Sea floating type fan heaving plate type selection method

Abstract

The invention provides a model selection method for heaving plates of an offshore floating fan. Mathematical physical models of m different heaving plates and floating fan platforms can be established based on a CFD (computational fluid dynamics) method. Respectively designing a calculation threshold and a boundary condition for each mathematical physical model, and selecting a turbulence model; and grid encryption is carried out near each mathematical physical model area, different grids are divided, grid stability verification is carried out, and a grid division scheme is determined. And respectively carrying out a degree-of-freedom attenuation test on each mathematical physical model to obtain an inherent period and a damping coefficient of the floating fan platform. And finally, determining the heaving plate with the inherent frequency far away from the wave excitation frequency and the maximum damping coefficient of the floating fan platform as an optimal scheme. According to the method, model selection is carried out on the heaving plate based on the CFD method, expensive cost is not needed, accurate flow field information can be obtained by establishing different heaving plate models, the influence mechanism of the heaving plate on platform motion can be analyzed, and structural design can be optimized.

Description

Technical Field

[0001] The invention relates to the field of marine engineering technology, and in particular to a method for selecting a heave plate of an offshore floating wind turbine. Background Art

[0002] Wind power generation has a long history, and the offshore wind power industry has developed rapidly in recent years. As the capacity of a single unit continues to increase and the working sea area continues to deepen, floating foundations have more economic advantages than fixed foundations. In order to improve the stability of the floating platform, suppress the movement of the platform, and improve the power generation efficiency of the wind turbine, a suitable heave plate structure can be designed according to environmental conditions and the wind turbines carried. Heave plates of different structural forms can change the natural period and damping coefficient of the platform, and are the key to the safety, stability and economy of the floating wind power system. Heave plate selection is an important part of the design process of offshore floating wind turbines.

[0003] A large number of scholars have demonstrated the inhibitory effect of the heave plate on the movement of floating platforms. However, the numerical method based on potential flow theory ignores the viscosity of the fluid and cannot observe the influence of the heave plate on the flow characteristics. It can only give quantitative analysis results, and the accuracy needs to be improved. The water tank model test method requires processing and designing the model, preparing the test site instruments and facilities, etc., which requires a lot of time and human resources. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a method for selecting a heave plate for an offshore floating wind turbine, which aims to solve the problem that the viscosity of the fluid is ignored when selecting the heave plate based on the numerical method of potential flow theory in the related art, and the influence of the heave plate on the flow characteristics cannot be observed, while the water tank model test method requires a lot of time cost and human resources.

[0005] The present invention provides a method for selecting a heave plate of an offshore floating wind turbine, comprising:

[0006] Obtain a three-dimensional model of the floating wind turbine platform and m heave plates;

[0007] Executing a mathematical and physical model building step, the mathematical and physical model building step comprising selecting an untested one from the m three-dimensional models of the heave plates and assembling it on the three-dimensional model of the floating wind turbine platform to form a test model, and building a CFD-based mathematical and physical model based on the test model;

[0008] Based on the mathematical and physical model, the calculation threshold and boundary conditions are designed, and a turbulence model is selected. The mesh is encrypted near the mathematical and physical model area, different meshes are divided and mesh stability is verified, and a mesh division scheme is determined;

[0009] Performing a degree of freedom attenuation test on the mathematical physics model to obtain the natural period and damping coefficient of the floating wind turbine platform;

[0010] The number of executions of the mathematical and physical model establishment step is obtained. If the number of executions is less than m, the process proceeds to the mathematical and physical model establishment step. If the number of executions is equal to m, it is determined that the heave plate whose natural frequency of the floating wind turbine platform is far away from the wave excitation frequency and whose damping coefficient is the largest is the optimal solution.

[0011] According to the method for selecting a heave plate of an offshore floating wind turbine provided by the present invention, the floating wind turbine platform comprises:

[0012] The columns include three columns, and the axes of the three columns form a triangular prism;

[0013] A horizontal brace, the horizontal brace is connected to the top between two adjacent vertical columns and is perpendicular to the vertical columns;

[0014] A buoy, the buoy is connected to the bottom between two adjacent columns and is perpendicular to the columns;

[0015] An oblique brace is provided between the upright column and the horizontal brace.

