A device and method for locally thickening a three-pile foundation at sea under reciprocating flow.

Abstract

This invention discloses a device and method for locally thickening a three-pile foundation at sea under reciprocating flow conditions. The device includes: a reinforcing frame with three thickened sleeves respectively fitted onto the outer sides of the three piles; a sealing assembly formed at both ends of the thickened sleeves to create a sealed space; a fixing plate at the bottom of the thickened sleeves to fix the lower end of the sleeves to the seabed; a flow guide hood rotatably fitted onto the outer side of the thickened sleeves; multiple flow guide fins; and an air guiding mechanism. This invention absorbs vibration energy through the annular gap filled with flexible material between the thickened sleeves and the piles, suppressing seabed erosion and improving foundation adaptability. The fixed and adjustable fins at the bottom of the flow guide hood respond autonomously under reciprocating flow conditions—the adjustable fins adaptively deflect, ensuring the air curtain nozzles remain perpendicular to the water flow direction, effectively disrupting the vortex structure around the piles and significantly reducing the erosion depth. The fixing plate integrates anchoring and counterweight functions, combined with the flow guide hood to position the strong shear flow layer, achieving precise vortex suppression and anti-overturning reinforcement.

Description

Technical Field

[0001] This invention relates to the field of offshore wind power substructure technology, specifically to three-pile foundations, and more particularly to a device and method for locally thickening offshore three-pile foundations under reciprocating flow. Background Technology

[0002] Reciprocating currents refer to tidal currents whose rise and fall are in opposite or essentially opposite directions due to the influence of topography. In the field of marine science and technology, it is regarded as a periodic flow in which the elliptical tidal current degenerates into a straight line.

[0003] Offshore wind power, as a clean and environmentally friendly renewable energy source, has seen rapid development in recent years. In the offshore wind power sector, with the continuous advancement of wind power technology and the expansion of offshore wind farms into deeper waters, the construction of numerous offshore wind turbine foundations has brought increasing attention to the localized scouring that occurs around the foundations under the influence of wind, current, and wave loads. This scouring is caused by the cylindrical structure altering the water flow, creating horseshoe-shaped vortices around the pile that carry soil upwards, leading to soil loss and ultimately forming scour pits. The existence of these scour pits severely impacts the bearing capacity of the foundation and the vibration frequency of the wind turbine, resulting in significant losses.

[0004] Therefore, it is necessary to provide a device and method for locally thickening offshore three-pile foundations under reciprocating flow to solve the above-mentioned technical problems. Summary of the Invention

[0005] This invention overcomes the shortcomings of the prior art and provides a device and method for locally thickening a three-pile foundation at sea under reciprocating flow.

[0006] To achieve the above objectives, the technical solution adopted by this invention is: a device for locally thickening offshore three-pile foundations under reciprocating current, which is used to assist in the three-pile foundations of offshore wind turbines, comprising:

[0007] A reinforced frame is used to connect and support the three pile foundations;

[0008] Three thickened sleeves are respectively fitted onto the outside of the three piles of the three-pile foundation; wherein the inner diameter of the thickened sleeve is larger than the outer diameter of the corresponding pile, so that an annular gap is formed between the thickened sleeve and the pile.

[0009] A sealing assembly is disposed at both ends of the thickened sleeve to close both ends of the annular gap to form a sealed space;

[0010] A fixing plate is disposed at the bottom end of the thickened sleeve, and is used to fix the lower end of the thickened sleeve to the seabed;

[0011] A connecting rod connects the sealing assembly to the reinforcing frame;

[0012] A flow deflector is rotatably fitted onto the outside of the thickened sleeve, near the top of the thickened sleeve;

[0013] Multiple flow guide fins are arranged in a circumferential array at the bottom of the flow guide shroud;

[0014] And an air guiding mechanism, which is used to generate a bubble barrier perpendicular to the water flow direction.

[0015] In a preferred embodiment of the present invention, the air guiding mechanism includes:

[0016] Air guide grooves are formed on the circumferential wall of the air guide shroud;

[0017] Multiple nozzles are evenly distributed on the outer peripheral wall of the flow guide, with the inner end of each nozzle communicating with the air guide groove and the outer end equipped with a nozzle; and

[0018] An external air supply device is used to inject compressed air into the air guide groove through a pipeline;

[0019] In this configuration, at least some of the guide fins are configured to adaptively adjust their angle of attack according to the direction of water flow impact; and the nozzle angles of the plurality of nozzles are synchronously adjusted as the angle of attack of the adjustable guide fins changes, so that the nozzles always face a direction perpendicular to the direction of water flow impact.

[0020] In a preferred embodiment of the present invention, the sealing assembly includes:

[0021] A sealing ring is placed between the end of the thickened sleeve and the surface of the pile foundation.

