Numerical study of geometry-induced slug flow and energy dissipation in pipelines at low superficial velocities

초록

Gas-liquid slug flow in inclined pipelines is strongly affected by pipe inclination and gravity-driven backflow. This study investigates the initiation, spatiotemporal evolution, and energy dissipation of geometry-induced slug flow at low superficial velocities (U SG =0.2 m/s, U SL =0.1 m/s) using a validated three-dimensional SAS-VOF framework combined with Lagrangian slug tracking. As the inclination angle increases from 5 degrees to 20 degrees , the incipient slug frequency and liquid-level fluctuation amplitude near the bend increase overall, whereas the slug duty cycle shows a non-monotonic variation, indicating a transition toward shorter-duration and higher-intensity approximately periodic slugging. Inclination mainly regulates upstream slug initiation and early development, while the slug-passage frequencies in the mid-to-downstream sections remain comparatively similar. Energybudget analysis shows that turbulent kinetic energy dissipation is dominant across all stages and inclinations, while stronger backflow and shear-layer thickening at higher inclinations promote tail- and wall-dominated dissipation, accelerate slug attenuation, and shift slug extinction farther downstream. These results provide a unified physical picture of geometry-induced slug initiation, evolution, attenuation, and energy dissipation in inclined pipelines at low superficial velocities, and offer a mechanistic basis for pressure-gradient prediction, inclination optimization, and anti-slugging control.

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