Droplet Bag Formation in Turbulent Airflows

Novel numerical simulations investigating the deformation of liquid droplets in turbulent airflows are presented, which are of significance for many multiphase processes in scientific and engineering applications. We impose turbulence fluctuations on a uniform mean airflow at the inlet, and insert the droplet when a statistically stationary state is reached for the air-phase turbulence. Common dynamic and morphological evolution patterns are observed for all droplet-turbulence simulations, including considerable droplet centre-of-mass acceleration, tilting of the bag structure and formation of small-scale corrugations. We examine the ambient flow fields around the droplet and discuss physical mechanisms giving rise to different types of bag morphologies, with the aid of diagnostic metrics formerly developed for particle-turbulence interaction studies in the absence of a mean flow. Lastly, we discuss the implications of air-phase turbulence intermittency on the later bag film breakup process.