Mode switching and standing-travelling waves in slug flow-induced vibration of catenary riser

An experiment in a small-scale air-water test loop is performed to investigate the flow-induced vibration behaviors of flexible catenary riser conveying slug flow over wide range gas-to-liquid rate ratios from 1.0 4.5. The clamped-clamped model has an inner diameter 4 mm and aspect ratio with length about 360. non-intrusive high-speed cameras are employed simultaneously capture dynamics internal unsteady characteristics. space-time varying features presented discussed terms response amplitudes, frequencies, modal components, associated forces. Slug properties including translational velocities, lengths, fluctuation frequencies pressure changes reported. When increasing rates, experimental results highlight how variation frequency contributes mode-switching phenomenon time. This switching dominant first-mode second-mode leads transition standing wave travelling response. amplitudes amplified by increased velocity length, entailing momentum gravitational forces, as increased. Consequently, higher modes participate into exhibiting strong multi-mode competition.