The project is for NORTHNET, NORdic Thermal Hydraulic NETwork. The objective of the project is the CFD modelling of annular two-phase flow with dryout capability. In annular two-phase flow, the droplets are dispersed in the gas phase, with a thin liquid film attached to the wall. Current project will establish a three-field model to investigate the liquid film behavior, which is important to predict the dryout occurrence. Specifically the Lagrangian Particle Tracking will be employed in the droplet calculation, which needs a lot of CPU times.