Nonlinear Vibrations of an Extensible Flexible Marine Riser Carrying a Pulsatile Flow

Abstract

The influence of transported fluid on static and dynamic behaviors of marine risers is investigated. The internal flow of the transported fluid could have a constant, a linear, or a wave velocity. The riser pipe may possibly experience the conditions of high extensibility, flexibility, and large displacements. Accordingly, the mathematical riser models should be governed by the large strain formulations of extensible flexible pipes transporting fluid. Nonlinear hydrodynamic dampings due to ocean wave–pipe interactions implicate the high degree of nonlinearity in the riser vibrations, for which numerical solutions are determined by the state–space–finite-element method. It is revealed that the impulsive acceleration of internal flow could seriously relocate the vibrational equilibrium positions of the riser pipe. The fluctuation of the pulsatile flow relatively introduces the expansion of amplitudes and the reduction of frequencies of the riser vibrations. The pulsatile frequencies of the internal flow in wave aspect could reform the oscillation behavior of the conveyor pipe.