Disentangling Inertial Particle-Turbulence Mechanisms in the Absence of Gravity

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Volcanic ash transport, atmospheric pollutants, and dust storms on planet Mars are few examples of turbulent flows (i.e., flows with high velocity) laden with particles. Because of its importance and ubiquitousness, turbulent transport of particles has been widely investigated. However, numerous questions remain which limit a comprehensive understanding of this phenomenon and modeling capacities. For instance, it is still unclear whether small spherical particles in a turbulent environment settle slower, faster, or at the same speed than in a quiescent (no flow) fluid. Development of predictive models relies on generating refined experimental and numerical data to accurately characterize the subtle multi-scale physical mechanisms at play. This award aims at exploring particle-turbulence interactions in low-gravity conditions with the goal of separating gravitational and inertial forces to better understand and implement their influence in inertial particle models. Broader impacts are tailored to the participating students and researchers as well as the broader public.Utilizing the Dryden Drop Tower, a unique facility located at PSU, this award will perform a systematic experimental exploration of the single and collective particle interactions with turbulence in microgravity conditions. Microgravity experiments will provide the opportunity to explore the effects purely attributable to inertia. These will be systematically surveyed by considering particles with various response times (tunable by change in material and/or particle size). The objectives of the proposed investigation include: 1) dissociating the effects of particle inertia and gravity on particle-turbulence interactions for both finite-size and punctual single particles, 2) evaluating joint effects promoted by clustering and/or particle-particle interactions of finite size and point-particles in a turbulent flow under microgravity, and 3) developing Lagrangian stochastic models for finite size particles in gravity. Broader impact activities include STEM training at the post-graduate, graduate, and undergraduate level and international research visits. The Oregon Museum of Science and Industry science communication training program will provide a great opportunity for graduate student and post-doctoral researcher to effectively communicate their science with the broader public.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.