BR112020007661B1 - GENERALLY CYLINDRICAL ELEMENT ADAPTED FOR IMMERSION IN A BODY OF WATER - Google Patents

Abstract

A generally cylindrical element (10) is described which is adapted for immersion in water. The generally cylindrical element (10) has an external surface (11) that is, in use, in contact with water. The outer surface (11) has at least two rows of repeating shapes (20), for example hexagons (20), provided on the surface (11), where each row of repeating shapes (20) is separate from the other or the adjacent row. (s) by a groove arrangement (30). Each shape (20) within a row is separated from the adjacent shape or each other (20) by at least one slot (30). This surface configuration (11) reduces vortex-induced vibration (VIV) and/or drag that can act on the generally cylindrical element (10) when it is immersed in a body of water.

Description

FIELD OF INVENTION

[001] The present invention is related to preventing Vortex Induced Vibration (VIV) and reducing drag that occur in substantially cylindrical objects when they are positioned within a body of water and/or are operating within a flowing water current, such as in an offshore environment. These cylindrical objects are typically: - Distributed Buoyancy Modules (DBM); - Float for Drilling Riser (DRB); and - Cylindrical Protective Casings traditionally used as straps against VIV and which can be retrofitted to the external surface of DRB modules already installed in the water, where said DRB module does not currently have any VIV reduction element associated with it (or if it does, the operator wishes to replace this VIV reduction module with an improved version).

FUNDAMENTALS

[002] In fluid dynamics, Vortex Induced Vibrations (VIV) are movements induced on bodies that interact with an external fluid flow, produced by periodic irregularities or the movement that produces these periodic irregularities in this flow.

[003] A classic example is the VIV of a submarine cylinder. A person skilled in the art can very easily observe how this occurs in basic terms by placing a cylinder in water (such as in water held in a swimming pool or even in a bucket) and moving it through the water in a direction perpendicular to its geometric axis. Since real fluids always have some viscosity, the flow around the cylinder will slow down when in contact with its surface, forming the so-called boundary layer. At some point, however, this boundary layer may separate from the body due to its excessive curvature. Vortices are then formed by changing the pressure distribution along the surface. When the vortices are not formed symmetrically around the body (with regard to its intermediate plane), different support forces are developed on each side of the body, which therefore leads to transverse movement of the flow. This movement alters the nature of the vortex formation in such a way that it leads to a limited range of motion (unlike what would be expected in a typical resonance situation).

[004] It is important, therefore, to reduce or minimize VIV in cylindrical objects when they are positioned within and operating in the water column, typically between and possibly from the water surface to the seabed within a water current flow, such as in an offshore environment.

[005] Conventionally, it is known to attempt to reduce VIV in various ways. For example, Matrix Composites and Engineering of Henderson, WA, 6166, Australia produce the MATRIX LGS™ system (which is described in PCT Patent Publication WO2016/205900) and which comprises a cylindrical element positioned around an installed cylindrical frame. in a body of water (such as a marine riser, umbilical, cable or pipeline), wherein the cylindrical element comprises a plurality of elevated and longitudinally extending body portions that are adapted to reduce VIV.

[006] Likewise, the company Trelleborg of Houston, TX 77073, USA together with Diamond Offshore Drilling, Inc. of Houston, Texas 77094-1810, USA produce a Helical Buoyancy system that is arranged to be positioned around a structure cylindrical pipe installed in a body of water that requires buoyancy support (such as marine drilling risers, Intervention risers, bridge pipes, long runs of large piping, production risers, umbilicals, flow lines, and power cables) , wherein the helical buoyancy system comprises a cylinder consisting of two half-shells formed of buoyant material and where the cylinder is placed around the structure to be supported in the body of water and where the cylinder comprises helical grooves formed on its outer surface at the along its length. Additional details of the Helical Buoyancy System can be seen in US Patent Nos. US8,443,896 B2 and US9,322,221 B2.

SUMMARY OF THE INVENTION

[007] In accordance with the present invention, there is provided a generally cylindrical element adapted for immersion in a body of water, the generally cylindrical element provided with an outer surface arranged, in use, to be in contact with the water, the outer surface comprising: at least two rows of repeating shapes provided therein, each row of repeating shapes being separated from each adjacent row by a slot arrangement and each shape within a row being separated from adjacent shapes by at least one slot; wherein the external surface of the generally cylindrical element reduces Vortex Induced Vibration (VIV) and/or drag acting on the generally cylindrical element.

[008] Preferably, each of the repeated formats within each row is identical. This has the advantage of maximizing the number of formats within each row.

[009] Preferably, each row provided on the outer surface comprises repeated shapes identical to the shapes of each other row, such that all shapes provided on the outer surface are identical.

[010] The shapes can be triangles, squares, rectangles or pentagons, but most shapes are preferably hexagons. This has the advantage of maximizing the total number of shapes for a given surface area provided on the outer surface. More preferably, said said surface area comprises a hexagonal segmentation. This has the additional advantage that hexagonal patterns produce a more favorable flow pattern that improves VIV suppression efficiency; There are several reasons for this, but one of the main or most important reasons is that the hexagonal patterns and surrounding groove arrangement provide a plurality of flow separation points while minimizing drag on the generally cylindrical element.

[011] Preferably, the majority of the external surface and, more preferably, the entire external surface of the generally cylindrical element comprises a hexagonal segmentation in which every three adjacent hexagons meet at each contiguous vertex and the remainder of the hexagons repeat this arrangement by the entire external surface of the generally cylindrical element.

[012] Typically, the vertex between two adjacent sides of each shape, preferably each hexagonal shape, comprises a radius and preferably without a sharp corner and, more preferably, each vertex between each pair of adjacent sides of each hexagonal shape comprises a radius between 5mm and 250mm and, more preferably, said radius is between 150mm and 250mm.

[013] Typically, the hexagon arrangement comprises rows of hexagons stacked relative to each other, each row being separated from the next upper or lower row by an arrangement of grooves.

[014] Additionally or alternatively, the arrangement of hexagons on the outer surface of the generally cylindrical element may be considered to be in the form of staggered columns spaced equidistantly around the circumference of the outer surface, where any of the columns fits precisely into the next adjacent column (although it is staggered by half the height of a hexagon when compared to the first column) and so on for other columns that circumscribe the generally cylindrical element.

[015] The person skilled in the art will understand that the outer surface with this type of hexagonal segmentation provided therein, where the hexagons project outward from the outer surface due to the groove arrangements, presents the great advantage of maximizing the number of shapes within each row and/or column and/or along the entire external surface and this therefore provides the great advantage of providing the most efficient VIV and/or drag reduction possible to the generally cylindrical element.

[016] Preferably, the generally cylindrical element is further adapted to be placed around a substantially cylindrical structure which, in use, is located in the body of water, where the cylindrical structure may be a riser, umbilical, bridge tube, long extension of large piping, drainage line, power cable or similar.

[017] The generally cylindrical element may be a Distributed Buoyancy Module (DBM), Drilling Riser Float (DRB) or may be in the form of a cylindrical protective casing used as a VIV brace. When the cylindrical element is a Distributed Buoyancy Module (DBM) or a Drilling Riser Float (DRB) it is typically provided in the form of multiple half-shells, such as two semi-circular shells or four quarter-circle shells which when put together envelop the substantially cylindrical structure located in the body of water and which typically comprise buoyancy to assist in the buoyancy of the substantially cylindrical structure located in the body of water.

[018] Typically, when the generally cylindrical element is the DRB, it further comprises stacking planes to allow the individual shells to be stacked one on top of the other.

[019] Typically, when the generally cylindrical element is a DBM it further comprises a belt and/or support cavities to assist in transporting the DBM.

