A mooring line composite weight structure

Abstract

The application discloses a mooring line composite weight structure, which comprises a mooring line, a weight block main body and a plurality of annular damping plates. The weight block main body is fixedly sleeved on the mooring line, and the plurality of annular damping plates are fixedly arranged on the outer surface of the weight block main body in an axial direction. Each annular damping plate is provided with a plurality of through holes, and the outer edge of each annular damping plate is provided with a flange part. The through holes, the flange parts and the plurality of annular damping plates jointly form a cooperative energy dissipation structure, which is used for generating perforation jet flow, edge separation and multi-stage wake interference when the composite weight structure moves with the mooring line, so as to enhance the hydrodynamic damping. The application can provide a concentrated weight, significantly improve the hydrodynamic damping, suppress the dynamic tension fluctuation of the mooring line, prolong the fatigue life, and is suitable for the mooring system of a floating wind turbine and other marine floating structures.

Description

Technical Field

[0001] This invention relates to the field of offshore wind turbines, and more particularly to a composite counterweight structure for mooring cables. Background Technology

[0002] As offshore wind power expands from nearshore shallow waters to deep seas, floating wind turbines are gradually becoming an important technological approach for deep-sea wind energy development. Floating wind turbines are typically connected to a seabed anchoring system via mooring cables. The mooring system needs to provide sufficient horizontal restoring stiffness for the floating platform to limit low-frequency motion responses such as sway, roll, and bow roll. Furthermore, it needs to suppress dynamic tension fluctuations under the combined effects of waves, wind loads, and ocean currents, reducing fatigue damage to the mooring cables, shackles, connecting rings, anchoring ends, and platform connection ends.

[0003] In existing catenary mooring systems, concentrated counterweights are often placed in the middle or near the seabed section of the mooring cable to alter its catenary shape and improve the system's geometric stiffness and horizontal restoring force. Traditional counterweights primarily function based on their own weight, with design focuses typically on mass, installation location, ease of manufacture, and corrosion resistance. Their shapes are often cylindrical, spherical, blocky, or near-streamlined, without a structural design centered on hydrodynamic energy dissipation mechanisms. Therefore, while traditional counterweights generate some additional hydrodynamic force as they move with the mooring cable, their damping function is usually a passive byproduct, not a structural design objective. Consequently, they struggle to provide a designable, adjustable, and amplifiable hydrodynamic energy dissipation capability to address the vibrations and dynamic tension fluctuations of the mooring cable caused by wind, waves, and currents.

[0004] Therefore, how to provide a mooring cable counterweight structure that can significantly enhance hydrodynamic damping, effectively suppress dynamic tension fluctuations of mooring cables, and extend their fatigue life is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a mooring cable composite counterweight structure that can significantly enhance hydrodynamic damping and effectively suppress dynamic tension fluctuations of mooring cables.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A mooring cable composite counterweight structure includes a mooring cable, a counterweight body, and multiple annular damping plates. The counterweight body is fixedly sleeved on the mooring cable, and the multiple annular damping plates are fixedly fixed to the outer surface of the counterweight body at axial intervals. Each annular damping plate has multiple flow-through holes and a flanged portion on its outer edge. The flow-through holes, the flanged portion, and the multiple annular damping plates together constitute a synergistic energy-dissipating structure, which is used to generate perforated jets, edge separation, and multi-stage wake interference when the composite counterweight structure moves with the mooring cable, thereby enhancing hydrodynamic damping.

[0008] As a further improvement to the above technical solution, a clamp is also included, wherein the main body of the counterweight is clamped to the mooring cable by the clamp.

[0009] As a further improvement to the above technical solution, the annular damping plate is fixed to the main body of the counterweight through multiple ribs.

[0010] As a further improvement to the above technical solution, the main body of the counterweight is formed by splicing together multiple counterweight segments.

[0011] As a further improvement to the above technical solution, the folding direction of each flange on the plurality of annular damping plates is folding in the same direction, adjacent reverse folding, or double-sided folding.

[0012] As a further improvement to the above technical solution, an anti-slip pad is provided between the counterweight body and the mooring cable to restrict the axial movement of the counterweight body.

[0013] As a further improvement to the above technical solution, the axial distance between two adjacent annular damping plates is 0.15 to 1.00 times the outer diameter of the annular damping plate.

