WO2009046166A1 - Systèmes et procédés de réduction des vibrations induites par tourbillon et/ou traînée - Google Patents

Systèmes et procédés de réduction des vibrations induites par tourbillon et/ou traînée Download PDF

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Publication number
WO2009046166A1
WO2009046166A1 PCT/US2008/078541 US2008078541W WO2009046166A1 WO 2009046166 A1 WO2009046166 A1 WO 2009046166A1 US 2008078541 W US2008078541 W US 2008078541W WO 2009046166 A1 WO2009046166 A1 WO 2009046166A1
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WO
WIPO (PCT)
Prior art keywords
fins
devices
collar
multiple finned
diameter
Prior art date
Application number
PCT/US2008/078541
Other languages
English (en)
Inventor
Donald Wayne Allen
Dean Leroy Henning
Li Lee
Original Assignee
Shell Oil Company
Shell Internationale Research Maatschappij B.V.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Shell Oil Company, Shell Internationale Research Maatschappij B.V. filed Critical Shell Oil Company
Priority to BRPI0818644A priority Critical patent/BRPI0818644A2/pt
Priority to MX2010003690A priority patent/MX2010003690A/es
Priority to GB1005690A priority patent/GB2466154A/en
Publication of WO2009046166A1 publication Critical patent/WO2009046166A1/fr
Priority to NO20100633A priority patent/NO20100633L/no

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15D—FLUID DYNAMICS, i.e. METHODS OR MEANS FOR INFLUENCING THE FLOW OF GASES OR LIQUIDS
    • F15D1/00—Influencing flow of fluids
    • F15D1/10—Influencing flow of fluids around bodies of solid material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B39/00—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude
    • B63B39/005—Equipment to decrease ship's vibrations produced externally to the ship, e.g. wave-induced vibrations
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02B—HYDRAULIC ENGINEERING
    • E02B17/00—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor
    • E02B17/0017—Means for protecting offshore constructions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B21/00—Tying-up; Shifting, towing, or pushing equipment; Anchoring
    • B63B21/50—Anchoring arrangements or methods for special vessels, e.g. for floating drilling platforms or dredgers
    • B63B21/502—Anchoring arrangements or methods for special vessels, e.g. for floating drilling platforms or dredgers by means of tension legs
    • B63B2021/504—Anchoring arrangements or methods for special vessels, e.g. for floating drilling platforms or dredgers by means of tension legs comprising suppressors for vortex induced vibrations
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B35/00—Vessels or similar floating structures specially adapted for specific purposes and not otherwise provided for
    • B63B35/44—Floating buildings, stores, drilling platforms, or workshops, e.g. carrying water-oil separating devices
    • B63B2035/442—Spar-type semi-submersible structures, i.e. shaped as single slender, e.g. substantially cylindrical or trussed vertical bodies
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B21/00—Tying-up; Shifting, towing, or pushing equipment; Anchoring
    • B63B21/50—Anchoring arrangements or methods for special vessels, e.g. for floating drilling platforms or dredgers
    • B63B21/502—Anchoring arrangements or methods for special vessels, e.g. for floating drilling platforms or dredgers by means of tension legs
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
    • F16L1/00—Laying or reclaiming pipes; Repairing or joining pipes on or under water
    • F16L1/12—Laying or reclaiming pipes on or under water
    • F16L1/123—Devices for the protection of pipes under water

