Vibration analysis of the subsea dynamic umbilical under parametric excitations

As a key component of the submarine production, the subsea dynamic umbilical is a multilayer composite structure which connects the offshore facilities with the submarine production control system. However, due to complex dynamics characteristics of the umbilical, its non-linear dynamic response in the transverse direction may cause a parametric vibration at a dangerously high level which may lead to disastrous accidents, such as environmental pollution, property losses and even fatalities. Therefore, the parametric instability analysis of the umbilical is deserved to be studied further. In this paper, based on the deduced governing motion equation and the Hill's infinite determinant, the parametric instability behavior of the umbilical is investigated. Numerical simulations for the lateral response of the umbilical are performed under several typical cases with consideration of the coupling of modes. Besides, the influences of the umbilical damping variation on the system parameter stability regions are emphatically analyzed. The simulation results demonstrate that enhancing the damping of system can effectively reduce unstable regions. Furthermore, several useful guidelines are also proposed to optimize the design of the umbilical.