ABSTRACT

Engineering analyses of vortex-induced vibration (VIV) of steel catenary risers (SCR) are presently performed either by experimental tests in model scale or by semi-empirical numerical prediction tools which are depending on experimental data to obtain force coefficients for their hydrodynamic force calculations. This paper presents a new alternative for VIV predictions of SCRs by use of computational fluid dynamics (CFD) techniques. The CFD analyses allows the analysts to perform numerical predictions without any input coefficients and tuning parameters from experimental test. This ability makes the present numerical method a useful validation tool for VIV analyses made by semi-empirical programs, since it approaches the physics of the phenomenon in a very different way. The present numerical method is validated against experimental tests and other numerical tests, and the predicted riser response is found to be in good agreement.

INTRODUCTION

Over the last years the steel catenary riser (SCR) concept has become increasingly popular as transportation line for hydrocarbons up and down between the seafloor and the surface vessel. The extension of the pipeline into a riser is a very cost effective design, but at the same time it introduces new challenges for the engineer. One of the new challenges is the prediction of vortex-induced vibrations (VIV). When a risers is exposed to a sheared current there will always be induced some kind of vortex-induced vibration. In order to be able to predict the fatigue damage caused by these transverse vibrations it is crucial to know which modes that will dominate the response of the risers and what amplitudes they are responding at. For a SCR this prediction is different from a vertical riser since a) the flow is not perpendicular to the riser

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