Low-drag-force reclaimed water buoy

Abstract

The invention discloses a low-drag-force reclaimed water buoy, which belongs to the technical field of offshore oil and gas development equipment, and comprises a buoy assembly which comprises at least two internally hollow buoys and has smooth and continuous outer contours to inhibit edge flow separation, and the central axes of the buoys are arranged in parallel; the bearing assembly comprises a curved-surface supporting plate and a plurality of apron boards installed on the outer curved surface of the curved-surface supporting plate, the inner curved surface of the curved-surface supporting plate is erected on one sides of the buoys, the inner curved surface of the curved-surface supporting plate is provided with at least two curvature centers collinear with the central axes of the buoys, and a continuously and gradually changing fluid channel is formed between the outer contour of each buoy and the inner curved surface of the curved-surface supporting plate; by means of the scheme, the problem that due to the fact that flow separation at the edge of a traditional reclaimed water buoy is violent, drag force is large is solved, the two symmetrically-arranged capsule type buoys can provide large net buoyancy, mooring restoring force is improved, and the motion amplitude is reduced.

Description

Technical Field

[0001] This invention relates to the field of marine oil and gas development equipment technology, and in particular to a low-drag mid-water pontoon. Background Technology

[0002] To meet the strategic needs of building a maritime power, the development of deep-sea oil and gas resources has become a key measure for expanding the marine economy and ensuring energy security. Floating Production Storage and Offloading (FPSO) units, due to their integrated functions of oil and gas processing, storage and transportation, and power supply for living quarters, as well as their excellent resistance to wind and waves and deep-water adaptability, have become core marine engineering equipment. Pliant-wave type flexible risers are the main riser type connected to FPSOs. Mid-water buoys generally serve as underwater support structures to reduce riser tension and prevent riser interference or even collisions. Therefore, the hydrodynamic characteristics of mid-water buoys directly affect the dynamic response and structural integrity of the riser system.

[0003] Existing medium-water pontoons are generally multi-channel medium-water pontoons, suitable for supporting mooring, risers, and cables. These pontoons typically use pontoon units with large displacement volumes to provide buoyancy and sharp corner girder or plate beams to limit riser movement. This leads to significant flow separation near the riser channel and at the pontoon edge, resulting in a significant increase in drag force and exacerbating the risk of riser vibration and fatigue damage. This not only limits development efficiency but also poses a threat to offshore operational safety due to structural failure. Therefore, this invention provides a low-drag medium-water pontoon. Compared to conventional medium-water pontoons, by optimizing the shape of the pontoon unit and the edge corner of the skirt at the riser channel, flow separation can be suppressed to a certain extent, reducing drag force. This, in turn, reduces the motion amplitude of the medium-water pontoon and suppresses the dynamic response of the riser. Summary of the Invention

[0004] The purpose of this invention is to provide a low-drag mid-water pontoon, solving the problems existing in the prior art. To achieve the above objective, this invention adopts the following technical solution: A low-drag mid-water pontoon includes: A pontoon assembly comprising at least two internally hollow pontoons having a smooth, continuous outer profile to suppress edge flow separation, the central axes of the pontoons being arranged in parallel. The support assembly includes a curved support plate and several skirts mounted on the outer curved surface of the curved support plate. The inner curved surface of the curved support plate is mounted on one side of the pontoon, and its inner curved surface has at least two curvature centers that are collinear with the central axis of the pontoon. A continuously gradually changing fluid channel is formed between the outer contour of the pontoon and the inner curved surface of the curved support plate. The outer curved surface of the curved support plate and the skirts cooperate to form a channel for cable passage.

[0005] Preferably, each of the pontoons includes a cylindrical thin-walled structure and a hemispherical thin-walled structure connected to both ends of the cylindrical thin-walled structure, wherein the radius of curvature of the hemispherical thin-walled structure matches the radius of the cylindrical thin-walled structure.

[0006] Preferably, each of the hollow pontoons is provided with a pressure-resistant structure, the pressure-resistant structure comprising: Several annular ribs are coaxial with the cylindrical thin-walled structure and arranged sequentially along its axial direction and fixed to its inner wall. Several longitudinal bones are arranged in sequence along the circumference of the cylindrical thin-walled structure, parallel to the central axis of the structure and fixed to its inner wall. A number of annular ribs located within the hemispherical thin-walled structure, coaxial with the cylindrical thin-walled structure, and arranged sequentially along its axial direction and fixedly connected to the inner wall of the hemispherical thin-walled structure.