[0014] As a further improvement to the above technical solution, the plurality of flow through holes are uniformly arranged circumferentially along the annular damping plate, the diameter of the flow through holes near the outer edge of the annular damping plate is larger than the diameter of the flow through holes near the inner edge of the annular damping plate, and the porosity of the flow through holes on the annular damping plate is 5% to 45%.

[0015] As a further improvement to the above technical solution, the main body of the counterweight is made of corrosion-resistant material, and its inner side is provided with a clamping groove that is compatible with the outer diameter of the mooring cable.

[0016] As a further improvement to the above technical solution, a protective layer is provided between the clamp and the main body of the counterweight.

[0017] Compared with the prior art, the advantages of the present invention are as follows:

[0018] This invention fixes the main body of the counterweight onto the mooring cable, and fixes multiple annular damping plates at axial intervals around its outer periphery. Each annular damping plate has multiple through holes and a flanged portion on its outer edge. The through holes, flanged portions, and the axially spaced arrangement of the multiple annular damping plates together constitute a synergistic energy dissipation structure. When the composite counterweight structure moves with the mooring cable in the water, this synergistic energy dissipation structure can simultaneously generate multiple hydrodynamic energy dissipation mechanisms: the through holes allow some water flow to accelerate through, forming a perforated jet and a vortex behind the hole; the flanged portions induce forced separation of water flow at the outer edge, expanding the low-pressure area on the back side and enhancing differential pressure damping; the axial gaps between the multiple damping plates allow the jet and wake of the front plate to couple with the flow around the rear plate in stages, forming multi-stage wake interference. The various parts of the synergistic energy dissipation structure superimpose and synergistically enhance each other, efficiently converting the mechanical energy of the mooring cable's movement into fluid thermal energy and vortex dissipation energy. Compared to traditional counterweights that rely solely on the weight of the main body to change the catenary profile, this invention significantly increases the projected area facing the current and the equivalent drag coefficient while providing centralized counterweight, adjusting the catenary profile, and restoring stiffness. This greatly improves hydrodynamic damping, effectively suppresses dynamic tension fluctuations in the mooring cable, and slows down the accumulation of fatigue damage. It achieves the integrated function of centralized counterweight and enhanced hydrodynamic damping, thereby improving the service safety and durability of the floating wind turbine mooring system. Attached Figure Description

[0019] The invention will now be described in more detail with reference to embodiments and the accompanying drawings.

[0020] Figure 1 This is a front view of the mooring cable composite counterweight structure according to an embodiment of the present invention.

[0021] Figure 2 This is a cross-sectional view of the mooring cable composite counterweight structure according to an embodiment of the present invention.

[0022] Figure 3 This is an exploded view of the mooring cable composite counterweight structure according to an embodiment of the present invention.

[0023] Figure 4 This is a schematic diagram illustrating the working principle of the mooring cable composite counterweight structure according to an embodiment of the present invention.

[0024] The labels in the diagram represent: 1. Mooring cable; 2. Main body of counterweight; 21. Counterweight sub-body; 22. Clamping groove; 3. Annular damping plate; 31. Flow through hole; 32. Flanged part; 4. Clamping clamp; 5. Rib plate. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0026] Figures 1 to 4An embodiment of a mooring cable composite counterweight structure according to the present invention is shown. This structure is used in a floating wind turbine platform that floats on the sea surface and is connected to a seabed anchor point via a mooring cable 1. The composite counterweight structure is fixedly installed in the middle or near-seabed section of the mooring cable 1 and moves with the mooring cable 1.

[0027] like Figure 1 and Figure 2 As shown, the mooring cable composite counterweight structure of this embodiment includes a mooring cable 1, a counterweight block body 2, and multiple annular damping plates 3. There are two or more annular damping plates 3; in this embodiment, three annular damping plates 3 are preferred.

[0028] The main body 2 of the counterweight is fixedly sleeved on the mooring cable 1, and three annular damping plates 3 are fixedly fixed to the outer surface of the main body 2 along the axial direction. Each annular damping plate 3 is provided with multiple flow-through holes 31, which are distributed circumferentially on the annular damping plate 3. Each annular damping plate 3 has a flange 32 on its outer edge. In this embodiment, the flanges are arranged in the same direction and face the expected dominant flow direction. During reciprocating motion, the same-direction arrangement can enhance damping in one direction and weaken it in another direction. The flow-through holes 31, the flanges 32, and the annular damping plates 3 together constitute a synergistic energy-dissipating structure, which is used to generate perforated jets, edge separation, and multi-stage wake interference when the composite counterweight structure moves with the mooring cable 1, so as to enhance hydrodynamic damping.

