Pulsation characteristics and nonlinear instability of slurry transport in a vibrating deep-sea mining riser

Deep-sea mining risers are prone to vortex-induced vibrations (VIV) in complex seas, yet the pulsation characteristics of coarse particle-liquid flow remain unclear. This study integrates VIV analysis and fluid-particle coupling simulation to investigate how two-degree-of-freedom (2-DOF) riser vibration influences particle spontaneous spiraling, aggregation, and concentration pulsation. Results show nonlinear evolution patterns involving collisions, clustering, spiral flows, and localized jets over time and space. Vibration frequency dictates pulsation modes, with concentration fluctuations dominated by twice the transverse frequency (fy) alongside 1–2 Hz disturbances. Proposed dimensionless vibration intensity parameter (fyAy∗) and concentration fluctuation index (Acv∗) to quantify particle pulsation strength, a critical threshold fyAy∗ >0.97 triggers severe fluctuations, rapidly destabilizing transport with clogging risks. Established a cubic polynomial model linking fyAy∗ and Acv∗, revealed the nonlinear instability mechanism linking vibration parameters to pulsating slurry transportation characteristics, providing theoretical guidance for optimizing operational control to ensure riser safety and efficiency.