[020] When the cylindrical element is in the form of a cylindrical protective casing used as a belt against VIV, it can be manufactured in halves (that is, in two split semi-circumferential pieces of 180° each, which when put together involve or envelop the cylindrical structure and form a generally cylindrical element). Alternatively, the cylindrical protective casing can be manufactured in threes (i.e., in tripartite circumferential pieces of 120° each, which when put together envelop the cylindrical structure and form a generally cylindrical element). Alternatively, when the cylindrical element is in the form of a cylindrical protective housing used as an anti-VIV brace, it may be transversely C-shaped and typically comprises a cut formed along the entire length on one side such that it can be slid along the along the entire length of the substantially cylindrical structure located in the body of water. When the cylindrical element is in the form of a cylindrical protective housing used as a VIV brace, it typically comprises arrangements of brace recesses and/or sockets and flange/bolt and nut at each end thereof and/or along its longitudinal length. (particularly when it is provided in a % or half configuration, as discussed above).

[021] Alternatively, the generally cylindrical element may be formed integrally with the substantially cylindrical structure, such as a submarine conduit, typically on the external surface thereof. As an option, the internal surface or through hole of the generally cylindrical element is joined directly to the external surface of the subsea conduit. As an option, a protective coating layer may be provided between the inner surface or through hole of the generally cylindrical element and the outer surface of the subsea conduit typically in a coaxial manner, and in this case the protective coating layer is preferably bonded to the respective surface on each of its external and internal surfaces.

[022] Typically, lashings and straps are provided to prevent accidental removal of the generally cylindrical element present around the substantially cylindrical structure located in the body of water.

[023] Preferably, said groove arrangements comprise a groove having a profile depth = 0.01 to 0.1 times the outer diameter (O.D.) of the generally cylindrical element and, more preferably, said groove arrangements comprise a groove having a profile depth = approximately 0.05 times the outer diameter (O.D.) of the generally cylindrical element.

[024] Preferably, said groove arrangements comprise a groove with a profile width = 0.04 to 0.3 times the outer diameter (O.D.) of the generally cylindrical element. More preferably said groove arrangements comprise a groove with a profile width = 0.25 to 0.3 times the outer diameter (O.D.) of the generally cylindrical element.

[025] The groove arrangement may comprise a groove with a square or rectangular shape.

[026] The groove arrangement may more preferably comprise angled side faces that may be angled between 40 to 80 degrees relative to the radius of the generally cylindrical element. In this case, the angled side faces of the groove arrangement may be angled in the region of 60 degrees with respect to the radius of the generally cylindrical element.

[027] Alternatively, the profile of the groove arrangement may be completely round (i.e., semicircular), where the cut diameter may be = 0.03 to 0.15 times the outer diameter (O.D.) of the generally cylindrical element. More preferably said groove arrangements comprise a groove having a cut diameter = 0.07 to 0.09 times the outer diameter (O.D.) of the generally cylindrical element.

[028] Typically, the groove arrangement for each row of shapes comprises an upper groove and a lower groove, where each of the upper and lower grooves encompasses the entire 360 degree circumference of the generally cylindrical element in that longitudinal cross section, such that that each of said grooves is continuous around 360 degrees of the generally cylindrical element (that is, it does not have a separate starting or ending point). This has the significant advantage over conventional helical grooves that the groove arrangements of the present invention do not need to be cut as deeply as conventional helical grooves, as they provide much greater groove coverage than conventional helical grooves. Additionally, because there is no separate start or end point for the grooves, they provide a much smoother exit point for water coming out of contact with the groove arrangement and therefore the outer surface of the element. generally cylindrical.

[029] Said formats may comprise corners with radius edges that may vary from 5mm-250mm and, more preferably, in the range of 50mm to 70mm.

[030] Preferably, the groove arrangement provides at least one and, preferably, a plurality of separate paths for water flow when navigating around the circumference of the generally cylindrical element, such that water flowing around the outer circumference of the generally cylindrical element from one side to the other (which would occur when the generally cylindrical element is substantially vertical within a body of water that is flowing next to that generally cylindrical element) encounters many points of flow separation. Preferably, said flow separation points comprise corner points of the hexagonal shapes or, alternatively, the flow separation points may comprise a side portion of the hexagonal shapes. Typically, water flowing along the flow path within the groove arrangement from one side of the generally cylindrical element to the other will encounter a flow separation point at which point it will be separated into a first flow path and a second flow path. flow. Preferably, there are a number of flow separation points provided around the outer surface of the generally cylindrical element and which are preferably met by water flowing around 180 degrees of the generally cylindrical element. This flow separation characteristic, particularly provided by the shape arrangement being staggered when viewed along each row and/or along each column of hexagonal shapes, provides significantly greater flow separation, which in turn significantly reduces VIV, and this provides significant technical advantages to embodiments of the present invention. Preferably, the flow separation point comprises the corner of a shape and optionally the flow separation point is less than 90 degrees, such that water flowing in the groove arrangement is forced to change direction by less than 90 degrees in order to keep the drag coefficient of the generally cylindrical element as low as possible. Optionally the flow separation point can be 60 degrees such that water flowing in the groove arrangement is forced to change direction by 60 degrees no matter which of the two paths the water takes around the hexagonal shape and therefore , the drag coefficient of the generally cylindrical element is kept as low as possible.

[031] Preferably, the depth of the repeated shapes is substantially equal to the corner radius at the edge of each shape.

[032] As an option, the width of the groove in the circumferential direction is substantially equal to the outermost radius of the element multiplied by 0.50 to 0.60. Additionally as an option, the width of the groove in the diagonal direction is substantially equal to the outermost radius of the element multiplied by 0.55 to 0.60.

[033] Preferably, the repeating angle comprises a hexagon with equal sides and uniformly shaped, with the angle surrounding each corner fixed at 120 degrees.

[034] Preferably, the shape pattern comprises multiple rows of 3 hexagons of fixed 120° wrapped angles spaced equidistantly per row around the circumference of the generally cylindrical element, optionally with the adjacent row comprising 3 similarly shaped hexagons, but offset by half a step out of phase (i.e. 60°).

[035] The attached drawings illustrate currently exemplary embodiments of the invention and together with the general description given above and the detailed description of the embodiments given below, act to explain, by way of example, the principles of the invention.

[036] In the following description, equal parts are marked throughout the report and drawings respectively with the same reference numerals. The drawings are not necessarily staggered. Some features of the invention may be shown in enlarged scale or somewhat schematically and some details of conventional elements may not be shown for clarity and conciseness. The present invention can be implemented in different ways. Specific embodiments of the present invention are shown in the drawings and will be described in detail, with the understanding that the present invention is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to that illustrated and described herein. It is important that it be fully recognized that the different teachings of the embodiments discussed below can be employed separately or in any suitable combination with the aim of producing the desired results.

[037] The various aspects of the present invention can be reproduced alone or in combination with one or more of the other aspects, as will be appreciated by those skilled in the relevant art. The various aspects of the invention may be provided as an option in combination with one or more of the optional features of the other aspects of the invention. Likewise, the optional features described in relation to an embodiment can typically be combined alone or together with other features in different embodiments of the invention. Additionally, any feature disclosed in the report may be combined alone or collectively with other features of the report to form an invention.

[038] Various embodiments and aspects of the invention will now be described in detail with reference to the attached figures. Still other aspects, features and advantages of the present invention are readily apparent from the complete description thereof, including the figures, which illustrate some exemplary embodiments, aspects and implementations. The invention can also be presented in other and different embodiments and aspects, and its many details can be modified in various aspects, all without departing from the scope of the present invention.

[039] Any approach to documents, acts, materials, devices, articles and the like is included in the report solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters form the basis of the prior art or are of common general knowledge in the field of the present invention.

[040] Therefore, the drawings and descriptions should be considered illustrative in nature and not restrictive. Furthermore, the terminology and phraseology used herein are used solely for descriptive purposes and should not be construed as limiting the scope. Terms, such as "including", "comprising", "having", "containing" or "involving" and variations thereof, are intended to be broad in nature and encompass the subject matter listed after the mention of them, equivalent subject matter and additional not recited, and is not intended to exclude other additives, components, integers or steps. In this disclosure, whenever a composition, element or group of elements is preceded by the transitional expression "comprising", it is understood that we also contemplate the same composition, element or group of elements in the transitional phases "consisting essentially of", "consisting ", "selected from the group consisting of", "including" or "is" preceding the recitation of the composition, element or group of elements and vice versa. In this disclosure, the words "typically" or "as an option" are to be understood as intended to indicate optional or non-essential features of the invention that are present in some examples, but that may be omitted in others without departing from the scope of the invention.

