turbine dynamic response under the wave-current coupling of the present invention, the longitudinal surge response at a flow rate of 0.084m / s;

[0071] Fig.16 This is a comparison diagram of the wind turbine dynamic response under the wave-current coupling of the present invention, the longitudinal surge response at a flow rate of 0.14m / s;

[0072] Fig.17 This is a comparison diagram of the wind turbine dynamic response under the wave-current coupling of the present invention, the heave response at a flow rate of 0.084m / s;

[0073] Fig.18 This is a comparison diagram of the wind turbine dynamic response under the wave-current coupling of the present invention, the heave response at a flow rate of 0.14m / s;

[0074] Fig.19 This is a comparison diagram of the wind turbine dynamic response under the wave-current coupling of the present invention, the pitch response at a flow rate of 0.084m / s;

[0075] Fig. 20 This is a comparison diagram of the wind turbine dynamic response under the wave-current coupling of the present invention, the pitch response at a flow rate of 0.14m / s;

[0076] In the figure, 1 is the lower buoy, 2 is the upper buoy, and 3 is the center buoy. DETAILED DESCRIPTION

[0077] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0078] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0079] It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. In the description of the present invention, it should be noted that the orientation or position relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. is based on the orientation or position relationship shown in the drawings, or the orientation or position relationship in which the invention product is usually placed when used, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance. In addition, the terms "horizontal", "vertical", etc. do not mean that the components are absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted. In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0080] Example: See Figure 1-Figure 20 ,

[0081] A hydrodynamic load model for an offshore floating platform considering wave-current coupling includes the following steps:

[0082] a) Obtain relevant parameters of the floating platform; wherein the floating platform includes a plurality of buoys in a cylindrical structure, and the buoys are mutually connected and fixed by connecting rods; the relevant parameters include the draft of the floating platform, the diameter of the buoy, and the natural frequency of the floating platform in the six degrees of freedom. Specifically, this embodiment takes the existing OC4 DeepCwind platform as the research object, and the buoy includes a central buoy 3 and three combined buoys. The three combined buoys are located at the three vertices of an equilateral triangle centered on the central buoy 3, and a wind turbine is installed on the central buoy. Specifically, in this embodiment, the combined buoy includes an upper buoy 2 and a lower buoy 1. The diameter of the upper buoy 2 is smaller than that of the lower buoy 1. The diameter of the upper buoy 2 is 12m, and the diameter of the lower buoy 1 is 24m. The stability is better, and the current speed is 0.084m / s and 0.14m / s for testing.

[0083] b) Determine the analysis parameters of the forced vibration of the floating platform and the sea current velocity of the sea area where the floating platform is located according to the relevant parameters of the floating platform. The analysis parameters are determined by establishing a viscous numerical wave pool through a CFD numerical simulation tool and conducting a forced vibration test on the floating platform to simulate the forced vibration of the floating platform under the action of waves.

[0084] Specifically, the amplitude, frequency, and direction range of the forced vibration test are determined based on the natural frequency of the floating platform in the six degrees of freedom. A viscous numerical wave pool is established using CFD numerical simulation tools, and the division of the calculation domain is determined based on the forced vibration test parameters. The analysis parameters include:

[0085] The vibration equation is expressed as follows:

[0086] x(t)=asin(ωt) (1)

[0087] Keulegan-Carpenter number, or KC number, is expressed as follows:

[0088]

[0089] The Reynolds number is expressed as follows:

[0090]

[0091] The frequency parameter is expressed as follows:

[0092]

[0093] Where a is the forced vibration amplitude, T is the vibration period, ω is the vibration frequency, υ is the fluid kinematic viscosity, D is the diameter of the float, and u is the flow rate of the fluid.

[0094] The reduced ocean current velocity is expressed by the following formula:

[0095]

[0096] Where T is the vibration period, U0 is the current velocity, and D is the diameter of the buoy.

[0097] c) Establishing a hydrodynamic load model of a floating platform under the influence of reduced current velocity and the analysis parameters.

[0098] Specifically, the motion equation of a floating platform under the action of waves and currents is:

[0099]

[0100] In the formula, {F G} is gravity, {F B} is the buoyancy, {FM} is the mooring force, {F R} is the hydrostatic restoring force, {F H} is the hydrodynamic force. Determine the hydrodynamic load acting on the floating platform,

[0101] F H =F w,F-K +F w,d +F m,a +F m,r +F d (twenty four)

[0102] In the formula, F w,F-K is the Froude-Krylov force, F w,d is the diffraction force, these two items are also called wave excitation force, F m,a is the hydrodynamic inertia force, F m,r is the radiation damping force, and these two items belong to the excitation force of the floating body motion, F d is the viscous resistance.

