Flexible Pipes: Slug Flow and Structure Coupling

Abstract

In this thesis, a computational scheme for coupled internal multiphase flow and structural dynamic of flexible pipes is presented and tested. The model consists of a 1D simulator based on a slug tracking model, and a 3D structural dynamic simulator based on lumped mass formulation. Internal fluids weight, friction and centrifugal force were integrated in the structural analysis as well as environmental forces such pipe-soil contact and external drag, among others.

The models were coupled using a domain-decomposition method where the structure and the flow are computed independently using separated solvers and data is transmitted between them in order to include coupling effects. The resulting software is a stand-alone application capable of predicting the two-way coupling of multiphase flow in flexible pipes.

The coupled model has been tested by comparing simulations with experimental data from small scale setups. Different scenarios were studied such as floating pipe, submerged lazy wave shaped pipe, pigging of a submerged pipe, garden hose instability and a blowout case. The developed model was able to reproduce qualitatively or quantitatively key features observed during the experimental tests.