[041] All numerical values in this disclosure are understood to be modified by "approximately". All singular forms of the elements, or any other components described herein, including (without limitation) components of the apparatus described herein are understood to include the plural forms thereof and vice versa.

BRIEF DESCRIPTION OF THE DRAWINGS

[042] The embodiments of the present invention will now be described, by way of example only, with reference to the attached drawings, in which:

[043] Fig. 1 is a side view of a first embodiment of a generally cylindrical element adapted for submerging in a body of water and being profiled to reduce Vortex Induced Vibration (VIV) and/or drag, in accordance with the present invention;

[044] Fig. 2 is a perspective view of a lower end in use of the generally cylindrical element of Fig. 1;

[045] Fig. 3 is a side view of an intermediate portion 10M of the generally cylindrical element 10 of Fig. 1, showing in more detail the external surface of the generally cylindrical element 10;

[046] Figs. 4(a) - 4(f) are three-dimensional representations of side views of other embodiments of a generally cylindrical element adapted for submersion in a body of water and being profiled to reduce VIV and/or drag, in accordance with the present invention;

[047] Figs. 5(a) - 5(f) are line drawings of side views of Figs. 4(a) - 4(f);

[048] Figs. 6(a) - 6(f) are perspective views of Figs. 5(a) - 5(f);

[049] Fig. 6(g) is another perspective view of the most preferred segmentation patterns applied to the generally cylindrical element of Figs. 4(d), 5(d) and 6(d), particularly showing dimension examples;

[050] Fig. 7(a) is a perspective view of yet another embodiment of a generally cylindrical element in the form of a Distributed Buoyancy Module (DBM) attached to/around the outer surface of a generally cylindrical structure in form of a conduit, such as a riser located in a body of water, where the DBM is in accordance with the present invention;

[051] Fig. 7(b) is a top perspective view of one of the semicircular half-shells that when connected together to another corresponding semicircular half-shell form the DBM of Fig. 7(a);

[052] Fig. 7(c) is a side view of the semicircular half-shell of Fig. 7(b);

[053] Fig. 7(d) is a perspective view from below of the semicircular half-shell of Fig. 7(b).

[054] Fig. 8(a) is a perspective view of yet another embodiment of a generally cylindrical element in the form of a Drilling Riser Float (DRB) attached to/around the outer surface of a generally cylindrical structure. in the form of an arrangement of a drilling riser located in a body of water and five conductors located around the outer circumference of the drilling riser, where the DRB is in accordance with the present invention;

[055] Fig. 8(b) is the DRB and drill riser/conductor arrangement of Fig. 8(a), but with a semicircular half-shell of a section of the DRB removed to aid in clarity of understanding of the person knowledgeable in the technique;

[056] Fig. 8(c) is the DRB and the drilling riser/conductor arrangement of Fig. 8(b), but only showing the section where said semicircular half-shell of the DRB has been removed;

[057] Fig. 8(d) is a close-up view of the exposed upper end of the DRB and the drilling riser/conductor arrangement of Fig. 8(a);

[058] Fig. 8(e) is a perspective view of a section of the DRB shown in isolation;

[059] Fig. 8(f) is a perspective view of one side (outer) of a semicircular half-shell of said section of the DRB shown in Fig. 8(e);

[060] Fig. 8(g) is a perspective view of the other (internal) side of the semicircular half-shell of the DRB shown in Fig. 8(f);

[061] Fig. 8(h) is a cross-sectional view through the DRB of Fig. 8(e);

[062] Fig. 8(i) is a close-up side view of a hexagonal shape and surrounding groove arrangement as provided on the outer surface of the DRB of Fig. 8(a);

[063] Fig. 8(j) is a cross-sectional view of a first example of a groove of the groove arrangement provided on the outer surface of the DRB of Fig. 8(a) as having a rectangular or square profile (i.e. , a “U” shaped profile).

[064] Fig. 8(k) is a cross-sectional view of a second example of a groove of the groove arrangement provided on the outer surface of the DRB of Fig. 8(a) as having a tapered/angled side face profile (i.e. a cross between a “U” profile and a “V” profile).

[065] Fig. 8(l) is a cross-sectional view of a third example of a groove of the groove arrangement provided on the outer surface of the DRB of Fig. 8(a) as having a semicircular or fully rounded profile;

[066] Fig. 9 is a perspective view of an embodiment of a generally cylindrical element adapted for submersion in a body of water and being profiled to reduce Vortex Induced Vibration (VIV) and/or drag, in accordance with the present invention, and particularly in the form of two semicircular half-shells which when placed together around a submarine conduit, such as a pipe, can be screwed together (either at the time of the first installation of a submarine conduit such as the one mentioned, or as way of retrofitting an already installed submarine conduit as mentioned) to act as a cylindrical protective casing for the submarine conduit;

[067] Figs. 10(a) and 10(b) are perspective views of another embodiment of a generally cylindrical element adapted for submersion in a body of water and being profiled to reduce Vortex Induced Vibration (VIV) and/or drag, in accordance with the present invention, and particularly in the form of two semicircular half-shells which when placed together around a submarine conduit, such as a pipe, can be tied together (either at the time of the first installation of a submarine conduit as mentioned, or as a way of retrofitting an already installed submarine conduit such as the one mentioned) to act as a cylindrical protective casing for the submarine conduit.

[068] Figs. 11 (a) and 11 (b) are perspective views of yet another embodiment of a generally cylindrical element adapted for submerging in a body of water and being profiled to reduce Vortex Induced Vibration (VIV) and/or drag, in accordance with with the present invention, and particularly in the form of two semicircular half-shells which when placed together around a subsea conduit, such as a pipe, can be screwed or tied together (either at the time of first installation of a subsea conduit such as the aforementioned, or as a means of retrofitting to an already installed subsea conduit as mentioned) to act as a cylindrical protective casing for the subsea conduit, wherein each of the two semicircular shells comprises a semicircular cylindrical flexible substrate formed within the remainder of the material (the which is typically a molded material); It is

[069] Fig. 12 is a perspective view of yet another embodiment of a generally cylindrical element adapted for submerging in a body of water and being profiled to reduce Vortex Induced Vibration (VIV) and/or drag, in accordance with the present invention, and which is firmly and integrally fitted to a submarine conduit at the time of manufacturing such conduit, joining it to it.

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

[070] Fig. 1 shows an embodiment of a generally cylindrical element 10 adapted for immersion in a body of water (not shown) and which is in accordance with the present invention. The generally cylindrical element 10 is substantially tubular and comprises a through hole 15 and an external surface 11.

[071] In certain embodiments of the present invention, the generally cylindrical element 10 may be the actual (i.e. integral) outer surface of a substantially cylindrical structure (not shown) which, in use, is located in the body of water, where the substantially cylindrical structure may be a riser (not shown), umbilical, bridge tube, long length of large piping, flow line, power cable or the like. Alternatively and more preferably, the substantially cylindrical element 10 is a substantially tubular component separate from the substantially cylindrical structure (not shown), wherein, in use, the substantially cylindrical element 10 is adapted to be placed around said generally cylindrical structure. such that the generally cylindrical structure is located within the through hole 15 of the generally cylindrical element 10, such that the generally cylindrical element 10 envelops the section of said generally cylindrical structure located within it and therefore acts as a jacket in relation to the generally cylindrical structure located inside it.

[072] Importantly, in all embodiments, the generally cylindrical element 10 is provided with an arrangement or pattern of repeating shapes 20 on its outer surface 11, as will be described in more detail subsequently, and which acts to reduce Vibration Induced by Vortex (VIV) and/or drag acting on the generally cylindrical element 10 (and therefore acts to reduce VIV and/or drag on any substantially cylindrical structure located within the through hole 15 of the generally cylindrical element 10).