[0029] like Figure 4 As shown, when the floating wind turbine platform moves under the action of wind, waves and currents, the mooring cable 1 moves back and forth accordingly, and the main body 2 of the counterweight block and the annular damping plate 3 fixed on it move together in the water.

[0030] The counterweight body 2 changes the catenary shape of the mooring cable 1 by its own weight, providing horizontal restoring stiffness.

[0031] When water flows and impacts the annular damping plate 3, some of the water flow is blocked by the plate, creating a high-pressure zone on the upstream side. Figure 4 The high pressure P1 in the middle), forms a low pressure wake region on the back flow side ( Figure 4 The low pressure P2 in the middle generates pressure differential damping (P1-P2). Part of the water flow passes through the flow-through hole 31, forming an accelerated jet and generating vortices behind the hole, consuming flow energy. When the water flow reaches the flange 32, forced boundary layer separation occurs, expanding the low-pressure area on the back flow side and enhancing edge vortex dissipation.

[0032] The aforementioned jet and wake enter the axial gap between the first and second annular damping plates 3, interacting with the flow around the second annular damping plate 3 (flow around: the process by which water is forced to flow around the surface of the plate when impacting the second annular damping plate 3), generating vortex coupling and energy dissipation. This process continues as the water flows through multiple annular damping plates 3, consuming water energy at each stage, thus forming a synergistic energy dissipation effect of perforated jet, edge separation, and multi-stage wake interference, achieving enhanced hydrodynamic damping. Through this series of processes, the mechanical energy of the mooring cable 1 is converted into fluid thermal energy and vortex dissipation energy. This structure, while retaining the traditional counterweight adjustment of the catenary profile and stiffness restoration, significantly increases the upstream projected area and equivalent drag coefficient, effectively suppressing dynamic tension fluctuations in the mooring cable and mitigating fatigue damage, achieving an integrated function of centralized counterweight and enhanced hydrodynamic damping.

[0033] like Figure 3 As shown, this embodiment also includes a clamp 4, which clamps the counterweight body 2 onto the mooring cable 1. Specifically, the counterweight body 2 is formed by splicing together multiple counterweight segments 21. In this embodiment, a two-segment counterweight segment 21 is used as an example. The two segments 21 can be joined together radially along the mooring cable 1. The inner side of the counterweight body 2 is provided with a clamping groove 22 that matches the outer diameter of the mooring cable 1. Each counterweight segment 21 has one clamping groove segment, and the clamping groove segments on two counterweight segments 21 are spliced ​​together to form a complete clamping groove 22. After the two segments 21 are joined together, the two clamping groove segments are joined together to form a complete clamping groove 22 to cover and position the mooring cable 1, and finally clamped by the clamp 4.

[0034] In this embodiment, the counterweight body 2 can be made of cast steel, ductile iron, reinforced concrete, steel-shell concrete, high-density composite materials, or other corrosion-resistant materials suitable for marine environments to adapt to the long-term marine service environment. Its surface can be provided with an anti-corrosion coating, sacrificial anode, or cathodic protection structure. An anti-slip pad is provided between the counterweight body 2 and the mooring cable 1. The anti-slip pad restricts the axial movement of the counterweight body 2 and also prevents damage to the mooring cable 1. Similarly, a protective layer is provided between the clamp 4 and the counterweight body 2.

[0035] This embodiment achieves convenient installation and reliable clamping of the composite counterweight structure on the mooring cable through the cooperation of the segmented counterweight block body and the clamp, making it particularly suitable for retrofitting existing mooring cables. The inner clamping groove is precisely matched with the outer diameter of the mooring cable, and combined with corrosion-resistant materials, it ensures structural stability and durability for long-term service. While retaining the traditional counterweight function, it also works in conjunction with the hydrodynamic energy dissipation mechanism of the annular damping plate to effectively reduce fatigue damage to the mooring cable and improve the safety and service life of the floating wind turbine mooring system.

