Parametric Resonance of the Free Hanging Marine Risers in Ultra-Deep Water Depths

The study is focused in the parametric instability of the deep-sea risers due to the platform heave motions. As offshore hydrocarbon resources exploration and exploitation moving to much deeper waters, risers play more important roles than before, and face with many technological challenges. The riser resonance can produce disastrous results, such as environment pollution and economical loss. In this work, firstly, the governing motion equation of the marine riser is formulated. Then the stability behavior of the risers with and without nonlinear damping is investigated by employing the Floquet theory. During the numerical solution of the governing equation, the coupling between the modes was considered. Finally, special attention has been paid to the effect of damping for the parametric unstable region changes. The results show that damping can effectively reduce unstable regions. Several useful suggestions are proposed for the design of deep-sea riser structures