Novel OC4-DeepCWind semi-submersible platform

Abstract

The invention belongs to ocean engineering, and particularly relates to a novel OC4-DeepCWind semi-submersible platform which is used for solving the problems that a cylindrical upper stand column of an existing OC4 platform is large in wave load, overweight in structural weight, insufficient in stability and the like under deep water and severe sea conditions. According to the scheme, an upper stand column of an existing OC4 platform offset column is optimized into a rounded triangular prism, dynamic responses of floating bodies before and after optimization are basically the same, and the dynamic responses of the floating bodies are judged to be basically the same according to set conditions. After the scheme is optimized, not only is the weight of the structure reduced, but also the wave force is more uniformly dispersed on the surface and the wave climbing effect is weakened through the geometrical shape of the rounded triangular prism, so that the impact load of waves on the platform is reduced, the anti-wave capability and the stability of the platform are improved, the shaking frequency of the platform is reduced, and the service life of the structure is prolonged.

Description

Technical Field

[0001] This case involves marine engineering, and in particular, a new type of 0C4-DeepCWind semi-submersible platform. Background Art

[0002] In the marine environment, the platform structure needs to withstand multiple environmental loads such as waves, wind, and currents. In particular, the impact of wave loads on the platform will have a significant impact on the stability and safety of the structure. The columns on the traditional OC4-DeepCWind (Open Collaboration for Offshore Wind Energy, deep-sea wind power floating platform) semi-submersible platform usually adopt a cylindrical structure design. This design performs well in shallow water environments, but it exposes the following disadvantages in deep water and complex sea conditions:

[0003] 1. Large wave load: The cross-section of the cylindrical upper column is large and is directly impacted by the wave force. The wave force is proportional to the cross-sectional area. Therefore, under the action of waves, the cylindrical structure is subjected to significant wave loads, resulting in a significant increase in the wave climbing effect, which affects the stability and safety of the platform.

[0004] 2. Heavy weight: To ensure structural strength, cylindrical upper columns usually require thicker walls and larger diameters, which increases the weight of the platform. Excessive structural weight not only increases material costs, but also poses challenges to the buoyancy and overall design of the platform, especially in deepwater environments, where excessive weight can affect the self-stability of the platform.

[0005] 3. Insufficient structural stability: The cylindrical upper column structure is prone to vibration under wave impact, with a large vibration amplitude, which is not conducive to the long-term stability of the platform and may cause fatigue damage, thereby reducing the service life of the platform.

[0006] To this end, some designs have tried truss structures to reduce the load-bearing area, but their stability is low and the maintenance cost is high. Summary of the invention

[0007] In view of the problem that the traditional 0C4-DeepCWind offshore platform is subjected to large wave loads in deep water and complex sea conditions, resulting in insufficient platform stability and safety, this case proposes a new type of 0C4-DeepCWind semi-submersible platform. By optimizing the upper column structure design, it not only reduces the structure's wave-facing area and wave loads, but also improves the overall torsional rigidity and stability. At the same time, the rounded corner design can effectively weaken the wave climbing effect and reduce the damage to the platform structure caused by wave impact. And achieve optimization effects in terms of weight, size and position control of the rounded triangular prism, so that it can better adapt to complex sea conditions. The specific technical solution is as follows.

