Vibrations and fatigue damage of a flexible catenary riser excited by the internal stochastic fluid density

Flexible catenary risers have been extensively used in deep seas to transport oil and natural gas. Oil and natural gas may be simultaneously produced in seabed wells, and their flow rates may change with time. Consequently, the total fluid density of oil and natural gas combinations may change stochastically. In this study, the stochastic changes in the total fluid density are simulated using a mathematical model that satisfies Gaussian distributions in time and space. Subsequently, the vibrations and fatigue damage of a long flexible catenary riser excited by an internal stochastic fluid density are parametrically studied. When the internal stochastic fluid density fluctuates with larger mathematical expectations, more frequency components, or larger amplitudes, the vibrations of the riser become more intense, and the fatigue damage increases.