[073] The person skilled in the art will understand that the combination of the shapes 20 and the arrangement of grooves 30 provided around the shapes 20 alters the way in which the vortices (not shown) are formed compared to a cylindrical structure having an outer surface uniform (flat) 11. The person skilled in the art will also appreciate that providing the generally cylindrical element 10 with said outer surface 11 will mean that additional (conventional) VIV braces that would normally be provided additionally around some cylindrical or tubular structures used submarines will not be necessary, because the generally cylindrical element 10 will provide sufficient and possibly more than sufficient VIV and/or drag reduction.

[074] As shown in Fig. 1, the generally cylindrical element 10 comprises an upper end 12U and a lower end 12L, and comprises a length sufficient for installation within the water as required for the particular application.

[075] In the embodiment, as shown in Fig. 1, the outer surface 11 comprises a plurality of repeating shapes 20, where each preferred shape 20 is a hexagon, such that the majority of the outer surface 11 or more preferably the entire outer surface 11 of the generally cylindrical element 10 comprises a hexagonal segmentation 21 in which every three adjacent hexagons 20 (shown in Fig. 3 e.g. hexagons 20A, 20B and 20C) meet at each contiguous vertex 22 and the remainder of the hexagons 20 repeat this arrangement across the entire external surface 11 of the generally cylindrical element 10.

[076] The person skilled in the art should note that it is preferable that each vertex 22 between two adjacent sides of each hexagonal shape 20 comprises a radius and not an acute corner and, more preferably, each vertex 22 between each adjacent pair of sides of each hexagonal shape 20 comprises a radius between 5mm and 250mm and more preferably said radius being between 150mm and 250mm.

[077] In the embodiment of the generally cylindrical element 10 as shown in Figs. 1-3, the arrangement of hexagons 20 may also be considered in terms of rows 40A, 40B, 40C, 40D of hexagons 20 stacked on top of each other, each row 40 being separated from the next upper or lower row 40 by an arrangement of 30 slots.

[078] Additionally, the arrangement of hexagons 20 on the outer surface 11 of the generally cylindrical element 10 can be considered to be in the form of staggered columns 50 spaced equidistantly around the circumference of the outer surface 11, where the first column 50A shown in Fig. 3 fits closely with the next column 50B (which has been scaled by half the height of a hexagon 20 when compared with the first column 50A) and so on for the other columns 50C, 50D and 50E as shown in Fig. 3. 3.

[079] The person skilled in the art will understand that the outer surface 11 having this hexagonal segmentation 21 provided therein, where the hexagons 20 projecting out of the outer surface 11 due to the groove arrangements 30, present the great advantage of maximizing the number of shapes 20 within each row 40 and/or column 50 and/or across the entire surface of the outer surface 11 and this therefore has the great advantage of providing the most efficient VIV and/or drag reduction possible in relation to the generally cylindrical element 10.

[080] Shapes 20 and groove arrangements 30 may be formed on the outer surface 11 of the generally cylindrical element 10 by any suitable means, such as molding the generally cylindrical element 10 as an integral component of a part with the groove arrangement. 30 and the hexagonal segmentation 21 provided therein (and this molding operation could be a pumped, injected or rotomolded operation). Alternatively, the generally cylindrical member 10 may begin as a homogeneous tubular and groove arrangements 30 may be cut into the outer surface of the homogeneous tubular (not shown) in order to form the shape arrangement 20 and, in particular, the preferred arrangement of the hexagonal segmentation 21 provided on the outer surface 11. Other suitable manufacturing techniques could also be used. A less preferred manufacturing technique is using a homogeneous tubular and attaching by some suitable fastening means, such as adhesive or screws etc., the shapes 20 to the outer surface 11 of the homogeneous tubular (not shown) in this type of hexagonal segmentation arrangement. 21, such that the groove arrangements 30 are provided by the resulting gaps or channels between the various fixed shapes 20.

[081] Hexagonal segmentation 21 is very efficient in reducing VIV and, in fact, it is designed to reduce VIV by a minimum of 80% and also to reduce drag below 1.2 for Reynolds numbers ranging from 1, 4e5 to 4.2e64.

[082] The dimensions of the groove arrangements 30 are as follows: - a groove profile depth equal to 0.01 to 0.1 times the outer diameter (O.D.) of the generally cylindrical element 10, with a preferred groove arrangement 30 having a profile depth equal to 0.0.2 to 0.03 times the O.D. of the generally cylindrical element 10; - a profile width equal to 0.04 to 0.1 times the O.D. of the generally cylindrical element 10 with a preferred profile width equal to 0.05 to 0.07 times the O.D. of the generally cylindrical element 10; - the slot arrangement 30 typically comprises angled side faces 60 which may be angled between 40 to 80 degrees relative to the radius of the generally cylindrical element 10 and preferably the angled side faces 60 of the slot arrangement 30 are angled in the region of 60 degrees in relation to the radius of the generally cylindrical element 10; - alternatively, the profile of the groove arrangement 30 may be a complete circle, where the diameter of the cut may be equal to 0.03 to 0.15 times the O.D. of the generally cylindrical element 10 and more preferably said groove arrangements 30 when arranged in a complete circle comprise a groove having a cut diameter equal to 0.07 to 0.09 times the O.D. of the generally cylindrical element 10.

[083] The person skilled in the art will therefore understand that the hexagonal segmentation 21 (and therefore each row 40 and/or each column 50 within the hexagonal segmentation 21) encompasses the entire 360 degree circumference of the generally cylindrical element. 10 and will further understand that each groove 30 on the upper and lower sides of each row 40 is continuous around 360 degrees of the outer surface 11 such that it has no separate starting or ending point. This presents significant advantages in terms of VIV reduction and/or drag reduction because the groove arrangement 30 provides a much smoother exit point for water to no longer contact the outer surface 11 (compared to a completely "smooth" outer surface). ").

[084] The person skilled in the art will also appreciate that although the hexagonal segmentation 21 is the most preferred shape profile provided on the outer surface 11, other less preferred shapes 20 could also be used, such as triangles, squares, rectangles, pentagons or other suitable formats. The most preferable suitable shapes are shapes that have symmetry (and are therefore capable of being fitted closely into a segmentation). It is also preferred that all shapes 20 within segmentation 21 are identical to each other in order to increase the number of shapes 20 that can be fitted or provided on the outer surface 11 and therefore although different shapes can be provided within the separate rows 40, it is preferred that all shapes 20 within a segmentation are identical, and it is more preferred that all shapes are hexagons 20 and therefore the segmentation is a hexagonal segmentation 21. It is further preferred that the slot arrangement 30 provides at least one, and preferably a plurality of separate paths for water flow when navigating around the circumference of the generally cylindrical element 10, such that water flows around the outer circumference of the generally cylindrical element 10 from one side to the other. another (which could occur when the generally cylindrical element 10 is substantially vertical within a body of water that is flowing close to that generally cylindrical element 10) finds many flow separation points 23 in the form of the corner points 23 of the hexagonal shapes 20 For example, water flowing along flow path 25A within slot arrangement 20 from left to right in Fig. 3 will encounter flow separation point 23A at which point it will be separated into flow 25A1 and flow 25A2. Furthermore, water flowing along flow path 25B within the slot arrangement 20 from left to right in Fig. 3 will encounter flow separation point 23B at which point it will be separated into flow 25B1 and flow 25B2. As another example, water flowing along flow path 25C within slot arrangement 20 from left to right in Fig. 3 will encounter flow separation point 23C at which point it will be separated into flow 25C1 and in the 25C2 stream. This flow separation characteristic, provided particularly by the arrangement of formats 20 being staggered when viewed along each row 40 and/or along each column 50 provides significantly greater flow separation and which, in turn, greatly reduces VIV. and this provides significant technical advantages for embodiments of the present invention. Furthermore, in this exemplary embodiment of the invention, it is preferred that the flow separation point 23 (i.e., the corner 23 of the shape) is less than 90 degrees, such that the water flowing in the groove arrangement 20 (such as along the flow path 25A) is forced to change direction by less than 90 degrees in order to keep the drag coefficient of the generally cylindrical element 10 as low as possible. Thus, in the embodiment employing hexagonal segmentation 21, the flow separation point 23 (i.e., the corner 23 of the shape) is 60 degrees such that water flowing in the groove arrangement 20 (such as along the path flow path 25A) is forced to change direction by 60 degrees no matter which of the two paths (i.e. path 23A1 or 25A2) the water takes around the hexagonal shape 20C and therefore the drag coefficient of the generally cylindrical element 10 is kept as low as possible.