[0008] A novel 0C4-DeepCWind semi-submersible platform, the semi-submersible platform comprises a main column, an offset column, a cross brace and an oblique brace, wherein the offset column is located around the main column, the offset column is composed of a base column and an upper column, the straight line determined by the cross-sectional centers of the base column and the upper column is perpendicular to the cross-sectional center, the base columns are connected by a cross brace, the upper columns are connected by a cross brace, the upper ends of the main columns and the upper ends of the upper columns are connected by a cross brace, the lower ends of the main columns and the base columns are connected by a cross brace, the lower ends of the main columns and the upper ends of the upper columns are connected by an oblique brace, the main columns, the base columns and the cross brace are cylinders, the oblique brace is an oblique cylinder, and the upper columns of the three identical offset columns of the semi-submersible platform are rounded triangular prisms , each rounded triangular prism has a face facing the main column, and there is a fulcrum for the horizontal brace or the diagonal brace on the face, and the rounded corner corresponding to the face faces outward; for the cross sections of the three rounded triangular prisms located on the same plane, the three sides of each cross section are extended and intersected, and each cross section forms a triangle, and the circumscribed circle of the triangle is the first circle; the semi-submersible platform to which the rounded triangular prism belongs is regarded as the first semi-submersible platform, and the semi-submersible platform to which the cylinder of the same height belongs is regarded as the second semi-submersible platform, and the circle determined by the cross section of the cylinder is the same as the first circle, then the dynamic responses of the floating bodies of the first semi-submersible platform and the second semi-submersible platform are basically the same, and the basically same dynamic responses of the floating bodies are judged by setting conditions.

[0009] In one implementation of the above technical solution, the setting condition is: the absolute value of the pitch error of the first semi-submersible platform and the second semi-submersible platform does not exceed a first set value, and the absolute value of the heave error does not exceed a second set value.

[0010] In one implementation of the above technical solution, the angle formed by extending the two sides of the rounded corner and intersecting them is the first angle, and the circle determined by the three vertices of the first angles is the second circle, and the three vertices of the first angles divide the circumference of the second circle equally.

[0011] In one implementation of the above technical solution, the straight line where the center of the second circle and the center of the first circle are located is taken as the y-axis, and the center of the first circle is taken as the origin, then the straight line where the vertex of the first angle and the center of the second circle are located is the first straight line, and the angle range between the first straight line and y is [0°, 45°].

[0012] In one implementation of the above technical solution, the radius of the rounded corner is in the range of [1 meter, 2 meters].

[0013] In one implementation of the above technical solution, the radius of the rounded corner is 1.5 meters.

[0014] In one implementation of the above technical solution, the triangle is an equilateral triangle.

[0015] Beneficial technical effects of this case: By changing the upper column from a cylinder to a rounded triangular prism, the design of this case effectively reduces the impact of wave loads on the platform. The rounded triangular prism structure can reduce the frontal impact area of ​​waves, disperse and weaken the direct effect of wave forces on the structure, thereby significantly reducing wave loads. In addition, the structural shape of the rounded triangular prism helps to reduce the overall weight of the platform, while improving the torsional rigidity and stability of the structure, making the platform more stable and safe under the action of waves. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0017] Figure 1 , schematic diagram for comparison between the original model and the optimized model.

[0018] Figure 2 , schematic diagram of standard platform structure.

[0019] Figure 3 , Schematic diagram of dynamic response comparison before and after model optimization.

[0020] Figure 4 , Schematic diagram of the time history of wave loads under different conditions.

[0021] Figure 5 , Schematic diagram of the time history of wave loads under different conditions before and after model optimization. DETAILED DESCRIPTION

[0022] In the field of marine engineering, the 0C4-DeepCWind semi-submersible platform is widely used to support heavy equipment such as wind turbines and drilling rigs. Its structure needs to resist multiple marine loads such as waves, wind, and currents for a long time. However, the cylindrical upper column of the existing 0C4 platform faces challenges such as large wave loads, heavy structural weight, and insufficient stability in deep water and harsh sea conditions. In particular, the large cross-sectional area of ​​the cylindrical structure causes it to be subjected to concentrated forces under the action of waves, resulting in an increase in the platform's swaying amplitude, affecting safety and stability. Although there are truss structures that reduce the force-bearing area, their stability still needs to be improved, and the maintenance cost is high.

[0023] Based on this, this case proposes a new type of 0C4-DeepCWind semi-submersible platform, in which the cross section of the upper column is changed to a rounded triangular prism, so that the improved rounded triangular prism and the original column can determine the position and fillet radius of the rounded triangular prism while the dynamic response of the floating body is basically consistent, so that the improved 0C4-DeepCWind semi-submersible platform can take advantage of the geometric advantages of the circle and triangle in the rounded triangular prism, reduce the wave-facing area of ​​the structure, reduce the wave load, and improve the overall torsional rigidity and stability. At the same time, the use of rounded corners can effectively weaken the wave climbing effect, reduce the damage to the platform structure caused by wave impact, and achieve optimization in weight control, providing a better design option for the platform in complex sea conditions.