Definitions

  • the present invention relates to systems and methods for reducing drag and/or vortex-induced vibration ("VIV"). Description of the Related Art
  • VIV vortex-induced vibration
  • Drilling for and/or producing hydrocarbons or the like from subterranean deposits which exist under a body of water exposes underwater drilling and production equipment to water currents and the possibility of VIV.
  • Equipment exposed to VIV includes structures ranging from the smaller tubes of a riser system, anchoring tendons, or lateral pipelines to the larger underwater cylinders of the hull of a mini spar or spar floating production system (hereinafter "spar").
  • the magnitude of the stresses on the riser pipe, tendons or spars may be generally a function of and increases with the velocity of the water current passing these structures.
  • the first kind of stress may be caused by vortex-induced alternating forces that vibrate the structure ("vortex-induced vibrations") mainly in a direction perpendicular to the direction of the current.
  • vortex-induced vibrations When fluid flows past the structure, vortices may be alternately shed from each side of the structure. This produces a fluctuating force on the structure transverse to the current. If the frequency of this harmonic load is near the resonant frequency of the structure, large vibrations transverse to the current can occur. These vibrations can, depending on the stiffness and the strength of the structure and any welds, lead to unacceptably short fatigue lives.
  • stresses caused by high current conditions in marine environments have been known to cause structures such as risers to break apart and fall to the ocean floor.
  • the second type of stress may be caused by drag forces, which push the structure in the direction of the current due to the structure's resistance to fluid flow.
  • the drag forces may be amplified by vortex-induced vibration of the structure. For instance, a riser pipe that is vibrating due to vortex shedding will generally disrupt the flow of water around it more than a stationary riser. This may result in more energy transfer from the current to the riser, and hence more drag.
  • Many types of devices have been developed to reduce vibrations of sub sea structures. Some of these devices used to reduce vibrations caused by vortex shedding from sub sea structures operate by stabilization of the wake. These methods include use of streamlined fairings, wake splitters and flags.
  • Devices used to reduce vibrations caused by vortex shedding from sub-sea structures may operate by modifying the boundary layer of the flow around the structure to prevent the correlation of vortex shedding along the length of the structure.
  • Examples of such devices include sleeve-like devices such as helical strakes, shrouds, fairings and substantially cylindrical sleeves.
  • VIV and/or drag reduction devices Elongated structures in wind in the atmosphere can also encounter VIV and/or drag, comparable to that encountered in aquatic environments. Likewise, elongated structures with excessive VIV and/or drag forces that extend far above the ground can be difficult, expensive and dangerous to reach by human workers to install VIV and/or drag reduction devices.
  • Fairings may be used to suppress VIV and reduce drag acting on a structure in a flowing fluid environment. Fairings may be defined by a chord to thickness ratio, where longer fairings have a higher ratio than shorter fairings. Long fairings are more effective than short fairings at resisting drag, but may be subject to instabilities. Short fairings are less subject to instabilities, but may have higher drag in a flowing fluid environment.
  • U.S. Patent Number 6,223,672 discloses an ultrashort fairing for suppressing vortex-induced vibration in substantially cylindrical marine elements.
  • the ultrashort falling has a leading edge substantially defined by the circular profile of the marine element for a distance following at least about 270 degrees thereabout and a pair of shaped sides departing from the circular profile of the marine riser and converging at a trailing edge.
  • the ultrashort fairing has dimensions of thickness and chord length such that the chord to thickness ratio is between about 1.20 and 1.10.
  • U.S. Patent Number 6,223,672 is herein incorporated by reference in its entirety.
  • U.S. Patent Number 4,398,487 discloses a fairing for elongated elements for reducing current-induced stresses on the elongated element.
  • the fairing is made as a stream-lined shaped body that has a nose portion in which the elongated element is accommodated and a tail portion.
  • the body has a bearing connected to it to provide bearing engagement with the elongated element.
  • a biasing device interconnected with the bearing accommodates variations in the outer surface of the elongated element to maintain the fairing's longitudinal axis substantially parallel to the longitudinal axis of the elongated element as the fairing rotates around the elongated element.
  • the fairing is particularly adapted for mounting on a marine drilling riser having flotation modules.
  • U.S. Patent Number 4,398,487 is herein incorporated by reference in its entirety.
  • Co-pending U.S. Application Serial Number 60/955,471 filed on August 13, 2007, and having attorney docket number TH 3245, discloses a system for reducing drag and/or vortex induced vibration of a structure, the system comprising a multiple sided device comprising from 4 to 6 sides.
  • Co-pending U.S. Application Serial Number 60/955,471 is herein incorporated by reference in its entirety.
  • prior art short fairing 104 installed about structure 102.
  • Structure 102 may be subjected to a flowing fluid environment, where short fairing 104 may be used to suppress vortex induced vibration (VIV).
  • Short fairing 104 has chord 106 and thickness 108. Chord to thickness ratio of short fairing 104 may be less than about 1.5, or less than about 1.25. While short fairing 104 is effective at reducing vortex induced vibration, short fairing 104 may be subject to drag forces 1 10 in a flowing fluid environment.
  • prior art long fairing 204 is illustrated installed about structure 202. Structure 202 may be in a flowing fluid environment where structure 202 is subject to vortex induced vibration.
  • long fairing 204 may have reduced drag when subjected to a flowing fluid environment.
  • Long fairing 204 has chord 206 and thickness 208.
