A semi-submersible platform with movable wave deflectors

Abstract

This invention discloses a semi-submersible offshore platform with movable wave-breaking plates, belonging to the field of floating wind turbine turbulence. It comprises multiple platform components connected by trusses. Each platform component includes a column with a vertically oriented axis. Several movable wave-breaking plates are provided on the outer wall of the column, spirally distributed around the column's axis. Each movable wave-breaking plate includes an anti-roll plate fixed to the column's peripheral wall. A hinge is located at the lower end of the anti-roll plate; one side of the hinge is fixedly connected to the anti-roll plate, and the other side is connected to an arc-shaped cover plate. The hinge's rotation axis is horizontally oriented. The side of the arc-shaped cover plate facing the column's outer wall bulges upwards, allowing it to rotate around the hinge's axis under buoyancy. This invention can reduce vortex-induced motion and decrease platform oscillation.

Description

Technical Field

[0001] This invention belongs to the field of floating wind turbine disturbance, specifically relating to a semi-submersible offshore platform with a movable wave deflector. Background Technology

[0002] Among various energy types, marine energy stands out due to its renewable and clean nature. Semi-submersible platforms are the most widely used method for developing marine resources.

[0003] Research on Dynamic Response of Semi-Submersible Platform for Floating Wind Turbine with Novel Spiral Baffles [J]. Yu Jingmei; Liu Yaohong; Chang Yun; Zhao Guang. Thermal Power Engineering. 2023(07). The results show that: in the frequency domain analysis, the baffles can significantly reduce the excitation torque of the heave wave on the platform, and have a certain improvement on the platform's heave, roll, pitch radiation damping and added mass. The peak value of the platform's frequency domain amplitude response operator (RAO) is significantly reduced. After installing the baffles, the platform's natural period increases and its anti-resonance performance is better. In the time domain analysis, the baffle arrangement pitch has little effect on the platform's motion response in the heave and pitch directions, but it significantly suppresses the roll motion response.

[0004] However, in the aforementioned semi-submersible wind turbine platform, when waves around the column move upwards along the column, alternating vortex shedding occurs at the separation point of the boundary layer on both sides. The alternating vortex shedding on both sides of the floating structure causes the appendage structure to be subjected to periodic pulsating forces, resulting in periodic, large-amplitude vortex-induced motion. This causes the floating structure to be compressed in both the downstream and crossstream directions, generating relative motion with the waves. At this time, the floating structure influences the wave flow pattern in the opposite direction, changing the vortex discharge state of the surrounding wake, i.e., vortex-induced motion occurs. This vortex-induced motion leads to platform oscillation. Summary of the Invention

[0005] The present invention provides a semi-submersible offshore platform with a movable wave deflector, which is designed to reduce vortex-induced motion and decrease platform oscillation.

[0006] To achieve the above objectives, the present invention provides a semi-submersible offshore platform with movable wave-breaking plates, comprising multiple platform components connected by trusses. The platform components are characterized in that each component includes a column with a vertically oriented axis. Several movable wave-breaking plates are provided on the outer wall of the column, and these plates are spirally distributed around the column's axis. Each movable wave-breaking plate includes an anti-roll plate fixed to the peripheral wall of the column. A hinge is provided at the lower end of the anti-roll plate; one side of the hinge is fixedly connected to the anti-roll plate, and the other side of the hinge is connected to an arc-shaped cover plate. The hinge's rotation axis is horizontally oriented. The side of the arc-shaped cover plate facing the outer wall of the column bulges upwards, and the arc-shaped cover plate can rotate around the hinge's axis due to buoyancy.

[0007] Furthermore, several first connecting rings are fixed on the outer wall of the arc-shaped cover plate facing the column, and several second connecting rings are fixed on the outer wall of the column. The first connecting rings and the second connecting rings are arranged in a one-to-one correspondence. Hook springs are arranged between the first connecting rings and the second connecting rings, and the two ends of the hook springs are connected to the first connecting rings and the second connecting rings respectively. The hook springs are in a stretched state.

