Near-contact motion and coalescence of inertial droplets in turbulence: simulations, laboratory experiments and field measurements

Cornell University, Ithaca NY

Investigators

Abstract

PI: Collins, Lance Proposal Number: 1605195 A comprehensive research approach, involving high fidelity computations, experiments in a laboratory and field experiments is proposed to understand and predict the behavior of drops suspended in turbulent flows. This problem is very important for the behavior of clouds in the atmosphere. In addition to atmospheric applications, there are many other application areas with engineering interest, where this work can have an impact, including diesel engines, sprays, atomization, and powder manufacturing and inhalation drug therapy. Despite more than a half-century of research, there remains considerable uncertainty on how turbulence enhances the coalescence rate of suspended droplets. This study addresses that uncertainty through the direct measurement of droplet collision/coalescence rates in direct numerical simulations (DNS), experiments and in field measurements over a wide range of conditions. The focus of the study will be on the direct measurement of coalescence rates of droplets driven by turbulence. This has application to a wide range of multiphase flows, but the application of primary importance to this proposal is the processing of clouds in the atmosphere. Under certain conditions, clouds evolve faster than microphysical models can predict. It is believed that atmospheric turbulence could explain the acceleration of cloud formation. This study will bring together a synergistic combination of three scientific tools for analyzing natural turbulent flow phenomena: DNS; laboratory experiments; and field measurements. The overarching goal is to generate definitive coalescence data from high-resolution DNS and state-of-the-art laboratory and field experiments under conditions of near parametric similarity. This investigation will include the first experimental measurements of the coalescence rate for inertial droplets in a turbulent flow field, both in the laboratory and in natural conditions. Only with this collective effort can this be achieved - any one or two of these techniques alone will not sufficient. In addition to the engineering impacts of the proposed work, the proposed activities include educational and outreach activities that are targeted towards encouraging underrepresented minorities into the academy.