[0016] According to the method for selecting a heave plate for an offshore floating wind turbine provided by the present invention, the heave plate comprises a first disc, the diameter of the first disc being greater than the diameter of the bottom surface of the column;

[0017] Alternatively, the heave plate includes a second disc and two first rectangular plates, the diameter of the second disc is equal to the diameter of the bottom surface of the column, the first rectangular plates extend along the radial direction of the second disc, and the two first rectangular plates are located below the buoys connected to the corresponding columns;

[0018] Alternatively, the heave plate includes a third circular disk and two second rectangular plates, the diameter of the third circular disk is larger than the diameter of the bottom surface of the column, the first rectangular plate extends radially along the second circular disk, and the two first rectangular plates are located below the buoy connected to the corresponding columns.

[0019] According to the method for selecting the offshore floating wind turbine heave plate provided by the present invention, the overlapping area between the first disk and the floating wind turbine platform is A1, the overlapping area between the second disk and the two first rectangular plates and the floating wind turbine platform is A2, and the overlapping area between the third disk and the two second rectangular plates and the floating wind turbine platform is A3, wherein A1<A2<A3.

[0020] According to the method for selecting the heave plate of an offshore floating wind turbine provided by the present invention, the boundary conditions are designed according to the size of the mathematical and physical model, including:

[0021] Define the left boundary as the velocity inlet, the right boundary as the pressure outlet, the front boundary and the rear boundary as the symmetry plane, the top boundary as the free slip wall, and the bottom boundary as the no-slip wall;

[0022] The velocity inlet and the pressure outlet are arranged to be in periodic contact to form a fully developed boundary.

[0023] According to the method for selecting the heave plate of an offshore floating wind turbine provided by the present invention, the turbulence model adopts the IDDES model.

[0024] According to the method for selecting the heave plate of an offshore floating wind turbine provided by the present invention, mesh encryption is performed near the mathematical and physical model area, different meshes are divided and mesh stability verification is performed, and determining the mesh division scheme includes:

[0025] The hybrid grid discretization form is adopted to divide the computational domain into two parts: the external fluid domain and the internal Overset dynamic grid core domain.

[0026] A cut hexahedral grid is used to verify grid independence. When the number of grids increases, the grid quality and Overset interpolation quality no longer change or the change is lower than the preset value, the optimal grid division scheme is determined.

[0027] According to the method for selecting the heave plate of an offshore floating wind turbine provided by the present invention, the degree of freedom attenuation test of the mathematical physics model includes:

[0028] The mathematical physics model is subjected to free decay tests in three directions of heave, roll and pitch, and a free decay curve is obtained.

[0029] According to the method for selecting the heave plate of an offshore floating wind turbine provided by the present invention, obtaining the natural period of the floating wind turbine platform includes:

[0030] The damping ratio ζ is obtained based on the free decay curve. The damping ratio ζ is obtained by the formula Calculated, where δ = 1 / nln(z0 / z n ), z0 is the initial amplitude in the free decay curve, z n is the amplitude at the nth cycle;

[0031] Based on the free decay curve and the damping ratio, the natural frequency with damping is determined to be ω d =2π / T d The natural frequency without damping is Where T d is the time interval between two peaks;

[0032] Based on the natural frequency ω without damping n , determine the natural period of the floating wind turbine platform as T n =2π / ω n .

[0033] According to the offshore floating wind turbine heave plate selection method provided by the present invention, obtaining the damping coefficient of the floating wind turbine platform includes:

[0034] Based on the natural frequency ω without damping n , the damping coefficient of the floating wind turbine platform is determined to be C = 2(M + A)ω n , where M is the platform mass and A is the additional mass.

