Towards reliable assessment of pyroclastic density current hazards

实现火山碎屑密度电流危害的可靠评估

基本信息

批准号：
NE/V014242/1
负责人：
Eric Breard
金额：
$ 81.26万
依托单位：
University of Edinburgh
依托单位国家：
英国
项目类别：
Fellowship
财政年份：
2022
资助国家：
英国
起止时间：
2022 至无数据
项目状态：
未结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FV014242%2F1
关键词：
Towards reliable assessment pyroclastic density

项目摘要

In a world where the human population keeps growing and is pushed to living in hazardous volcanic areas, volcanoes are increasingly becoming a larger threat to life. Volcanoes that erupt explosively have had devastating societal impacts, including covering countries in ash, changing the climate, and the extensive loss of human life. The most serious class of volcanic hazards is caused by volcanic flows, which include landslides, debris flows and the most dangerous of all, pyroclastic flows. Pyroclastic flows, made of scorching ash and gas, can burn and bury entire cities within minutes. These hot currents are typically composed of a basal dense avalanche and overriding dilute turbulent ash-cloud surge. Pyroclastic flows do not solely affect the ground, as they can also form large plumes of fine ash particles that rise to the altitude of cruising flights and can disrupt aviation paths. Predicting the propagation of these flows has been one of the largest challenges in geosciences because we lack a fundamental understanding of how complex granular media flow, i.e. our understanding of their rheology is very incomplete. This gap in our knowledge makes the impacts from pyroclastic flows very difficult to predict. The ability to forecast future pyroclastic flow velocity and inundation areas would help to limit the loss of human life and reduce economic impacts by informing mitigation strategies such as evacuations. Unfortunately, this goal cannot be achieved until we capture the physics of these currents and implement it in numerical models. The dense avalanche layer is a highly complex granular flow made of particles spanning a wide range of sizes (from microns to meters). The gas-particle coupling leads to elevated gas pressure and enables the transformation of the highly frictional granular avalanche into a mixture analogous to a liquid. While our understanding of granular flows has grown significantly in the past decade, previous studies have focused on steady configurations and simplified mixtures of grains. In nature, pyroclastic flows evolve over time as particles fragment and abrade by colliding with each other, and flows propagate across a variety of topographic obstacles such as valleys that control their behaviour, making their behaviour transient. Without a physical description of unsteady rheology of natural volcanic mixtures, we may never capture their behaviour accurately. Another major challenge we face is the time that current models require to run simulations of pyroclastic flows on highly resolved digital-elevation models. At the moment, all models use Central Processing Unit (CPU) computing to simulate volcanic flows, and require supercomputers to solve hundreds of scenarios taking days to weeks to complete. This project will take advantage of recent advances in computing abilities and analytical techniques available in physics and engineering and apply these to geosciences. These techniques will be used to study the dissipation energy from unsteady pyroclastic mixtures, enabling physical descriptions of the processes to be implemented in a new generation of volcanic flow model based on graphic cards. This new model will use Graphic Processing Unit (GPU) computing that can be undertaken on any laptop. This new model will allow highly resolved calculations and will radically transform our ability to forecast pyroclastic flow hazards and their interaction with topography, and enable volcanologists to undertake rapid hazard assessment when most needed: during volcanic unrest. Combining the findings and development from this study with other fields in geosciences will lead to important advances in how volcanic hazard assessment is undertaken and help limit loss of life.

在这个人口不断增长并被推动居住在危险的火山区域的世界中，火山越来越成为对生命的更大威胁。爆发的火山遭受了毁灭性的社会影响，包括覆盖灰烬中的国家，改变气候以及人类生命的广泛丧失。最严重的火山危害是由火山流造成的，其中包括滑坡，碎屑流以及最危险的火山碎屑流。由炎热的灰分和气体制成的火山碎屑流可以在几分钟之内燃烧和埋葬整个城市。这些热电流通常由基底密集的雪崩和稀释的湍流灰云浪涌组成。火山碎屑流不仅会影响地面，因为它们还可以形成大量的细灰颗粒，这些细灰颗粒升至巡航飞行的高度并可能破坏航空路径。预测这些流量的传播一直是地球科学中最大的挑战之一，因为我们对复杂的颗粒介质流程的理解缺乏基本的理解，即我们对他们的流变学的理解非常不完整。在我们的知识上，这种差距使火山碎屑流的影响很难预测。预测未来的火山碎屑流速度和淹没区的能力将有助于限制人类生命的丧失，并通过告知缓解策略（例如撤离）来减少经济影响。不幸的是，直到我们捕获这些电流的物理学并以数值模型实现它，才无法实现这个目标。密集的雪崩层是一种高度复杂的颗粒流，由跨尺寸（从微米到米）组成的颗粒组成。气粒子耦合导致气压升高，并使高度摩擦的颗粒雪崩转化为类似于液体的混合物。尽管我们对颗粒流的理解在过去十年中已经显着增长，但以前的研究集中在稳定的构型和简化的晶粒混合物上。在自然界中，火山碎屑流随着时间的流逝而随着颗粒的碎片而发展，并通过相互碰撞而磨料，并在各种地形障碍物（例如控制其行为的山谷）上传播，从而使其行为瞬变。如果没有对自然火山混合物不稳定流变的物理描述，我们可能永远不会准确捕捉它们的行为。我们面临的另一个主要挑战是，当前模型需要在高度分辨的数字高程模型上对火山碎屑流进行模拟。目前，所有型号都使用中央处理单元（CPU）计算来模拟火山流，并要求超级计算机求解数百个场景花费数天到几周才能完成。该项目将利用物理和工程中提供的计算能力和分析技术方面的最新进展，并将其应用于地球科学。这些技术将用于研究不稳定的火山碎屑混合物中的耗散能量，从而在基于图形卡的新一代火山流模型中实现了该过程的物理描述。该新模型将使用可以在任何笔记本电脑上进行的图形处理单元（GPU）计算。该新模型将允许高度解决的计算，并从根本上改变我们预测火山碎屑流危害及其与地形的相互作用的能力，并使火山学家能够在最需要时进行快速危害评估：在火山动乱期间。将这项研究的发现和发展与地球科学领域的其他领域相结合将导致如何进行火山危害评估并有助于限制生命损失。