[085] The generally cylindrical element 10 and the shapes 20 provided therein are formed from any suitable material and the suitable material may be from a material that floats in water.

[086] Alternative surface segmentation configurations are shown in Figures 4-6. For the sake of brevity, where features are the same across all configurations, details of these configurations will not be repeated and the reader is referred to the paragraphs above. Equal resources are marked with the format X10, X11, where the end numerals indicate the resource as marked in Figures 1-3.

[087] Figs 4-6a show the cylindrical element 210 having an external surface 211 that comprises repeated hexagonal shapes 220, elongated along an axis that is offset from the longitudinal and transverse axes of the element 210, with rounded points. Between the shapes 220 are the slots 230. The cylindrical member 210 has an upper end 212U and a lower end 212L as before. The water flowing around the element 210 within the grooves 230 meets at least one vertex 223 of the hexagonal shapes 220 and divides along different flow paths. Compared to the configuration of the slots 30 and shapes 20 illustrated in Figs. 1-3, water traveling around element 210 will generally always be directed at an off-center angle relative to the axes of the cylindrical element 210 (whereas in Fig. 1, for example, it can be seen that some grooves 30 are aligned with the transverse axis or plane of the element 10).

[088] Figs 4-6b show the cylindrical element 310 again having an outer surface 311 comprising repeated elongated hexagonal shapes 320 with rounded points, but the shapes 320 in this example are less elongated than those in Figs. 4-6a. The elongation of the shapes 320 again is along an axis of each shape 320 that is offset from the longitudinal and transverse axes of the cylindrical element 310. As before, water flowing along the grooves 330 meets the apexes 323 of the shapes 320 and splits into separate flow paths. The slots 330 are angled with respect to the longitudinal and transverse directions of the member 310.

[089] Figs 4-6c show the cylindrical element 410 having an outer surface 411 with repeating hexagonal shapes 420. The shapes 420 are again elongated along an axis that is offset from the longitudinal and transverse axes of the cylindrical element 410. However In this example, the shapes 420 are elongated to a lesser degree than that shown in Figs. 4-6a and 4-6b, and the vertices 423 of each shape 420 have a smaller radius and are therefore more pointed. The water flowing around the element 410 in the grooves 430 meets at least one vertex 423 of the shapes 420, but may also be oriented toward a flat side 424 or a portion of a flat side 424 of a shape 420. The water is divided into different flow paths, and/or diverted by a flat side 424 of a shape 420.

[090] Figs 4-6d show the cylindrical element 510 having an outer surface 511 comprising hexagonal shapes 520 in a pattern repeated across the surface 511. The grooves 530 distance the shapes 520 from each other. In this example, the slots 530 are wider than the slots 30 shown in Figs. 13, i.e., the shapes 520 are further spaced apart than the shapes 20 in Figs. 1-3. The shapes 520 are rotated compared to the alignment of the shapes 20 in the example illustrated in Figs. 1-3, so that they are now side by side downwards (i.e., the shapes 520 have been rotated by 30° relative to the arrangement of shapes 20 illustrated in Figs. 1-3, so that at least two vertices 523A , 523B, 523C, 523D are aligned along the longitudinal axis of the cylindrical element 510). In computer models of water flow through and around each of the various shape and groove arrangements described here, the arrangement illustrated in Figs. 4-6d has been found to be particularly effective in reducing VIV and this is therefore the most preferred segmentation model applied to the surface 511 of the generally cylindrical element 510. Water flowing around the element 510 in the grooves 530 meets at least at least one vertex 523 of the shapes 520, but may also be oriented toward a flat side 524A, 524B or a portion of a flat side 524A, 524B of a shape 520. The water is divided into different flow paths, and/or or offset by a flat side 524A, 524B of a shape 520.

[091] Figs 4-6e show the cylindrical element 610 having an external surface 611 comprising hexagonal shapes 620 that have been elongated along the longitudinal axis of the cylindrical element. The shapes 620 are arranged in a repeating pattern across the surface 611. Similar to Figs 4-6d, the shapes 620 are arranged so that two or more vertices 623A, 623B, 623C, 623D are aligned along the longitudinal axis of the cylindrical element 610. Water flows around the grooves 630 and generally encounters a sharp corner/apex 623 of at least one shape 620 as it travels around the cylindrical element 610. This acts to divide the flow along different flow paths as before. The flow may also be oriented toward a flat side 624A, 624B or a portion of a flat side 624A, 624B of a shape 620.

[092] Figs 4-6f show the cylindrical element 710 having an outer surface 711 comprising hexagonal shapes 720 in a pattern repeated across the surface 711. The grooves 730 distance the shapes 720 from each other. The shapes 720 are elongated along the longitudinal axis of the cylindrical element 710 and relatively densely concentrated compared to the shapes 520, 620 illustrated in Figs 4-6d and 4-6e. The elongation of shapes 720 is greater than shapes 620 of Figs. 4-6e and results in two relatively sharp vertices 723A, 723B, which are aligned along the longitudinal axis of the cylindrical element 710. Water flowing around the cylindrical element 710 in the grooves 730 may meet an apex (e.g., the upper apex 723A) of a shape 720, or may flow toward a flat side 724 or a portion of a flat side 724 of a shape 720. Water flowing through the grooves 430 and contacting an apex 723A of a shape 720 can be divided into different flow paths. Water flowing along the grooves 730 and in a flat section 724 of a shape 720 may be diverted to flow in a different direction within the grooves 730.

[093] Fig. 6(g) shows example dimensions of the most preferred segmentation patterns applied to the surface 511 of the generally cylindrical element 510. In this example, the generally cylindrical element 510 has the following example dimensions: - Largest diameter external 510D (of element 510) = 1222mm (and thus, the outermost aio 510RE = 611 mm); Depth R 520D (groove depth, i.e. the height of each 520 format) = 60mm; - Radius 520R (from the corner to the edge of each 520 format) = 60mm; Thus, Depth R 520D = Radius 520R; - Internal radius 520IR (from element 510 from center point C to external surface 511) = 551 mm;

[094] Circumferential R 530C (groove width between two adjacent shapes 520 in the direction around the circumference) = 319.972mm;

[095] Diagonal R 530D (width of the groove between two adjacent shapes 520 in the diagonal direction between two adjacent and parallel flat sides 524a and 524c shown in Fig. 6(g) = 350.054mm.

[096] The person skilled in the art will understand that the various dimensions are reliable to vary according to the requirements of the particular use application and will vary particularly depending on the internal radius 520IR of the cylindrical element 510 in question, but the various dimensions ( for example, Depth R 520D, Radius 520R, Circumferential R 530C and Diagonal R 530D) are all preferably a relatively fixed ratio of the Internal Radius 520IR, as will be described subsequently in more detail. Simply put, the greater the Internal Radius 520IR of the cylindrical element 510 in question, the greater the Depth R 520D, but the relative proportions between the two are preferably substantially constant, because the relative dimensions share some common feature relationships, such as will now be described. In all examples shown in Figs. 4-6, some common resource relationships have been identified that lead to increased VIV suppression by the cylindrical element. They are: - Depth R (i.e. the depth of the repeated shapes) = Outermost diameter (of the element multiplied by 0.05); - Depth R (i.e. the depth of the repeated shapes) = Radius (from the corner to the edge of each shape); - Circumferential R (Slot width in circumferential direction) = Outermost radius of the element multiplied by 0.50 to 0.60 (i.e., for the example shown in Fig. 6g, the outermost Radius 510OR = 611 mm multiplied by 0.525 = approx 320mm); - Diagonal of R (Slot width in diagonal direction) = Outermost radius of the element multiplied by 0.55 to 0.60 (i.e. for the example shown in Fig. 6g, Outermost radius 510OR = 611 mm multiplied by 0.572 = approx 350mm); - Angle of repeated shape = Hexagon with equal sides and uniformly shaped, with the angle around each corner fixed at 120; - Preferred shaped model comprises multiple rows of 3 fixed 120° inclusive angle hexagons spaced equidistantly per row around the circumference of the generally cylindrical element, with the adjacent row comprising 3 similarly shaped hexagons but offset by half a step out of phase (i.e., 60°) i.e., that pattern shown in Fig. 6(g).