[0103] The hydrodynamic load without current acting on the platform is determined according to Morrison equation:

[0104] F H (t) = F(t) - F B -F R (t) (25)

[0105]

[0106] In the formula, F B is the buoyancy, F R is the hydrostatic restoring force. a is the hydrodynamic additional mass coefficient, C d is the hydrodynamic resistance coefficient, V is the characteristic volume, A is the characteristic area, ρ w is the fluid density.

[0107] Identify the hydrodynamic load coefficient of the floating platform at different oscillation frequencies by Fourier averaging method:

[0108]

[0109]

[0110] c1) Determine the hydrodynamic loads on the floating platform taking into account the effects of ocean currents,

[0111]

[0112] In the formula, ρ w is the fluid density, A is the characteristic area, V is the characteristic volume, C dcis the hydrodynamic resistance coefficient considering the effect of ocean current, U0 is the ocean current velocity, C mc The hydrodynamic added mass coefficient considering the effect of ocean current;

[0113] c2) Determine the hydrodynamic load coefficient of the floating platform at different oscillation frequencies and current velocities, i.e.,

[0114]

[0115]

[0116] In the formula, T is the vibration period, ω is the vibration frequency, and U m is the maximum forced vibration velocity.

[0117] c3) Establish a hydrodynamic load model for floating platforms that takes into account the effects of reduced current velocity, KC number and frequency parameters.

[0118]

[0119]

[0120] Where i is the floating platform component, k is the direction of the hydrodynamic added mass and the resistance coefficient, is the hydrodynamic added mass coefficient of platform component i, is the hydrodynamic resistance coefficient of platform component i, is the hydrodynamic added mass coefficient of platform component r, is the hydrodynamic resistance coefficient of platform component r, is the correction factor of the hydrodynamic added mass coefficient considering the interaction between platform components. is the correction factor of the hydrodynamic resistance coefficient considering the interaction between platform components. is the correction factor of the hydrodynamic added mass coefficient considering the influence of vibration frequency, is the correction factor of the hydrodynamic resistance coefficient considering the influence of vibration frequency, is the correction factor of the hydrodynamic added mass coefficient considering the effect of ocean currents, The correction factor of the hydrodynamic resistance coefficient considering the effect of ocean current;

[0121] c4) Determine the global hydrodynamic load coefficient matrix of the floating platform based on the hydrodynamic load coefficient of a single buoy determined by the hydrodynamic load model of the floating platform,

[0122]

[0123]

[0124] In the formula, the global hydrodynamic added mass coefficient matrix is ​​calculated using the following formula:

[0125]

[0126]

[0127]

[0128]

[0129]

[0130] The global hydrodynamic resistance coefficient matrix is ​​calculated using the following formula:

[0131]

[0132]

[0133]

[0134]

[0135]

[0136] In the formula, a three-dimensional coordinate system is established with the projection of the center of gravity of the floating platform on the still water surface as the origin. In this embodiment, the origin of the coordinate is the intersection of the still water surface and the axis of the central buoy, the still water surface is the mutually perpendicular x-axis and y-axis, the vertical plane is the z-axis, and θ x is the angle between the float and the x-axis, θ z is the angle between the buoy and the z-axis, N is the number of buoys of the floating platform in the water, z G is the coordinate of the center of gravity of the floating platform on the z-axis.

[0137] The hydrodynamic load model proposed in the present invention is used to predict the dynamic response of the wind turbine on the OC4 DeepCwind platform, and the prediction results are compared with OpenFAST and experimental results to verify the prediction performance of the model. Figure 1-Figure 6 This is the result of the forced vibration test. Figure 7-Figure 9 This is a comparison diagram of the wind turbine dynamic response under the action of regular waves. Figure 10-Figure 15 This is a comparison diagram of wind turbine dynamic response under wave-current coupling.

[0138] The present invention provides a wind turbine hydrodynamic load model that takes into account the effect of ocean currents, which can accurately predict the dynamic response of the wind turbine according to different wave conditions and ocean current environments in the marine environment, improve the accuracy and optimization rate of load analysis and response evaluation, and then improve the power generation of wind turbines, thereby obtaining greater power generation and economic benefits. The present invention constructs a wind turbine hydrodynamic load model that takes into account the effect of ocean currents, and analyzes the influence of reduced ocean current velocity and forced vibration frequency on the hydrodynamic load coefficient, thereby improving the prediction accuracy of hydrodynamic loads and dynamic responses. Overall, the accuracy of the prediction of the hydrodynamic load of floating wind turbines under the action of wave-current coupling is improved, the applicability is improved at the source, the accuracy of the wind turbine load evaluation analysis is improved, and at the same time, the dynamic response of offshore wind turbines can be accurately predicted, increasing the safety performance, economic benefits and energy utilization of wind turbine operations.

