TWO-WAY COUPLED FLUID-STRUCTURE INTERACTION OF GAS-LIQUID SLUG FLOW IN A FLEXIBLE RISER: SMALL-SCALE EXPERIMENTS AND SIMULATIONS

Flexible risers might be subjected to large pressure and density fluctuations when transporting multiphase mixtures as different flow patterns may take place. Those fluctuations might induce large forces on the structure, which in turn may modify the global geometry of the riser. In this paper, results from one-way and two-way coupled fluid-structure simulations are compared against small-scale experiments of a flexible lazy wave riser transporting gas-liquid flow. Different gas flow rates are tested in order to obtain a range of slug frequencies. Predicted values of pipeline pressure, top tension, and riser displacement are compared with experimental data. The numerical prediction of the coupled behavior shows fairly good agreement with the experiments, having bias from 5% to 25% in slug frequency.