[097] There are three main fields of application for the generally cylindrical element 10, they are: Distributed buoyancy modules (DBM) 62 - as shown in Figs. 7(a) to 7(d)

[098] DBM's 62 are typically used at selected points on the outside of a conduit 64, such as a riser 64 that extends into a body of water between a surface vessel (not shown) or platform and a subsea structure (not shown). shown), where the function of the DBM 62 is to provide the conduit 64 with buoyancy at a required location (e.g., to enable the conduit 64 to be installed in a "quiet wave" or "quiet S" configuration). The generally cylindrical member 10 may be secured by any suitable means, such as by fastening or strapping to the exterior of the DBM 62, but, more preferably, the generally cylindrical member 10 is fully integrated with the DBM 62, such that the outer surface 11 of element 10 is the outer (integrated) surface 11 of the DBM 62 and in this scenario, the DBM 62 is not an integrated cylinder, but rather is provided in the form of two half-shells 62U; 62L which, when put together, form a cylinder or jacket around the outer surface of the riser 64. Most or all of the DBM 62 is formed from a buoyant material). The generally cylindrical element in the shape of the DBM 62 is provided with suitable strap recesses 66 and support cavities 68 to facilitate transport, installation and gripping of the generally cylindrical element in the shape of the DBM 62. Drilling Riser Float (DRB) 70, as shown in Figs. 8(a) to 8(l)

[099] DRB modules 70 are typically installed along the entire length of a riser 71 (which typically has an arrangement of conductors 72 provided around its outer circumference along its length - five are shown in Fig. 8( a), particularly risers 71 which are used in deep water and ultra-deep water, to reduce the weight of the drilling riser 71 to a manageable level. The generally cylindrical member 10 is suitable for either a) application, fixing or otherwise gripping to the outer surface of a DRB or more preferably b) as shown in Fig. 8(a) the outer surface of a DRB 70 may integrally comprise the shaped profile of the outer surface 11 as shown in Figs. 1-3. The DRB 70 is typically supplied in 70L half-shells; 70R (as shown in Figs. 8(a) to 8(h) or a quarter shell (not shown) which when put together surround/envelope the drilling riser 71 and the conductor arrangement 72. This DRB 70 (not shown ) is preferably provided with stacking planes that allow the individual shells 70L; 70R to be stacked on top of each other. The two half-shells 70L; 70R are preferably secured together around the riser 71 and the conductor arrangement 72 by a suitable securing means, such as screws (not shown) that pass through screw holes 75 provided on either side of each half-shell 70L; 70R at the top and bottom ends and which are secured in place with nuts (not shown) in order to pull/compress the two half-shells 70L; 70R towards/against each other Cylindrical Protective Casings Traditionally Used as VIV Straps - first embodiment based on Figs 1-3.

[0100] Some subsea conduits, such as cables, flow lines, pipes and large pipelines may be conventionally provided with subsea VIV suppression belts, which typically comprise helically arranged and radially extending fins that act to reduce the VIVI. Instead of providing these conventional fins, the generally cylindrical element 10 having the outer surface 11 as shown in Figs. 1-3 could be used in reverse, where the generally cylindrical element 10 would typically have a cut formed all the way along one side and where the generally cylindrical element 10 is therefore C-shaped and is open and fitted around of the circumference of the cable, flow line or large pipe to be protected, such that the generally cylindrical C 10 shaped element completely envelops the section of cable, flow line or large pipe around which it is put on, just like a shirt. Cylindrical Protective Casings Traditionally Used as VIV Straps - second embodiment, as shown in Fig. 9

[0101] In an alternative embodiment to the generally cylindrical C-shaped element 10 of Figs. 1 to 3, the generally cylindrical element 100A as shown in Fig. 9 (having a hexagonal segmentation 21 as previously described provided on its outer surface 111) may be provided for fitting into a submarine conduit 110, such as a submarine cable, pipe flexible bridge, flow line, riser, section of pipe or large piping (either at the time of the first installation of this type of underwater conduit or as a way of retrofitting an already installed underwater conduit such as conduit 110).

[0102] The generally cylindrical element 100A of Fig. 9 comprises two parts or a pair of semicircular shells 102a, 102b which when placed together around this conduit 110 (a tube 110 is shown in Fig. 9) completely encircle for 360 degrees this conduit section 110 around which shells 102a, 102b are placed. The half-shells 102a, 102b may be secured together with a suitable number (two such fastening means are shown in Fig. 9 at each end of the generally cylindrical member 100) of fastening means, such as a threaded screw 104 passing through of screw holes 105 formed throughout the passage path of the side wall of the half-shells 102a, 102b and which can be secured in place by screws and washers 106b. The generally cylindrical element 100A of Fig. 9 therefore acts as a protective casing or jacket in relation to the conduit 110 and thereby provides the conduit 110 with underwater VIV suppression by virtue of the hexagonal segmentation 21 provided on its outer surface 111 .

[0103] The two parts or pair of semicircular shells 102a, 102b are typically formed from a relatively light, relatively strong and non-brittle material, such as polyurethane (PU) or the like. Additionally, buoyant material, such as polystyrene (not shown) or other suitable material may be added to the inner surface of the through hole of the generally cylindrical member 100A (such that the float material lies in the annulus between the inner through hole of the generally cylindrical element 100A and the outer surface of the conduit 110) if the operator needs to add buoyancy to the conduit 110.

[0104] Additional generally cylindrical elements 100B identical to the first generally cylindrical element 100A may be provided adjacent to each end of the first generally cylindrical element 100A and so on until the entire length or a sufficient length of conduit 110 is fully enveloped by the element generally cylindrical 100A; 100B of Fig. 9, such as a shirt.

[0105] Each generally cylindrical element 100 is provided with a suitably shaped cooperating or mating surface on an outer end surface 109 at one end (which may be, for example, a lower end in use) and on an inner end surface 108 (which may be, in use, a higher end) at the other end. The mating surfaces may be suitably shaped cooperative surfaces, such as radially acting mortise and groove arrangements, or the like. During installation around the conduit 110, the second generally cylindrical member 100B is placed around the conduit 110, with its upper end 108 having an inner mating surface situated in an overlapping manner with respect to the outer end mating surface 109. lowermost of the first generally cylindrical element 100A, such that the respective radially acting slot and groove arrangements engage each other. This installation method is repeated for the length of the conduit 110 which requires VIV suppression by the generally cylindrical elements 100 and the respective slot and groove arrangements acting radially prevent axial separation of adjacent generally cylindrical elements 100A; 100B. Cylindrical Protective Casings Traditionally Used as VIV Straps - third embodiment, as shown in Figs 10(a) and 10(b)

[0106] Figs. 10(a) and 10(b) show an alternative embodiment of a generally cylindrical element 120 to the generally cylindrical element 100 of Fig. 9, wherein the generally cylindrical element 120 as shown in Fig. 10 again comprises a hexagonal segmentation 21, as previously described, provided on its external surface 131.

