Collaborative Research: Measurement of Particle Aggregation in Laboratory-scale Flows for Improved Models of Volcanic Ash Fallout and Entrainment

火山喷发产生火山灰云，这对航空旅行和基础设施都是危险的。在紧急情况下，预报员使用数值模型预测火山灰的运输，但他们通常假设颗粒单独落下，以简化分析。在现实中，细小的火山灰颗粒结合在一起形成更大的团簇，加快了它们的下落速度。这使得火山灰可以从云层中掉落出来。聚集率取决于许多因素，包括水分、电荷和湍流。关于这些性质的影响，特别是对湍流的影响，现有的数据有限，尽管在一些喷发中，聚集影响了高达95%的尘埃。因此，需要更好的聚集过程的实验测量，以及包括这一现象的更先进的模型。这项研究的目的是通过高精度的实验和升级的模型来改进对火山灾害的预测。灰烬聚集将在两种不同的相关流动条件下进行研究：均匀湍流和高速射流。高分辨率光学技术将被用来研究流动、湍流和颗粒聚集。结果将被整合到最先进的分析模型中，包括一些用于预测的模型。此外，这项研究将通过俄勒冈州科学与工业博物馆(OMSI)的一系列实践演示向更广泛的公众展示。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 eruptions produce clouds of ash, which are hazardous to air travel and infrastructure. In emergencies, forecasters predict the transport of ash using numerical models, but they typically assume that particles fall as individuals to simplify the analysis. In reality, fine ash particles combine together into larger clusters, accelerating their rate of fall. This allows the ash to fall out of the cloud. Rates of aggregation depend on many factors, including moisture, electric charge, and turbulence. There is limited existing data on the effects of these properties, particularly for turbulent flows, even though aggregation affects up to 95% of fallout in some eruptions. Hence, there is a need for better experimental measurements of aggregation processes, along with more advanced models that include the phenomenon.This study aims to improve forecasting of volcanic hazards through both high-accuracy experiments and upgraded models. Ash aggregation will be examined in two different, relevant flow conditions: homogeneous turbulence and high-speed jets. High-resolution optical techniques will be used to study the flow, turbulence, and particle clustering. The results will be integrated into state-of-the-art analytical models, including some used for forecasting. Further, this research will be presented to the broader public through a series of hands-on demonstrations at the Oregon Museum of Science and Industry (OMSI).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.