Simulation of a Taylor bubble in counter-current flow using an interface-capturing methodIsmail, Bayan (Avtor) Tiselj, Iztok (Mentor) Vihavainen, Juhani (Komentor) Taylor bubblecounter-current flowCLSVOFANSYS Fluentcapillary wavesA two-dimensional axisymmetric numerical model was developed in ANSYS Fluent to investigate the hydrodynamics of a Taylor bubble in a vertical counter-current water flow. The liquid-gas interface was captured using the Coupled Level Set and Volume of Fluid (CLSVOF) method. We evaluated the influence of spatial resolution on interface reconstruction, falling liquid film dynamics, internal gas circulation within the bubble, and the model’s capability to predict subtle capillary waves observed in experimental investigations at the THELMA laboratory. The model successfully reproduced the primary hydrodynamic features, including the rounded bubble nose, the falling liquid film, the primary vortex inside the bubble, and the key recirculation zones in the liquid wake behind the bubble tail. The results demonstrate that accurately resolving these phenomena requires a computational grid where the cell aspect ratio (axial-to-radial length) does not exceed 2:1. The primary limitations of the axisymmetric formulation arise in resolving secondary flow structures. The counter-rotating secondary vortex in the bubble tail was notably underpredicted compared to experimental measurements. Furthermore, the accuracy of the axisymmetric model is inherently constrained in the liquid wake; while it captures the dominant vortices and predicts their unsteady nature, it cannot reproduce the intrinsically three-dimensional wake dynamics. This limitation is critical, as both 3D reference simulations and experimental data confirm the three-dimensional characteristics of these regions. Simulations on a very fine grid demonstrated that the axisymmetric model can capture interfacial capillary waves; however, their spatial locations were mispredicted due to discrepancies in the internal velocity field. Moreover, the ultra-fine grid triggered an unphysical breakup along the symmetry axis at the bubble tail and generated a spurious vortex near the bubble nose along the axis, highlighting numerical artifacts of the implemented CLSVOF formulation in ANSYS Fluent.20262026-10-15 08:15:54Magistrsko delo/naloga189769VisID: 168610COBISS_ID: 301898243sl