ISS: Uncovering transient dynamics and equilibrium states of particle aggregates in fluids

花粉沉积，古生态，与水质有关的藻类生长，塑料污染，以及风暴在水体中输送的海盐，都是流体-气体界面中的颗粒的第一个例子。经过一段时间后，当颗粒沉积时，动力学发生变化，所涉及的过程可以成为流体饱和的颗粒介质的过程。这一提议特别令人感兴趣的是外部振动携带颗粒的流体，用于分离不同颗粒大小和材料，或使颗粒材料流态化，从而改善其流动特性，如颗粒传输和强化传热。该项目的目的是探索和量化在失重情况下界面和整体流体中的颗粒的瞬时动力学，并导致改进的聚集模型。这项拟议的研究代表着朝着理解大体积流体和气体/流体界面中颗粒聚集的重要一步，在这些界面上，时间尺度相对较大，而对地球的影响相对较小。这有助于在地球上不断发生的粒子传输过程的总体平衡中改进这些传输现象的模型。这个项目的结构是为了对参与的学生和更广泛的公众产生更广泛的影响。将对非受迫和受迫界面和整体流体中粒子的聚集动力学进行系统的实验探索。关于这些力在没有重力的情况下如何影响粒子聚集率的新知识和理解将被创造出来。为了阐明液气界面和无重力作用的流体中的聚集现象，建议在国际空间站上进行一系列实验。波特兰州立大学将进行落塔实验，以缩小与研究相关的参数，以便与Zin Technologies合作，在国际空间站上进行相对较长的失重实验。该项目有三个主要目标：1.)实验研究了毛细管漂浮对颗粒毛细浸泡的影响，研究了流体饱和颗粒介质在零g非受迫和外谐强迫作用下的长期颗粒动力学。量化在强制和非强制零重力环境中凝聚/聚集、颗粒-流体和/或颗粒-颗粒相互作用所促进的集体效应；开发真实地表示无重力对惯性粒子的影响的团聚模型。更广泛的影响活动协调如下：1.)研究生和本科生一级的STEM培训。)利用波特兰州立大学的现有课程以及b.)提供与合作公司Zin Technologies和NASA宇航员对接的经验；以及2.)俄勒冈州科学与工业博物馆的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重要的机会，让他们与更广泛的公众有效地交流他们的科学。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。

Pollen deposition, paleoecology, algae growth linked to water quality, plastic pollution, and storm transported sea salt in bodies of water are at first examples of particles in fluid-gas interfaces. After a certain time, when and if particles sediment, the dynamics change and the involved processes can become those of a fluid-saturated granular media. Of particular interest for this proposal are externally vibrated particle-laden fluids that are used to segregate different particle sizes and materials, or to fluidize the granular material and thus improve its flow characteristics such as particulate transport and enhanced heat transfer. This project aims at exploring and quantifying transient dynamics of particles in an interface and bulk fluid in the absence of gravity and leading to improved aggregation models. The proposed research represents an important step forward towards the understanding of aggregation of particles in a bulk fluid and gas/fluid interface where times scales are relatively large and the effects are relatively small on Earth. This can aid the improvement of models of these transport phenomena in the overall balance of particle transport processes constantly occurring on Earth. This project is structured such to have a broader impact on the participating students and the broader public.A systematic experimental exploration of aggregation dynamics of particles in an unforced and forced interface and bulk fluid will be pursued. New knowledge and understanding about how these forces affect particle agglomeration rates in the absence of gravity will be created. To elucidate aggregation at liquid-gas interfaces and in a bulk fluid free from gravitational effects, a set of experiments to be performed on the International Space Station is proposed. Drop tower experiments at Portland State University will be performed to narrow parameters relevant to the study to inform relatively long experiments on the International Space Station under zero gravity in collaboration with ZIN Technologies. This project has three main objectives: 1.) Experimentally disentangle the effects on particles of capillary immersion from capillary floating and study the long-term particle dynamics of fluid saturated granular media through a zero-g environment unforced and subjected to an external harmonic forcing; 2.) Quantify collective effects promoted by agglomeration/clustering, particle-fluid and/or particle-particle interactions in a forced and unforced zero-g environment; and 3.) Develop agglomeration models truly representing effects in the absence of gravity on inertial particles. Broader impact activities are coordinated as: 1.) STEM training at the graduate and undergraduate level by a.) Leveraging existing programs at Portland State University as well as b.) Providing experiences to interface with partner company ZIN Technologies and NASA astronauts; and 2.) Oregon Museum of Science and Industry science communication training program will provide an important opportunity for the 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.