[0022] A clamp is attached to the outside of the thickened sleeve and presses against the sealing ring, thereby fixing the sealing ring to the surface of the pile foundation.

[0023] In a preferred embodiment of the present invention, the annular void is filled with a filling material.

[0024] In a preferred embodiment of the present invention, the reinforced frame includes:

[0025] The support section is used to connect to the lower end of the tower of the offshore wind turbine.

[0026] Multiple fixing parts are provided on the lower side of the supporting part;

[0027] The two ends of the connecting rod are respectively connected to the clamp and the fixing part.

[0028] In a preferred embodiment of the present invention, the axial length of the flow guide is at least one-third of the axial length of the thickened sleeve.

[0029] In a preferred embodiment of the present invention, the plurality of guide fins include:

[0030] The first guide fin is a fixed semi-elliptical plate-shaped structure, with its large surface perpendicular to the axis of the guide shroud;

[0031] The second guide fin is a rotatable flat plate structure;

[0032] The first guide fin and the second guide fin are distributed alternately along the circumference.

[0033] In a preferred embodiment of the present invention, a plurality of nozzles are evenly distributed in the area directly above the second guide fin, and the same number of nozzles are correspondingly located above each second guide fin.

[0034] In a preferred embodiment of the present invention, it further includes:

[0035] A movable disc is located at the connection end between the second guide fin and the guide shroud;

[0036] The movable groove is formed in the wall of the flow guide cover;

[0037] A transmission rod is disposed in the movable groove, and its lower end is rotatably connected to the surface of the movable disk;

[0038] The nozzle is rotatably connected to the wall of the shroud; the side of the transmission rod is rotatably connected to the outer surface of the plurality of nozzles to form a linkage mechanism; the spray angle of the outer end of the nozzle relative to the axis of the shroud is adjustable between 90° and 135°.

[0039] A method for locally thickening a three-pile foundation at sea under reciprocating flow includes the following steps:

[0040] S1. Fix the reinforced frame to the seabed and connect it to the wind turbine tower. After installing thickened sleeves on the outside of the three pile foundations to form a sealed space, fill the space with filling material and anchor the bottom of the thickened sleeves to the seabed through the fixing plate.

[0041] S2. When the water flow impacts the guide fin, the second guide fin adaptively adjusts its angle of attack according to the flow direction, so that the large surface of the fin is parallel to the water flow, and the first guide fin is driven by the tangential force to rotate the guide shroud around the thickened sleeve.

[0042] S3. Adjust the nozzle spray angle to be perpendicular to the water flow direction through the linkage mechanism, start the external air supply equipment to deliver compressed air to the air guide groove, and form a bubble barrier perpendicular to the water flow through the nozzle to destroy the vortex structure around the pile and suppress seabed erosion.

[0043] In a preferred embodiment of the present invention, the structural installation of S1 specifically includes the following steps:

[0044] S11. Based on the calculated data, the thickened sleeve is fitted onto the designated position on the outside of the pile foundation to form an annular gap;

[0045] S12. Install a sealing ring at the bottom of the sleeve, fill with filling material, install the top sealing ring, and tighten it with clamps to seal.

[0046] S13. Drill holes at the designated location on the seabed, install the pile foundation, and then anchor the bottom end of the thickened sleeve to the seabed using a fixing plate.

[0047] S14. Fix the support part of the reinforcement frame to the bottom of the wind turbine tower. After connecting the tower to the pile foundation with multiple crossbeams, connect the clamps to the fixing part of the reinforcement frame with connecting rods.

[0048] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0049] (1) This invention provides a local thickening device for offshore three-pile foundations under reciprocating flow. The device absorbs vibration energy through an annular gap filled with flexible material between the thickened sleeve and the pile, suppressing seabed scouring and improving foundation adaptability. The fixed and adjustable fins at the bottom of the flow guide respond autonomously under reciprocating flow—the adjustable fins adaptively deflect to ensure the air curtain nozzle remains perpendicular to the water flow direction, effectively disrupting the vortex structure around the pile and significantly reducing the scouring depth. The fixed plate integrates anchoring and counterweight functions, combined with the flow guide to position the strong shear flow layer, achieving precise vortex suppression and anti-overturning reinforcement. This device forms a closed loop of "buffering-flow guidance-vortex suppression," solving the safety problem of horseshoe-shaped vortices forming around the piles under reciprocating flow in traditional three-pile foundations, ultimately leading to scouring pits.

