Falling liquid films are widely utilized due to their excellent heat and mass transfer performance combined with short residence times. Previous studies have employed two-dimensional (2D) CFD simulations to investigate the hydrodynamics of falling films on vertical tube surfaces. However, two-dimensional models fail to represent circumferential velocity gradients, whose presence is critical because they may induce tangential velocity components. This study examines the hydrodynamics of palm-based vegetable oil falling film flow over the outer surface of a vertical tube across different flow rates. The analysis particularly addresses tangential velocity distributions through three-dimensional (3D) transient isothermal CFD simulations with a Volume of Fluid (VOF) multiphase model. The results show that for flow rates of 15 LPM (Re≈25) or higher, the film remains smooth over a longer distance before undergoing a sudden transition to three-dimensional wavy flow in the lower section. In contrast, at lower flow rates, wave formation begins much earlier, approximately 0.3–0.5 m downstream of the inlet. The axial velocity profiles in the upper section exhibit semi-parabolic, symmetric shapes, while at the lower sections, both 1 LPM and 18 LPM cases exhibit asymmetric distributions, indicating circumferential velocity gradients. Tangential velocity is most pronounced in the lower sections, reaching maximum values of 0.159 m/s, 0.081 m/s, 0.088 m/s, and 0.0802 m/s for flow rates of 1, 3, 9, and 18 LPM, respectively. © 2026 Elsevier Inc.