[0107] However, the generally cylindrical element 120 of Fig. 10 differs from the generally cylindrical element 100 of Fig. 9 in that the generally cylindrical element 120 of Fig. 10 is installed in and secured around the conduit 110 by a different attachment means. As shown in Fig. 10, the outer surface of each of the two parts or pair of semicircular shells 122a, 122b comprises a respective semicircular recess or groove 123a, 123b in the same longitudinal position on the outer surface 141 of the respective half-shell 122a, 122b . There is a respective semicircular recess or groove 123a, 123b at each end of each of the two pairs or pair of semicircular shells 122a, 122b, such that when the two half-shells 122, 122b are brought together around the submarine conduit 110 , the two respective semicircular recesses 123a, 123b combine to form a fully circular recess 123 of sufficient width to accept a circular belt 134 that is located around the 360° circumference of the two half-shells 122, 122b within the recess 123 and in that the strap 134 is tightened and secured within the recess 123 by a tie or lock 135, such that the two half-shells 122, 122b are secured or locked together around the subsea conduit 110. The two recesses 123a, 123b are shown in Fig. 10(a) with one recess 123a being provided adjacent to the uppermost end 128, in use, and the other recess 123b being provided adjacent to the lowermost end 129 in use 129 of the generally cylindrical member 120, but other recesses 123 could be provided additionally spaced along the length of the generally cylindrical element 120 if they were necessary (particularly if the generally cylindrical element 120 is particularly long).

[0108] In all other respects (including having an outer end surface 129 similar to the outer end surface 109 of Fig. 9 and including having an inner end surface 128 similar to the inner end surface 108 of Fig. 9), The generally cylindrical element 120 of Fig. 10 is similar to the generally cylindrical element 100 of Fig. 9 and may be installed for the same purpose of VIV suppression around similar submarine conduits 110, such as a submarine cable, flexible point pipe , flow line, riser, section of pipe or large piping (either at the time of the first installation of this type of underwater conduit 110 or as a way of retrofitting an already installed underwater conduit 110). Cylindrical Protective Casings Traditionally Used as VIV Straps - fourth embodiment, as shown in Figs 11 (a) and 11 (b)

[0109] Figs. 11(a) and 11(b) show a further alternative embodiment of a generally cylindrical element 140 (although only one half thereof is shown in Figs. 11(a) and 11(b)) to the generally cylindrical element 100 of Fig. 9 and 120 of Figs. 10(a) and 10(b), where the generally cylindrical element 140, as shown in Figs. 11 (a) and 11 (b) again comprise a hexagonal segmentation 21, as previously described, provided on its outer surface 141.

[0110] The generally cylindrical element 140 of Figs. 11(a) and 11(b) may be installed in and secured around the conduit 110 by any suitable securing means, such as: - a threaded screw 104 passing through screw holes (not shown in Figs. 11 (a) ) and 11 (b)) and secured in place by screws and washers 106b in a manner similar to the fastening means shown in Fig. 9; or - a circular strap 134 being located around the 360° circumference of the generally cylindrical member 140 within a recess (not shown in Figs. 11(a) and 11(b)) and in which the strap 134 is tightened and secured inside the recess by a tie or lock 135, such that the two half-shells 142 are secured or locked together around the submarine conduit 110.

[0111] However, each of the two half-shells 142 of the generally cylindrical element 140 of Figs. 11(a) and 11(b) differs from those of the generally cylindrical element 100 of Fig. 9 and 120 of Fig. 10 in that each of the two half-shells 142 comprises a semicircular cylindrical flexible substrate 145 formed within the remainder of the material (which is typically molded polyurethane) that forms the half-shell 142. The semicircular cylindrical flexible substrate 145 comprises a large plurality of holes 146 formed through its side wall in order to reduce the weight thereof 142. flexible substrate is preferably formed from a suitable flexible material and the half-shell 142 is typically manufactured by casting PU into a mold and around the substrate 145, such that the substrate 145 is enveloped by and encapsulated by the PU, but provides a backbone to the PU once the PU has been prepared. Therefore, the flexible substrate 145 allows for greater flexibility of the generally cylindrical element 140, a lower material requirement, and improved product durability compared to other embodiments.

[0112] This embodiment of the generally cylindrical element 140 of Figs. 11 (a) and 11 (b) has the advantage that a given thickness T2 thereof will be stronger than the same thickness of the generally cylindrical element 100 of Fig. 9 and 120 of Figs. 10(a) and 10(b). This embodiment of the generally cylindrical element 140 of Figs. 11(a) and 11(b) therefore presents the advantage that it can be made thinner (see relatively thin side wall T2 of the generally cylindrical element 140 as shown in Fig. 11(a) compared to the relatively thick side wall T1 of the generally cylindrical element 120, as shown in Fig. 10(b)) without sacrificing its strength. Therefore, the sidewall thickness T2 of the generally cylindrical member 140 of Figs. 11 (a) and 11 (b) is less than sidewall thickness T1 of the generally cylindrical element 120 of Figs. 10(a) and 10(b), and the generally cylindrical member 140 of Figs. 11 (a) and 11 (b) will probably be considerably lighter and thus easier to install in a conduit 110 than the other embodiments.

[0113] An operator will typically be able to retrofit the generally cylindrical element 140 of Figs. 11 (a) and 11 (b) on the external surface of an already installed submarine conduit 110 by: - pulling the submarine conduit 110 out of the water through a “moonpool” of a marine vessel /boat (not shown); - installation of the generally cylindrical element 140 on the external surface 141 of the underwater conduit 140; and - lowering the submarine conduit 110 with the applied generally cylindrical element 140 mounted on its outer surface back into the water via the “moon pool”.

[0114] This embodiment of the generally cylindrical element 140 of Figs. 11 (a) and 11 (b) presents a further significant advantage that, due to its thinner external diameter than that of the other embodiments, it will be easier/possible to retrofit into an already installed subsea conduit 110 in situations where the subsea conduit 110 must be pulled upward through a “moon pool” that has an opening that is slightly wider than the outer diameter of the underwater conduit 110, compared to other wider embodiments, e.g., 100, 120, which would not be possible to pass back through the moon pool.

[0115] The generally cylindrical element 140 of Figs. 11 (a) and 11 (b) therefore acts as a protective casing or jacket for the conduit 110 and thereby provides the conduit 110 with underwater VIV suppression by virtue of the hexagonal segmentation 21 provided on its outer surface 141.

[0116] Any of embodiments 100, 120, 140 of the generally cylindrical element could be chosen by an operator to replace the existing underwater protection system/buoyancy system as appropriate. Cylindrical Protective Casings Traditionally Used as VIV Straps - fifth embodiment, as shown in Fig. 12 and being installed directly in the submarine conduit

[0117] In yet another alternative embodiment to the generally cylindrical C-shaped element 10 of Figs. 1 to 3, the generally cylindrical element 160 as shown in Fig. 12 (having a hexagonal segmentation 21, as previously described, provided on its outer surface 161) may be fitted fixedly or integrally into a subsea conduit 110, such as a cable. submarine, a flexible bridge pipe, flow line, riser, section of pipe or large piping at the time of manufacturing such conduit 110 by joining it thereto.

[0118] The generally cylindrical element 160 of Fig. 12 therefore forms an integrated outer sheath or cover to the submarine conduit 110 and completely encompasses the conduit 110 by 360 degrees along that longitudinal section of the conduit 110 that it covers (which will be typically the entire length of the conduit 110).

[0119] The inner surface 163 of the generally cylindrical element 160 of Fig. 12 may be joined directly to the outer surface 111 of the conduit 110, or a cylindrical conduit or pipe insulation/lining 165 may optionally be sandwiched in a coaxial manner between the inner surface 163 of the generally cylindrical element 160 and the outer surface 111 of the conduit 110 and both are preferably joined thereto. The pipe insulation/lining 165 may be formed from any suitable material. The pipe insulation/lining 165 may be formed from a buoyant material, such as polystyrene (not shown) or other suitable buoyant material if the operator needs to add buoyancy to the conduit 110.

[0120] The generally cylindrical element 160 of Fig. 12 therefore acts as a protective casing or jacket for the conduit 110 and thereby provides the conduit 110 with underwater VIV suppression by virtue of the hexagonal segmentation 21 provided on its surface external 161.

[0121] Other applications of embodiments according to the present invention are possible, where VIV reduction and/or drag reduction is required particularly within underwater environments, without departing from the scope of the invention.

[0122] Modifications and improvements can be made to the embodiments described above without departing from the scope of the invention.