[0035] The present invention adopts the above technical solution, which has the following advantages:

[0036] The method for selecting the offshore floating wind turbine heave plate provided by the present invention can assemble three-dimensional models of m different heave plates onto the three-dimensional model of the floating wind turbine platform to generate m test models, and each test model establishes a mathematical and physical model based on CFD. The calculation threshold and boundary conditions are designed for each mathematical and physical model, and a turbulence model is selected. The grid is encrypted near each mathematical and physical model area, different grids are divided and the grid stability is verified, and the grid division scheme is determined. A degree of freedom attenuation test is performed on each mathematical and physical model to obtain the natural period and damping coefficient of the floating wind turbine platform. Finally, it is determined that the heave plate with the natural frequency of the floating wind turbine platform far away from the wave excitation frequency and the largest damping coefficient is the optimal solution. The present invention selects the heave plate based on the CFD method without expensive costs. By establishing different heave plate models, accurate flow field information can be obtained, which is conducive to analyzing the influence mechanism of the heave plate on the platform movement and can optimize the structural design. Moreover, the heave plate selection method of the present invention can obtain the hydrodynamic characteristics of the platform without the need for a water tank model test, and serves the selection of floating wind turbines, and has the advantages of being economical, efficient, accurate and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 It is a schematic flow chart of a method for selecting a heave plate of an offshore floating wind turbine provided by an embodiment of the present invention;

[0039] Figure 2 is a schematic diagram of calculation thresholds and boundaries provided by an embodiment of the present invention;

[0040] Figure 3 is a schematic structural diagram of a first heave plate provided by an embodiment of the present invention;

[0041] Figure 4 is a schematic structural diagram of a second heave plate provided by an embodiment of the present invention;

[0042] Figure 5 is a schematic structural diagram of a third heave plate provided by an embodiment of the present invention;

[0043] Figure 6 is a schematic diagram of a test model of a floating wind turbine platform equipped with a first type of heave plate provided in one embodiment of the present invention;

[0044] Figure 7 is a schematic diagram of a test model of a floating wind turbine platform equipped with a second type of heave plate provided in one embodiment of the present invention;

[0045] Figure 8 It is a schematic diagram of an experimental model of a floating wind turbine platform equipped with a third type of heave plate provided in one embodiment of the present invention. Description of the drawings:

[0047] 100: floating wind turbine platform; 200: heave plate; 310: velocity inlet; 320: pressure outlet; 330: free slip wall; 340: no slip wall; 350: symmetry plane. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. 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.

[0049] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0050] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0051] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like 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 an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between 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.

[0052] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0053] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0054] The present invention provides a method for selecting a heave plate of an offshore floating wind turbine, comprising establishing a mathematical and physical model of a floating wind turbine platform equipped with a heave plate, wherein the mathematical and physical model is established using a CFD method. Based on the mathematical and physical model, a calculation threshold and boundary conditions are designed, and a turbulence model is selected. Grid encryption is performed near the mathematical model area, different grids are divided, and grid stability verification is performed to determine a grid division scheme. After the above steps are completed, a degree of freedom attenuation test is performed on the mathematical and physical model to obtain the natural period and damping coefficient of the floating wind turbine platform. The above steps are repeated, and a heave plate is replaced each time until all heave plates are replaced. Then, the heave plate with the natural frequency of the floating wind turbine platform far away from the wave excitation frequency and the largest damping coefficient is taken as the optimal solution. The method for selecting a heave plate of an offshore floating wind turbine provided by the present invention selects the heave plate based on the CFD method, without expensive costs. By establishing different heave plate models, accurate flow field information can be obtained, which is conducive to analyzing the influence mechanism of the heave plate on the platform movement and optimizing the structural design. Moreover, the heave plate selection method of the present invention can obtain the hydrodynamic characteristics of the platform without the need for a water tank model test, and serves the selection of floating wind turbines, and has the advantages of being economical, efficient, accurate and reliable.

[0055] Combine the following Figures 1 to 8 The invention describes a method for selecting a heave plate for an offshore floating wind turbine.