[0024] The following will be combined with the accompanying drawings to clearly and completely describe how to implement the technical solution of this case. Obviously, the described implementation method is only a part of the implementation method of this case, not all of the implementation methods. Based on the implementation method in this case, all other implementation methods obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0025] (I) Numerical simulation conditions

[0026] The stability of floating offshore wind power platforms is a basic requirement and important guarantee for the efficiency and safety of wind power generation systems. Through rich experience in numerical simulation, the shape of the offset column upper column of the OC4-DeepCWind semi-submersible platform was optimized, and the original cylindrical upper column was replaced with a rounded triangular prism. This unique design significantly reduces the contact area between the offset column upper column and the waves, and the corners of the rounded triangular prism also play a role in diverting the waves. Therefore, in theory, the optimized platform will be subject to smaller wave loads.

[0027] See also Figure 1 , which is a comparison diagram of the original model and the optimized model. From top to bottom, they are the free view, top view and top view of the same perspective. From the model schematic diagram, it can be seen that the semi-submersible platform includes main columns, offset columns, cross braces and diagonal braces. The height of the main column is the same as that of the offset column. The offset column consists of a base column and an upper column. The upper column is located on the base column and has the same center line. Figure 1 The semi-submersible platform shown in the figure is composed of three offset columns and one main column. The upper end of the main column is connected to the upper end of each upper column through a cross brace. The base columns are connected by a cross brace. The upper ends of every two upper columns are connected by a cross brace. The lower end of the main column is connected to the upper end of the base column by a diagonal brace. The main column, base column, and cross brace are cylinders, and the diagonal brace is an oblique cylinder. The upper columns of the three identical offset columns of the optimized model are rounded triangular prisms, each of which has a face facing the main column, and there is a fulcrum with a cross brace or a diagonal brace on the face, and the rounded corner corresponding to the face is facing outward.

[0028] The improvement of this solution is that the cross section of the upper column is changed from a circle to a rounded triangle.

[0029] The original and optimized platform structures are as follows: Figure 2 As shown, Figure 2 The left side is a top view of the standard platform structure, and the right side is a side view. The cross section of the upper column of the offset column of the optimized model is an equilateral triangle inscribed in the cross section circle of the upper column of the offset column of the original model, and a 1.5-meter fillet is applied to it. Although the fillet radius is 1.5 meters when implemented here, the range of the fillet radius can be [1 meter, 2 meters]. Although an equilateral triangle is inscribed here, other triangles can also be selected for processing, and selecting an equilateral triangle can reduce the amount of calculation.

[0030] During the optimization, the positions and connection relationships of the main column, horizontal brace, diagonal brace, and base column remain unchanged, but the position of the side of the rounded triangular prism facing the main column cannot be determined, that is, the rounded triangular prism has different positional characteristics when it rotates around its vertical center line. The cross-section circle of the column on the offset column of the original model is taken as the first circle, and the angle formed by the two sides of the rounded corner extending and intersecting is taken as the first angle. The circle determined by the vertices of the three first angles is taken as the second circle, and the vertices of the three first angles bisect the circumference of the second circle. The straight line where the center of the second circle and the center of the first circle are located is taken as the y-axis, and the center of the first circle is taken as the origin. The straight line where the vertex of the first angle and the center of the second circle are located is the first straight line, and the angle range between the first straight line and y is [0°, 45°], preferably 0°, that is, the first straight line coincides with the y-axis. This angle range reflects the adjustable range of the position of the rounded triangular prism.

