Three-phase flow induced vibration characteristics for mining riser in deep-sea natural gas hydrate extraction

During the lifting process of deep-sea natural gas hydrate, the mining riser is susceptible to complex fatigue failure due to the combined effects of internal gas–liquid–solid three-phase flow, external ocean loads, and the large aspect ratio of itself. The gas–liquid–solid three-phase flow induced vibration (FIV) model for deep-sea hydrate extraction riser is established using finite element method and Hamiltonian principle. The simulation experimental device for nonlinear vibration of mining riser under internal and external flow excitation is developed and conducted a simulation experiment for gas–liquid–solid three-phase FIV of vertical pipes. The experimental test results are compared with the theoretical model calculation results to verify the correctness of the model. Using frequency domain and time domain analysis methods, the influences of external environmental parameters and multiphase flow parameters on the nonlinear FIV response of the riser are explored. The results showed that the vibration amplitude in the cross-flow (CF) direction of the riser is larger, and the change in internal flow parameters had a more significant impact on the CF vibration. The longitudinal vibration of the riser is composed of low-frequency high-amplitude vibration caused by gravity and platform heave, and high-frequency low-amplitude vibration induced by internal and external flow field loads. The increase in shear flow velocity will significantly increase the displacement of the riser along in-line flow direction, thereby suppressing CF vibration. The research results can be widely applied to the vibration problems caused by gas liquid solid three-phase flow in the energy collection process, which has important research significance and significant engineering value for improving the safety of operation columns.