Collaborative Research: ABR: Multiscale Dynamics in Explosive Volcanic Eruptions

合作研究：ABR：火山喷发的多尺度动力学

• 批准号: 1144198
• 负责人: Michael Manga
• 金额: $ 18万
• 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: 2012
• 资助国家: 美国
• 起止时间: 2012-07-01 至 2016-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1144198&HistoricalAwards=false
• 关键词: Collaborative; Research; ABR; Multiscale; Dynamics

Explosive volcanic eruptions are some of the most energetic granular flows on the planet, the largest of which can have global impact. Even the more common, smaller, events encompass scales of several kilometers. However, mass and energy transfer in these flows are fundamentally controlled by processes at much smaller spatial and temporal scales, where individual particles interact with each other, with gas, or with the surface over which the flows travel. Our past work on steam explosions, ash production, and heat transfer have shown that subgrid models developed from experiments can be coupled to large-scale numerical simulations. More importantly, these subgrid relations are critical for predicting the dynamics reflected in volcanic deposits and in ash dispersal patterns; models that neglect subgrid processes can fail to produce the energy transfer manifest in volcanic deposits by several orders of magnitude. Our ability to predict large-scale behavior of volcanic flows can ultimately be limited by our understanding of very small-scale, or microphysical, processes. In this study, the investigators will examine a suite of particle-scale mass and energy transfer mechanisms in the laboratory with the aim of understanding the physics of these processes and to incorporate them into large-scale simulations of explosive volcanic eruptions. This project will support an ongoing effort in predictive computational volcanology. Specifically they team will focus on 1) heat transfer between particles and gas at high Reynolds numbers and using clast cooling proxies to examine entrainment in pyroclastic density currents, 2) particle deposition and resuspension, including the role of particle impacts in generating depositional features, 3) large-scale experiments of gas-particle density driven flows, and 4) and the production of fine ash particles in the conduit and in pyroclastic density currents. All these processes contribute to production and dispersal of ash and larger pyroclasts to the immediate environment of the volcanic edifice and also to the wider dispersal of ash in the atmosphere. Understanding the physics of these processes is crucial in determining the potential aviation, climactic, and local hazards of eruptions. All of the proposed experiments will be conducted with materials and at conditions similar to those in natural flows, minimizing the potential difficulties with scaling to large-scale multiphase flows. In the methodology proposed, the numerical models are integrally connected to the experimental data. The strength of numerical models is the ability to solve non-linear, complexly coupled equations and determine emergent behavior, and the strength of the experiments is to understand in detail the physical processes operating at small scales.

爆炸性的火山喷发是地球上最有活力的颗粒状流，其中最大的是全球影响。即使是较常见的，较小的事件也包含数公里的尺度。但是，这些流中的质量和能量转移从根本上是通过较小的空间和时间尺度的过程控制的，其中各个颗粒彼此相互作用，与气体或流传递的表面相互作用。我们过去在蒸汽爆炸，灰分生产和传热方面的工作表明，从实验开发的亚网格模型可以耦合到大规模的数值模拟。更重要的是，这些亚网格关系对于预测火山沉积物和灰分分散模式中反映的动力学至关重要。忽略亚网格过程的模型可能无法通过几个数量级产生火山沉积物中的能量传递。我们预测火山流的大规模行为的能力最终会受到我们对非常小的或微物理过程的理解的限制。在这项研究中，研究人员将检查实验室中的粒子尺度质量和能量转移机制，目的是了解这些过程的物理学，并将它们纳入爆炸性火山喷发的大规模模拟中。该项目将支持预测计算火山学方面的持续努力。他们具体而言，他们团队将重点关注1）在高雷诺数处的颗粒和气体之间的热传递，并使用Clast冷却代理检查夹带着碎屑密度电流的夹带，2）粒子沉积和恢复悬浮液，包括粒子在产生deposition的作用，3）在产生deposition的特征，3）凝聚和颗粒的大量凝聚和4）和4）和4）的生产，以及4）的生产。密度电流。所有这些过程都有助于灰烬和更大的火山壳的生产和扩散，以对火山建筑物的直接环境，也有助于大气中灰分的更广泛的分散。了解这些过程的物理学对于确定喷发的潜在航空，高潮和局部危害至关重要。 所有提出的实验将使用与自然流中类似的材料进行进行，从而最大程度地减少了扩展到大型多相流的潜在困难。在提出的方法中，数值模型积分连接到实验数据。数值模型的强度是能够求解非线性，复杂耦合方程并确定新兴行为的能力，实验的强度是详细了解在小尺度上运行的物理过程。