[0008] As shown by the average drag curve, within the calculated reduced velocity range, the average drag of the column with the added hook spring structure changes significantly with increasing velocity, indicating that the vertical drag of the column is greatly affected by vortex-induced motion. In contrast, the average drag of the column with the added hook spring structure changes very little with increasing velocity, indicating that the presence of the hook spring significantly increases the vertical damping of the column within the calculated reduced velocity range, reduces the influence of vortex-induced motion, and makes the motion more stable. Furthermore, from the root mean square response curve of the lift coefficient, compared to the fixed side plate, the amplitude of the root mean square response of the lift coefficient decreases at different reduced velocities after adding the hook spring structure, and the curve changes from a large change with increasing velocity to a more gradual change. This indicates that the presence of the hook spring reduces the effect of the incoming flow pressure on the column vibration, resulting in a smaller and more stable lift. Therefore, it shows that adding the hook spring suppresses the influence of the incoming flow pressure on the column's motion response, and the constraint and damping effect provided by the hook spring effectively reduces the platform's vertical motion response.

[0009] Furthermore, the arc-shaped cover plate is provided with several through holes, which penetrate the arc-shaped cover plate, and the axial direction of the through holes is along the vertical direction.

[0010] The contact area between the arc-shaped cover plate and the waves can be changed, which intensifies the collision, impact and mutual compression of water particles in the opening when the waves flow through, thereby enhancing the nonlinearity of wave motion, aggravating wave breaking, strengthening water turbulence, increasing wave energy loss, increasing the platform's wave absorption effect, and thus increasing the reliability of the movable wave deflector in high wind and wave environments, enhancing the wave deflector's ability to weaken the impact of ocean currents.

[0011] Furthermore, the anti-sway baffle is elastic, and the arc-shaped cover plate rotates upward by 135 degrees or more, with the arc-shaped cover plate abutting against the surface of the anti-sway baffle.

[0012] A flexible anti-sway baffle is installed. When the arc-shaped cover plate reverses at an angle exceeding 135°, the arc-shaped cover plate contacts and presses against the column wall, stopping the rotation of the pivot. When wave force continues to act, it prevents the arc-shaped cover plate from continuing to reverse. This structure enables the arc-shaped cover plate to maintain its effectiveness under large wave force, maintain its flipped shape when wave force continues to act, maintain the vertical motion damping of the platform, and hinder the upward movement of waves, thereby reducing the vertical motion of the floating platform. On the other hand, it also protects the wave-blocking structure of the flexible anti-sway baffle, reducing structural damage caused by excessive reversal and extending its service life.

[0013] Beneficial effects:

[0014] 1. The lifting of the arc-shaped cover plate delays the interaction between the bottom and top shear layers of the column, causing the boundary layer to separate and move downstream. This change disperses the wake eddies brought by the ocean current, interferes with eddy shedding, and reduces the eddy shedding frequency. Under the state of free decay in still water, the inherent periodic changes of the platforms before and after the additional wave-breaking plate structure cause the oscillation frequency of the column under wave action to be far away from its natural frequency, suppressing the generation of periodic eddy resonance and reducing the vertical motion response of the structure.

[0015] 2. Both the platform with the added wave-damping structure (the platform in this scheme) and the platform with the added traditional helical side plates (the columns in existing papers) have changed natural periods compared to the original platform without the added wave-damping structure. Moreover, the platform with the added wave-damping structure has a greater change in natural period than the platform with the added traditional helical side plates, changing from 39.8s to 36.9s. The change in natural period causes the oscillation frequency of the column under wave action to be far away from its natural frequency, suppressing the generation of periodic vortex-induced resonance. At this time, the coupling effect between the vortex and the column structure is very small. The pulsating vortex-induced force that can act on the column can only excite a small amplitude of column movement, avoiding the resonance effect from increasing the amplitude of platform movement and reducing the vertical motion response of the structure.

[0016] 3. The presence of the hook spring significantly increases the vertical damping of the column within the calculated folded velocity range, reduces the influence of vortex-induced motion, and makes the motion more stable. Furthermore, the root mean square response curve of the lift coefficient shows that, compared to the fixed side plate, the amplitude of the root mean square response of the lift coefficient decreases at different folded velocities after adding the hook spring structure. The curve also changes from a large change with increasing velocity to a more gradual change, indicating that the presence of the hook spring mitigates the effect of the incoming flow pressure on the column vibration, resulting in smaller and more stable lift. This further demonstrates that adding the hook spring suppresses the influence of the incoming flow pressure on the column's motion response. The constraint and damping effect provided by the hook spring effectively reduce the platform's vertical motion response. Attached Figure Description

[0017] Figure 1This is a schematic diagram of the overall structure of a semi-submersible platform at sea.

