Particle clustering in dilute pyroclastic density currents and plumes

稀火山碎屑密度流和羽流中的颗粒聚集

• 批准号: 2042173
• 负责人: Michael Manga
• 金额: $ 32.42万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-11-01 至 2024-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2042173&HistoricalAwards=false
• 关键词: Particle; clustering; dilute; pyroclastic; density

Pyroclastic density currents are hot and fast-moving mixtures of solid particles and gas produced by explosive volcanic eruptions. They travel great distances over the land surface, up to many tens of kilometers, pose substantial hazards, and alter landscapes. Spreading volcanic plumes in the atmosphere transport particles from explosive eruptions to even greater distances, many hundreds of kilometers. The formation of clusters of particles in these explosive eruptions is a critical process because clusters affect the concentration of particles and thus the speed of the flows and the distance they travel. Clustering, however, remains a poorly understood process. By quantifying the controls on clustering, it is possible to constrain particle concentration in geophysical turbulent gas-particle mixtures which is essential for understanding flow dynamics. Pyroclastic density currents are the most devastating of all volcanic hazards, in part because they propagate over the ground surface and with great speed. Volcanic plumes present substantial hazards to communities and aviation as they can disperse ash over great distances. Results will provide new insight into particle concentration and hence flow speed, dynamic pressure, sedimentation rates, and hazard. The experiments will have relevance outside the field of volcanology because turbulent particle-laden flows are common in both nature and industrial processes such as snow avalanches and chemical reactors. The research effort provides multidisciplinary training opportunities for students and enables collaboration between academic and government organizations.Laboratory experiments will be used to identify the controls on clustering and the implications for volcanic particle-laden flows. The concentration of particles in volcanic particle-laden flows controls the flow density and hence flow velocity, distance travelled, and hazard. In dilute, turbulent spreading plumes and pyroclastic density currents, particle concentration is controlled by sedimentation which in turn is controlled by how particles interact with the surrounding gas and with each other. A critical, but not well characterized, process controlling particle sedimentation and concentration in dilute flows is the clustering of particles, in which zones of higher concentration develop. The experimental setup will be designed to permit a large number of experiments and hence to explore relationships between parameters and processes including the role of particle size and size distribution. A novel acoustic sensing method will be developed and tested to measure particle concentration. The experimental results will be used to interpret the deposits from historical eruptions to identify when and how clustering affects eruption dynamics and the dispersal of erupted particles. A quantitative description of clustering will improve the ability to relate field deposits to the dynamics of these currents. The experimental results can be used to improve models for pyroclastic hazards.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.

火山碎屑密度电流是由爆炸性火山喷发产生的固体颗粒和气体的热和快速移动混合物。他们在陆地表面上走很远，最多数十公里，构成了重大危害，并改变了景观。大气中的火山羽流从爆炸性喷发到更大的距离，数百公里。这些爆炸性喷发中颗粒簇的形成是一个关键过程，因为簇会影响颗粒的浓度，因此会影响流量的速度及其行进距离。但是，聚类仍然是一个鲜为人知的过程。通过量化聚类的控件，可以在地球物理湍流气体粒子混合物中限制颗粒浓度，这对于理解流动动力学至关重要。火山碎屑密度电流是所有火山危害中最具破坏性的，部分原因是它们在地面上传播并以极高的速度传播。火山羽质对社区和航空充满了巨大危害，因为它们可以在很大的距离内散布灰烬。结果将为粒子浓度以及流速，动态压力，沉积速率和危害提供新的见解。该实验将在火山学领域之外具有相关性，因为含湍流的颗粒流在自然和工业过程中都是常见的，例如雪雪崩和化学反应堆。研究工作为学生提供了多学科培训机会，并可以在学术组织和政府组织之间进行合作。实验室实验将用于确定群集的控制及其对火山粒子含量流量的影响。火山粒子流动中颗粒的浓度控制流动密度，因此流速，行进距离和危险。在稀释，湍流的扩散羽流和火山碎屑密度电流中，颗粒浓度受沉积控制，而沉积又受颗粒与周围气体相互作用以及彼此之间的相互作用的控制。稀释流中控制粒子沉积和浓度的过程的关键但没有很好的表征是颗粒的聚类，其中较高浓度的区域发展。 实验设置将旨在允许大量实验，因此探索参数和过程之间的关系，包括粒径和大小分布的作用。将开发并测试一种新型的声学传感方法，以测量颗粒浓度。实验结果将用于解释历史喷发中的沉积物，以确定聚类何时以及如何影响喷发动力学和喷发颗粒的分散。聚类的定量描述将提高将现场沉积物与这些电流的动力学联系起来的能力。实验结果可用于改善火山碎屑危害的模型。该奖项反映了NSF的法定任务，并使用基金会的知识分子优点和更广泛的影响审查标准，被认为值得通过评估。

项目成果

Electric Discharge in Erupting Mud

喷发泥浆中的放电

• DOI: 10.1029/2022gl100852
• 发表时间: 2022
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Springsklee, C.;Manga, M.;Scheu, B.;Cimarelli, C.;Dingwell, D. B.
• 通讯作者: Dingwell, D. B.

The Influence of Grain Size Distribution on Laboratory‐Generated Volcanic Lightning

粒度分布对实验室火山闪电的影响

• DOI: 10.1029/2022jb024390
• 发表时间: 2022
• 期刊: Journal of Geophysical Research: Solid Earth
• 作者: Springsklee, C.;Scheu, B.;Manga, M.;Cigala, V.;Cimarelli, C.;Dingwell, D. B.
• 通讯作者: Dingwell, D. B.