[0056] The present invention provides a method for selecting a heave plate of an offshore floating wind turbine, comprising the following steps:

[0057] Step S100 , obtaining a three-dimensional model of the floating wind turbine platform 100 and the m heave plates 200 .

[0058] Step S200 , selecting an untested one from the three-dimensional models of the m heave plates 200 and assembling it on the three-dimensional model of the floating wind turbine platform 100 to form a test model, and establishing a CFD-based mathematical and physical model based on the test model.

[0059] Step S300: design calculation thresholds and boundary conditions based on the mathematical and physical model, select a turbulence model, perform mesh encryption near the mathematical and physical model area, divide different grids and verify grid stability, and determine a grid division scheme.

[0060] Step S400 : performing a degree of freedom attenuation test on the mathematical physics model to obtain the natural period and damping coefficient of the floating wind turbine platform 100 .

[0061] Step S500, obtaining the number of executions of the mathematical and physical model establishment step. If the number of executions is less than m, executing steps S200 to S400. If the number of executions is equal to m, determining that the heave plate 200 whose natural frequency of the floating wind turbine platform 100 is far away from the wave excitation frequency and whose damping coefficient is the largest is the optimal solution.

[0062] Specifically, the CFD method can be regarded as a numerical simulation of the flow under the control of the basic flow equation. The continuity equation can be expressed as

[0063]

[0064] Where ρ is density, t is time, and u, v, and w are the components of the velocity vector u in the three coordinate directions.

[0065] Based on Newton's second law, the momentum conservation equations in the x, y, and z directions are obtained as follows:

[0066]

[0067]

[0068]

[0069] In the formula, P represents the pressure acting on the microelement, τ xx , τ xy , τ xz represents the component of the viscous stress τ acting on the surface of the microelement, F x 、F y 、F z Represents the volume force acting on the infinitesimal element.

[0070] Specifically, firstly, a three-dimensional model of the floating wind turbine platform 100 is drawn according to the two-dimensional drawings of the floating wind turbine platform 100 , and a three-dimensional model of the heave plate 200 is drawn according to m different two-dimensional drawings of the heave plates 200 .

[0071] Then, a three-dimensional model of a heave plate 200 that has not been tested is selected from the three-dimensional models of the m heave plates 200, and the three-dimensional model of the heave plate 200 is imported into the three-dimensional model file of the floating wind turbine platform 100. The three-dimensional model of the heave plate 200 is assembled onto the three-dimensional model of the floating wind turbine platform 100 to form a test model, and the test model is used as an input for CFD calculation to form a mathematical and physical model.

[0072] According to experience, the heave plate 200 is installed at the bottom of the floating wind turbine platform 100 for the best effect. Therefore, the three-dimensional model of the heave plate 200 can be installed at the bottom of the three-dimensional model of the floating wind turbine platform 100 .

[0073] Based on the mathematical and physical model established in the above steps, the calculation threshold and boundary conditions are designed, and the turbulence model is selected. The grid is encrypted near the above mathematical and physical model area, different grids are divided and the grid stability is verified, and finally the grid division scheme is determined.

[0074] After the above preparations are completed, a degree of freedom attenuation test is performed on the above mathematical and physical model to obtain the natural period and damping coefficient of the floating wind turbine platform 100 .

[0075] The execution times of step S200 are accumulated. If the execution times are less than m, it means that the m heave plates 200 have not completed the test. At this time, steps S200 to S400 are continued to be executed until the execution times are equal to m. At this time, the m heave plates 200 have completed the test.

[0076] Then, the m natural periods and damping coefficients obtained above are summarized, and the heave plate 200 whose natural frequency of the floating wind turbine platform 100 is far away from the wave excitation frequency and whose damping coefficient is the largest is selected and determined as the optimal solution.

[0077] The present invention selects the heave plate 200 based on the CFD method without expensive costs. By establishing a test model with three-dimensional models of different heave plates 200 installed, accurate flow field information can be obtained, which is conducive to analyzing the influence mechanism of the heave plate 200 on the platform movement and optimizing the structural design. Moreover, the present invention can obtain the hydrodynamic characteristics of the platform without the need for a water tank model test, serving the selection of floating wind turbines, and has the advantages of being economical, efficient, accurate and reliable.