[0018] Figure 2 This is a structural diagram of the anti-sway baffle, hinge, and curved cover plate;

[0019] Figure 3 This is a schematic diagram of the structure after the anti-sway baffle is flipped up;

[0020] Figure 4 This is a structural diagram of the platform components;

[0021] Figure 5 This is a simulation flow field diagram of the original column without any additional structures;

[0022] Figure 6 This is a simulated flow field diagram of the additional wave-damping structure column;

[0023] Figure 7 This is a schematic diagram of boundary layer separation.

[0024] Figure 8 This is a top view of the overall structure of a movable wave deflector suitable for offshore semi-submersible platforms, showing the incoming flow conditions.

[0025] Figure 9 This is a comparison chart of the free decay curves of the platform with the additional wave-damping structure and other platforms;

[0026] Figure 10 This is a comparison chart of the heave history curves of the platform with additional wave-damping structure and other platforms;

[0027] Figure 11 This is a root mean square curve of the lift coefficient before and after adding or removing the hook spring structure to the additional wave-damping platform;

[0028] Figure 12 Curve of average drag coefficient before and after adding or removing hook spring structure to additional wave-damping platform;

[0029] 1. Anti-sway baffle; 2. Column; 3. Hinge; 4. Arc-shaped cover plate; 5. Second connecting ring; 6. Hook spring; 7. Through hole; 8. Truss; 9. Platform assembly. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] See Figure 1 and Figure 4A semi-submersible offshore platform with a movable wave deflector includes at least three platform components 9 fixedly connected by a truss 8. In this embodiment, three platform components 9 are used, and in a top view, the line connecting the three platform components 9 forms a triangle.

[0032] Taking a platform component 9 as an example, the platform component 9 includes a column 2, the axis of the column 2 is set vertically, and a number of movable wave baffles are provided on the outer wall of the column 2. The number of movable wave baffles are spirally distributed on the outer peripheral wall of the column 2 with the axis of the column 2 as the axis.

[0033] See Figure 2 The movable wave deflector includes an anti-sway baffle 1, which is a flat plate and is fixedly connected to the outer wall of the column 2. The anti-sway baffle 1 is vertically arranged, and a hinge 3 is provided at the lower end of the anti-sway baffle 1. One side of the hinge 3 is fixedly connected to an arc-shaped cover plate 4, and the other side of the hinge 3 is fixedly connected to the anti-sway baffle. The axis of rotation of the hinge 3 is horizontal, and the arc-shaped cover plate 4 can rotate relative to the anti-sway baffle 1 around the axis of rotation of the hinge 3.

[0034] The side of the arc-shaped cover plate 4 facing the outer wall of the column 2 (referred to as the lower side wall) bulges upward, that is to say, the lower side wall of the arc-shaped cover plate 4 does not contact the outer wall of the column 2.

[0035] In addition, several first connecting rings (not shown) are fixedly connected to the lower surface of the arc-shaped cover plate 4, and several second connecting rings 5 ​​are fixedly connected to the outer wall of the column 2. The first connecting rings and second connecting rings 5 ​​are arranged in a one-to-one correspondence. Hook springs 6 are correspondingly arranged between the first connecting rings and second connecting rings 5. The two ends of the hook springs 6 are hooked onto the first connecting rings and second connecting rings 5 ​​respectively. The hook springs 6 are in a stretched state. Under the action of the hook springs 6 and the weight of the arc-shaped cover plate 4, the arc-shaped cover plate 4 presents... Figure 2 In this state, as the arc-shaped cover plate 4 rotates upward relative to the anti-sway baffle 1 (i.e., during the upward rotation of the arc-shaped cover plate 4), the hook spring 6 is continuously stretched. A suitable gap is left between two adjacent movable wave deflectors in the longitudinal direction, allowing the arc-shaped cover plate 4 to flip upward without being restricted by other movable wave deflectors.