[0050] (2) This invention pre-sets annular gap between the thickened sleeve and the pile foundation, fills it with flexible material, and then seals both ends with a sealing assembly consisting of a sealing ring and clamps. Simultaneously, the reinforced frame is rigidly connected to the clamps via connecting rods, providing external support for the tower. This annular gap, filled with flexible material, forms a "flexible liner layer," effectively absorbing the vibration energy of the pile foundation under wind, waves, and currents. Its direct effect is to suppress the transmission of vibration energy to the seabed, preventing the softening of sedimentary layers caused by vibration and accelerated erosion. Compared to the traditional method of rigid contact between the casing and the pile foundation, this invention effectively solves the risk of stress concentration and weld cracking caused by rigid connections under complex wave loads. It significantly improves the adaptability of the pile foundation under complex hydrological conditions, and the flexible materials such as sandbags used for filling have both counterweight and buffering functions, synergistically extending the overall service life of the three-pile foundation.

[0051] (3) This invention uses a fixed first guide fin and an adjustable second guide fin arranged in a circular array at the bottom of the guide shroud, and uses a movable disk and transmission rod to link the rotation of the second guide fin with the nozzle angle adjustment. This allows the second guide fin to adaptively deflect according to the water flow direction, accurately calibrating the nozzle spray angle and ensuring that the bubble barrier released by the nozzle always impacts the mainstream direction perpendicularly. Its direct effect is to efficiently destroy the core structure of the horseshoe vortex around the pile and significantly suppress the entrainment effect of the water flow on the seabed sediments. Compared with the shortcomings of existing passive protection devices such as grids and ballast blocks, which cannot adapt to the changes in the reciprocating flow direction and thus cause fluctuations or even failures in the vortex suppression effect, this invention can ensure that the air curtain coverage area accurately matches the vortex generation area and significantly reduce the scour depth.

[0052] (4) The design of the fixing plate and the flow guide in this invention includes a fixing plate located at the bottom of the thickened sleeve, which integrates reinforcing ribs and a counterweight area, achieving dual protection of mechanical anchoring and counterweight anti-overturning. The axial length of the flow guide is not less than one-third of the length of the thickened sleeve, and it is positioned close to the strong shear flow layer below the sea surface. The bidirectional nozzles set at its top can cover the key vortex suppression area of ​​0-3D (D is the pile diameter) around the pile foundation. This design directly enhances the anchoring stability of the thickened sleeve and ensures that the air curtain can accurately act on the high-speed water flow and vortex-prone areas.

[0053] (5) The nozzle of this invention is hinged to the guide shroud wall via a trunnion. The transmission rod transmits the deflection angle of the second guide fin to the nozzle in a specific ratio, enabling continuous adjustment of the nozzle's outer end spray angle within the range of 90° to 135°. This mechanism ensures that the nozzle's spray direction closely follows the flow direction changes sensed by the second guide fin, maintaining a real-time perpendicularity to the water flow impact direction, maximizing the cutting efficiency of the bubble barrier on the pile perimeter eddies. Compared to existing technologies that rely on underwater sensors and electric actuators to adjust the nozzle angle, the purely mechanical linkage structure of this invention has no electronic components, possessing extremely high environmental adaptability and reliability, and achieving maintenance-free operation throughout its entire life cycle. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1 This is a schematic diagram of a preferred embodiment of the offshore three-pile foundation local thickening device of the present invention;

[0056] Figure 2 This is a perspective view of a preferred embodiment of the offshore three-pile foundation partial thickening device of the present invention;

[0057] Figure 3 This is a perspective view of the thickened sleeve according to a preferred embodiment of the present invention;

[0058] Figure 4 This is a cross-sectional view of the thickened sleeve according to a preferred embodiment of the present invention;

[0059] Figure 5 This is a perspective view of the transmission rod according to a preferred embodiment of the present invention;

[0060] Figure 6 This is a flowchart of a preferred embodiment of the method for locally thickening a three-pile foundation at sea according to the present invention;

[0061] Figure 7 This is a flowchart of the structural installation method of a preferred embodiment of the present invention.

[0062] In the diagram: 100, tower; 110, pile foundation; 200, reinforced frame; 210, support part; 220, fixing part; 300, thickened sleeve; 310, annular gap; 320, filling material; 400, sealing assembly; 410, sealing ring; 420, clamp; 500, fixing plate; 510, screw; 600, connecting rod; 700, guide shroud; 710, movable disc; 720, transmission rod; 800, guide fin; 810, first guide fin; 820, second guide fin; 900, air guiding mechanism; 910, nozzle; 930, nozzle. Detailed Implementation

[0063] The technical solutions of the embodiments 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, and 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.

[0064] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0065] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the scope of protection of this application. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0066] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art will understand the specific meaning of the above terms in this application based on the specific circumstances.

