Time-Domain Simulation of Riser VIV in Sheared Current

Abstract

Riser vortex-induced vibrations (VIV) have attracted significant attentions in recent years in offshore oil and gas industry. There is an increasing interest in using computational fluid dynamics (CFD) approach for deepwater riser VIV time-domain simulations. Our previous study has demonstrated that the long riser (L/D = 1400) VIV response in uniform current can be predicted with reasonable accuracy by time domain simulations with Chimera over-set data grid technique. This paper is to further that study and investigate the riser VIV in sheared current profiles. The riser studied in this paper is a long marine riser with constant tension distribution. Its prototype has an outer diameter (OD) of 0.027m and a mass ratio of 1.6. The fluid domain is discretised using approximately one million elements. A linearly sheared current is imposed in perpendicular to the riser, and the flow field is calculated using an unsteady Reynolds-Averaged Navier-Stokes (RANS) numerical method in conjunction with a Chimera domain decomposition approach with overset grids. The critical parameters including riser VIV root-mean-square (rms) a/D, vorticity, drag and lift coefficients are processed, and compared to those of uniform current and experimental data. The simulation results show that the riser VIV under sheared current behaves differently from uniform current. It is also shown that the presented CFD approach provides reasonable results and is suitable for long riser VIV evaluation in deepwater and complex current conditions.