[0031] It should be noted that the optimization goal of this case is to compare the hydrodynamic coefficient (drag coefficient Cd) of the original model and the optimized model while ensuring that the dynamic response of the floating body is basically consistent. The dynamic response of the floating body is basically consistent through the set conditions. The radius of the rounded corner of the rounded corner of the triangular prism in the above optimized model, the first straight line determined by the rounded corner and

[0032] The semi-submersible platform corresponding to the optimized model is used as the first semi-submersible platform, and the semi-submersible platform corresponding to the original model is used as the first semi-submersible platform, then the dynamic responses of the floating bodies of the two are basically the same, and the dynamic responses of the floating bodies are basically the same. The setting conditions are determined by setting conditions. In one embodiment, the setting conditions are: the absolute value of the sway error of the first semi-submersible platform and the second semi-submersible platform does not exceed the first set value, and the absolute value of the heave error does not exceed the second set value.

[0033] In one embodiment, the original model and the optimized model meet the set conditions, which means that the absolute value of the longitudinal sway error does not exceed 2%, and the absolute value of the heave error does not exceed 2.5%. It can be considered that the dynamic response of the floating body is basically consistent. The dynamic response of the two models is as follows Figure 3shown. Figure 3 The left side is a comparison diagram of Surge before and after optimization. Figure 3 On the right is a schematic diagram comparing Heave before and after optimization. In the two figures, the red line corresponds to 0C4-Original, which is the dynamic response before optimization, and the green line corresponds to 0C4-Optimize, which is the dynamic response after optimization.

[0034] The numerical parameters before and after optimization are shown in Table 1.

[0035] Table 1 Detailed design parameters of standard floating platform

[0036]

[0037] (II) Numerical simulation method

[0038] The simulation of the fluid around the pile leg involves two phases: water and air. We assume that both water and air are incompressible fluids. The governing equations for the flow of three-dimensional incompressible viscous fluids include the mass conservation equation and the Navier-Stokes equations, which are solved by using an open source field Operation and run solve. The continuity equation and momentum equation are expressed in Cartesian coordinates as follows:

[0039]

[0040] in, and Represent the velocity and gravity acceleration respectively. P, ρ, μ represent the pressure, density and dynamic viscosity coefficient respectively. represents the surface tension, is a wave damping term, which is used to eliminate the influence of reflected waves. The absorption coefficient α is defined as:

[0041]

[0042] Where ζ is the damping coefficient, which is 3.5 in the simulation, and x in is the starting position of the damping zone, and L is the length of the damping zone.

[0043] The static boundary method (SBM) is used to generate regular waves. The incident wave boundary is fixed, and the velocity and free surface position of the water particles are specified according to the corresponding wave theory. Stokes waves are used at the fixed inlet wave boundary, and more complex correction terms are added to more accurately describe the behavior of the waves. The regular wave profile is expressed as:

[0044]

[0045] The wave velocity field is defined as follows, where u represents the velocity in the direction of wave propagation and w represents the velocity perpendicular to the direction of wave propagation:

[0046]

[0047] Where λ, T, H, k, ω, d represent the incident wavelength, wave period, wave height, wave number, angular frequency and water depth respectively. z represents the vertical position from the water surface to the bottom of the water, and together with the wave number k and water depth d, it describes the velocity distribution of waves under different water depth conditions.

[0048] The water-air interface is captured by using the volume of fluid (VOF) method, which distinguishes different states of fluid by the volume fraction α, which is defined as follows:

[0049]

[0050] The volume fraction governing equation is as follows:

[0051]

[0052] in represents the velocity. The density ρ and viscosity μ of the two fluids are calculated by the weight function of the volume fraction α, which is defined as follows:

[0053]

[0054] Among them, ρ1 and ρ2 represent the density of water and air respectively; μ1 and μ2 represent the viscosity of water and air respectively.

[0055] The governing equations and VOF equations are discretized by the finite volume method (FVM). The PIMPLE algorithm, which combines the Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) and Pressure-Implicit with Splitting of Operators (PISO), is used to solve the coupling of velocity and pressure. The implicit Euler scheme is used for time discretization. Gaussian linear interpolation is used for gradient calculation. The Laplace term is discretized using the Gaussian linear scheme. The upwind scheme is used to handle the convection term, and the Gaussian linear correction scheme is used to handle the viscous diffusion term. The Gaussian interface compression scheme is used to discretize the volume fraction equation to accurately capture the free surface.

