EAR-PF: TURBULENT AIR ENTRAINMENT IN PYROCLASTIC DENSITY CURRENTS

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。本杰明·安德鲁斯博士被授予NSF地球科学博士后奖学金，以在伯克利大学开发研究和教育的综合计划。他的调查将集中在火山碎屑密度流，一个共同的和潜在的破坏性危险的火山爆发。 当火山爆发时，浮石、火山灰和气体的混合物比大气密度更大，可以以每小时100英里以上的速度沿着火山侧翼向下传播。 火山碎屑异重流中空气卷吸过程的定量知识对于理解和预测异重流行为至关重要。 虽然以前的研究已经检查了密度流，大多数这些实验室实验已被不适当地缩放应用于火山碎屑流或忽略了夹带流体的膨胀，许多计算模型已处理夹带作为一个恒定速率的过程。 本研究探讨湍流空气夹带在火山碎屑密度流的定量相关夹带和湍流的流动温度，喷发速率，颗粒大小和密度的目标。 在拟议的实验中，密度流包括热，在空气中的细粒颗粒将被引导通过一个充满空气的坦克，以模拟火山碎屑密度流运输。 在模拟过程中，罐中的仪器将监测流动结构、速度场和温度，并在模拟后测量所产生的存款厚度。 从这些数据中，安德鲁斯博士将描述空气夹带如何随时间、空间和颗粒特性而变化，以及它如何受局部湍流速度场的控制。 通过改变喷发速率和颗粒大小，密度和温度，实验将模拟火山碎屑密度流，并捕获夹带和膨胀的动力学。 这项研究对火山灾害的预测和缓解有着重大的好处，因为火山碎屑流可以摧毁其路径上的任何东西，火山灰羽流可以对航空构成重大威胁。 拟议的实验将是第一个定量研究的火山碎屑密度流内的空气卷吸和密度演化。 这项研究的结果将改善对火山碎屑密度流的位置、移动速度以及火山灰羽流上升高度的预测。 本科生将通过这项研究介绍到现场和实验室工作。 安德鲁斯博士将在拉森火山国家公园领导为期一周的本科野外课程，目的是教授野外火山学方法，并促进学生对火山碎屑沉积物的研究。 两名学生将通过伯克利大学的本科研究学徒计划直接参与火山碎屑密度流实验。 这些学生将研究夹带和流动行为的具体控制，然后将他们的研究项目发展为荣誉论文。

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.