[0036] In this embodiment, a through hole is provided in the middle of the annular damping plate 3, through which the annular damping plate 3 is fitted onto the outer periphery of the counterweight body 2. The outer diameter of the annular damping plate 3 is larger than the outer diameter of the counterweight body 2, thereby increasing the upstream projection area of ​​the composite counterweight structure when moving in the water. The axial distance between two adjacent annular damping plates 3 is 0.15 to 1.00 times the outer diameter of the annular damping plate 3.

[0037] In this embodiment, the annular damping plate 3 is fixed to the counterweight body 2 by multiple ribs 5. Specifically, each annular damping plate 3 is connected to the counterweight body 2 by four ribs 5, with two ribs 5 located on one end face of the annular damping plate 3 and the other two ribs 5 located on the other end face. Preferably, the ribs 5 are triangular plates. The ribs 5 are evenly arranged around the circumference of the counterweight body 2. The ribs 5 support the annular damping plate 3, improve the bending stiffness and overall stability of the damping plate, prevent excessive warping or local vibration of the damping plate under wave alternating loads, and transfer the hydrodynamic load on the damping plate to the fixing system formed by the counterweight body 2 and the clamp 4.

[0038] In this embodiment, the flow-through holes 31 are preferably circular. Multiple flow-through holes 31 are uniformly arranged circumferentially along the annular damping plate 3. The diameter of the flow-through holes 31 near the outer edge of the annular damping plate 3 is larger than that near the inner edge of the annular damping plate 3. The porosity of the flow-through holes 31 on the annular damping plate 3 is 5%–45%. The function of the flow-through holes 31 is to allow a portion of the water flow to pass through the annular damping plate 3 while ensuring the overall projected area, forming local acceleration, jet contraction, shear layer separation, and post-hole vortex at the orifice opening. It also allows the perforated jet to enter the wake region of the adjacent annular damping plate 3, enhancing multi-stage vortex dissipation. The flow-through holes 31 can also release instantaneous peak pressure under extreme sea conditions, reducing the peak structural stress of the annular damping plate 3.

[0039] The implementation principle of the mooring cable composite counterweight structure in this embodiment is as follows:

[0040] When the floating wind turbine platform moves under the influence of wind, waves, and currents, the mooring cable 1 reciprocates accordingly, and the composite counterweight structure fixed to it moves synchronously in the water.

[0041] The counterweight body 2 changes the catenary shape of the mooring cable 1 by its own weight, thereby improving the geometric stiffness and horizontal restoring force of the mooring system.

[0042] When the multi-ring damping plate 3 moves with the mooring cable 1, its plate body blocks the water flow and forms a pressure difference between the front and back (pressure difference damping). The flow through hole 31 causes part of the water flow to accelerate through, generating a through jet and a vortex behind the hole. The flange 32 induces the water flow to be forcibly separated at the outer edge, expanding the low-pressure area on the back side (edge ​​vortex dissipation).

[0043] The jet and wake generated by the first annular damping plate 3 enter the axial gap between it and the second annular damping plate 3, and couple with the flow around the second annular damping plate 3 to form multi-stage wake interference, which consumes water flow energy step by step.

[0044] The above process converts the mechanical energy of the mooring cable's motion into fluid vortex dissipation energy and thermal energy, thereby suppressing dynamic tension fluctuations, mitigating fatigue damage, and achieving the integrated function of concentrated counterweight and enhanced hydrodynamic damping.

[0045] The key feature of the mooring cable composite counterweight structure of this invention lies in the integrated design of "centralized counterweight of the mooring cable" and "hydrodynamic energy dissipation of the opening-flanging-multi-ring damping plate" into a single structure, rather than simply setting the counterweight and damper side by side. The specific advantages are as follows:

[0046] (i) Simultaneously achieve gravity stiffness adjustment and hydrodynamic damping enhancement

[0047] While retaining the traditional counterweight function, the counterweight structure is equipped with multiple perforated and flanged annular damping plates on the outer periphery (the perforations are the flow holes), which enables the counterweight structure to simultaneously perform differential pressure damping, perforated jet energy dissipation, edge separation energy dissipation, and multi-stage wake interference energy dissipation, thus becoming a composite functional component.