[0036] The arc-shaped cover plate 4 has several through holes 7, which penetrate the arc-shaped cover plate 4. The axis of the through holes 7 is along the vertical direction. In this embodiment, the material density of the arc-shaped cover plate 4 is low. After the water level exceeds the lower end of the arc-shaped cover plate 4, the arc-shaped cover plate 4 can rotate around the axis of the hinge due to the buoyancy of the water.

[0037] In this embodiment, the anti-sway baffle 1 is made of neoprene rubber, which has good elasticity. When the arc-shaped cover plate 4 rotates upward, the upper surface of the arc-shaped cover plate 4 will eventually abut against the anti-sway baffle 1. The anti-sway baffle 1 absorbs energy, reduces the impact of the arc-shaped cover plate 4 on the anti-sway baffle 1, and protects the arc-shaped cover plate 4. When the arc-shaped cover plate 4 rotates upward by 135 degrees or more, it will abut against the surface of the anti-sway baffle 1.

[0038] When the waves cause the curved cover plate 4 to move upward, the hook spring 6 is stretched under tension, converting the potential energy of the ocean current into the elastic potential energy of the hook spring 6. This prevents the curved cover plate 4 from flipping upward, increasing the damping of the platform's vertical movement, and simultaneously buffering the vertical movement effect of the waves. When the ocean current moves downward at this location, the curved cover plate 4 reverses downward until it returns to its original position. At this time, the extension of the hook spring 6 decreases and gradually decreases, which promotes the faster flipping of the curved cover plate 4.

[0039] like Figure 8 Compared to the semi-submersible platform used in the "Research on Dynamic Response of a Novel Spiral Turbine Floating Semi-Submersible Wind Turbine Platform" (hereinafter referred to as the existing paper) mentioned in the background technology, the movable wave deflector in this scheme has a spirally distributed arc-shaped cover plate, which disrupts the spatial consistency of the column's cross-sectional shape. When the arc-shaped cover plate flips downward, it achieves a local radial flow diversion effect around the column, causing the vortices on both sides of the wake to fall off at different heights, resulting in wake turbulence (see...). Figure 6 ), to avoid periodic vortex shedding (i.e. Figure 5 (Phenomenon), and the curved cover will also divert the incoming flow, forming multiple small water streams (see Figure 8 This reduces the energy of the boundary layer on the surface of the column.

[0040] As waves around the column move upwards along the column, their boundary layers on both sides (see...) Figure 7 At the separation point (see) Figure 7 Alternating vortex shedding occurs at point ), causing the column to be compressed in both the downstream and transverse directions, such as... Figure 8 As shown, relative motion with the waves is generated. At this time, the column affects the wave flow state in the opposite direction, changing the vortex state of the wake around it, that is, vortex-induced motion occurs. The arc-shaped cover plate is lifted by the waves and moves upward around the rotation axis.

[0041] like Figure 7 In addition, the flipping of the arc-shaped cover plate delays the interaction between the bottom and top shear layers of the column, causing the boundary layer separation to move downstream (from dashed line A to dashed line B). This change disperses the wake eddies brought by the ocean current, interferes with eddy shedding, and reduces the eddy shedding frequency. Under the state of free decay in still water, the inherent periodicity of the platforms before and after the additional wave-breaking plate structure changes, thereby causing the oscillation frequency of the column under wave action to move away from its natural frequency, suppressing the generation of periodic eddy resonance, and reducing the vertical motion response of the structure.

[0042] Figure 5 and Figure 6 The flow field comparison diagrams of the two papers, which include the addition of the movable wave-damping plate and the one without it in the background technology paper, show that the column without the wave-damping plate experiences periodic alternating vortex shedding on both sides under the action of water flow, and there is a significant wake vortex, which increases the disturbance to the platform. After the movable wave-damping plate structure is added, the vortices on both sides of the column are significantly weakened, and the arc-shaped cover plate disperses the wake vortex brought by the ocean current, interferes with the vortex shedding, reduces the vortex shedding frequency, and reduces the platform's motion response.

[0043] To investigate the effect of this device in reducing vortex-induced resonance and decreasing vertical motion response, three simulation devices were constructed: the original column without additional structure, the column with a traditional spiral side plate structure (the column in existing papers), and the column with the movable wave-breaking plate.

