Vortex-induced vibration (VIV) of tubings and pipings is of practical interest to oil industry. When VIV occurs to pipes, it induces alternative stress that results in the reduction of pipe fatigue life. The objective of the paper is to investigate VIVs in tubings or pipings with non-linear geometry.

This paper categorizes the occurrence of cross-flow and in-line VIVs of pipes based on flow directions and pipe orientations. The complexity of VIV for pipes with non-linear geometry, as compared to straight pipes, is demonstrated. We devised a scheme to incorporate power balance principal into finite element method (FEM) to analyze the cross-flow VIV for tubings and pipings with non-linear geometry. A main feature in our approach is the modeling of lifting forces (excitations) and hydrodynamic damping in FEM. At present stage, most commercial VIV packages mainly deal with risers or pipelines that are either straight or with large radii, and they only considered curvature component associated with the cross-flow direction of the flow (d.o.f.), that is the direction perpendicular to the flow velocity. Stress calculation near the bends and elbows of the pipes, is not accurate. Our approaches, on the other hand, consider the responses in all 6 d.o.f of each element along the pipes and it is a truly three dimensional vibration analysis. Our approach provides an alternative to complement the existing method for solving the VIV problem for tubings and pipings with highly non-linear geometry.

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