[0078] In some embodiments of the present invention, the floating wind turbine platform 100 includes columns, buoys, cross braces and diagonal braces. Among them, there are three columns, the axes of the three columns are parallel, and the axes of the three columns form a triangular prism. There are three cross braces, which are connected to the top between two adjacent columns, and the three cross braces form a triangle. There are three buoys, which are connected to the bottom between two adjacent columns, and the three buoys form a triangle. The diagonal brace is set between the middle of the cross brace and the adjacent columns.

[0079] In some embodiments of the present invention, parameters such as the size, thickness and installation position of the heave plate 200 may affect the damping effect. Three sets of three-dimensional models of the heave plate 200 are designed in the embodiments of the present invention.

[0080] The first heave plate includes a first circular disk, and the outer diameter of the first circular disk is greater than the diameter of the bottom surface of the column.

[0081] The second heaving plate includes a second circular disc and two first rectangular plates. The outer diameter of the second circular disc is equal to the diameter of the bottom surface of the column. The two first rectangular plates extend radially along the second circular disc, and the two first rectangular plates are arranged in a V shape. When the second circular disc is connected to the column, the two first rectangular plates are covered under the two buoys connected to the column.

[0082] The third vertical swing plate combines the characteristics of the first vertical swing plate and the second vertical swing plate, including a third disc with the same shape as the first vertical swing plate and a second rectangular plate with the same shape as the first rectangular plate of the second vertical swing plate, and the installation form is the same as the second vertical swing plate.

[0083] Define the overlapped area of ​​the first heave plate and the platform as A1, the overlapped area of ​​the second heave plate and the platform as A2, and the overlapped area of ​​the third heave plate and the platform as A3. The three heave plates 200 satisfy A1. <A2<A3。

[0084] In some embodiments of the present invention, designing boundary conditions according to the size of the mathematical and physical model includes the following steps:

[0085] Step S310 , define the left boundary as the velocity inlet 310 , the right side as the pressure outlet 320 , the front boundary and the rear boundary as the symmetry plane 350 , the top boundary as the free slip wall 330 , and the bottom boundary as the no-slip wall 340 .

[0086] Step S320: Set the velocity inlet 310 and the pressure outlet 320 to be in periodic contact to form a fully developed boundary.

[0087] Specifically, the calculation threshold and boundary conditions are designed based on the mathematical and physical model established above, see Figure 2 , the left boundary can be defined as the velocity inlet 310, the right boundary can be defined as the pressure outlet 320, the front boundary and the rear boundary can be respectively set as the symmetry plane 350, the top boundary can be set as the free slip wall 330, and the bottom boundary can be set as the no slip wall 340. In order for the fluid to form a stable field more quickly, the velocity inlet 310 and the pressure outlet 320 are set to be in periodic contact to form a fully developed boundary.

[0088] In some embodiments of the present invention, the turbulence model may use an IDDES model which has lower mesh dependence and higher accuracy in simulating turbulent stress in the transition zone.

[0089] In some embodiments of the present invention, mesh encryption is performed near the mathematical and physical model area, different meshes are divided and mesh stability is verified, and determining the mesh division scheme includes the following steps:

[0090] Step S330, using a hybrid grid discretization form to divide the computational domain into two parts: an external fluid domain and an internal Overset dynamic grid core domain;

[0091] Step S340: Use a cut hexahedral grid to verify grid independence. When the number of grids increases, the grid quality and Overset interpolation quality no longer change or the change is lower than a preset value, the optimal grid division scheme is determined.

[0092] Specifically, in order to conduct numerical experiments on the free decay motion of offshore floating platforms, it is necessary to focus on the unsteady flow of gas and liquid media and the interpolation of the Overset dynamic mesh interface, while taking into account the computational efficiency and accuracy. It is necessary to adopt a hybrid mesh discretization form as a whole, and divide the computational domain into two parts: the external fluid domain and the internal Overset dynamic mesh core domain. A cut-type hexahedral mesh is used to verify the mesh independence. When the number of meshes increases, the mesh quality and Overset interpolation quality no longer change or change very little, which is the optimal mesh division scheme.