[0067] Offshore wind turbine foundation types include gravity foundations, monopile foundations, tripod (multi-pile) foundations, jacket foundations, pressure tank foundations, and floating foundations. This application specifically refers to tripod foundations, similar to those commonly used on small oil and gas extraction platforms. Lightweight and economical tripod steel casings have steel frames distributed beneath the tower's piles, each bearing the pressure from the tower on three piles. Due to soil conditions and frost load limitations, small-diameter steel piles and tubular steel structures are used, along with either plugged or molded connection methods. The tripod enhances the structural rigidity and strength, and its central axis provides basic support for the wind turbine tower.

[0068] Figure 1This illustration shows a schematic diagram of a partial thickening device for a three-pile foundation 110 at sea under reciprocating current conditions, as described in this embodiment. The three-pile foundation 110 comprises three piles 110, each divided into two sections: the upper section is below sea level but above the seabed, while the lower section is inserted into a cavity drilled into the seabed. The piles 110 are fixed to the seabed by grouting and cementing with riprap. The piles 110 are interconnected by crossbeams and fixedly connected to the lower end of a tower 100, providing support for the tower 100. The upper end of the tower 100 extends above sea level and is used to install wind turbine generators. Furthermore, the length and diameter of the piles 110 and the tower 100 are appropriately determined based on the scale of the offshore wind turbine generator to be supported, the installation area, and the condition of the sedimentary layers.

[0069] This invention provides a local thickening device for offshore three-pile foundation 110 under reciprocating flow action, which is used to assist in the three-pile foundation 110 of offshore wind turbine units. It includes: a reinforcing frame 200, a thickened sleeve 300, a sealing component 400, a fixing plate 500, a connecting rod 600, a flow guide 700, a flow guide fin 800, and an air guiding mechanism 900.

[0070] Figure 3 A three-dimensional view of the thickened sleeve is shown. Figure 4A cross-sectional view of the thickened sleeves is shown. Specifically, the reinforcing frame 200 is used to connect and support the three pile foundations 110; three thickened sleeves 300 are respectively fitted onto the outer side of the upper section of the three pile foundations 110, i.e., the portion above the seabed. The inner diameter of each thickened sleeve 300 is larger than the outer diameter of the corresponding pile foundation 110, creating an annular gap 310 between the thickened sleeve 300 and the pile foundation 110. The difference between the inner diameter of the thickened sleeve 300 and the outer diameter of the pile foundation 110 is not particularly limited, but when the axis of the sleeve coincides with the axis of the pile foundation 110, the distance between the inner wall surface of the thickened sleeve 300 and the outer periphery of the pile foundation 110 is preferably 5 cm or more and 30 cm or less, more preferably 8 cm or more and 20 cm or less, and even more preferably 10 cm or more and 15 cm or less. If the distance is less than 5cm, it is difficult to pass the pile 110 through the hole in the thickened sleeve 300. If the distance exceeds 30cm, the pile 110 may tilt within the thickened sleeve 300, and it is difficult to seal the annular gap 310, posing a significant construction risk. Furthermore, in this local thickening device, when the distance is greater than 10cm, any filling material 320 can be filled into the annular gap 310. There are no particular restrictions on the filling material 320, but sandbags or sandbags are preferred. Because sandbags and sandbags have irregular shapes and can deform under external forces, they are suitable as filling materials 320 within the annular gap 310. In addition, when the pile 110 sways due to the influence of offshore windmill blades, it can absorb the swaying caused by rotation, waves, ocean currents, etc. By preventing and suppressing the vibration of the pile 110, the state of the surrounding sediment layer can be prevented from softening due to the vibration of the pile 110.

[0071] A sealing assembly 400 is disposed at both ends of the thickened sleeve 300 to close both ends of the annular gap 310 to form a sealed space. The sealing assembly 400 includes a sealing ring 410 and a clamp 420. The material of the sealing ring 410 is not particularly limited; any flexible material suitable for underwater environments is acceptable, preferably flexible rubber. The sealing ring 410 is placed between the end of the thickened sleeve 300 and the surface of the pile foundation 110, forming a flexible connection between the thickened sleeve 300 and the pile foundation 110, absorbing the vibration of the pile foundation 110. The clamp 420 is disposed on the outside of the thickened sleeve 300 and presses against the sealing ring 410, fixing the sealing ring 410 to the surface of the pile foundation 110. When the pile foundation 110 inevitably tilts slightly due to wind and waves, the annular gap 310 can temporarily accommodate the displacement of the pile foundation 110, preventing direct rigid collision between the thickened sleeve 300 and the pile foundation 110. At this time, the thickened sleeve 300 acts as a "reaction wall" to provide reverse support force, while the air layer in the annular gap 310 acts as a buffer transition zone, delaying the inclination to be transmitted to the deposition layer.