[0056] 3. ...

[0057] In this scheme, the ratio of the numerical simulation size of the OC4-DeepCWind semi-submersible platform to the standard size is 1: 10. The accuracy of the numerical method is verified by different incident wave parameters such as water depth D, wave height H, immersion depth d, and wave period T as shown in Table 2, and different incident wave parameters such as wave height H, wave steepness H / λ, wavelength λ, wave period T, and KC number as shown in Table 3.

[0058] Table 2 Wave test case 1

[0059]

[0060] Table 3 Wave test case 2

[0061]

[0062] Figure 4 The wave force of a horizontally placed cylinder under the action of waves progresses with time at different wave heights ( Figure 4 1 in the first row), different immersion depths ( Figure 4 ) and different wave periods ( Figure 4 The results show that the theoretical value (Analytical solution (LIU, 2020)), experimental value (Experimental data (LIU, 2020)) and numerical simulation value (Numerical simulation (Present)) show a highly consistent trend, which verifies the accuracy and rationality of the numerical method of this study. Under different wave heights, the amplitude of the wave load increases significantly with the increase of wave height. This phenomenon can be explained by wave theory, that is, the greater the wave height, the stronger the nonlinearity of the wave, the more energy the wave carries, and the greater the wave load applied to the cylinder. This trend is consistent with the performance of inertial force and resistance in Morison equation. Due to the enhancement of wave nonlinearity, the error between numerical simulation and analytical solution increases from 1.88% at H = 0.03m to 6.82% at H = 0.09m. However, the error with the experimental value of a = 0.09m is only 0.39%.

[0063] At different immersion depths, due to the simple shape of the horizontal cylinder and the lack of optimized force structure, the surface area, contact water volume and hydrodynamic pressure of the cylinder increase linearly with the immersion depth. Therefore, it can be observed that with the increase of immersion depth, the cylinder will be subjected to greater water pressure and hydrodynamic force, resulting in an increase in the peak value of wave load. This phenomenon is very important in actual marine engineering, because the immersion depth is a parameter that needs to be considered when designing marine structures. The errors between the numerical simulation and the analytical solution at d = 0.075m and d = 0.113m are 4.47% and 9.11%, respectively. In addition, Liu et al. (2020) also found that when the immersion depth is small (d / D < 0.3), the wave load changes greatly; when the immersion depth is large (d / D> 0.3), the trend of increasing wave load remains almost unchanged.

[0064] Under different wave periods, the phenomenon that the force on the cylinder increases with the increase of the wave period is consistent with the Morrison equation (Wade et al., 1976), Keulegan-Carpenter number (Sarpkaya, T., 1986) and wave diffraction theory. That is, when the wavelength is smaller than the diameter of the cylinder, the wave force is dominated by the resistance term, and the flow and local effects are dominant at this time. The flow effect causes part of the energy to be dissipated in the form of eddy currents, thereby reducing the net force on the structure, and the wave load increases with the increase of the period. The errors of the numerical simulation and the analytical solution at T = 0.9s and T = 1.0s are 4.77% and 4.40% respectively.

[0065] Figure 5 The first row is the performance of the model before (0C4-Original) and after (0C4-Optimize) optimization at different wave heights. As the wave height increases, the wave load on the 0C4-DeepCWind semi-submersible platform will increase significantly, mainly because the wave height directly affects the kinetic energy of the water body and the amplitude of the wave load. The higher the wave, the greater the change in buoyancy acting on the platform, resulting in more drastic force fluctuations between the crest and the trough of the platform. Compared with the original model, the optimized platform can better control the fluctuation of the wave load amplitude at higher wave heights. Specific data show that when H = 0.25m, the wave load on the optimized platform is reduced by 12.47%; when H = 0.5m, the force fluctuation remains in a relatively small range, and the wave load is reduced by 12.98%. These results show that the optimized design improves the platform's wave resistance and reduces the negative impact of waves on the platform.