  • Chord to thickness ratio of long fairing 204 may be greater than about 1.7, or greater than about 1.8, greater than about 2.0, or greater than about 2.25.
  • long fairing 204 may have lower drag than short fairing 104, long fairing 204 may be subject to flutter, galloping, and/or a plunge-torsional instability. Long fairing 204 may experience lateral displacement 210 and/or torsional displacement 212.
  • apparatus and methods for reducing VIV on structures in flowing fluid environments which do not suffer from certain disadvantages of the prior art apparatus and methods; improved VIV suppression devices; high stability devices; devices which delay the separation of the boundary layer, devices which provide decreased VIV and/or devices which provide reduced drag; devices suitable for use at a variety of fluid flow velocities; and/or devices that have a high stability.
  • One aspect of invention provides a system for reducing drag and/or vortex induced vibration of a structure, the system comprising a multiple finned device comprising from 4 to 6 fins substantially aligned along a longitudinal axis of the structure.
  • Another aspect of invention provides a method for modifying a structure subject to drag and/or vortex induced vibration, said method comprising positioning at least one multiple finned device around the structure, the multiple finned device comprising from 4 to 6 fins substantially aligned along a longitudinal axis of the structure.
  • Advantages of the invention may include one or more of the following: improved VIV reduction; improved device stability; delaying the separation of the boundary layer over the device body; lower cost devices; devices that are easier to install; devices that require a low density of coverage over the length of the structure, and/or lighter weight devices.
  • Figure 1 shows a prior art short fairing.
  • Figure 2 shows a prior art long fairing.
  • Figure 3 shows a three-finned VIV suppression device.
  • Figure 4 shows a four- finned VIV suppression device.
  • Figure 5 shows a six- finned VIV suppression device.
  • Figure 6 shows a plurality of VIV suppression devices installed along the length of a structure.
  • Figure 7 shows a plurality of VIV suppression devices installed along the length of a structure.
  • Device 304 is illustrated installed about structure 302.
  • Structure 302 may be in a flowing fluid environment with flow 310a, where structure 302 is subject to vortex induced vibration.
  • Device 304 may be used to suppress the vortex induced vibration of structure 302.
  • Device 304 includes three fins 322 extending radially outward from structure 302. Fins 322 may be substantially aligned with a longitudinal axis of structure 302.
  • Device 304 has chord 306 and thickness 308, which may vary if device 304 rotates relative structure 302. Chord 306 is measured parallel to flow 310a, and thickness 308 is measured perpendicular to flow 310a.
  • Chord to thickness ratio of device 304 as shown in Figure 3 may be less than about 1.5, or less than about 1.25, or less than about 1.1 , for example about 1.
  • Chord to thickness ratio of device 304 as shown in Figure 3 may be greater than about 0.6, or greater than about 0.75, or greater than about 0.9, for example about 1.
  • Structure 302 has a diameter or a major axis.
  • Each fin 322 has a radial height, the length which the fin 322 extends outwardly from structure 302.
  • a fin's radial height may be from about 5% to about 200% of structure's 302 diameter, for example from about 10% to about 50%, or from about 15% to about 30%.
  • Device 304 may be subject to fluid flow 310a.
  • Device 304 includes three fins 322. All of the fins may have the same length, two of the fins may have the same length, or each fin may have a different length.
  • the fins may be substantially straight, or may have a slight convex or concave curvature.
  • Each of the fins may have a length from about 1.25 to about 3 times a diameter of structure 302, for example from about 1.5 to about 2 times, or about 1.75 times.
  • the fins may make an angle from about 30 to about 150 degrees with each other, for example from about 45 to about 120 degrees, or from about 50 to about 90 degrees, or about 60 degrees.
  • the fins 322 may be substantially straight along a length of structure 302. For example, fins 322 may rotate less than about 15 degrees, 10 degrees, or less than about 5 degrees along one diameter length of structure 302. Fins may not be helically wound about structure, like a helical strake would be.
  • the dashed lines of structure 304 represent a virtual triangle shape in the current 310a created by fins 322. Fins 322 create voids and changes in the current 310a that affect the current 310a similar to the effect of a triangle.
  • Device 304 may be able to rotate about structure 302, or it may be in a fixed angular orientation.
  • Device 304 may have a collar mounted above and/or below device 304 to secure device at a fixed location along the length of structure 302 and/or to provide a bearing surface for device 304 to rotate.
  • Device 304 may be molded, welded, bent, cast, glued, or otherwise formed with manufacturing techniques as are known in the art.
  • Device 304 may be made of metals such as steel or aluminum, polymers such as polyethylene or polypropylene, or composite materials such as fiberglass or carbon fiber composites, or other materials as are known in the art.
  • Device 404 is illustrated installed about structure 402.
  • Structure 402 may be in a flowing fluid environment with flow 410a, where structure 402 is subject to vortex induced vibration.
  • Device 404 may be used to suppress the vortex induced vibration of structure 402.
  • Device 404 includes four fins 422 extending radially outward from structure 402. Fins 422 may be substantially aligned with a longitudinal axis of structure 402.
  • Device 404 has chord 406 and thickness 408, which may vary if device 404 rotates relative structure 402. Chord 406 is measured parallel to flow 410a, and thickness 408 is measured perpendicular to flow 410a. Chord to thickness ratio of device 404 as shown in Figure 4 may be less than about 1.5, or less than about 1.25, or less than about 1.1 , for example about 1. Chord to thickness ratio of device 404 as shown in Figure 4 may be greater than about 0.6, or greater than about 0.75, or greater than about 0.9, for example about 1.
  • Structure 402 has a diameter or a major axis. Each fin 422 has a radial height, the length which the fin 422 extends outwardly from structure 402. A fin's radial height may be from about 5% to about 200% of structure's 402 diameter, for example from about 10% to about 50%, or from about 15% to about 30%.
