EAGER: Collaborative Research: Towards Elucidating the Transport Mechanisms of Fine Volcanic Ash

这一试点研究项目通过确定使用新型仪器测定大气中细火山灰迁移特性的可行性，解决减少火山灰影响的一般性问题。众所周知，火山灰对航空、基础设施、农业以及人类和动物健康构成危害。随着航空在过去50年中作为全球旅行和运输的关键组成部分的出现，了解火山灰在大气中悬浮多久以及它被运输多远的重要性变得更加重要。空气中的灰尘会磨损飞机的外部，进入现代喷气发动机，并在覆盖内部零件时熔化，从而造成损坏和故障。例如，2010年冰岛埃亚菲亚德拉火山爆发是航空史上最具破坏性的事件，给航空业和全球经济造成了数十亿美元的损失。这其中大部分是不必要的，更好地了解细灰的运输可以减少未来的损失。然而，目前对火山灰运输的理解只能解释一般的空气运动，但不能完全解决有多少或多长时间的火山灰留在大气中，以及有多少福尔斯下降，因为它的顺风。为了解决这一问题，该项目通过在一个专门用于模拟缓慢大气流的科学风洞中进行灰流实验，重点研究灰与大气之间的相互作用。细灰在大气中停留的时间取决于它的终端速度（在重力的影响下），但目前的公式是基于相对较大和准球形的雨滴，使它们不适用于细灰，这是较小的（60 #956;m），非球形，并可能具有复杂的表面和内部结构。因此，目前无法准确预测火山灰云中构成航空和其他危险的细颗粒的清除率。为了提供观测数据来解决这个问题，UNH和Lehigh大学的新设施正在用于这项试点研究，以设计测量具有各种尺寸和形状的细灰的终端速度的实验。新的流动物理设施（FPF）是世界上最大的低湍流慢流风洞，专为学术研究而设计。现在，它第一次被用来分析细灰颗粒在层流和湍流条件下的空气动力学特性。利哈伊光学技术中心包括最先进的SEM（立体声和单声道），提供用于表征风洞（FPF）中使用的细灰形状和尺寸的方法。这一试点研究的结果将为随后的两种类型的火山灰颗粒（简单和复合）的终端速度的经验公式，最近出现了从以前的NSF支持的火山灰形态研究的阶段。这将导致对控制大气中火山灰空气动力学的基本物理学的理解（高度范围从150到1000 mb）。

This pilot study project addresses the general problem of reducing volcanic ash impact by determining the viability of using novel instrumentation to determine the transport properties of fine volcanic ash in the atmosphere. Volcanic ash is known to present hazards to aviation, infrastructure, agriculture, and human and animal health. With the emergence of aviation in the last 50 years as a key component of global travel and transport, the importance of understanding how long ash is suspended in the atmosphere, and how far it is transported has taken on greater importance. Airborne ash abrades the exteriors of aircraft, enters modern jet engines and melts while coating the interior parts thus causing damage and failure. For example, the 2010 Eyjafjallajökull eruption in Iceland was the most disruptive event in aviation history, with billions of dollars of losses to the aviation industry and global economy. Much of this was unnecessary and better knowledge of the transport of fine ash could minimize such losses in the future. However, present understanding of ash transportation can only account for general air movements, but cannot fully address how much or how long ash remains in the atmosphere, and how much falls out as it travels downwind. To address this lacking, this project focuses on the interaction between ash and atmospheric air by performing experiments of ash flow in a special scientific wind tunnel designed to simulate slow atmospheric currents. The time fine ash stays in the atmosphere depends on its terminal velocity (under the influence of gravity), but current formulations for this are based on raindrops that are relatively large and quasi-spherical, rendering them inapplicable to fine ash, which is smaller (60 μm), non-spherical, and can have complex surface and internal structure. As a result, it is not presently possible to accurately predict the removal rates of fine particles from the volcanic ash clouds that pose aviation and other hazards. To provide observational data to resolve this problem, the novel facilities at UNH and Lehigh University are being used in this pilot study to design experiments for measuring terminal velocities of fine ash with a range of sizes and shapes. The new Flow Physics Facility (FPF) at UNH is the largest low turbulence slow flow wind tunnel in the world designed for academic research. Now, for the first time, it is being used to analyze the aerodynamic properties of fine ash particles in both laminar and turbulent conditions. The Center for Optical Technologies at Lehigh includes state of the art SEMs (stereo and mono) that provide the means for characterizing the shapes and sizes of fine ash to be used in the wind tunnel (FPF). The results of this pilot study will set the stage for subsequent empirical formulations for terminal velocities of the two types of ash particles (simple and compound) that have recently emerged from a previous NSF-supported study of volcanic ash morphology. This will lead to an understanding of the fundamental physics that controls the aerodynamics of volcanic ash in the atmosphere (altitude range from 150 to 1000 mb).