Study on vortex-induced vibration of non-uniform flow riser based on fluid-solid coupling

Because marine riser is under complex ocean current environment, fatigue damage tends to happen due to vortex-induced vibration, which has a strong impact on the safety issue of deepwater drilling and completion. Vortex-induced vibration (VLV) induced by non-uniform flow loads on deep water riser coupling in complex Marine environments has been studied relatively infrequently at home and abroad. Therefore, CFD-FEM bidirectional fluid-solid coupling method was used to establish a vortex-induced vibration model of 1500m deep water riser and non-uniform flow in waves and currents. Vortex-induced vibration and mechanical behavior of riser in transverse and flow direction were studied from riser motion characteristics, tension factors and other aspects. The results show that the danger zone of vortex-induced vibration of riser under the action of non-uniform flow occurs in one third of the upper end. Increasing the tension can increase the riser's natural frequency and reduce the amplitude of vortex-induced vibration, but may aggravate the riser's high stress and low cycle fatigue damage.