[0066] Figure 5 The second row shows the performance of the model before and after optimization at different immersion depths. As the immersion depth increases, the wave load on the 0C4-DeepCWind semi-submersible platform gradually decreases, which is different from the force law of the horizontal cylinder. The reason for this phenomenon is that the platform provides buoyancy through multiple offset columns, and the design purpose is to disperse the wave and fluid pressure to make the buoyancy and force more stable. Although the force on multiple pillars increases with the increase of immersion depth, the wave energy is mainly concentrated near the free surface. As the depth increases, the wave energy decays rapidly, resulting in a decrease in the overall force on the platform (A.Robertson et al., 2014). The design of the platform effectively improves stability and reduces the force of waves on the platform. When the immersion depth increases from d = 1.0m to d = 1.5m, the negative force of the original model is greatly reduced, and the optimized model shows excellent stability. At d = 1.0m, the wave load on the optimized platform is reduced by 30.10%, while at d = 1.5m, the wave load is reduced by 15.67%.

[0067] Figure 5 The third row shows the performance of the model before and after optimization at different wave periods. Since the wavelength is larger than the cylinder diameter, the wave load is mainly dominated by the inertial force, so the wave load decreases with the increase of the wave period. At T = 3.8s, the optimized platform is slightly less stressed than the original design, by about 2.37%. However, some irregular fluctuations appeared in the trough area, probably because the nonlinear effect of hydrodynamics is more significant under shorter wave periods, but these irregularities gradually stabilized over time. At T = 4.0s, the stress on the optimized platform was significantly reduced, by 20.49%, and the stress curves before and after optimization showed relatively smooth changes at the crests and troughs, without obvious abnormal fluctuations.

[0068] Overall, the optimized 0C4-DeepCWind semi-submersible platform has demonstrated better wave load control capability and stability under different wave heights, immersion depths and wave periods, further improving its wave resistance performance in complex sea conditions.

[0069] (IV) Summary

[0070] In summary, compared with the cylindrical structure, the rounded triangular prism upper column design of the present invention has significant advantages in reducing wave loads, reducing structural weight and enhancing vibration resistance. It is more suitable for application in deep water and complex sea conditions, and helps to improve the operating stability, durability and economy of the platform.

[0071] Specifically, the rounded triangular prism cross-section greatly reduces the wave-facing area compared to the cylindrical one, dispersing the concentrated wave force. When the waves contact the upper column, they can be dispersed along different planes and corners, weakening the direct impact of the wave force, significantly reducing the wave climbing effect, and making the platform more stable in severe sea conditions. Therefore, compared with the cylindrical structure, the rounded triangular prism structure can effectively reduce the wave load, which helps to improve the safety and long-term operation stability of the platform.

[0072] The rounded triangular prism design reduces the amount of material while maintaining strength, reducing the overall weight and making the platform easier to build, transport and maintain. Compared with the cylindrical structure, the reduced weight not only reduces the material cost, but also improves the buoyancy and self-stability of the platform, which is particularly suitable for deep-water environments.

[0073] The rounded triangular prism geometry gives it higher torsional rigidity, effectively suppressing wave-induced structural vibrations. The multi-plane and rounded design evenly distributes the impact of wave forces, rather than concentrating them in a single direction, thereby reducing vibration frequency, fatigue damage, and extending the service life of the platform. Compared with the traditional cylindrical design, the rounded triangular prism has significantly improved vibration resistance, helping the platform maintain structural integrity during long-term operation.

[0074] It should be noted that the cross-sectional design and optimization scheme of this case may have potential applications in other fields, in addition to being applied to offshore platform pile legs. For example, similar structural designs may be applicable to engineering projects that require stable structures, such as bridges and wind turbine brackets.

[0075] Through the above description of the embodiments, those skilled in the art can clearly understand that although the cross-sectional design of a rounded triangle has been adopted in the present disclosure, there may be further fine-tuning of the shape to optimize the performance in a specific engineering environment. This may include adjusting parameters such as angles and fillet radius to adapt to different water flow and wave conditions.