Claims (31)

1. Generally cylindrical element (10) adapted for immersion in a body of water, the generally cylindrical element (10) CHARACTERIZED by the fact that it has an external surface (11) arranged, in use, to be in contact with the water, the outer surface (11) comprising: at least two rows (40A, 40B, 40C, 40D) of repeating shapes (20) provided thereon, each row (40A, 40B, 40C, 40D) of repeating shapes (20) being separate from each row (40A, 40B, 40C, 40D) adjacent by a groove arrangement (30) and each shape (20) within a row (40A, 40B, 40C, 40D) being separated from adjacent shapes (20) by at least a groove; wherein the groove arrangement (30) for each row (40A, 40B, 40C, 40D) of repeating shapes (20) comprises an upper groove and a lower groove, wherein each of the upper and lower grooves encircles the complete circumference of 360 degrees of the generally cylindrical element (10), so that each of said upper and lower grooves is continuous around the generally cylindrical element (10); wherein the groove arrangement (30) provides at least one separate path for a flow of water to follow around the circumference of the generally cylindrical member (10), such that water flowing within the groove arrangement (30) meets at least one flow separation point (23A, 23B, 23C); wherein the external surface of the generally cylindrical element (10) reduces Vortex Induced Vibration (VIV) and/or drag acting on the generally cylindrical element (10). 2. Generally cylindrical element (10), according to claim 1, CHARACTERIZED by the fact that each of the shapes (20) repeated within each row (40A, 40B, 40C, 40D) is identical. 3. Generally cylindrical element (10), according to claim 1 or 2, CHARACTERIZED by the fact that each row (40A, 40B, 40C, 40D) provided on the outer surface (11) comprises repeating shapes (20) identical to the shapes (20) from each other row (40A, 40B, 40C, 40D), such that all shapes (20) provided on the outer surface (11) are identical. 4. Generally cylindrical element (10), according to any one of claims 1 to 3, CHARACTERIZED by the fact that the shapes comprise at least three sides. 5. Generally cylindrical element (10), according to claim 4, CHARACTERIZED by the fact that the shapes (20) comprise six sides to form a hexagonal shape (20A, 20B, 20C). 6. Generally cylindrical element (10), according to any one of claims 1 to 5, CHARACTERIZED by the fact that the repeated shapes (20) are arranged on the external surface (11) in a segmentation (21). 7. Generally cylindrical element (10), according to claim 5, CHARACTERIZED by the fact that the external surface (11) of the generally cylindrical element (10) comprises a hexagonal segmentation (21) in which every three hexagonal shapes (20A, 20B, 20C) adjacent meet at contiguous vertices (22) and the rest of the hexagonal shapes (20) repeat the arrangement on the external surface (11) of the generally cylindrical element (10). 8. Generally cylindrical element (10), according to any one of claims 1 to 7, CHARACTERIZED by the fact that at least one vertex (22) between two adjacent sides of each repeated shape (20) comprises a radius. 9. Generally cylindrical element (10), according to any one of claims 1 to 8, CHARACTERIZED by the fact that each repeated shape (20) projects from the external surface (11) of the generally cylindrical element (10) due to the arrangements slot (30). 10. Generally cylindrical element (10), according to any one of claims 1 to 9, CHARACTERIZED by the fact that the generally cylindrical element (10) is adapted to be placed around a cylindrical structure which, in use, is located in the body of water. 11. Generally cylindrical element (10), according to claim 10, CHARACTERIZED by the fact that the generally cylindrical element (10) is formed by two or more sections that, when placed together, envelop the cylindrical structure. 12. Generally cylindrical element (10), according to any one of claims 1 to 9, CHARACTERIZED by the fact that the generally cylindrical element (10) is formed entirely by a cylindrical structure which, in use, is located in the body of water . 13. Generally cylindrical element (10), according to claim 10, CHARACTERIZED by the fact that the generally cylindrical element (10) is shaped transversely in C and comprises a cut formed along the entire length on one side, such so that it can slide along the length of the cylindrical structure. 14. Generally cylindrical element (10), according to any one of claims 1 to 13, CHARACTERIZED by the fact that the groove arrangement (30) comprises angled side faces (60). 15. Generally cylindrical element (10), according to claim 14, CHARACTERIZED by the fact that the angled side faces (60) are angled between 40 to 80 degrees in relation to the radius of the generally cylindrical element (10). 16. Generally cylindrical element (10), according to any one of claims 1 to 13, CHARACTERIZED by the fact that the groove arrangement (30) comprises a semicircular profile. 17. Generally cylindrical element (10), according to claim 16, CHARACTERIZED by the fact that the width of the groove arrangement (30) is within the range of 0.50 to 0.60 times the outermost radius of the element generally cylindrical (10). 18. Generally cylindrical element (10), according to any one of claims 1 to 17, CHARACTERIZED by the fact that the flow separation point (23) comprises a vertex (22) of a shape (20) where two sides of the format (20) meet. 19. Generally cylindrical element (10), according to any one of claims 1 to 18, CHARACTERIZED by the fact that the flow separation point (23) comprises one side of the shape (20). 20. Generally cylindrical element (10), according to any one of claims 1 to 19, CHARACTERIZED by the fact that when the water flow within the groove arrangement (30) encounters a flow separation point (23), the direction of at least a portion of the water flow is changed to less than 90°. 21. Generally cylindrical element (10), according to any one of claims 1 to 20, CHARACTERIZED by the fact that the groove arrangement (30) provides a plurality of separate paths for water flow when navigating around the circumference of the element generally cylindrical (10), so that water flowing around the outer circumference of the generally cylindrical element (10) from one side to the other encounters a number of flow separation points (23A, 23B, 23C). 22. Generally cylindrical element (10), according to any one of claims 1 to 21, CHARACTERIZED by the fact that water flowing along the flow path within the groove arrangement (30) from one side of the generally cylindrical element (10) for the other will find a flow separation point (23A, 23B, 23C) at which point will be separated into a first flow path (25A1, 25B1, 25C1) and a second flow path (25A2, 25B2, 25C2 ). 23. Generally cylindrical element (10), according to any one of claims 10 to 13, CHARACTERIZED by the fact that it is provided in multiple partially circular shells which, when put together, envelop the cylindrical structure located in the body of water and which comprise buoyancy for assist in the buoyancy of the cylindrical structure located in the body of water. 24. Generally cylindrical element (10), according to claim 23, CHARACTERIZED by the fact that it further comprises stacking planes to allow individual shells to be stacked one on top of the other. 25. Generally cylindrical element (10), according to claim 23 or 24, CHARACTERIZED by the fact that it further comprises belt recesses (66) and/or screw holes to assist in coupling the shells together around a structure cylindrical that, in use, is located in a body of water. 26. Generally cylindrical element (10), according to claim 23 or 24, CHARACTERIZED by the fact that it further comprises belt recesses (66) and/or support cavities (68) to assist in transporting the generally cylindrical element (10 ) or its shells. 27. Generally cylindrical element (10), according to any one of claims 1 to 22, CHARACTERIZED by the fact that a protective coating layer is provided between the inner surface/through hole (15) of the generally cylindrical element (10) and the outer surface of the submarine conduit (110) in a coaxial manner. 28. Generally cylindrical element (10), according to claim 27, CHARACTERIZED by the fact that the protective coating layer is attached to the respective surface on each of its external and internal surfaces. 29. Generally cylindrical element (10), according to any one of claims 1 to 22, CHARACTERIZED by the fact that the internal surface/through hole (15) of the generally cylindrical element (10) is joined directly to the external surface of the conduit submarine (110). 30. Generally cylindrical element (10), according to any one of claims 1 to 29, CHARACTERIZED by the fact that said groove arrangements (30) comprise a groove having a profile depth = 0.01 to 0.1 times the outermost diameter (O.D.) of the generally cylindrical element (10). 31. Generally cylindrical element (10), according to claim 27, CHARACTERIZED by the fact that said groove arrangements (30) comprise a groove having a profile depth = 0.05 times the outermost diameter (O.D.) of the generally cylindrical element (10).