New types of current profile criteria are described that are designed to take into account the vertical coherence of deepwater currents in offshore engineering. Reasoning is given why traditional types of current profile criteria can be inappropriate for deepwater locations. The paper describes current profile occurrence criteria that consist of a discrete number of characteristic profiles, each of which has an associated percentage frequency of occurrence. These criteria are appropriate for riser fatigue calculations, including Vortex Induced Vibration (VIV) modelling, and operability assessments. Use of these criteria can reduce the level of overconservatism associated with the traditional criteria, potentially leading to significant cost savings. Two possible methods of deriving these criteria are described, one of which uses Empirical Orthogonal Function (EOF) analysis to simplify the vertical structure of current profiles. The relative merits of each analysis technique are assessed.

Issue Section:
Technical Papers
Keywords:
petroleum industry, mechanical engineering, ocean waves, flexible structures, fatigue, vibrations
Topics:
Currents, Design, Electroosmosis, Fatigue, Pipeline risers, Risers (Casting), Vortex-induced vibration, Ocean engineering, Modeling, Time series, Petroleum industry
1.
Jeans, G., and Feld, G., 2001, “A Method for Deriving Extreme Current Profiles to Support Design of Deep Water Drilling Risers,” Proceedings of the 20th International Conference on Offshore Mechanics and Arctic Engineering, OMAE01/OFT-1181, Rio de Janeiro, Brazil.
2.
Forristall, G. Z., and Cooper, K. C., 1997, “Design Profiles Using Empirical Orthogonal Function (EOF) and Inverse FORM Methods,” Proceedings of the 29th Annual Offshore Technology Conference, OTC 8267, Houston, TX.
Copyright © 2003
 by ASME
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