[0093] In some embodiments of the present invention, performing a degree of freedom decay test on a mathematical physics model includes performing a free decay test on the mathematical physics model in three directions of heave, roll and pitch, and obtaining a free decay curve.

[0094] Specifically, free decay tests in three directions of heave, roll and pitch are performed for different heave plates 200. The vortex change cloud diagrams around different heave plates 200 are observed. Obvious vortices will be formed around the heave plates 200, converting the motion potential energy of the floating body into the kinetic energy of the fluid, thereby increasing the platform motion damping and maintaining the stability of the floating wind turbine structure. Based on the flow field distribution characteristics around the heave plates 200, the differences in the motion performance of different heave plates 200 are explained, providing a qualitative analysis direction for the optimization of the heave plates 200.

[0095] In some embodiments of the present invention, obtaining the natural period and damping coefficient of the floating wind turbine platform 100 includes the following steps:

[0096] Step S410: Obtain the damping ratio ζ based on the free decay curve. The damping ratio ζ is calculated by the formula Calculated, where δ = 1 / nln(z0 / z n ), z0 is the initial amplitude in the free decay curve, z n is the amplitude at the nth cycle;

[0097] Step S420: Based on the free decay curve and the damping ratio, determine the natural frequency with damping as ω d =2π / T d The natural frequency without damping is Where T d is the time interval between two peaks;

[0098] Step S430: Based on the natural frequency ω without damping n , determine the natural period of the floating wind turbine platform 100 as T n =2π / ω n , the damping coefficient of the floating wind turbine platform 100 is C=2(M+A)ω n , where M is the platform mass and A is the additional mass.

[0099] Specifically, for a small initial displacement, the platform motion can be described as: Where M is the platform mass, A is the added mass, z is the displacement over time, C is the linear damping coefficient, and K is the restoring stiffness. The damping ratio is obtained from the free decay curve: where δ = 1 / nln(z0 / z n ), z0 is the initial amplitude in the attenuation curve, and zn is the amplitude at the nth cycle. The natural frequency with damping is ω d =2π / T d The natural frequency without damping is Where Td is the time interval between two peaks, and the natural period T is n =2π / ω n Therefore, the linear damping coefficient is: C = 2(M + A) ωn, and the heave plate 200 with a platform natural period Tn far from the wave frequency and the lowest damping coefficient C is selected as the optimal solution.

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A method for selecting a heave plate for an offshore floating wind turbine, characterized in that: include: Obtaining a three-dimensional model of a floating wind turbine platform (100) and m heave plates (200); Executing a mathematical and physical model establishment step, the mathematical and physical model establishment step comprising selecting an untested one from the m three-dimensional models of the heave plates (200) and assembling it on the three-dimensional model of the floating wind turbine platform (100) to form a test model, and establishing a CFD-based mathematical and physical model based on the test model; Based on the mathematical and physical model, the calculation threshold and boundary conditions are designed, and a turbulence model is selected. The mesh is encrypted near the mathematical and physical model area, different meshes are divided and mesh stability is verified, and a mesh division scheme is determined; Performing a degree of freedom attenuation test on the mathematical physics model to obtain the natural period and damping coefficient of the floating wind turbine platform (100); The number of executions of the mathematical and physical model establishment step is obtained; if the number of executions is less than m, the step of establishing the mathematical and physical model is turned to; if the number of executions is equal to m, the heave plate (200) whose natural frequency of the floating wind turbine platform (100) is far from the wave excitation frequency and whose damping coefficient is the largest is determined to be the optimal solution.

