Droplet entrainment is a crucial process for annular flow in terms of heat and mass transfer. Disturbance wave is believed to be a fundamental phenomenon which is closely related to entrainment. A 3D numerical simulation on disturbance waves and entrainment is carried out by using volume of fluid (VOF) method where no periodic boundary condition is used. Since VOF tracks the interface implicitly, a systematic method is developed for post-processing, with which disturbance waves. ripples, base film, and entrainment process are clearly visualized, and the stochastic and chaotic nature of two-phase flow is confirmed. Surfacewise distributions are generated for main wave parameters, and the streamwise developments of such quantities are shown to be consistent with experimental observations. Predictions for main wave parameters are in reasonable agreement with the experiment and empirical correlations. Current work shows the capability and promising application of investigating disturbance waves and entrainment with VOF method. (C) 2018 Elsevier Ltd. All rights reserved.