[0072] A fixing plate 500 is provided at the bottom of the thickened sleeve 300 to fix the lower end of the thickened sleeve 300 to the seabed. The fixing plate 500 is a disc-shaped structure with several mounting holes on its surface, and the thickened sleeve 300 is anchored to the seabed surface by alloy screws 510. Furthermore, multiple reinforcing ribs are provided on the upper surface of the fixing plate 500 to enhance the connection strength between the fixing plate 500 and the thickened sleeve 300. Even further, the upper surface of the fixing plate 500 has one or more areas (not shown in the figure) for accommodating heavy objects, including stones, gravel, metal, concrete blocks, etc., which can be piled up in these areas to increase the stability of the thickened sleeve 300.

[0073] Figure 2 A perspective view of a partial thickening device for offshore three-pile foundations is shown. The reinforced frame 200 includes a support portion 210 and multiple fixing portions 220. The support portion 210 is used to connect to the lower end of the offshore wind turbine tower 100. The multiple fixing portions 220 are located on the lower side of the support portion 210. The two ends of the connecting rod 600 are respectively connected to the clamp 420 and the fixing portions 220. It should be noted that the support portion 210 is an equilateral triangular steel plate platform with a flange interface at the center for bolt connection to the bottom flange of the tower 100. The non-connection area is bent downwards to prevent the accumulation of mud and sand on the surface of the support portion 210. Three main beams extend from the edge of the support portion 210. The end of each main beam is welded to the crossbeam of the three-pile foundation 110. The surface of the main beam is provided with fixing portions 220, which are also flange interfaces. The connecting rod 600 connected to the flange is fixedly connected to the clamp 420. The reinforcement frame 200 evenly distributes the load of the tower 100 to the three pile foundations 110, avoiding local stress concentration, and provides a second support for the tower 100 in addition to the pile foundations 110, so that the tower 100 has higher stability.

[0074] In this embodiment, the flow guide 700 is rotatably sleeved on the outside of the thickened sleeve 300, and the flow guide 700 is close to the top of the thickened sleeve 300. It should be noted that the flow guide 700 can be rotated by a ceramic bearing sleeved on the outside of the thickened sleeve 300, or an annular track can be provided on the surface of the thickened sleeve 300, and multiple rollers / balls can be provided on the upper end of the flow guide 700. The rotation of the flow guide 700 can be achieved by the movable characteristics of the rollers / balls in the annular track. The axial length of the flow guide 700 is at least one-third of the axial length of the thickened sleeve 300. The flow guide 700 is close to the top of the thickened sleeve 300, that is, away from the seabed sediment disturbance area, reducing the risk of the transmission mechanism being blocked by silt. In addition, the ocean reciprocating current forms the strongest shear flow layer 1-3 meters below the water surface. The closer to the seabed, the more stable the water flow. The flow guide 700 is located in the top area of ​​the thickened sleeve 300, which is closer to the strong shear flow layer. It can directly intercept high-speed water flow and maximize the destructive effect of the air curtain on the core area of ​​the vortex.

[0075] In this embodiment, multiple guide fins 800 are welded in a circumferential array to the bottom of the guide shroud 700. The number of guide fins 800 is at least 8. The guide fins 800 drive the guide shroud 700 to rotate around the thickened sleeve 300 by withstanding the impact of the water flow.

[0076] In this embodiment, the air guiding mechanism 900 includes: an air guiding groove, multiple nozzles 910, and an external air supply device; wherein, the air guiding groove is formed on the circumferential wall of the flow guide shroud 700; the multiple nozzles 910 are evenly distributed on the outer circumferential wall of the flow guide shroud 700, the inner end of each nozzle 910 is connected to the air guiding groove through a flexible air pipe, and the outer end is provided with a conical diffusion nozzle 930, which is divided into upper and lower parts, one pointing vertically upward and the other vertically downward when the nozzle 910 is horizontal; the external air supply device is used to inject compressed air into the air guiding groove through a pipeline; wherein, the model of the external air supply device is not particularly limited, for example, an air compressor, installed on the tower 100, and powered by a wind turbine. The air guiding mechanism 900 in this local thickening device injects compressed air into the air guiding groove, and forms an alternating air curtain layer through the bidirectional conical diffusion nozzle 930 at the end of the nozzle 910. When air pressure of 0.8-1.2 MPa is supplied by the air compressor of tower 100, the 0.5-2 mm microbubbles released at nozzle 930 form a turbulent gas-liquid two-phase flow barrier. This bubble curtain interferes with the water boundary layer through a Reynolds stress-dominated turbulent kinetic energy dissipation mechanism, causing the separation point of pile 110 around the flow to shift backward. Under the action of the bidirectional nozzle 930, the upward-spraying bubble swarm suppresses the reverse eddy near the water surface, while the downward-spraying bubble swarm penetrates to the 3D region above the seabed (D is the diameter of the pile), weakening the horseshoe vortex's entrainment effect on the sedimentary layer.