[0007] Preferably, the inner curved surface of the curved support plate is fixedly connected with a plurality of float mounting plates for connecting the outer wall of the float along its circumference, and adjacent outer walls of the float are fixedly connected with a float connecting plate perpendicular to its central axis.

[0008] Preferably, the plurality of skirts include a first edge skirt, a plurality of middle skirts and a second edge skirt arranged sequentially at intervals along the central axis of the curved support plate and fixed to its outer curved surface, and forming a channel for cable passage at the intervals, which is limited by the plate body of the adjacent skirts and supported by the outer curved surface of the curved support plate.

[0009] Preferably, the central skirt is a circumferentially closed ring plate with a flow-guiding ring surface formed on its periphery, and its edge corners adopt a gradually tapering smooth transition structure; the edge skirt is a strip plate.

[0010] Preferably, multiple support rods are provided between the closed inner walls of the middle skirt plate, and reinforcing ribs are provided along the circumference of the closed inner walls; multiple diagonal tie rods are provided between the edge skirt plate and the edge of the curved support plate, and reinforcing ribs are provided along the length of the edge skirt plate.

[0011] Preferably, the inner curved surface of the curved support plate is provided with a plurality of reinforcing ribs parallel to its central axis; the edge of the curved support plate is provided with a plurality of reinforcing ribs coinciding with its edge line.

[0012] Preferably, it also includes a mooring connection assembly, which includes a plurality of lugs connected to the edge of the curved support plate.

[0013] Preferably, the medium-water float is applied to a pleant wave type flexible riser, and the curved support plate, together with the skirt plate, forms two channels for supporting cables and one channel for supporting the riser.

[0014] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall structure of a low-drag-force water pontoon according to the present invention; Figure 2 This is a schematic diagram of the structure of each skirt panel of the present invention; Figure 3 This is a schematic diagram of the curved support plate and its internal structure of the present invention; Figure 4 This is a cross-sectional schematic diagram of the interior of the float of the present invention; Figure 5 This is a schematic diagram of the spatial positions of a low-drag buoy, riser, and FPSO according to the present invention.

[0016] Figure Labels 1. Float; 101. Cylindrical thin-walled structure; 102. Hemispherical thin-walled structure; 103. Annular rib; 104. Longitudinal rib; 105. Annular rib plate; 2. Curved support plate; 201. First type of reinforcing rib; 202. Second type of reinforcing rib; 203. Float mounting plate; 204. Float-to-float connecting plate; 3. Edge skirt; 301. Diagonal tie rod; 302. Fourth type of reinforcing rib; 4. Middle skirt; 401. Support rod; 402. Third type of reinforcing rib; 5. Lifting lug; 6. Riser; 7. Cable; 8. Mooring cable; 9. Floating production storage and unloading unit. Detailed Implementation

[0017] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0018] like Figure 1-4 As shown, this embodiment provides a low-drag mid-water pontoon, which is applied to the floating production storage and offloading (FPSO) system 9, and serves as the underwater support structure for the riser 6. It is used to reduce the tension of the riser 6 and prevent interference or collision between risers 6.

[0019] The low-drag medium-water pontoon is mainly composed of three parts: the pontoon assembly, the support assembly, and the mooring connection assembly. These parts are interconnected by steel structure connectors to form an integral structure.

[0020] The pontoon assembly, as the core buoyancy unit of the greywater pontoon, consists of two hollow pontoons 1 with equal volumes. The two pontoons 1 are arranged in a parallel and symmetrical manner, with their central axes parallel to each other and located in the same horizontal plane, and a preset distance is maintained between the two pontoons 1.

[0021] Each pontoon 1 adopts a capsule-shaped structure design, consisting of a cylindrical thin-walled structure 101 and two hemispherical thin-walled structures 102 connected to both ends of the cylindrical thin-walled structure 101. The radius of curvature of the hemispherical thin-walled structure 102 is strictly matched with the radius of the cylindrical thin-walled structure 101, so that the pontoon 1 forms a complete and continuous smooth streamlined outer contour, effectively suppressing flow separation at the edge of the pontoon 1. In addition, the thin-walled structure of the pontoon 1 has a uniform wall thickness to ensure structural uniformity and consistency of mechanical properties. To ensure sealing, the cylindrical thin-walled structure 101 and the hemispherical thin-walled structure 102 can be connected by interference fit, sealing ring connection, or integrated welding.

