EXPERIMENTAL STUDY ON VIV OF SPAN OF SUBSEA PIPELINE AND IMPROVED MODEL OF LIFT FORCE

Tests for the vortex-induced vibration (VIV) of the models of subsea pipeline with internal flow have been carried out. The results show that if there is a big difference between vortex shedding frequency and natural frequency of cylinder, the lift force acting on oscillating cylinder is a stochastic force with narrow bandwidth and if there is a little difference between them, the response of models is periodic oscillation. It is also revealed that the frequency of vortex shedding on oscillating cylinder will change with not only the velocity of fluid and the diameter of the cylinder, but also natural frequency of the cylinder.