Dynamic analysis of large strain deformation of flexible pipes conveying two-phase fluids Part I: linear vibration analysis

Abstract

This work presents dynamic response of large strain deformed subsea flowlines and jumpers conveying two-phase fluid. Large strain deformation theory is used to analyze the effects of high pressure-high temperature two-phase flow on critical velocity in flexible pipes. Starting with natural frequency of simply supported flexible pipes, corresponding nonlinear transport equations are derived and subsequently expanded using the method of multiple scales perturbation. Frequency response obtained from the linearized leading order equations established that buckling and flutter-like instabilities attend critical velocities. Furthermore, the buckling velocity of transverse pipe decreases with increasing temperature, pressure or tension. Clearly, the transverse buckling velocity is higher in large strain deformation model compared with small strain model. In addition; whereas the critical velocity in the longitudinal direction is independent of temperature, pressure and tension for small strain models; these variables determine the path to failure in large strain deformed pipes.

Keywords: Large strain deformation, small strain deformation, simply supported pipe