  • Device 404 may be subject to fluid flow 410a.
  • Device 404 includes four fins 422. All of the fins may have the same length, two of the fins may have the same length, or each fin may have a different length.
  • the fins may be substantially straight, or may have a slight convex or concave curvature.
  • Each of the fins may have a length from about 1.25 to about 3 times a diameter of structure 402, for example from about 1.5 to about 2 times, or about 1.75 times, where the length is measured along the longitudinal axis of structure 402.
  • Fins 422 may be the same or different materials, lengths and/or heights, and could have a variable height along the length.
  • the fins may make an angle from about 30 to about 150 degrees with each other, for example from about 45 to about 120 degrees, or from about 50 to about 100 degrees, or about 90 degrees.
  • the angle between the fins 422 may be constant along the length of structure 402, or it may vary along the length.
  • the fins 422 may be substantially straight along a length of structure 402.
  • fins 422 may rotate less than about 15 degrees, 10 degrees, or less than about 5 degrees along one diameter length of structure 402. Fins may not be helically wound about structure, like a helical strake would be.
  • the dashed lines of structure 404 represent a virtual square shape in the current 410a created by fins 422. Fins 422 create voids and changes in the current 410a that affect the current 410a similar to the effect of a sqaure.
  • Device 404 may be able to rotate about structure 402, or it may be in a fixed angular orientation.
  • Device 404 may have a collar mounted above and/or below device 404 to secure device at a fixed location along the length of structure 402 and/or to provide a bearing surface for device 404 to rotate.
  • Device 404 may be molded, welded, bent, cast, glued, or otherwise formed with manufacturing techniques as are known in the art.
  • Device 404 may be made of metals such as steel or aluminum, polymers such as polyethylene or polypropylene, or composite materials such as fiberglass or carbon fiber composites, or other materials as are known in the art.
  • Figure 5 Figure 5:
  • Device 504 is shown installed about structure 502.
  • Structure 502 may be in a flowing fluid environment with flow 510a, where structure 502 is subject to vortex induced vibration.
  • Device 504 may be used to suppress the vortex induced vibration of structure 502.
  • Device 504 includes six fins 522 extending radially outward from structure 502. Fins 522 may be substantially aligned with a longitudinal axis of structure 502.
  • Device 504 has chord 506 and thickness 508, which may vary if device 504 rotates relative structure 502. Chord 506 is measured parallel to flow 510a, and thickness 508 is measured perpendicular to flow 510a. Chord to thickness ratio of device 504 as shown in Figure 5 may be less than about 1.5, or less than about 1.25, or less than about 1.1 , for example about 1. Chord to thickness ratio of device 504 as shown in Figure 5 may be greater than about 0.6, or greater than about 0.75, or greater than about 0.9, for example about 1.
  • Structure 502 has a diameter or a major axis.
  • Each fin 522 has a radial height, the length which the fin 522 extends outwardly from structure 502.
  • a fin's radial height may be from about 5% to about 200% of structure's 502 diameter, for example from about 10% to about 50%, or from about 15% to about 30%.
  • Device 504 may be subject to fluid flow 510a.
  • Device 504 includes six fins
  • All of the fins may have the same length, two of the fins may have the same length, or each fin may have a different length.
  • the fins may be substantially straight, or may have a slight convex or concave curvature.
  • Each of the fins may have a length from about 1.25 to about 3 times a diameter of structure 502, for example from about 1.5 to about 2 times, or about 1 .75 times.
  • the fins may make an angle from about 30 to about 150 degrees with each other, for example from about 45 to about 120 degrees, or from about 50 to about 90 degrees, or about 60 degrees.
  • the fins 522 may be substantially straight along a length of structure 502. For example, fins 522 may rotate less than about 15 degrees, 10 degrees, or less than about 5 degrees along one diameter length of structure 502. Fins may not be helically wound about structure, like a helical strake would be.
  • the dashed lines of structure 504 represent a virtual hexagon shape in the current 510a created by fins 522. Fins 522 create voids and changes in the current 510a that affect the current 510a similar to the effect of a hexagon.
  • Device 504 may be able to rotate about structure 502, or it may be in a fixed angular orientation.
  • Device 504 may have a collar mounted above and/or below device 504 to secure device at a fixed location along the length of structure 502 and/or to provide a bearing surface for device 504 to rotate.
  • Device 504 may be molded, welded, bent, cast, glued, or otherwise formed with manufacturing techniques as are known in the art.
  • Device 504 may be made of metals such as steel or aluminum, polymers such as polyethylene or polypropylene, or composite materials such as fiberglass or carbon fiber composites, or other materials as are known in the art.
  • Figure 6 :
  • structure 602 is illustrated with a plurality of multiple finned devices 604a, 604b, 604c, and 604d installed about structure 602 in order to suppress vortex induced vibration of structure 602, when structure 602 is subjected to fluid flow 610.
  • collars may be provided between adjacent devices or placed between every few devices.
  • devices 604a-604d may be installed before structure is installed, for example in a subsea environment.
  • devices 604a-604d may be installed as a retrofit installation to structure 602 which has already been installed, for example in a subsea environment.
  • Device 604a has height 624a and distance 626a between adjacent devices 604a and 604b.
  • Device 604a has length 606.
  • Portion of structure 602 covered with devices 604a-604d has height 608.
  • Device 604b has height 624b
  • device 604c has height 624c
  • device 604d has height 624d.
  • Devices 604a-604d may cover from about 10% to about 100% of height 608, for example from about 20% to about 80%, or from about 30% to about 50%.
  • Length 606 may be from about 1.25 times the diameter of structure 602 to about 3 times, for example from about 1.5 to about 2 times the diameter.