[0022] Each pontoon 1 has a pressure-resistant structure inside its hollow interior to withstand water pressure in deep water environments and prevent buckling failure of the pontoon 1. The pressure-resistant structure includes three types of components: annular ribs 103, longitudinal ribs 104, and annular rib plates 105.

[0023] Annular ribs 103 are disposed inside the cylindrical thin-walled structure 101. Multiple annular ribs 103 are arranged coaxially with the cylindrical thin-walled structure 101, and are evenly arranged sequentially along the axial direction of the cylindrical thin-walled structure 101. The outer edge of each annular rib 103 is fixedly connected to the inner wall of the cylindrical thin-walled structure 101. The specific connection method is not limited and can be adhesive, welding, snap-fit, or bolted. In this embodiment, the annular ribs 103 are made of angle steel, and 10 are evenly arranged along the longitudinal direction of the cylindrical thin-walled structure 101, with equal spacing between adjacent annular ribs 103.

[0024] The longitudinal ribs 104 are also disposed inside the cylindrical thin-walled structure 101. Multiple longitudinal ribs 104 are arranged parallel to the central axis of the cylindrical thin-walled structure 101 and are evenly arranged sequentially along the circumferential direction of the cylindrical thin-walled structure 101. The outer surface of each longitudinal rib 104 is fixedly connected to the inner wall surface of the annular rib 103. The specific connection method is not limited and will not be described in detail here. The multiple longitudinal ribs 104 and multiple annular ribs 103 together form a crisscrossing grid-like reinforcing structure. In this embodiment, the longitudinal ribs 104 are made of T-shaped steel, and 10 are evenly arranged at 36° angles along the circumference of the cylindrical thin-walled structure 101. The 10 longitudinal ribs 104 and the 10 annular ribs 103 together constitute 10 sets of fully symmetrical annular reinforcing units.

[0025] Annular ribs 105 are respectively disposed inside the two hemispherical thin-walled structures 102. Multiple layers of annular ribs 105 are coaxially arranged with the cylindrical thin-walled structure 101, arranged sequentially from the outside to the inside along the radial direction of the hemispherical thin-walled structure 102. The diameter of each layer of annular ribs 105 adapts to the radial variation of the hemispherical thin-walled structure 102, and its outer edge is fixedly connected to the inner wall of the hemispherical thin-walled structure 102; the specific connection method is not limited. In this embodiment, two layers of annular ribs 105 are disposed within each hemispherical thin-walled structure 102. The annular ribs 105 closer to the cylindrical thin-walled structure 101 have a larger diameter, while the annular ribs 105 closer to the top of the hemispherical thin-walled structure 102 have a smaller diameter.

[0026] The support assembly supports the riser 6 and the cable 7, and limits their movement to prevent interference or collision. The support assembly includes a curved support plate 2 and several skirt plates mounted on the outer curved surface of the curved support plate 2.

[0027] The curved support plate 2 has an overall arc-shaped curved panel structure with two working surfaces: an inner curved surface and an outer curved surface. The inner curved surface of the curved support plate 2 faces the float assembly and is mounted above the two floats 1. The inner curved surface of the curved support plate 2 adopts a special double curvature center design, with at least two curvature centers, each collinear with the central axis of the two floats 1. This design allows the inner curved surface of the curved support plate 2 to fit the outer contour of the two floats 1, forming a continuous and gradually changing fluid channel between the inner curved surface of the curved support plate 2 and the outer contour of the floats 1, which facilitates smooth water flow and reduces flow resistance. The curved support plate 2 has a concave pressure-bearing surface with a continuous curvature transition to withstand the pressure from the riser 6 and the cable 7, as well as the forces of the complex marine environment.