2. The method for selecting a heave plate for an offshore floating wind turbine according to claim 1, characterized in that: The floating wind turbine platform (100) comprises: The columns include three columns, and the axes of the three columns form a triangular prism; A horizontal brace, the horizontal brace is connected to the top between two adjacent vertical columns and is perpendicular to the vertical columns; A buoy, the buoy is connected to the bottom between two adjacent columns and is perpendicular to the columns; An oblique brace is provided between the upright column and the horizontal brace.

3. The method for selecting a heave plate for an offshore floating wind turbine according to claim 1, characterized in that: The heave plate (200) comprises a first disc, the diameter of the first disc being greater than the diameter of the bottom surface of the column; Alternatively, the heave plate (200) comprises a second circular disk and two first rectangular plates, the diameter of the second circular disk is equal to the diameter of the bottom surface of the column, the first rectangular plates extend in the radial direction of the second circular disk, and the two first rectangular plates are located below the buoys connected to the corresponding columns; Alternatively, the heave plate (200) comprises a third circular disk and two second rectangular plates, the diameter of the third circular disk is greater than the diameter of the bottom surface of the column, the first rectangular plate extends radially along the second circular disk, and the two first rectangular plates are located below the buoy connected to the corresponding column.

4. The method for selecting a heave plate for an offshore floating wind turbine according to claim 3, characterized in that: The overlapping area between the first circular disk and the floating wind turbine platform (100) is A1, the overlapping area between the second circular disk and the two first rectangular plates and the floating wind turbine platform (100) is A2, and the overlapping area between the third circular disk and the two second rectangular plates and the floating wind turbine platform (100) is A3, wherein A1<A2<A3.

5. The method for selecting a heave plate for an offshore floating wind turbine according to claim 1, characterized in that: Designing boundary conditions according to the size of the mathematical and physical model includes: Define the left boundary as the velocity inlet (310), the right boundary as the pressure outlet (320), the front boundary and the rear boundary as the symmetry plane (350), the top boundary as the free slip wall (330), and the bottom boundary as the no slip wall (340); The velocity inlet (310) and the pressure outlet (320) are arranged to be in periodic contact to form a fully developed boundary.

6. The method for selecting a heave plate for an offshore floating wind turbine according to claim 1, characterized in that: The turbulence model adopts the IDDES model.

7. The method for selecting a heave plate for an offshore floating wind turbine according to claim 1, characterized in that: The mesh is encrypted near the mathematical and physical model area, different meshes are divided and mesh stability is verified, and the mesh division scheme is determined to include: The hybrid grid discretization form is adopted to divide the computational domain into two parts: the external fluid domain and the internal Overset dynamic grid core domain. A cut hexahedral grid is used to verify grid independence. When the number of grids increases, the grid quality and Overset interpolation quality no longer change or the change is lower than the preset value, the optimal grid division scheme is determined.

8. The method for selecting a heave plate for an offshore floating wind turbine according to claim 1, characterized in that: The degree of freedom decay test of the mathematical physics model includes: The mathematical physics model is subjected to free decay tests in three directions of heave, roll and pitch, and a free decay curve is obtained.

9. The method for selecting a heave plate for an offshore floating wind turbine according to claim 8, characterized in that: Obtaining the natural period of the floating wind turbine platform (100) comprises: The damping ratio ζ is obtained based on the free decay curve. The damping ratio ζ is obtained by the formula Calculated, where δ = 1 / nln(z0 / z n ), z0 is the initial amplitude in the free decay curve, z n is the amplitude at the nth cycle; Based on the free decay curve and the damping ratio, the natural frequency with damping is determined to be ω d =2π / T d The natural frequency without damping is Where T d is the time interval between two peaks; Based on the natural frequency ω without damping n , determine the natural period of the floating wind turbine platform (100) as T n =2π / ω n .

10. The method for selecting a heave plate for an offshore floating wind turbine according to claim 9, characterized in that: Obtaining the damping coefficient of the floating wind turbine platform (100) includes: Based on the natural frequency ω when there is no damping n , the damping coefficient of the floating wind turbine platform (100) is determined to be C=2(M+A)ω n , where M is the platform mass and A is the additional mass.

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