  • Height 624a may be from about 1 times the diameter of structure 602 to about 6 times, for example from about 1.25 to about 3 times the diameter, or from about 1.5 to about 2 times the diameter.
  • Distance 626a may be from about 1 times the diameter of structure 602 to about 10 times, for example from about 1.5 to about 6 times the diameter, or from about 2 to about 4 times the diameter.
  • Figure 7 Referring now to Figure 7, structure 702 is illustrated with a plurality of multiple finned devices installed about structure 702 in order to suppress vortex induced vibration of structure 702, when structure 702 is subjected to fluid flow 710.
  • collars 724a-724d may be provided between adjacent devices or placed between every few devices.
  • devices may be installed before structure is installed, for example in a subsea environment.
  • devices may be installed as a retrofit installation to structure 702 which has already been installed, for example in a subsea environment.
  • the first device includes collar 724a and collar 724b, which hold a plurality of fins 722a between them and adjacent to structure 702.
  • the second device includes collar 724b and collar 724c, which hold a plurality of fins 722b between them and adjacent to structure 702.
  • the third device includes collar 724c and collar 724d, which hold a plurality of fins 722c between them and adjacent to structure 702.
  • a system for reducing drag and/or vortex induced vibration of a structure comprising a multiple finned device comprising from 4 to 6 fins substantially aligned along a longitudinal axis of the structure, the device free to rotate about the structure.
  • the device comprises a height from about 5% to about 200% of a diameter of the structure.
  • the device comprises a height from about 10% to about 50% of a diameter of the structure.
  • the device is installed about the structure.
  • the device comprises a length along a major axis of the structure from 0.5 to 10 times a diameter of the structure.
  • the device comprises 4 fins.
  • the device comprises a fin at an angle from 30 to 60 degrees with a fluid flow encountering the structure. In some embodiments, the device comprises an even number of fins. In some embodiments, the device comprises a first collar at a top of the device and a second collar at a bottom of the device, the fins connected to the first collar at the top of the device and the second collar at the bottom of the device. In some embodiments, the system also includes a plurality of multiple finned devices along a length of the structure. In some embodiments, the system also includes a collar connected to a first set of fins above the collar and a second set of fins below the collar.
  • a method for modifying a structure subject to drag and/or vortex induced vibration comprising positioning at least one multiple finned device around the structure, the multiple finned device comprising from 4 to 6 fins substantially aligned along a longitudinal axis of the structure.
  • the positioning comprises positioning at least two multiple finned devices about the structure.
  • the method also includes positioning a collar, a buoyancy module, and/or a clamp around the structure.
  • the device comprises a four finned shape.
  • the method also includes locking the device at a preferred angular orientation based on ambient expected currents acting on the structure.
  • a system for reducing drag and/or vortex induced vibration of a structure comprising a first multiple finned device comprising from 4 to 10 fins; a second multiple finned device comprising from 4 to 10 fins, spaced at a distance along a longitudinal axis from the first device.
  • at least one of the first and the second device comprises a height from about 5% to about 200% of a diameter of the structure.
  • a space between the first device and the second device is from about 0.25 to about 20 times a diameter of the structure.
  • the system also includes one or more collars located about the structure, above and/or below at least one of the first and the second device.
  • At least one of the first and the second device comprises a length measured along a longitudinal axis of the structure from 0.5 to 10 times a diameter of the structure. In some embodiments, at least one of the first and the second device comprises 4 fins. In some embodiments, at least one of the first and the second device comprises 2 fins at an angle between about 30 and 60 degrees with a fluid flow encountering the structure. In some embodiments, at least one of the first and the second device comprises an even number of fins. In some embodiments, at least one of the first and the second device comprises a collar connected to and holding a plurality of fins about and adjacent to the structure. In some embodiments, the system also includes a plurality of multiple finned devices spaced along a length of the structure.
  • a coverage density of the devices is from about 5% to about 90%. In some embodiments, a coverage density of the devices is from about 10% to about 80%. In some embodiments, a coverage density of the devices is from about 20% to about 50%.
  • a system for reducing drag and/or vortex induced vibration of a structure comprising a multiple finned device comprising from 4 to 6 fins substantially aligned along a longitudinal axis of the structure.
  • the device comprises a chord to thickness ratio of less than 1.5. In some embodiments, the device comprises a chord to thickness ratio of less than 1.25. In some embodiments, the device is installed about the structure.
  • the device comprises a height from 0.5 to 10 times a diameter of the structure. In some embodiments, the device comprises 4 fins. In some embodiments, the device comprises 2 fins aligned substantially parallel with a fluid flow encountering the structure. In some embodiments, the device comprises an even number of fins. In some embodiments, the device comprises a first collar at a top of the device and a second collar at a bottom of the device, the fins connected to the first collar at the top of the device and the second collar at the bottom of the device. In some embodiments, the system also includes a plurality of multiple finned devices along a length of the structure.
  • the system also includes a collar connected to a first set of fins above the collar and a second set of fins below the collar.