[0139] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the technical solution. Those skilled in the art should understand that those modifications or equivalent substitutions of the technical solution of the present invention that do not depart from the purpose and scope of the technical solution should be included in the scope of the claims of the present invention.

Claims

1. A hydrodynamic load model for an offshore floating platform considering wave-current coupling, characterized in that: The following steps are included: a) Obtain relevant parameters of the floating platform; b) determining the analysis parameters of the forced vibration of the floating platform and the sea current velocity of the sea area where the floating platform is located according to the relevant parameters of the floating platform; the analysis parameters are determined by establishing a viscous numerical wave pool through a CFD numerical simulation tool and conducting a forced vibration test on the floating platform, and the analysis parameters include: The vibration equation is expressed as follows: x(t)=a sin(ωt)#(1) Keulegan-Carpenter number, or KC number, is expressed as follows: The Reynolds number is expressed as follows: The frequency parameter is expressed as follows: Where a is the forced vibration amplitude, T is the vibration period, ω is the vibration frequency, υ is the fluid kinematic viscosity, D is the diameter of the float, and u is the flow rate of the fluid; c) establishing a hydrodynamic load model of a floating platform under the influence of reduced current velocity and the analysis parameters; The reduced ocean current velocity is expressed by the following formula: Where T is the vibration period, U0 is the current velocity, and D is the diameter of the buoy; Specifically, step c includes: c1) Determine the hydrodynamic loads on the floating platform taking into account the effects of ocean currents, In the formula, ρ w is the fluid density, A is the characteristic area, V is the characteristic volume, C dc is the hydrodynamic resistance coefficient considering the effect of ocean current, U0 is the ocean current velocity, C mc The hydrodynamic added mass coefficient considering the effect of ocean current; c2) Determine the hydrodynamic load coefficient of the floating platform at different oscillation frequencies and current velocities, i.e., In the formula, T is the vibration period, ω is the vibration frequency, and U m is the maximum forced vibration velocity; c3) Establish a hydrodynamic load model for floating platforms that takes into account the effects of reduced current velocity, KC number and frequency parameters. Where i is the floating platform component, k is the direction of the hydrodynamic added mass and the resistance coefficient, is the hydrodynamic added mass coefficient of platform component i, is the hydrodynamic resistance coefficient of platform component i, is the hydrodynamic added mass coefficient of platform component r, is the hydrodynamic resistance coefficient of platform component r, is the correction factor of the hydrodynamic added mass coefficient considering the interaction between platform components. is the correction factor of the hydrodynamic resistance coefficient considering the interaction between platform components. is the correction factor of the hydrodynamic added mass coefficient considering the influence of vibration frequency, is the correction factor of the hydrodynamic resistance coefficient considering the influence of vibration frequency, is the correction factor of the hydrodynamic added mass coefficient considering the effect of ocean currents, The correction factor of the hydrodynamic resistance coefficient considering the effect of ocean current; c4) Determine the global hydrodynamic load coefficient matrix of the floating platform, In the formula, the global hydrodynamic added mass coefficient matrix is ​​calculated using the following formula: The global hydrodynamic resistance coefficient matrix is ​​calculated using the following formula: In the formula, a three-dimensional coordinate system is established with the projection of the center of gravity of the floating platform on the still water surface as the origin. The still water surface is the mutually perpendicular x-axis and y-axis, the vertical plane is the z-axis, and θ x is the angle between the float and the x-axis, θ z is the angle between the buoy and the z-axis, N is the number of buoys of the floating platform in the water, z G is the coordinate of the center of gravity of the floating platform on the z-axis.

2. The hydrodynamic load model of an offshore floating platform considering wave-current coupling according to claim 1, characterized in that: The floating platform comprises a plurality of buoys in a cylindrical structure, and the buoys are mutually connected and fixed by connecting rods; the relevant parameters include the diameter of the buoy and the natural frequency of the floating platform in six degrees of freedom directions.

3. The hydrodynamic load model of an offshore floating platform considering wave-current coupling according to claim 2 is characterized in that: The buoy comprises a central buoy and three combined buoys, the three combined buoys are located at three vertices of an equilateral triangle centered on the central buoy, and a fan is installed on the central buoy.

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