Fatigue due to vortex-induced vibrations (VIV) is one of the major uncertainties today in the design of slender offshore structures, such as risers, pipelines, umbilicals, tendons and mooring lines, required for oil and gas production in deep waters. The absence of reliable tools for quantitative analyses of this phenomenon is a technological barrier, which is being faced by several research groups. This paper presents valuable VIV results achieved by the author, using “wake oscillator” and “vortex tracking” models, when researching for his M. Sc. dissertation. Time domain analyses were performed using a commercial software. First results describe the response of the evaluated models for two degrees-of-freedom rigid cylinders by tracing lateral displacement versus flow velocity curves. These curves are plotted over others previously published in recognized recommended practices, articles and theses. Afterwards, VIV analyses results for a steel catenary 10-inch diameter riser in three-dimensional current profiles were compared to measured values. The considered riser, installed in 910m water depth offshore Brazil, is possibly the only monitored SCR with no VIV suppression devices in the world today. The results were considered satisfactory, despite some discrepancies: the model which appeared to be one of the most attractive for the rigid cylinder case, failed to predict VIV in the SCR under an irregular current profile, for example. Vortex tracking models presented excessive low frequency response in the SCR analyses. Authors believe that this response is unrealistic, and these frequencies can be dissipated by using a more adequate damping model than that employed by the utilized program.

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