  • a method for modifying a structure subject to drag and/or vortex induced vibration comprising positioning at least one multiple finned device around the structure, the multiple finned device comprising from 4 to 6 fins substantially aligned along a longitudinal axis of the structure.
  • the positioning comprises positioning at least two multiple finned devices about the structure.
  • the method also includes positioning a collar, a buoyancy module, and/or a clamp around the structure.
  • the device comprises a four finned shape.
  • the method also includes locking the device at a preferred angular orientation based on ambient expected currents acting on the structure.
  • a system for reducing drag and/or vortex induced vibration of a structure comprising a multiple finned device comprising from 4 to 10 fins, the device free to rotate about the structure.
  • the device comprises a chord to thickness ratio of less than 1.5. In some embodiments, the device comprises a chord to thickness ratio of less than 1.25.
  • the system also includes one or more collars located about the structure, above and/or below the device. In some embodiments, the device comprises a length from 0.5 to 10 times a diameter of the structure. In some embodiments, the device comprises 4 fins. In some embodiments, the device comprises 2 fins aligned substantially parallel with a fluid flow encountering the structure.
  • the device comprises an even number of fins. In some embodiments, the device comprises a collar connected to and holding a plurality of fins about and adjacent to the structure. In some embodiments, the system also includes a plurality of multiple finned devices along a length of the structure.
  • the VIV systems and methods disclosed herein may be used in any flowing fluid environment in which the structural integrity of the system can be maintained.
  • flowing-fluid is defined here to include but not be limited to any fluid, gas, or any combination of fluids, gases, or mixture of one or more fluids with one or more gases, specific non-limiting examples of which include fresh water, salt water, air, liquid hydrocarbons, a solution, or any combination of one or more of the foregoing.
  • the flowing-fluid may be "aquatic,” meaning the flowing-fluid comprises water, and may comprise seawater or fresh water, or may comprise a mixture of fresh water and seawater.
  • devices of the invention may be used with most any type of offshore structure, for example, bottom supported and vertically moored structures, such as for example, fixed platforms, compliant towers, tension leg platforms, and mini-tension leg platforms, and also include floating production and subsea systems, such as for example, spar platforms, floating production systems, floating production storage and offloading, and subsea systems.
  • bottom supported and vertically moored structures such as for example, fixed platforms, compliant towers, tension leg platforms, and mini-tension leg platforms
  • floating production and subsea systems such as for example, spar platforms, floating production systems, floating production storage and offloading, and subsea systems.
  • devices may be attached to marine structures such as subsea pipelines; drilling, production, import and export risers; tendons for tension leg platforms; legs for traditional fixed and for compliant platforms; space- frame members for platforms; cables; umbilicals; mooring elements for deepwater platforms; and the hull and/or column structure for tension leg platforms (TLPs) and for spar type structures.
  • device may be attached to spars, risers, tethers, and/or mooring lines.
  • the multiple finned device may be formed as a hollow plastic moulding whose interior communicates with the exterior to permit equalization of pressure.
  • the multiple finned device may be formed by a single plastic moulding, such as by rotational moulding, so that it may be hollow.
  • the multiple finned device may be manufactured of polythene, which may be advantageous due to its low specific gravity (similar to that of water), toughness and low cost. Openings may be provided to allow water to enter the multiple finned device to equalize internal and external pressures.
  • the multiple finned device could also be formed as a solid polyurethane moulding.
  • the principal material used in constructing the multiple finned device may be fiberglass.
  • the multiple finned device may be constructed from any metallic or non-metallic, low corrosive material such as a aluminum or multi-layer fiberglass mat, polyurethane, vinyl ester resin, high or low density polyurethane, PVC or other materials with substantially similar flexibility and durability properties. These materials provide the multiple finned device with the strength to stay on the structure, but enough flex to allow it to be snapped in place during installation.
  • the fiberglass may be 140-210 MPa tensile strength (for example determined with ISO 527-4) that may be formed as a bi-directional mat or the multiple finned device can be formed of vinyl ester resin with 7-10% elongation or polyurethane.
  • the use of such materials eliminates the possibility of corrosion, which can cause the multiple finned device shell to seize up around the elongated structure it surrounds.
  • Collars may be provided to connect the multiple finned device to the structure and/or to provide spacing between adjacent multiple finned devices along the structure, and/or as a mechanism to hold the fins in place as illustrated above in Figure 7.
  • Collars may be formed by a single plastics moulding, such as nylon, or from a metal such as stainless steel, copper, or aluminum.
  • the internal face of the collar's bearing ring may serve as a rotary bearing allowing the multiple finned device to rotate about the structure's longitudinal axis and so to weathervane to face a current. Only the collar may make contact with the structure, its portion interposed between the multiple finned device and the structure serving to maintain clearance between these parts.
  • This bearing surface may be (a) low friction and even "self lubricating" and/or (b) resistant to marine fouling. These properties can be promoted by incorporation of anti-fouling and/or friction reducing materials into the material of the collar.
  • the material of the collar may contain a mixture of an anti-fouling composition which provides a controlled rate of release of copper ions, and/or also of silicon oil serving to reduce bearing friction.
