Fragmentation of droplets is a fundamental process, with implications across multiple phenomena and applications. Threshold of fragmentation, refers to the minimum external impulse (flow velocity) required for the droplet to fragment. The parameters relevant to this process are ambient and drop densities and viscosities, surface tension of the liquid constituting the drop, droplet diameter, and ambient flow velocity. The resulting non-dimensional parameters are, density ratio (r), ambient and drop Ohnesorge numbers (Oho, Ohd), and the Weber number (Wecr) associated with threshold of fragmentation. Previous research on the topic have focused on water-air analogous droplet-ambient systems, thus relatively limited in the range of r and Ohd. We quantify the effect of of all the parameters relevant in this process across a wider parameter space through extensive highly-resolved volume of fluid (VoF) based multiphase flow simulations. For the VoF simulations we use the opensource incompressible Navier-Stokes solver Basilisk. We find that the non-dimensional parameters r, Oho, and Ohd have substantial effect on the competition between pressure field around the droplet, the shear stresses on its upstream surface, and the droplet’s response to these forces, which ultimately dictates its internal fluid flow. This competition manifests in threshold fragmentation morphologies (e.g. forward bag, bag plume) beyond the backward bag observed during previous experiments. We derive a non-dimensional number (Cbreakup) that predicts threshold of droplet fragmentation through bag break, across the non-dimensional parameter space, better than the critical Weber number (Wecr). Finally, we systematically quantify the effect initial shape has on the threshold of fragmentation, and achieve a reasonably complete understanding of the threshold fragmentation of Newtonian droplets.
About the Speaker
Som got is graduate degrees in Civil Engineering from University of Illinois Urbana-Champaign (UIUC) in 2017. After that he got his post-doctoral training in scientific computing and mathematics at UIUC and CUNY, respectively. Since 2019, he is an Assistant Professor in the Mechanical and Aerospace Engineering department at Utah State University. He was selected for the Bayfield Visiting Researcher award in Fluid Dynamics by the Energy and Environment Institute (EEI) at the University of Hull, UK in 2019; and for NNSA’s Argonne Training Program on Extreme-Scale Computing (ATPESC) in 2017. He is interested in studying complex flow and transport phenomena in the natural and the built environment using high-fidelity computational fluid dynamic (CFD). Some of the phenomena he is currently interested in are salinity-driven gravity currents and exchange flows, dynamics of moving bodies in stratified environments, dispersal of aerosols and particles in different environments, and dynamics of fragmenting droplets.
Host is Professor Leonardo Chamorro