Size distributions and dynamic characteristics of droplets in gas–liquid annular flow

Droplet breakup and coalescence models are integrated into the previously developed thin liquid film method (TLFM) to investigate in detail the evolution of the droplet population and its dynamic behavior. Validation against experimental data demonstrates that the improved TLFM accurately predicts macroscopic parameters and effectively captures the microscopic dynamics of gas–liquid annular flow. During the evolution of droplet population, atomization and deposition dominate droplet generation and extinction, respectively. Breakup and coalescence primarily influence the variation in the number of small droplets. Due to a sorting and screening mechanism within the gas core, large droplets move at lower velocities near its periphery, while small droplets travel faster near the center. The droplet fluctuation velocities in the axial and transverse directions follow Gaussian distributions with a mean of zero, with the axial fluctuation velocity exhibiting significantly greater variance than those in the transverse directions.