  • the multiple finned device may be mounted to the structure itself, or flanges can be used on the devices to keep them from sliding off each other, and then a single collar (or bend restrictor, connector, etc.) can be used to hold a long string of devices in place. That is, the multiple finned device may be mounted directly upon the structure (or on a cylindrical protective sheath conventionally provided around the structure). A number of such multiple finned devices may be placed adjacent one another in a string along the structure. To prevent the multiple finned devices from moving along the length of the structure, clamps and/or collars may secured to the structure at intervals, for example between about every one to five multiple finned devices.
  • the clamps and/or collars may be of a type having a pair of half cylindrical clamp shells secured to the structure by a tension band passed around the shells.
  • the multiple finned device may be designed so that it can freely rotate about the structure in order to provide more efficient handling of the wave and current action and VIV bearing on the structure.
  • the multiple finned devices may not be connected, so they can rotate relative to each other.
  • Bands of low-friction plastic rings for example a molybdenum impregnated nylon, may be connected to the inside surface of the multiple finned device that defines an opening to receive the structure.
  • a low friction material may be provided on the portion of the multiple finned device that surrounds a structure, for example strips of molydbodeum impregnated nylon, which may be lubricated by sea water.
  • a first retaining ring, or thrust bearing surface may be installed above and/or below each multiple finned device or group of multiple finned devices. Buoyancy cans may also be installed above and/or below each multiple finned device or group of multiple finned devices.
  • the methods and systems of the invention may further comprise modifying the buoyancy of the multiple finned device. This may be carried out by attaching a weight or a buoyancy module to the multiple finned device.
  • the multiple finned device may include filler material that may be either neutrally or partially buoyant.
  • the multiple finned device may be partially filled with a known syntactic foam material for making the device partially buoyant in sea water. This foam material can be positively buoyant or neutrally buoyant for achieving the desired results.
  • At least one copper element may be mounted at the structure and/or the multiple finned device to discourage marine growth at the device - structure interface so that the device remains free to weathervane to orient most effectively with the current, for example a copper bar.
  • the multiple finned devices may be made of copper, or be made of copper and one or more other materials.
  • the height and/or length of the multiple finned device can vary considerably depending upon the specific application, the materials of construction, and the method employed to install the multiple finned device.
  • numerous devices may be placed along the length of the marine structure, for example covering from about 5%, 10%, 15%, or 25%, to about 50%, or 75%, or 100% of the length of the marine structure with the devices.
  • multiple finned devices may be placed on a marine structure after it is in place, for example, suspended between a platform and the ocean floor, in which divers or submersible vehicles may be used to fasten the devices around the structure.
  • devices may be fastened to the structure as lengths of the structure are assembled. This method of installation may be performed on a specially designed vessel, such as an S-Lay or J-Lay barge, that may have a declining ramp, positioned along a side of the vessel and descending below the ocean's surface, that may be equipped with rollers. As the lengths of the structure are fitted together, multiple finned devices may be attached to the connected sections before they are lowered into the ocean.
  • the multiple finned devices may comprise one or more members.
  • two-membered devices suitable herein include a clam-shell type structure wherein the device comprises two members that may be hinged to one another to form a hinged edge and two unhinged edges, as well as a device comprising two members that may be connected to one another after being positioned around the circumference of the marine structure.
  • friction- reducing devices may be attached to the interior surface of the device.
  • Clam-shell devices may be positioned onto the marine structure by opening the clam shell device, placing the device around the structure, and closing the clam-shell device around the circumference of the structure.
  • the step of securing the device into position around the structure may comprise connecting the two members to one another.
  • the device may be secured around the structure by connecting the two unhinged edges of the clam-shell structure to one another. Any connecting or fastening device known in the art may be used to connect the member to one another.
  • clamshell type devices may have a locking mechanism to secure the device about the structure, such as male-female connectors, rivets, screws, adhesives, welds, and/or connectors.
  • a locking mechanism to secure the device about the structure, such as male-female connectors, rivets, screws, adhesives, welds, and/or connectors.
  • the methods and systems of the invention may further comprise positioning a second device, or a plurality of devices around the circumference of a structure.
  • the devices may be adjacent one another on the structure, or stacked on the structure.
  • the devices may comprise end flanges, rings or strips to allow the devices to easily stack onto one another, or collars or clamps may be provided in between devices or groups of devices.
  • the devices may be added to the structure one at a time, or they may be stacked atop one another prior to being placed around/onto the structure. Further, the devices of a stack of devices may be connected to one another, or attached separately.
  • While the devices have been described as being used in aquatic environments, they may also be used for VIV and/or drag reduction on elongated structures in atmospheric environments.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Civil Engineering (AREA)
  • Combustion & Propulsion (AREA)
  • Ocean & Marine Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Structural Engineering (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)
  • Turbine Rotor Nozzle Sealing (AREA)
  • Exhaust Silencers (AREA)
  • Vibration Prevention Devices (AREA)
  • Earth Drilling (AREA)

