Patent ID: 6948884
Filing Date: 2005-09-27
Classification: E21B,F16L

Abstract:
1. A vortex-induced vibration (VIV) reduction mechanism for a substantially cylindrical structure for reduction of the effects of vortex-induced vibration (VIV) in the structure when the structure is submerged in flowing fluid, the mechanism comprising: a plurality of columnar segments disposed around the exterior surface of the structure in a vertically stacked arrangement, each of the segments having a vortex-shedding surface discontinuity provided by a notch formed by a radially inward-directed wall thickness discontinuity of the segment and oriented substantially parallel to the axis of the structure, the segments being arranged with respect to each other so that the surface discontinuity of each segment is circumferentially displaced from the surface discontinuity of an adjacent segment, whereby the surface discontinuities of the plurality of segments define a discontinuous, stepwise, approximately helical pattern of vortex-shedding discontinuities along the length of the structure, wherein each of the columnar segments has at least two vortex-shedding surface discontinuities equidistantly spaced around the exterior surface of the columnar segment, and wherein each columnar segment has a radius that varies continuously in length between each two successive vortex-shedding surface discontinuities.