Vortex induced vibrations of short side by side cylinders. (September 2021)

• Record Type: Journal Article
• Authors: Vedeld, Knut; Nestegård, Arne
• Is Part Of: Marine structures. Volume 79(2021)
• Publication Date: 2021-09
• Subjects: Piggy-back pipeline -- Vortex induced vibration -- Support design -- Staggered arrangement -- Piping systems -- Pipes; Naval architecture -- Periodicals; Offshore structures -- Periodicals; Architecture navale -- Périodiques; Structures offshore -- Périodiques; Naval architecture; Offshore structures; Periodicals; 620.4162
• DOI: 10.1016/j.marstruc.2021.102996
• Languages: English
• ISSNs: 0951-8339

Abstract

Abstract: Staggered cylinders of different diameters is a common configuration in offshore design, including e.g. clamped risers, piggy-back solutions and piping systems. Current design practice is not clearly formulated in relevant design codes such as DNVGL-RP-F105 and DNVGL-RP-C205. Conservatively, it is often assumed that flow acceleration due to a neighboring cylinder causes up to a doubling of the incoming flow velocity depending on incidence angle and difference in cylinder diameter. Doubling the incoming particle velocity compared to free stream would decrease the required support distance by around 30%. Particularly in conditions with significant diameter disparity, flow acceleration effects due to the larger cylinder of the two can thus cause strict requirements to support distances on the smaller. Designers may want to reduce the number of support points due to cost, maintenance requirements and rigid structure availability, particularly in piping system arrangements. Recent research on piggy-back pipeline vortex induced vibrations have complemented traditional understanding of such configurations, allowing for improved design guidelines. In the present study, a detailed meta study of available laboratory and numerical work is performed, and the resulting findings are translated into simple design guidelines for piggy-back and other staggered arrangements. The present paper provides clear recommendations for improvements to the relevant recommended practices. Highlights: Piggy-back pipeline systems are common for risers, offshore pipelines, piping systems and manifolds. Spacing between pipes in piggy-back systems causes unnecessary conservatism in design codes. The present study provides recommendations for improvement to current offshore design codes for piggy-back piping design.