An experimental study of oscillations induced by two-phase slug flows of water and air on a flexible catenary shaped submerged pipe

Abstract

In this paper, an apparatus is described to conduct an experimental study on a small-scale laboratory model of a submerged suspended flexible pipe, in a catenary layout, oscillating in response to the intermittent loads caused by the internal two-phase slug flow of water and air.The slug flows were obtained by injecting water and air into the pipe with sixteen combinations of flow rates. The flexible pipe was set in a catenary configuration inside a water tank with a depth of 2 m. The oscillations of the pipe were recorded by cameras registering the position of fifty-five targets attached to points along the body of the pipe, providing a time-history of the movement of the pipe.The flow rates of the liquid and gas phases, the speed of the slugs and their frequencies were measured, leading to an evaluation of slugs‘ lengths and hold-ups, and to the assessment of the fluid loads applied to the pipe due to gravity and curvature. The video images of the pipe movement were processed to provide the amplitudes and frequencies of oscillation of the pipe.The methodology developed in this work may be used for various geometries and flow regimes, and it could be employed to the validation of physical models and numerical simulations of pipes’ oscillations excited by fluid interactions through the comparison between the experimental results and the computer calculations.The application of the experimental results to offshore pipes in operations, carrying oil and gas from petroleum reservoirs submarine wells to floating facilities in the ocean, may be obtained by the proper scaling up in conjunction with computer simulations.