Cross Flow Response of Drilling Riser

A drilling riser is a vertical pipe used for drilling operation in offshore industry. The fatigue life assessment of drilling riser due to the vortex-induced vibration (VIV) in both cross-flow/in-line directions vibration is a challenging design issue. Many studies have typically ignored the negligible nonlinearity and applied linear structural mass-spring oscillator to model the cross-flow VIV. In this study, a Duffing equation including cubic nonlinear term is considered to capture the riser response due to current force. In case of considerable nonlinear restoring part in Duffing equation, the traditional perturbation methods are no longer valid but the Homotopy perturbation method (HPM) is applicable usually. In this paper, an approximate method was developed to obtain Duffing solution and the results were validated via HPM solutions