The dispersion of polydisperse non-spherical droplets in homogeneous isotropic turbulence

Predicting the motion of droplets in turbulence is essential in spray combustion. To model the spray in numerical simulations, the Lagrangian particle tracking method is widely used in research, which represents the spray as a discrete collection of spherical particles. One limitation of this approach is that it neglects the importance of droplet deformation. Past work from several authors has demonstrated the importance of droplet shape on droplet vaporization, combustion, and drag. Recently, we investigated non-spherical droplet dispersion in homogeneous isotropic turbulence (HIT), and found that non-spherical droplets have higher dispersion than spherical droplets for the same parameters [Lin and Palmore, ASME IMECE 2024]. However, that work only focuses on droplets of a particular size and does not investigate why this dispersion occurs. Real sprays consist of droplets in various sizes, shapes, and flow conditions. It is unknown how the dispersion and accumulation are related to these facts. Hence, this work investigates droplet-laden HIT flow for polydisperse non-spherical droplets utilizing an in-house code developed for multiphase flows. For each droplet diameter class, we directly extract relevant information such as average droplet deformation (via aspect ratio), droplet dispersion (via droplet velocity autocorrelation), and the preferential concentration (via Q-criterion value). This information is used gain insight into why dispersion is higher for non-spherical droplets.