초록 ▼

Smoothly curved protuberances (8, 26, 34) are added to an elongate body (2, 16, 18, 20, 22, 32) to modify the fluid flow to reduce the drag Force Fdrag and the forces induced by vortex shedding Fvortex. The protuberances can be arranged in diametrically opposed pairs with longitudinally adjacent pai

Smoothly curved protuberances (8, 26, 34) are added to an elongate body (2, 16, 18, 20, 22, 32) to modify the fluid flow to reduce the drag Force Fdrag and the forces induced by vortex shedding Fvortex. The protuberances can be arranged in diametrically opposed pairs with longitudinally adjacent pairs having different radial directions first to cope with fluid flow from a variety of different directions.

대표청구항 ▼

1. An elongate body having a diameter D transverse to a direction of fluid flow around said body, said body including a means for reducing drag and vortex shedding from said body, said means for reducing comprising a plurality of longitudinally spaced apart smoothly curved protuberances extending fr

1. An elongate body having a diameter D transverse to a direction of fluid flow around said body, said body including a means for reducing drag and vortex shedding from said body, said means for reducing comprising a plurality of longitudinally spaced apart smoothly curved protuberances extending from said body, said protuberances extending from said body a distance at least 0.1 D and having a surface which is smoothly curved in two orthogonal directions, said surface is shaped and dimensioned for modifying said fluid flow around said elongate body in a manner that reduces forces upon said elongate body produced by drag and vortex shedding.2. An elongate body as claimed in claim 1, wherein said protuberances extend in a plurality of different radial directions from a longitudinal axis of said elongate body.3. An elongate body as claimed in claim 2, wherein longitudinally adjacent protuberance, have radial directions differing by an angle within the range 30 to 90 degrees inclusive.4. An elongate body as claimed in claim 3, wherein longitudinally adjacent protuberances have radial directions differing by an angle of substantially 45 degrees.5. An elongate body as claimed in claim 1, wherein at least two of said protuberances are arranged as a pair of protuberances having a common longitudinal position along said elongate body and extending in opposite radial directions from said elongate body.6. An elongate body as claimed in claim 5, wherein all of said protuberances are arranged as pairs of protuberances.7. An elongate body as claimed in claim 1 having a maximum cross-sectional diameter excluding said protuberances of D.8. An elongate body as claimed in claim 7, wherein said protuberances extend from an outer surface of said elongate body excluding said protuberances by a distance within the range 0.1 D to 0.75 D inclusive.9. An elongate body as claimed in claim 8, wherein said protuberances extend from an outer surface of said elongate body excluding said protuberances by a distance within the range 0.25 D to 0.5 D inclusive.10. An elongate body as claimed in claim 3, wherein said radial directions of said protuberances vary along said longitudinal axis in a repeating pattern with a repeat distance within the range 3 D to 9 D inclusive.11. An elongate body as claimed in claim 1, wherein said protuberances have a cross-sectional shape substantially corresponding to at least a portion of an ellipse.12. An elongate body as claimed in claim 1, wherein said elongate body has a cross-sectional shape substantially corresponding to a circle.13. An elongate body as claimed in claim 1, wherein said elongate body is one of:an offshore riser; a support member of an offshore platform; a pipe; an underwater cable; a chimney; and a support tower for a wind turbine. 14. An elongate body as claimed in claim 1, wherein said fluid flow is liquid flow.15. An elongate body as claimed in claim 1, wherein said fluid flow is gas flow.16. An elongate body as claimed in claim 1, wherein said protuberances are formed as fairings fixed to said elongate body.17. A method of reducing fluid flow induced forces upon an elongate body produced by drag and vortex shedding, said body having a dimension D transverse to said fluid flow, said method comprising the step of providing a plurality of fluid flow modifying longitudinally spaced apart smoothly curved protuberances extending from said elongate body a distance equal to at least 0.1 D, said protuberances having a surface which is smoothly curved in two orthogonal directions.18. A kit for modifying fluid flow around an elongate body, said body having a dimension D transverse to said fluid flow, said kit comprising:a plurality of smoothly curved fairings for fixing to said elongate body; and a plurality of fairing fasteners for fixing said fairings to said elongate body to form a plurality of longitudinally spaced apart smoothly curved protuberances extending from said body a distance equal to at least 0.1 D, said protuberances having a surface which is smoothly curved in two orthogonal directions and being shaped and dimensioned to modify said fluid flow around said elongate body in a manner that reduces forces upon said elongate body produced by drag and vortex shedding. 19. An elongate body, said body having a dimension D transverse to said fluid flow, said body having a plurality of longitudinally spaced apart smoothly curved protuberances extending therefrom, said protuberances having a surface which is smoothly curved in two orthogonal directions, said protuberances extending a distance equal to at least 0.1 D in a plurality of different radial directions from a longitudinal axis of said elongate body.20. An elongate body as claimed in claim 19, wherein longitudinally adjacent protuberances have radial directions differing by an angle of substantially 45 degrees.21. An elongate body as claimed in claim 19, wherein at least two of said protuberances are arranged as a pair of protuberances having a common longitudinal position along said elongate body and extending in opposite radial directions from said elongate body.22. An elongate body as claimed in claim 19 having a maximum cross-sectional diameter excluding said protuberances of D.23. An elongate body as claimed in claim 22, wherein said protuberances extend from an outer surface of said elongate body excluding said protuberances by a distance within the range 0.1 D to 0.75 D inclusive.24. An elongate body as claimed in claim 23, wherein said protuberances extend from an outer surface of said elongate body excluding said protuberances by a distance within the range 0.25 D to 0.5 D inclusive.25. An elongate body as claimed in claim 19, wherein said elongate body is one of:an offshore riser; a support member of an offshore platform; a pipe; an underwater cable; a chimney; and a support tower for a wind turbine. 26. A method as claimed in claim 17, wherein, said protuberances extend in a plurality of different radial directions from a longitudinal axis of said elongate body.27. A method as claimed in claim 17, wherein longitudinally adjacent protuberances have radial directions differing by an angle of substantially 45 degrees.28. A method as claimed in claim 17, wherein at least two of said protuberances are arranged as a pair of protuberances having a common longitudinal position along said elongate body and extending in opposite radial directions from said elongate body.29. A method as claimed in claim 17, wherein said elongate body has a maximum cross-sectional diameter excluding said protuberances of D.30. A method as claimed in claim 29, wherein said protuberances extend from an outer surface of said elongate body excluding said protuberances by a distance within the range 0.1 D to 0.75 D inclusive.31. A method as claimed in claim 30, wherein said protuberances extend from an outer surface of said elongate body excluding said protuberances by a distance within the range of 0.25 D to 0.5 D inclusive.32. A method as claimed in claim 17, wherein said elongate body is one of:an offshore riser; a support member of an offshore platform; a pipe; an underwater cable; a chimney; and a support tower for a wind turbine.