[0077] At least some of the guide fins 800 are configured to adaptively adjust their angle of attack according to the direction of the water flow impact. Specifically, the plurality of guide fins 800 include: a first guide fin 810 and a second guide fin 820; the first guide fin 810 is a fixed semi-elliptical plate structure with its large surface perpendicular to the axis of the guide shroud 700, to receive the impact of the underwater water flow and drive the guide shroud 700 to rotate around the thickened sleeve 300; while the second guide fin 820 is a rotatable flat plate structure. When the underwater water flow impacts the second guide fin 820, it is subjected to tangential force, causing the second guide fin 820 to adaptively adjust its angle of attack according to the flow direction, so that the large surface of the fin is parallel to the water flow. The first guide fin 810 and the second guide fin 800 are distributed alternately along the circumference.

[0078] Furthermore, the nozzle 930 angles of the plurality of nozzles 910 are synchronously adjusted according to the change in the flow-facing angle of the adjustable guide fin 800, so that the nozzles 930 always face a direction perpendicular to the water flow impact direction. The plurality of nozzles 910 are evenly distributed in the area directly above the second guide fin 800, and the same number of nozzles 910 are correspondingly located above each second guide fin 800. Figure 5 A three-dimensional structural diagram of the transmission rod is shown. This locally thickened device also includes: a movable disk 710, a movable groove, and a transmission rod 720; the movable disk 710 is disposed on the connecting shaft surface between the second guide fin 800 and the guide shroud 700, and rotates with the rotation of the second guide fin 800; the movable groove is formed in the wall of the guide shroud 700, and the transmission rod 720 moves within the movable groove, its lower end rotatably connected to the surface of the movable disk 710. The nozzle 910 is rotatably connected to the wall of the guide shroud 700 via a trunnion; the side of the transmission rod 720 is rotatably connected to the outer surfaces of multiple nozzles 910, forming a linkage mechanism; allowing the spray angle of the outer end of the nozzle 910 relative to the axis of the guide shroud 700 to be adjustable between 90° and 135°. It should be noted that the connection position between the transmission rod 720 and the movable disc 710 is set according to the size of the nozzle 910 and the size of the movable disc 710. This ensures that the connection point rotates half a circle with the movable disc 710, from the highest point to the lowest point, driving the nozzle 910 to adjust its angle by a maximum of 45°. This adapts to the reciprocating flow and the oblique water flow impact that may occur under the influence of the three pile foundations 110. This ensures that the nozzle 930 always faces a direction perpendicular to the water flow impact direction. After being ejected from the nozzle 930, a bubble barrier perpendicular to the main water flow is formed, maximizing the vortex destruction effect of the bubble barrier.

[0079] It is worth noting that a bearing is provided on the connecting shaft surface of the second guide fin 800, the outer ring of the bearing is fixedly connected to the guide shroud 700, and the movable disk 710 rotates freely in the movable groove.

[0080] This invention utilizes a fixed first guide fin 810 and an adjustable second guide fin 800 arranged in a circular array at the bottom of the flow deflector 700. A movable disk 710 and a transmission rod 720 are used to link the rotation of the second guide fin 800 with the angle adjustment of the nozzle 910. This allows the second guide fin 800 to adaptively deflect according to the water flow direction, precisely calibrating the nozzle 910's spray angle from 0° to 45°, ensuring that the bubble barrier released by the nozzle 930 always impacts the mainstream direction perpendicularly. Its direct effect is to efficiently disrupt the core structure of the horseshoe vortex around the pile and significantly suppress the entrainment effect of the water flow on seabed sediments. Compared to existing technologies, such as passive protection devices like grids and ballast blocks, which cannot adapt to changes in the reciprocating flow direction, leading to fluctuating or even failed vortex suppression effects, this invention ensures that the air curtain coverage area precisely matches the vortex generation area, significantly reducing the scour depth.

[0081] It is worth noting that the bubble barrier released by nozzle 930 always impacts the mainstream direction perpendicularly, ensuring that the bubble barrier precisely cuts the core area of ​​the horseshoe vortex around the pile, maximizing the turbulent kinetic energy dissipation effect. The perpendicular impact energy strongly disrupts the water flow structure, causing the boundary layer separation point to shift backward, directly destroying the vortex's entrainment effect on seabed sediments, thereby significantly suppressing the scour depth. However, if the bubble barrier is not perpendicular to the mainstream, the bubble swarm will deviate from the high vortex intensity area, and the vortex suppression effect will be greatly reduced: during reciprocating flow changes, the tilted bubble curtain only covers the local flow field, unable to penetrate the vortex generation area, and unable to disturb the strong shear flow layer, resulting in the continuous deepening of the scour pit around the pile.