[0048] (ii) Hole opening, flanging, and multi-layer arrangement create synergistic effects

[0049] An opening alone may reduce the projected area, a flange alone may increase the instantaneous peak value, and multiple individual channels stacked together can easily cause shading. The combination of these three factors results in: the opening generating local jet penetration into the low-velocity wake region; the flange forcibly separating and expanding the low-pressure vortex region; and the multiple channels between the plates causing continuous coupling of the jet, edge vortex, and wake, forming a multi-stage energy dissipation chain of "orifice jet - flange separation - inter-plate wake coupling". Porosity, orifice shape, flange direction, and plate spacing must be matched together to maintain high equivalent damping while reducing peak load.

[0050] (III) Hydrodynamic enhancement and fatigue suppression

[0051] The extended annular damping plates with multiple perforations and flanges increase the projected area facing the flow. Simultaneously, the flanges induce forced separation, enhancing the pressure difference between the front and rear sections. The perforations generate a perforated jet and a vortex behind the perforation; the combination of these three factors significantly improves the equivalent drag coefficient. The axial gap between adjacent damping plates allows the jet and wake of the front plate to couple sequentially with the flow around the rear plate, forming multi-stage wake interference and enhancing flow unsteadiness. This synergistic energy dissipation converts the mechanical energy of the mooring cable into fluid thermal energy and vortex dissipation energy, thereby suppressing dynamic tension fluctuations, reducing alternating stress, and effectively extending the fatigue life of the mooring system.

[0052] It should be noted that, in addition to this embodiment, the folding direction of each flange 32 on the multiple annular damping plates 3 can also be adjacent reverse folding or double-sided folding (that is, each annular damping plate 3 is provided with flanges 32 on both sides).

[0053] Although the invention has been described with reference to preferred embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the invention. In particular, the technical features mentioned in the various embodiments can be combined in any manner as long as there is no structural conflict. The invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A composite counterweight structure for mooring cables, characterized in that, The composite counterweight includes a mooring cable (1), a counterweight body (2), and multiple annular damping plates (3). The counterweight body (2) is fixedly sleeved on the mooring cable (1). The multiple annular damping plates (3) are fixed axially at intervals on the outer surface of the counterweight body (2). The annular damping plates (3) are provided with multiple flow-through holes (31) and their outer edges are provided with flanges (32). The flow-through holes (31), the flanges (32), and the multiple annular damping plates (3) together constitute a synergistic energy-dissipating structure, which is used to generate perforated jets, edge separation, and multi-stage wake interference when the composite counterweight structure moves with the mooring cable (1), so as to enhance hydrodynamic damping.

2. The mooring cable composite counterweight structure according to claim 1, characterized in that, It also includes a clamp (4), the main body (2) of the counterweight block is clamped to the mooring cable (1) by the clamp (4).

3. The mooring cable composite counterweight structure according to claim 1, characterized in that, The annular damping plate (3) is fixed to the counterweight body (2) by multiple ribs (5).

4. The mooring cable composite counterweight structure according to any one of claims 1 to 3, characterized in that, The main body (2) of the counterweight is formed by splicing together multiple counterweight segments (21).

5. The mooring cable composite counterweight structure according to any one of claims 1 to 3, characterized in that, The folding direction of each flange (32) on the multiple annular damping plates (3) is folding in the same direction, folding in opposite directions of adjacent flanges, or folding on both sides.

6. The mooring cable composite counterweight structure according to any one of claims 1 to 3, characterized in that, An anti-slip pad is provided between the counterweight body (2) and the mooring cable (1) to restrict the axial movement of the counterweight body (2).

7. The mooring cable composite counterweight structure according to any one of claims 1 to 3, characterized in that, The axial distance between two adjacent annular damping plates (3) is 0.15 to 1.00 times the outer diameter of the annular damping plate (3).

8. The mooring cable composite counterweight structure according to any one of claims 1 to 3, characterized in that, The multiple flow holes (31) are evenly arranged around the annular damping plate (3). The diameter of the flow holes (31) near the outer edge of the annular damping plate (3) is larger than the diameter of the flow holes (31) near the inner edge of the annular damping plate (3). The porosity of the flow holes (31) on the annular damping plate (3) is 5% to 45%.

9. The mooring cable composite counterweight structure according to any one of claims 1 to 3, characterized in that, The main body (2) of the counterweight is made of corrosion-resistant material, and its inner side is provided with a clamping groove (22) that is compatible with the outer diameter of the mooring cable (1).

10. The mooring cable composite counterweight structure according to claim 2 or 3, characterized in that, A protective layer is provided between the clamp (4) and the counterweight body (2).

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