[0076] The above 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 technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0077] Through the description of the above implementation methods, those skilled in the art can clearly understand that the simulation calculation method involved in the present disclosure can be implemented by means of software plus necessary general hardware, and of course can also be implemented by special hardware including special integrated circuits, special CPUs, special memories, special components, etc. In general, all functions completed by computer programs can be easily implemented by corresponding hardware, and the specific hardware structures used to implement the same function can also be various, such as analog circuits, digital circuits or special circuits, etc. However, for the present disclosure, software program implementation is a better implementation method in most cases.

[0078] Although the embodiments of the present invention are described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments and application fields, which are merely illustrative and instructive, rather than restrictive. A person skilled in the art can make many forms under the guidance of this specification and without departing from the scope of protection of the claims of the present invention, all of which are protected by the present invention.

Claims

1. A novel OC4-DeepCWind semi-submersible platform, comprising a main column, an offset column, a cross brace, and an oblique brace, wherein the offset column is located around the main column, the offset column is composed of a base column and an upper column, the straight line determined by the cross-sectional centers of the base column and the upper column is perpendicular to the cross-sectional area, the base columns are connected by a cross brace, the upper columns are connected by a cross brace, the upper ends of the main columns and the upper ends of the upper columns are connected by a cross brace, the lower ends of the main columns and the base columns are connected by a cross brace, the lower ends of the main columns and the upper ends of the upper columns are connected by an oblique brace, the main columns, the base columns, the cross brace, and the oblique brace are cylinders, characterized in that: The upper columns of the three identical offset columns of the semi-submersible platform are rounded triangular prisms, each of which has a face facing the main column, a fulcrum for the horizontal brace or the diagonal brace, and the rounded corner corresponding to the face facing outwards; For the cross sections of three rounded triangular prisms located on the same plane, the three sides of each cross section are extended and intersected, and each cross section forms a triangle, and the circumscribed circle of the triangle is the first circle; The semi-submersible platform to which the rounded triangular prism belongs is regarded as the first semi-submersible platform, and the semi-submersible platform to which the cylinder of the same height belongs is regarded as the second semi-submersible platform. The circle determined by the cross-section of the cylinder is the same as the first circle. Then, the dynamic responses of the floating bodies of the first semi-submersible platform and the second semi-submersible platform are basically the same. The basically same dynamic responses of the floating bodies are judged by setting conditions.

2. The semi-submersible platform according to claim 1, characterized in that: The setting condition is that the absolute value of the pitch error of the first semi-submersible platform and the second semi-submersible platform does not exceed the first setting value, and the absolute value of the heave error does not exceed the second setting value.

3. The semi-submersible platform according to claim 1, characterized in that: The angle formed by extending the two sides of the rounded corner and intersecting them is the first angle, and the circle determined by the three vertices of the first angles is the second circle. The three vertices of the first angles divide the circumference of the second circle equally.

4. The semi-submersible platform according to claim 3, characterized in that: Take the straight line where the center of the second circle and the center of the first circle are located as the y-axis, and the center of the first circle as the origin, then the straight line where the vertex of the first angle and the center of the second circle are located is the first straight line, and the adjustment range of the angle between the first straight line and y is [0°, 45°].

5. The semi-submersible platform according to claim 1, characterized in that: The radius of the fillet outside the punch is in the range of [1m, 2m].

6. The semi-submersible platform according to claim 5, characterized in that: The radius of the rounded corner outside the punch is 1.5 meters.

7. The semi-submersible platform according to claim 1, characterized in that: The triangle is an equilateral triangle.

8. The semi-submersible platform according to claim 2, characterized in that: The first setting value is 2%, and the second setting value is 2.5%.

9. The semi-submersible platform according to claim 3, characterized in that: Take the straight line where the center of the second circle and the center of the first circle are located as the y-axis, and the center of the first circle as the origin, then the straight line where the vertex of the first angle and the center of the second circle are located is the first straight line, and the angle between the first straight line and y is 0°.

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