[0028] An orthogonal grid reinforcement structure is provided on the inner curved surface of the curved support plate 2 to improve its structural strength and stiffness. The orthogonal grid reinforcement structure includes first-type reinforcing ribs 201 arranged along the central axis parallel to the curved support plate 2. Multiple first-type reinforcing ribs 201 are arranged at equal intervals along the circumferential direction of the curved support plate 2, with each first-type reinforcing rib 201 extending to the edge of the curved support plate 2 at both ends. A second-type reinforcing rib 202 is also arranged coinciding with the edge line of the curved support plate 2. The two sets of reinforcing ribs intersect perpendicularly to each other, forming a crisscrossing array-like structural reinforcement system. The first-type reinforcing ribs 201 are made of I-beams, with a total of 7 ribs evenly distributed on the inner curved surface of the curved support plate 2. The second-type reinforcing ribs 202 are made of T-beams, with a total of 11 ribs evenly distributed on the edge of the curved support plate 2. Each reinforcing rib is fixedly connected to the inner curved surface of the curved support plate 2; the specific connection method is not limited.

[0029] The curved support plate 2 is connected to the pontoon assembly via a high-strength connecting plate. The connecting plate includes two types: pontoon mounting plate 203 and pontoon inter-assembly connecting plate 204.

[0030] The pontoon mounting plate 203 is used to connect the curved support plate 2 to the outer wall of the pontoon 1. Multiple pontoon mounting plates 203 are arranged sequentially along the circumferential direction of the inner curved surface of the curved support plate 2. The first end of each pontoon mounting plate 203 is fixedly connected to the inner curved surface of the curved support plate 2, and the other end has an arc edge adapted to the shape of the outer wall of the pontoon 1 and is fixedly connected to the outer wall of the pontoon 1. The pontoon mounting plate 203 is made of high-strength flat steel and has two shapes. One is a long plate with a hollow plate body and arc edges at both ends of the plate body length. This long plate can connect two pontoons 1 at the same time. The other is a short plate, which is on the same plane as the long plate and arranged on both sides of the long plate. The inner side has an arc edge and it connects to the side wall of one pontoon 1 respectively. One long plate and two short plates form a group, and a total of five groups are set. They are arranged at equal intervals along the central axis of the curved support plate 2 to firmly connect the curved support plate 2 to the two pontoons 1 below it.

[0031] The pontoon connecting plate 204 is used to connect the outer walls of two adjacent pontoons 1. The plate surface of the pontoon connecting plate 204 is arranged perpendicular to the central axis of the pontoon 1 and located in the gap space between the two pontoons 1. The two side edges of the pontoon connecting plate 204 have arc edges that are adapted to the outer walls of the pontoons 1 and are fixedly connected. The pontoon connecting plate 204 is composed of a longitudinal flat steel and multiple transverse flat steels. The longitudinal flat steel extends along the axial direction of the pontoon 1, and the multiple transverse flat steels are arranged perpendicular to the longitudinal flat steel and welded to the longitudinal flat steel to form a grid-like connecting structure. In this embodiment, a total of 10 transverse flat steels are provided, evenly distributed between the two pontoons 1. The fixing method of both the pontoon mounting plate 203 and the pontoon connecting plate 204 is not particularly limited and conventional fixing methods can be used.

[0032] Skirts are installed on the outer curved surface of the curved support plate 2 to limit the movement of the riser 6 and the cable 7. Several skirts are arranged sequentially at intervals along the central axis of the curved support plate 2, including a first edge skirt 3 located at the first edge of the curved support plate 2 in this direction, several middle skirts 4 located in the middle of the curved support plate 2, and a second edge skirt 3 located at another edge of the curved support plate 2. A gap is formed between adjacent skirts, which is laterally limited by the panels of the adjacent skirts and supported at the bottom by the outer curved surface of the curved support plate 2, together forming a channel for cable passage. In this embodiment, the skirts and the curved support plate 2 cooperate to form three channels, respectively for passing through one riser 6 and two cables 7.

[0033] The central skirt plate 4 adopts a circumferentially closed ring structure. This ring is not of equal diameter and has a certain length-to-width ratio. The long side is perpendicular to the central axis of the curved support plate 2, and its periphery forms a flow-guiding annular surface. The edges and corners of the central skirt plate 4 adopt a gradually tapering smooth transition structure to avoid forming sharp edges and effectively suppress flow separation in this area. The bottom edge of the central skirt plate 4 and the outer curved surface of the curved support plate 2 are still fixedly connected without specific limitations.

