Structure - Slug Flow Coupling: Small Scale Experiments with Submerged Flexible Pipes

Abstract

Multiphase flows include several flow regimes that exist with different conditions. The time varying forces in flexible pipes conveying two-phase flows results in very dynamic structural behavior. These varying forces contribute to fatigue stresses which have a major effect on a riser life time. Studying the dynamic response of flexible pipes conveying two-phase flows can reveal crucial information regarding induced vibrations and oscillations in risers. These information can be utilized in understanding operational hazards with flexible risers in oil and gas industry. An experimental investigation of flexible pipes is carried out in the lab. A small scale experimental loop was designed for testing structural behavior of flexible pipes conveying air and water two-phase flow. Experiments were recorded and video processing techniques were utilized for analyzing structural response. The amplitudes of structural oscillations were measured for several cases at different pipe lengths and flow superficial velocities. Two main geometries were investigated, a cantilever pipe in vertical and horizontal direction and a geometry representing a riser collapse inspired by a real accident from oil and gas industry. The experimental results were compared to numerical simulations from a structural dynamic analysis code. The work produced in this thesis was presented for publishing as a part of scientific paper shown in Appendix (A).