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There are many experimental studies dedicated to determining the effect of the proximity of a plane boundary on the vortex-induced vibration (VIV) of submarine pipeline spans, but they all only concerned the first mode VIV motion of the pipe. In this paper, a pipe model, 16 mm in diameter, 2.6 m in length and with a mass ratio (mass/displaced mass) of 4.30, was tested in a current tank. The reduced velocity was in the range of 0-16.7 and gap ratios at the pipe ends were 4.0, 6.0 and 8.0. The response of the model was measured using optical fiber strain gauges. Results of response amplitude and frequency were presented and the transition from the first dominant mode to the second one was shown. In the tests, it was found that the response amplitude experienced a continuous transition between the two modes, but the dramatic increase in the response frequency appeared with the shift in dominant mode from the first mode to the second one as the flow velocity increased. As the gap ratio decreased, the shift in the dominant mode took place at a higher reduced velocity.
There are many experimental studies dedicated to determining the effect of the proximity of a plane boundary on the vortex-induced vibration (VIV) of submarine pipeline spans, but they all only concerned about first mode VIV motion of the pipe. In this paper, a pipe model, 16 mm in diameter, 2.6 m in length and with a mass ratio (mass / displaced mass) of 4.30, was tested in a current tank. The reduced velocity was in the range of 0-16.7 and gap ratios at the pipe The responses of the model was measured using optical fiber strain gauges. Results of response amplitude and frequency were presented and the transition from the first dominant mode to the second one. In the tests, it was found that the response amplitude experienced a continuous transition between the two modes, but the dramatic increase in the response frequency with the shift in dominant mode from the first mode to the second one as the flow rate increased. reased, the shift in the dominant mode took place at a higher reduced velocity.