Session: 7.3 - Gas-Liquid flows

Paper Number: 157758

157758 - Liquid Phase Stabilization in Developing Gravity-Driven Slug Flows: Insights From PIV-PLIF Analysis 

Abstract: 

Liquid slugs interspersed between successive Taylor bubbles in two-phase slug flows are critical domains for spatial evolution, stabilization, and overall flow development in vertical pipes. The characteristics of velocity fields and the turbulent structures within liquid slugs fundamentally dictate phase interactions, the dynamic stability of Taylor bubbles, and key transport phenomena such as heat and mass transfer. These effects are especially pronounced under gravity-driven conditions, where the dynamics of liquid phase are governed by gravitational forces. Despite their pivotal role in the performance of two-phase systems, the stabilization mechanisms of liquid-phase flow and the modulating influence of gas density under such conditions remain inadequately characterized. In this study, particle image velocimetry-planar laser induced fluorescence (PIV-PLIF) technique was employed to investigate the liquid phase stabilization mechanism in the developing region of gravity-driven slug flows in a vertical pipe. Experiments were conducted for both air-water and CO₂-water systems under identical conditions to examine the impact of gas density on stabilization mechanisms along the pipe axis (at Z/D = 10, 30, 40, and 60) of a 25.4 mm diameter pipe. A comprehensive analysis was conducted for velocity vector fields, streamline contours, axial and radial velocity distributions, vorticity fields, and turbulence intensity. The stabilization process was systematically characterized by tracking the evolution of these parameters from the wake of a leading Taylor bubble to the emergence of a trailing Taylor bubble. Furthermore, temporal variations in velocity components, turbulence intensity, and Reynolds shear stress were examined at three radial positions (r/R = -0.5, 0, and 0.5) within the mid-region of the liquid slugs across the selected spatial locations. The results revealed a highly turbulent wake region trailing Taylor bubbles, characterized by large-scale vortical structures. As the liquid-phase flow develops within the liquid slug near the upcoming Taylor bubble, the radial velocity components attenuate, turbulence intensity and vorticity diminish, and streamline patterns converge toward linearity, signifying progressive stabilization. Temporal analyses also show a significant decline in velocity fluctuations, turbulence intensity, and shear stress along the axial distance. Notably, lower gas density induces elevated turbulence levels, facilitating a more rapid restoration of velocity profiles due to greater momentum diffusion, although the complete relaxation of turbulent structures requires a significantly extended axial distance.

Presenting Author: Shahriyar Ghazanfari Holagh University of Guelph

Presenting Author Biography: Shahriyar Ghazanfari Holagh is a Ph.D. candidate in Mechanical Engineering at the University of Guelph, focusing on multiphase transport phenomena in gas-liquid systems. He earned his bachelor's degree in Mechanical Engineering from the University of Tabriz in 2015 and completed his master's at Iran University of Science and Technology in 2018, where he studied the dynamics of bubbles in flow boiling. From 2018 to 2021, his research expanded to include the thermo-economic and environmental analysis of clean energy systems at the system-level design. In addition to his academic work, Shahriyar has nearly four years of industry experience primarily in the oil and gas sector, where he applied his knowledge to practical engineering challenges. He has co-authored over 40 journal articles and conference papers, which have collectively been cited more than 1,400 times.