[0034] The edge skirt 3 adopts a strip structure. The inner long side of the edge skirt 3 is fixedly connected to the outer curved edge of the curved support plate 2 without specific limitations. The outer long side of the edge skirt 3 is higher in the middle than on both sides, and the middle part is close to the adjacent middle skirt 4. Therefore, along the central axis of the curved support plate 2, an arc shape can be observed with the middle bulging above the outer curved surface and the two sides gradually approaching the outer curved surface. Along the direction perpendicular to the central axis of the curved support plate 2, an arc shape can be observed with the middle approaching the middle skirt 4 and the two sides approaching the edge of the curved support plate 2. Furthermore, all corners of the edge skirt 3 are chamfered to achieve a streamlined design and reduce flow separation at the edges.

[0035] The skirt is equipped with a spatial cross truss system to improve the structural strength of the skirt and prevent buckling failure under fluid loads.

[0036] Multiple support rods 401 are provided between the closed inner walls of the middle skirt plate 4. The support rods 401 span the closed inner cavity of the middle skirt plate 4, and their ends are fixedly connected to the inner walls on opposite sides of the middle skirt plate 4. The support rods 401 effectively suppress the relative deformation between adjacent skirt plate walls, preventing the middle skirt plate 4 from concave inward under external loads. In this embodiment, the support rods 401 are made of high-strength round steel, with a total of 8 rods evenly distributed within the closed inner cavity of the middle skirt plate 4. A third type of reinforcing rib 402 is also provided circumferentially on the closed inner wall of the middle skirt plate 4. The third type of reinforcing rib 402 extends circumferentially along the closed inner wall of the middle skirt plate 4 in a closed loop shape, and is fixedly connected to the inner wall of the middle skirt plate 4. The third type of reinforcing rib 402 and the support rods 401 together constitute a composite load-bearing system, significantly improving the overall rigidity of the middle skirt plate 4. In this embodiment, the third type of reinforcing rib 402 is made of angle steel.

[0037] Multiple diagonal braces 301 are provided between the edge skirt plate 3 and the second type of reinforcing ribs 202 on the edge of the curved support plate 2. One end of the diagonal brace 301 is fixedly connected to the surface of the edge skirt plate 3, and the other end extends obliquely and is fixedly connected to the second type of reinforcing rib 202 on the edge of the curved support plate 2. The multiple diagonal braces 301 are arranged in a triangle relative to the edge skirt plate 3, forming a stable triangular support structure. In this embodiment, the diagonal braces 301 are made of high-strength round steel, and a total of 6 are provided. A fourth type of reinforcing rib 302 is also provided along the length direction of the edge skirt plate 3. Multiple fourth type of reinforcing ribs 302 are evenly distributed along the length direction of the edge skirt plate 3, and each fourth type of reinforcing rib 302 is fixedly connected to the surface of the edge skirt plate 3. In this embodiment, the fourth type of reinforcing ribs 302 are made of angle steel, and a total of 14 are provided, evenly distributed on the edge skirt plate 3.

[0038] The mooring connection assembly is used to connect the mooring cable 8 and provide positioning and restoring force for the mid-water buoy. The mooring connection assembly includes multiple lugs 5, which are connected to the edge of the curved support plate 2.

[0039] In this embodiment, four lifting lugs 5 are provided, respectively located in a rectangular distribution at the four corners of the curved support plate 2. They are connected to the curved support plate 2 by bearing bases fixed to corresponding positions on the curved support plate 2. The lifting lugs 5 are provided with connection holes for threading the mooring cable 8. The four lifting lugs 5 can withstand the axial tension from the mooring cable 8, suppressing the movement performance of the mid-water buoy under the action of ocean currents and waves.

[0040] Specifically, during assembly, two pontoons 1 are first arranged symmetrically in parallel, and their outer walls are connected and fixed together by a connecting plate 204 to form a pontoon assembly. Then, a curved support plate 2 is placed above the pontoon assembly, with its inner curved surface facing the pontoon assembly. The inner curved surface of the curved support plate 2 is then connected and fixed to the outer wall of the pontoon 1 by a pontoon mounting plate 203. Next, edge skirts 3 and center skirts 4 are sequentially installed on the outer curved surface of the curved support plate 2 to form a support assembly. Finally, lifting lugs 5 are installed at the edge of the curved support plate 2 to form a mooring connection assembly. All fixing connections between components should be selected to ensure connection reliability and structural integrity.

