Disentangling Inertial Particle-Turbulence Mechanisms in the Absence of Gravity

火星上的火山灰运输、大气污染物和沙尘暴是携带颗粒的湍流(即高速流动)的少有例子。颗粒湍流输运由于其重要性和无处不在的特点，得到了广泛的研究。然而，仍然存在许多问题，限制了对这一现象的全面理解和建模能力。例如，目前尚不清楚小的球形颗粒在湍流环境中的沉降速度是比在静止(无流动)流体中更慢、更快还是相同。预测模型的发展依赖于产生精确的实验和数值数据，以准确地描述起作用的微妙的多尺度物理机制。该奖项旨在探索低重力条件下的粒子-湍流相互作用，目的是分离重力和惯性力，以更好地了解和实施它们在惯性粒子模型中的影响。更广泛的影响是为参与的学生和研究人员以及更广泛的公众量身定做的。利用位于PSU的独特设施Dryden Drop Tower，该奖项将对微重力条件下单个和集体粒子与湍流的相互作用进行系统的实验探索。微重力实验将提供探索纯粹归因于惯性的影响的机会。将通过考虑具有不同响应时间的颗粒(可通过改变材料和/或颗粒大小来调节)来系统地调查这些颗粒。该研究的目的包括：1)分离颗粒惯性和重力对有限尺寸和点状单个颗粒的颗粒-湍流相互作用的影响；2)评估在微重力作用下湍流中有限尺寸颗粒和点-颗粒的聚集和/或颗粒-颗粒相互作用所促进的联合效应；以及3)发展重力中有限尺寸颗粒的拉格朗日随机模型。更广泛的影响活动包括研究生、研究生和本科生的STEM培训和国际研究访问。俄勒冈州科学与工业博物馆科学传播培训计划将为研究生和博士后研究人员提供一个与更广泛的公众有效交流他们的科学的极好机会。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.