Two-Way Fluid-Structure Interaction in a Flexible Pipe Conveying Gas-Liquid Slug Flow

Some cases of marine operations with pipes conveying multiphase flows can show structural movements depending on the internal flow dynamics. A floating pipe conveying two-phase gas-liquid flow is an example where a two-way coupling between the internal flow and the structural dynamics is needed. The objectives of the paper is to demonstrate a method for dynamic coupling of slug flow and pipe structure simulations by comparing numerical results with small scale experiments on flexible pipes. Two small scale experimental setups for two-phase slug flow in floating and submerged flexible pipes were prepared. The experiments were designed to give unstable flows. The air and water flow rates were measured and the pipe movements were video recorded. A new coupled model was established, in which a structural dynamic model has been implemented into a dynamic slug tracking model. Forces due to the internal flow such as fluid weight, friction and centrifugal force were included in the structural model, as well as external fluid drag and soil contact forces among others. The implemented model can reproduce fairly well the dynamic forces due to the internal flow as well as predict the associated pipe deformations and movements. Slug flow can potentially have an impact on pipe dynamics, in particular for cases where severe slugging can occur.