Laboratory measurements of vortex-induced vibrations of a vertical tension riser in a stepped current

Chaplin, J.R., Bearman, P.W., Huera Huarte, F.J. and Pattenden, R.J. (2005) Laboratory measurements of vortex-induced vibrations of a vertical tension riser in a stepped current. [in special issue: Fluid-Structure and Flow-Acoustic Interactions involving Bluff Bodies] Journal of Fluids and Structures, 21 (1), 3-24. (doi:10.1016/j.jfluidstructs.2005.04.010).

Record type: Article

Abstract

This paper presents an initial analysis of measurements of the vortex-induced vibrations of a model vertical tension riser in a stepped current. The riser, 28mm in diameter, 13.12m long and with a mass ratio (mass/displaced mass) of 3.0, was tested in conditions in which the lower 45% of it was exposed to a uniform current at speeds up to 1m/s, while the upper part was in still water. Its response in in-line and transverse directions was inferred from measurements of bending strains at 32 points along its length. Transverse vibrations were observed at modes up to the 8th with individual modal amplitudes up to about 80% of the riser’s diameter. However, in most cases the response included significant contributions from several modes, all at the same frequency. Some evidence was found of lock-in.

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