[0082] Figure 6 This embodiment illustrates a method for locally thickening a 110mm three-pile foundation at sea under reciprocating current. The method includes the following steps:

[0083] Step S1: Fix the reinforced frame 200 to the seabed and connect it to the wind turbine tower 100. After installing the thickened sleeve 300 on the outside of the three pile foundations 110 to form a sealed space, fill the space with filling material 320 and anchor the bottom of the thickened sleeve 300 to the seabed through the fixing plate 500.

[0084] Step S2: When the water flow impacts the guide fin 800, the rotatable second guide fin 800 adaptively adjusts the angle of the flow according to the flow direction, so that the large surface of the fin is parallel to the water flow, while the fixed first guide fin 810 is driven by the tangential force to rotate the guide shroud 700 around the thickened sleeve 300.

[0085] In step S3, during step S2, the second guide fin 800 adaptively adjusts its angle of attack according to the flow direction. During this process, the movable disk 710 driven by the shaft of the second guide fin 800 drives the transmission rod 720 to move vertically, forcing the nozzle 910 to deflect around the trunnion center. The linkage mechanism ensures that the axis of the nozzle 930 of the nozzle 910 is always perpendicular to the measured flow direction. The external air supply equipment delivers compressed air to the air channel, which is ejected as a bubble swarm through the upper and lower bidirectional nozzles 930 of the nozzle 910. The bubble curtain of the upper nozzle 930 suppresses the reverse pressure gradient eddy in the 0-2D depth range of the water surface, while the bubble curtain of the lower nozzle 930 penetrates into the 3D region above the seabed, interfering with the generation of horseshoe vortices, and simultaneously causing the boundary layer separation point of the pile foundation 110 to move backward.

[0086] Figure 7 A flowchart of the structural installation method is shown. Step S1, structural installation, specifically includes the following steps:

[0087] Step S11: Based on the calculated dimensions of the pile foundation 110 extending into the seabed and its exposed dimensions, the thickened sleeve 300 is fitted from top to bottom onto the designated position on the outer side of the upper section of the pile foundation 110 to form an annular gap 310 of 5 to 30 cm.

[0088] Step S12: Install the sealing ring 410 at the bottom of the sleeve, pour in the filling material 320, install the top sealing ring 410 and tighten it with the clamp 420 to seal.

[0089] Step S13: Drill installation holes for pile foundations 110 at the pre-explored seabed coordinate points, insert the lower sections of three pile foundations 110 into the holes and fix them with high-strength sulfoaluminate cement mortar or other materials. After installing the pile foundations 110, anchor the bottom end of the thickened sleeve 300 to the seabed through the fixing plate 500. Optionally, a concrete counterweight block with a single mass of 1.5 tons is stacked on the surface of the fixing plate 500 to enhance the overturning stability.

[0090] Step S14: Fix the support part 210 of the reinforcing frame 200 to the bottom of the wind turbine tower 100 with bolts. After connecting the tower 100 to the pile foundation 110 with multiple crossbeams, connect the clamp 420 to the fixing part 220 of the reinforcing frame 200 with the connecting rod 600.

