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.

火山碎屑密度流是由爆炸性火山喷发产生的固体颗粒和气体的热而快速移动的混合物。它们在陆地表面传播很远的距离，最远可达几十公里，造成巨大的危害，并改变景观。大气中扩散的火山羽流将爆炸喷发的粒子传输到更远的地方，数百公里。在这些爆炸性喷发中，颗粒团的形成是一个关键的过程，因为颗粒团会影响颗粒的浓度，从而影响气流的速度和行进的距离。然而，聚类仍然是一个知之甚少的过程。通过量化对聚类的控制，可以约束地球物理湍流气体-颗粒混合物中的颗粒浓度，这对理解流动动力学至关重要。火山碎屑密度流是所有火山灾害中最具破坏性的，部分原因是它们在地表以极快的速度传播。火山羽流对社区和航空造成了巨大的危害，因为它们可以将火山灰分散到很远的地方。结果将提供新的见解颗粒浓度，因此流速，动压，沉降率和危害。这些实验将在火山学领域之外具有相关性，因为在自然和工业过程（如雪崩和化学反应器）中，充满颗粒的湍流流都很常见。这项研究工作为学生提供了多学科的培训机会，并促进了学术和政府组织之间的合作。实验室实验将用于确定对聚集的控制和对火山颗粒流的影响。火山颗粒流中的颗粒浓度控制着流密度，从而控制着流速、行进距离和危险性。在稀释的湍流扩散羽流和火山碎屑密度流中，颗粒浓度由沉降控制，而沉降又由颗粒与周围气体以及彼此之间的相互作用控制。在稀流中，控制颗粒沉降和浓度的一个关键过程是颗粒的聚集，在其中形成了高浓度带，但这一过程尚未得到很好的描述。实验装置将被设计成允许进行大量的实验，从而探索参数和过程之间的关系，包括粒径和粒径分布的作用。将开发和测试一种新的声学传感方法来测量颗粒浓度。实验结果将用于解释来自历史喷发的沉积物，以确定何时以及如何聚集影响喷发动力学和喷发颗粒的扩散。对聚类的定量描述将提高将野外沉积物与这些洋流动力学联系起来的能力。实验结果可用于改进火山碎屑灾害模型。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.