Assessment of segment-level vortex-induced vibration response of a deepwater drilling riser using high-fidelity modelling

Abstract

Based on the literature reviewed, few studies have analysed the vortex-induced vibration response of a low-aspect-ratio computational fluid dynamics riser model, and the use of dynamic properties derived from a global riser model appears to be largely unexplored. A realistic deepwater drilling riser with buoyancy modules is modelled in OrcaFlex, an extensively-used offshore industry software, using a wake oscillator model. Separately, a short segment of this riser is modelled in CFD using Star-CCM+ in a two-way fluid-structure interaction setup. The segment’s physical, environmental, and dynamic properties are derived from a selected segment in the full-scale riser model in OrcaFlex. The dynamic current-induced VIV response of the segment is compared between OrcaFlex and Star-CCM+ to determine whether the responses are comparable. It is seen that both models display similar dominant response, dominant lift frequencies, and lock-in behaviour across a range of current velocity cases. The RMS cross-flow displacement and lift coefficient present a similar trend across cases, except in cases with significant changes in top tension, in which the RMS values diverge significantly between the full-scale riser model in OrcaFlex and the riser segment model in Star-CCM+. These results indicate that high-fidelity modelling of short riser segments can reproduce the VIV response metrics of a global wake oscillator riser model under various conditions, except in cases where the top tension is changed significantly and complicates global riser dynamics.