[0044] Under the conditions of static water free decay experiment, the motion of the experimental device in three-dimensional space was recorded using the Qualisys three-dimensional motion capture system, and relevant motion parameters were obtained, such as... Figure 9 and Figure 10 As shown in the curves, both the platform with the added wave-damping structure (the platform in this scheme) and the platform with the added traditional helical side plates (the columns in existing papers) have different natural periods compared to the original platform without the added wave-damping structure. Moreover, the platform with the added wave-damping structure has a larger change in natural period compared to the platform with the added traditional helical side plates, changing from 39.8s to 36.9s. The change in natural period causes the oscillation frequency of the column under wave action to be far away from its natural frequency, suppressing the generation of periodic vortex-induced resonance. At this time, the coupling effect between the vortex and the column structure is very small, and the pulsating vortex-induced force that can act on the column can only excite a small amplitude of column movement, avoiding the resonance effect from increasing the amplitude of platform movement and reducing the vertical motion response of the structure.

[0045] like Figure 11 and Figure 12 The results show the platform before and after the addition of the hook spring structure at a Reynolds number Re=1.5×10⁻⁶. 4Under experimental conditions of a wave period of 8.7s and a wave height of 6m, the lift and drag coefficients were measured. Data processing yielded the average drag coefficient and root mean square response of the lift coefficient at different reduced velocities. The drag average curve shows that, within the calculated reduced velocity range, the average drag on the column with the added hook spring structure changes significantly with increasing velocity, indicating that the vertical drag of the column is greatly affected by vortex-induced motion. Conversely, the average drag on the column with the added hook spring structure changes very little with increasing velocity, indicating that the presence of the hook spring significantly reduces the vertical damping of the column within the calculated reduced velocity range. With the addition of the hook spring, the influence of vortex-induced motion is reduced, and the motion becomes more stable. At the same time, from the root mean square response curve of the lift coefficient, compared with the fixed side plate, the root mean square response amplitude of the lift is reduced at different folding speeds after adding the hook spring structure. Moreover, the curve changes from a large change with the increase of speed to a gradual change. This indicates that the presence of the hook spring reduces the effect of the incoming flow pressure on the vibration of the column, making the lift smaller and the change more stable. This shows that adding the hook spring suppresses the influence of the incoming flow pressure on the column's motion response. The constraint and damping effect provided by the hook spring can effectively reduce the vertical motion response of the platform.

[0046] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A semi-submersible offshore platform having movable wave fenders, comprising a plurality of platform components connected by trusses, characterised in that, The platform assembly comprises a column, an axis of the column is vertically arranged, and a plurality of movable wave plates are arranged on the outer wall of the column in a spiral manner around the axis of the column. The movable wave plate comprises a rocking stop plate, the rocking stop plate is fixed on the peripheral wall of the column, the lower end of the rocking stop plate is provided with a hinge, one side blade of the hinge is fixedly connected with the rocking stop plate, the other side blade of the hinge is connected with an arc-shaped cover plate, and the rotation axis of the hinge is horizontally arranged; the side surface wall of the arc-shaped cover plate facing the outer wall of the column is upwardly raised, the arc-shaped cover plate can be rotated around the axis of the hinge under the buoyancy of water; a plurality of first connecting rings are fixed on the side surface wall of the arc-shaped cover plate facing the column, a plurality of second connecting rings are fixed on the outer wall of the column, the first connecting rings and the second connecting rings are arranged in one-to-one correspondence, a hook spring is arranged in correspondence between the first connecting ring and the second connecting ring, and the two ends of the hook spring are connected with the first connecting ring and the second connecting ring respectively, and the hook spring is in a stretched state.

2. A semi-submersible offshore platform with movable wave fenders as claimed in claim 1, wherein, A plurality of through holes are arranged on the arc-shaped cover plate, the plurality of through holes penetrate the arc-shaped cover plate, and the axis direction of the through hole is along the up-down direction.

3. A semi-submersible platform with movable wave fenders according to claim 1, characterized in that, The rocking stop plate is elastic, the arc-shaped cover plate is rotated upward by 135 degrees or more than 135 degrees, and the arc-shaped cover plate abuts against the surface of the rocking stop plate.

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