Abstract

L'invention concerne un système de réduction des vibrations induites par tourbillon et/ou traînée d'une structure, le système incluant un dispositif à ailettes multiples renfermant de 4 à 6 ailettes sensiblement alignées le long d'un axe longitudinal de la structure.
PCT/US2008/078541 2007-10-05 2008-10-02 Systèmes et procédés de réduction des vibrations induites par tourbillon et/ou traînée WO2009046166A1 (fr)

Priority Applications (4)

Application Number Priority Date Filing Date Title
BRPI0818644A BRPI0818644A2 (pt) 2007-10-05 2008-10-02 sistema para reduzir o arrasto e/ou a vibração induzida por vórtices de uma estrutura, e, método para modificar uma estrutura sobmetida a arrasto e/ou a vibrações induzidas po vótices
MX2010003690A MX2010003690A (es) 2007-10-05 2008-10-02 Sistemas y metodos para reducir el arrastre y/o la vibracion inducida por vortice.
GB1005690A GB2466154A (en) 2007-10-05 2008-10-02 Systems and methods for reducing drag and/or vortex induced vibration
NO20100633A NO20100633L (no) 2007-10-05 2010-05-03 Systemer og fremgangsmater for a redusere stromningsmotstand og/eller virvelindusert vibrasjon

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US97768607P 2007-10-05 2007-10-05
US60/977,686 2007-10-05

Publications (1)

Publication Number Publication Date
WO2009046166A1 true WO2009046166A1 (fr) 2009-04-09

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PCT/US2008/078541 WO2009046166A1 (fr) 2007-10-05 2008-10-02 Systèmes et procédés de réduction des vibrations induites par tourbillon et/ou traînée

Country Status (5)

Country Link
BR (1) BRPI0818644A2 (fr)
GB (1) GB2466154A (fr)
MX (1) MX2010003690A (fr)
NO (1) NO20100633L (fr)
WO (1) WO2009046166A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010129222A2 (fr) * 2009-04-28 2010-11-11 Shell Oil Company Systèmes et procédés pour réduire une vibration induite par une traînée et/ou un tourbillon

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3305194A (en) * 1960-03-08 1967-02-21 Robert G Conard Wind-insensitive missile
US3818833A (en) * 1972-08-18 1974-06-25 Fmc Corp Independent multiple head forward firing system

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3305194A (en) * 1960-03-08 1967-02-21 Robert G Conard Wind-insensitive missile
US3818833A (en) * 1972-08-18 1974-06-25 Fmc Corp Independent multiple head forward firing system

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010129222A2 (fr) * 2009-04-28 2010-11-11 Shell Oil Company Systèmes et procédés pour réduire une vibration induite par une traînée et/ou un tourbillon
WO2010129222A3 (fr) * 2009-04-28 2011-04-07 Shell Oil Company Systèmes et procédés pour réduire une vibration induite par une traînée et/ou un tourbillon

Also Published As

Publication number Publication date
GB2466154A (en) 2010-06-16
GB201005690D0 (en) 2010-05-19
BRPI0818644A2 (pt) 2017-05-23
NO20100633L (no) 2010-05-03
MX2010003690A (es) 2010-06-02

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