Severe slug flow-induced nonlinear dynamic behavior of a flexible catenary riser

An experiment is conducted in a small-scale air–water test loop to investigate the severe slug flow-induced vibration of a flexible catenary riser of aspect ratio (the riser length over its internal diameter) 200. The vibration displacement of the catenary riser as well as the internal flow features is simultaneously captured by high-speed cameras. Three stages are observed during a cycle of severe slugging in the riser, including the slug formation, gas blowout, and transition stages. The spatial-temporal dynamic behavior of the flexible catenary riser is closely related to the stage of severe slug flow, liquid slug length, and liquid inventory along the riser, presenting a resonance between the oscillation and the fluid pressure fluctuation.