EAR-PF: TURBULENT AIR ENTRAINMENT IN PYROCLASTIC DENSITY CURRENTS

EAR-PF：火山碎屑密度流中的湍流空气夹带

• 批准号: 0847366
• 负责人: Benjamin Andrews
• 金额: $ 16万
• 依托单位: Andrews Benjamin J
• 依托单位国家: 美国
• 项目类别: Fellowship Award
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-01 至 2011-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0847366&HistoricalAwards=false
• 关键词: EAR; PF; TURBULENT; AIR; ENTRAINMENT

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Dr. Benjamin Andrews is awarded an NSF Earth Sciences Postdoctoral Fellowship to develop an integrated program of research and education at Berkley University. His investigation will focus on pyroclastic density currents, a common and potentially devastating hazard of volcanic eruptions. When erupted, mixtures of pumice, ash, and gas are denser than the atmosphere, and can travel down the flanks of volcanoes at speeds in excess of 100 miles per hour. Quantitative knowledge of air entrainment processes in pyroclastic density currents is critical to understanding and predicting current behaviors. Although previous studies have examined density currents, most of those laboratory experiments have been improperly scaled for application to pyroclastic flows or ignored expansion of entrained fluid, and many computational models have treated entrainment as a constant rate process. This research examines turbulent air entrainment in pyroclastic density currents with the goals of quantitatively relating entrainment and turbulence to flow temperature, eruption rate, and particle size and density. In the proposed experiments, density currents comprising hot, fine-grained particles in air will be directed through an air filled tank to simulate pyroclastic density current transport. Instruments in the tank will monitor the flow structure, velocity field, and temperature during simulations, and measure the resulting deposit thicknesses after simulations. From those data, Dr. Andrews will describe how air entrainment varies with time, space, and particle properties, and how it is controlled by the local, turbulent velocity field. By varying eruption rates and particle sizes, densities, and temperatures the experiments will model pyroclastic density currents and capture the dynamics of entrainment and expansion. This research has significant benefits for volcanic hazard prediction and mitigation, as pyroclastic flows can destroy anything in their paths, and ash plumes can pose a significant threat to aviation. The proposed experiments will be the first quantitative study of air entrainment and density evolution within pyroclastic density currents. The results of this research will improve predictions of where pyroclastic density currents are emplaced, how fast they travel, and how high ash plumes ascend. Undergraduate students will be introduced to both field and laboratory work through this research. Dr. Andrews will lead a week-long undergraduate field course at Lassen Volcanic National Park with the goals of teaching field volcanology methods and facilitating student research on pyroclastic deposits. Two students will be directly involved in the pyroclastic density current experiments through Berkeley's Undergraduate Research Apprentice Program. Those students will study specific controls on entrainment and flow behavior, and then develop their research projects into honors theses.

该奖项是根据2009年《美国回收与再投资法》（公共法第111-5）.DR资助的。本杰明·安德鲁斯（Benjamin Andrews）被授予NSF地球科学博士后奖学金，以在伯克利大学（Berkley University）制定研究和教育计划。他的调查将集中于火山碎屑密度电流，这是火山喷发的常见且可能破坏的危害。 当爆发时，浮石，灰烬和气体的混合物比大气更稠密，并且可以以每小时超过100英里的速度沿着火山的侧面行驶。 在理解和预测当前行为的位置对空气碎屑密度电流中空气夹带过程的定量知识至关重要。 尽管以前的研究已经检查了密度电流，但大多数实验室实验都被不当缩放，以应用于火山碎屑流或忽略夹带流体的扩张，许多计算模型都将夹带视为恒定速率过程。 这项研究检查了湍流的空气夹带中的火山碎屑密度电流，其目标是将夹带和湍流与流动温度，喷发速率以及粒径和密度相关的目标。 在拟议的实验中，包括空气中的热颗粒颗粒的密度电流将通过空气填充罐进行指向，以模拟火山碎屑密度电流的传输。 储罐中的仪器将在模拟过程中监视流量结构，速度场和温度，并测量模拟后所得的沉积物厚度。 从这些数据中，安德鲁斯博士将描述空气夹带如何随时间，空间和粒子特性而变化，以及如何由局部湍流速度场控制。 通过改变喷发速率和粒径，密度和温度，实验将模拟火山碎屑密度电流并捕获夹带和膨胀的动力学。 这项研究对火山危害预测和缓解具有重大好处，因为火山碎屑流可以破坏其路径上的任何东西，而灰羽可能会对航空构成重大威胁。 提出的实验将是对火山碎屑密度电流内空气夹带和密度演化的首次定量研究。 这项研究的结果将改善对火山碎屑密度电流的位置的预测，它们的行进速度以及灰羽的上升程度。 通过这项研究，将向本科生介绍现场和实验室工作。 安德鲁斯博士将在拉森火山公园（Lassen Volcanic National Park）领导一个为期一周的本科野外课程，其目标是教授现场火山学方法，并促进学生对火山碎屑矿床的研究。 两名学生将通过伯克利的本科研究学徒计划直接参与火山碎屑密度当前的实验。 这些学生将研究有关夹带和流动行为的特定控制，然后将其研究项目发展为荣誉。