Numerical Simulation and Validation of Slug Flow Dynamics Using The Standard K-Epsilon Model

This study presents a Computational Fluid Dynamics (CFD) analysis of vertical air–water slug flow using the Volume of Fluid (VOF) method and the standard k-epsilon turbulence model while employing a structured hexahedral mesh to ensure high-quality discretization. The geometry consists of a vertical pipe with a 52.5 mm diameter and a total length of 8 m. A structured hexahedral mesh was employed, and mesh independence was confirmed using three mesh sizes: 100555, 246330, and 479457 cells. Transient void fraction data and Power Spectral Density (PSD) analyses were performed, revealing that the finest mesh accurately captured both the time-domain slug structure and dominant frequency (~3.2 Hz) of the flow. The model was validated against published experimental data, with the best case showing a void fraction deviation of only ~8.7%. Results confirm that the VOF method combined with the k-epsilon model reliably captures the primary and secondary oscillations of slug flow, offering a validated, practical tool for industrial two-phase flow prediction.