In-Line Motion of Subsea Pipeline Span Models Experiencing Vortex-Shedding

Abstract

Subsea pipeline spans, when experiencing bottom ocean currents, are prone to vortex-induced vibration (VIV). Experiments and computational fluid dynamics (CFD) are conducted to evaluate the effects of the pipe stiffness on its first mode in-line VIV motion, primarily in the reduced velocity range from approximately 1.0 to 4.0. Experimental results also indicated that there was obliqueness in motion trajectories, which could have impacts on VIV design of the free spans. The main findings of this investigation are presented in this paper.

The formula for motion magnitudes of cylinders experiencing vortex-shedding

“…Further experiments on first mode in-line VIV motions have been conducted by the authors and their colleagues at Shell. A portion of the data, which correlate well with our theory, have been published at a recent technical conference (Lee et al, 2009). More definitive tests are being planned to reinforce our conclusions.…”

Experimental investigation of vortex-induced vibrations of long free spans near seabed

“…Recently, Sreide et al [13] and Nielsen et al [14] investigated the cable effect on VIV and multi-mode vibration of long free spanning pipelines. Lee et al [15] investigated the pipe stiffness on its first mode in-line VIV motion.…”

Reduction of the loads on a cylinder undergoing harmonic in-line motion

“…Some studies show that the induced in-line motions are one order of magnitude smaller than the crossflow motions, 20,21 others emphasize the importance of the induced in-line motions even though they are small, and others show that they can be comparable to the cross-flow mo-tions, depending on the cylinder density 22,23 or its nondimensional natural frequency. 24 Tanida et al 12 carried out experiments on a one-degreeof-freedom circular cylinder oscillating harmonically in the in-line direction at the Reynolds numbers Re= 80 and 4000. The first part of their study considered a single circular cylinder oscillating in a uniform stream, whereas the second part was dedicated to the case of a circular cylinder oscillating in the wake of another cylinder ͑i.e., tandem arrangement͒.…”