[0091] Based on the preferred embodiments of the present invention described above, 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 device for locally thickening a three-pile foundation under reciprocating flow for offshore wind turbines, characterized in that, The application relates to a reinforced frame for connecting and supporting three pile foundations, three thickened sleeves respectively sleeved outside the three pile foundations, wherein the inner diameter of the thickened sleeves is larger than the outer diameter of the corresponding pile foundations, so that annular gaps are formed between the thickened sleeves and the pile foundations, sealing assemblies arranged at the two ends of the thickened sleeves for sealing the two ends of the annular gaps to form sealed spaces, fixing plates arranged at the bottom ends of the thickened sleeves for fixing the lower ends of the thickened sleeves to the seabed, connecting rods connecting the sealing assemblies and the reinforced frame, a flow guide cover rotatably sleeved outside the thickened sleeves and close to the top of the thickened sleeves, a plurality of flow guide fins including first flow guide fins and second flow guide fins, which are respectively arranged in a circumferential array at the bottom of the flow guide cover, and a gas guiding mechanism for generating a bubble barrier perpendicular to the water flow direction. The gas guiding mechanism comprises a gas guiding groove arranged in the circumferential wall of the flow guide cover, a plurality of nozzles uniformly distributed on the outer circumferential wall of the flow guide cover, the inner ends of the nozzles being communicated with the gas guiding groove, and the outer ends of the nozzles being provided with nozzles, and an external air supply device for pouring compressed air into the gas guiding groove through a pipeline. At least part of the flow guide fins are configured to adaptively adjust the flow-impingement angle thereof according to the water flow impact direction, and the nozzle angles of the plurality of nozzles are synchronously adjusted with the flow-impingement angle of the adjustable flow guide fins, so that the nozzles are always directed to a direction perpendicular to the water flow impact direction. The sealing assembly comprises a sealing ring arranged between the end of the thickened sleeve and the surface of the pile foundation, and a clamp arranged outside the thickened sleeve and pressing the sealing ring, so that the sealing ring is fixed to the surface of the pile foundation. The reinforced frame comprises a supporting part for connecting with the lower end of the tower of the offshore wind turbine, and a plurality of fixing parts arranged on the lower side of the supporting part. The axial length of the flow guide cover is at least one third of the axial length of the thickened sleeve. The first flow guide fins are fixed half-elliptical sheet structures with the large surface being perpendicular to the axis of the flow guide cover, and the second flow guide fins are rotatable flat plate structures. The first flow guide fins and the second flow guide fins are alternately and spacedly arranged along the circumference. The plurality of nozzles are uniformly distributed above the second flow guide fins, and each of the second flow guide fins is above the same number of nozzles.

2. A device for local thickening of a three-pile foundation at sea under reciprocating flow according to claim 1, characterized in that, The application further comprises a movable disc arranged at the connecting end of the second flow guide fin and the flow guide cover, a movable groove arranged in the wall of the flow guide cover, and a transmission rod arranged in the movable groove and rotatably connected with the surface of the movable disc at the lower end. The nozzles are rotatably connected with the wall of the flow guide cover, and the side surface of the transmission rod is rotatably connected with the outer surface of the plurality of nozzles, so that a linkage mechanism is formed, and the jet angle of the outer end of the nozzles relative to the axis of the flow guide cover can be adjusted between 90 degrees and 135 degrees. The application further comprises the following steps: ​ ​ 3. A device for local thickening of a three-pile foundation at sea under reciprocating flow according to claim 1, characterized in that, ​ ​ ​ 4. A device for local thickening of a three-pile foundation at sea under reciprocating flow according to claim 3, characterized in that, ​ ​ ​ ​ 5. A device for local thickening of a three-pile foundation at sea under reciprocating flow according to claim 1, characterized in that, ​ 6. A device for local thickening of a three-pile foundation at sea under reciprocating flow according to claim 1, characterized in that, ​ ​ 7. A device for local thickening of a three-pile foundation at sea under reciprocating flow according to claim 2, characterized in that, ​ 8. A device for local thickening of a three-pile foundation at sea under reciprocating flow according to claim 2, characterized in that, ​ ​ ​ ​ ​ 9. A method for local thickening of a three-pile offshore foundation under the action of reciprocating flow, based on a device for local thickening of a three-pile offshore foundation under the action of reciprocating flow according to any one of claims 1-8, characterized in that, ​ S1, fixing the reinforcing frame to the seabed and connecting the wind turbine tower, installing thickened sleeves outside the three pile foundations to form a sealed space, pouring filling material, and anchoring the bottom end of the thickened sleeves to the seabed through the fixing plate; S2, when the water flow impacts the guide fins, the second guide fins adaptively adjust the angle of attack according to the flow direction, so that the large surface of the fins is parallel to the water flow, and the first guide fins are driven by the tangential force to rotate the guide cover around the thickened sleeve; S3, adjust the jet angle of the nozzle to be perpendicular to the water flow direction through the linkage mechanism, start the external air supply equipment to transport compressed air to the air guide groove, form a bubble barrier perpendicular to the water flow through the nozzle to destroy the vortex structure around the pile and suppress the seabed erosion.

10. A method of locally thickening a three-pile offshore foundation under reciprocating flow action according to claim 9, characterized in that, The structure installation of S1 specifically comprises the following steps: S11, according to the measured data, the thickened sleeve is sleeved outside the designated position of the pile foundation to form an annular gap; S12, install a sealing ring at the bottom of the sleeve, pour the filling material, install the top sealing ring and press the sealing ring tightly through the clamp; S13, drill holes at the designated position of the seabed, install the pile foundation, and anchor the bottom end of the thickened sleeve to the seabed through the fixing plate; S14, fix the supporting part of the reinforcing frame to the bottom of the wind turbine tower, connect the tower and the pile foundation with multiple cross beams, and connect the clamp and the fixed part of the reinforcing frame with the connecting rod.

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