Experimental Study On VIV of a Flexible Pipe With Soil Support

Although there are many studies dedicated to the problem of vortexinduced vibration (VIV) of submarine pipeline spans, VIV experiments considering the effect of soil at the span shoulders are very rare. To investigate the effect of the soil on the VIV of submarine pipeline spans, a pipe model, 16mm in diameter, 2.6m in length and with mass ratios (mass/displaced mass) of 4.30 was tested in a current tank. The pipe was laid horizontally on the soil, and had a free span in length of 2.138m. The tests in still water and in a current were conducted. The flow velocity was in the range of 0-0.57m/s. The response of the model was measured using fiber optic strain gauges. The frequency responses and the time-domain tracing of cross-flow strain responses are presented and analyzed. The experimental results exhibit several valuable features: the natural frequency of the model has a fuzzy property, but the response frequency in a current has not and increases with the increase of flow velocity; the strain amplitude for the sandy soil case is larger than that for the clay soil case.