[0041] After assembly, as follows Figure 5 As shown, the mid-water pontoon is connected to the seabed anchor via mooring cable 8 and is suspended at a predetermined water depth. The riser 6 and cable 7 pass through the channel formed by the curved support plate 2 and the skirt plate, are supported by the outer curved surface of the curved support plate 2 and are laterally restrained by the skirt plate, thus realizing the underwater support function of the pleat wave type flexible riser 6 system.

[0042] Finally, it should be noted that the described embodiments are merely some, not all, of the embodiments of the present invention. Those skilled in the art will understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the claims and their equivalents; that is, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A low-drag mid-water pontoon, characterized in that, include: A pontoon assembly comprising at least two internally hollow pontoons having a smooth, continuous outer profile to suppress edge flow separation, the central axes of the pontoons being arranged in parallel. The support assembly includes a curved support plate and several skirts mounted on the outer curved surface of the curved support plate. The inner curved surface of the curved support plate is mounted on one side of the pontoon, and its inner curved surface has at least two curvature centers that are collinear with the central axis of the pontoon. A continuously gradually changing fluid channel is formed between the outer contour of the pontoon and the inner curved surface of the curved support plate. The outer curved surface of the curved support plate and the skirts cooperate to form a channel for cable passage.

2. The low-drag-force mid-water float according to claim 1, characterized in that, Each of the pontoons includes a cylindrical thin-walled structure and hemispherical thin-walled structures connected to both ends of the cylindrical thin-walled structure, wherein the radius of curvature of the hemispherical thin-walled structure matches the radius of the cylindrical thin-walled structure.

3. The low-drag-force mid-water float according to claim 2, characterized in that, Each of the pontoons has a hollow interior with a pressure-resistant structure, the pressure-resistant structure comprising: Several annular ribs are coaxial with the cylindrical thin-walled structure and arranged sequentially along its axial direction and fixed to its inner wall. Several longitudinal bones are arranged in sequence along the circumference of the cylindrical thin-walled structure, parallel to the central axis of the structure and fixed to its inner wall. A number of annular ribs located within the hemispherical thin-walled structure, coaxial with the cylindrical thin-walled structure, and arranged sequentially along its axial direction and fixedly connected to the inner wall of the hemispherical thin-walled structure.

4. The low-drag-force mid-water float according to claim 2, characterized in that, The inner curved surface of the curved support plate is fixedly connected with a plurality of float mounting plates for connecting the outer wall of the float along its circumference, and an inter-float connecting plate perpendicular to its central axis is fixedly connected between adjacent outer walls of the float.

5. The low-drag-force mid-water float according to claim 1, characterized in that, The skirts include a first edge skirt, several middle skirts, and a second edge skirt arranged sequentially and fixedly to the outer curved surface of the curved support plate along the central axis direction, and forming a channel for cable passage at the intervals, which is limited by the plate body of the adjacent skirts and supported by the outer curved surface of the curved support plate.

6. The low-drag-force mid-water float according to claim 5, characterized in that, The central skirt is a circumferentially closed ring plate with a flow-guiding ring surface formed on its periphery, and its edge corners adopt a gradually tapering smooth transition structure; the edge skirt is a strip plate.

7. The low-drag-force mid-water float according to claim 6, characterized in that, Multiple support rods are provided between the closed inner walls of the middle skirt panel, and reinforcing ribs are provided along the circumference of the closed inner walls; multiple diagonal tie rods are provided between the edge skirt panel and the edge of the curved support plate, and reinforcing ribs are provided along the length of the edge skirt panel.

8. The low-drag-force mid-water float according to claim 1, characterized in that, The inner curved surface of the curved support plate is provided with multiple reinforcing ribs parallel to its central axis; the edge of the curved support plate is provided with multiple reinforcing ribs coinciding with its edge line.

9. The low-drag-force mid-water float according to claim 1, characterized in that, It also includes a mooring connection assembly, which includes a plurality of lugs connected to the edge of the curved support plate.

10. The low-drag mid-water pontoon according to any one of claims 1-9, characterized in that, The aforementioned floating pontoon is applied to a pleant wave type flexible riser. The curved support plate, together with the skirt plate, forms two channels for supporting cables and one channel for supporting the riser.

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