Gas-Melt Flow Regimes in Basaltic Volcanic Conduits and their Characteristic Acoustic Signals

玄武岩火山管道中的气体熔体流动状态及其特征声信号

• 批准号: NE/G016593/1
• 负责人: Alison Rust
• 金额: $ 38.76万
• 依托单位: University of Bristol
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2009
• 资助国家: 英国
• 起止时间: 2009 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FG016593%2F1
• 关键词: Gas; Melt; Flow; Regimes; Basaltic

The ultimate goals of volcanology are to understand and predict volcanic eruptions. A major challenge for volcanologists is to figure out what is happening inside volcanoes even though we can only watch and make measurements at the top. Laboratory experiments can bridge this gap because it is possible to see and measure flow within a model volcano at the same time as record vibrations caused by the flow that are equivalent to vibrations measured by real volcano monitoring. The proposed project takes this approach to study how gases escape from volcanoes, and how the abundance of gas and flow patterns inside the volcano can be assessed from acoustic signals (sounds) measured with microphones. Volcanic eruptions come in all sorts of styles from lava flows pouring out the top, to brief events from large bubbles bursting, to continuous fountains of drops of magma, to highly explosive eruptions with fragments traveling upwards in columns many kilometres high. Gases provide the main driving force for volcanic eruptions and the various types of eruptions have been explained using the framework of gas-liquid flow patterns observed in laboratory experiments by engineers. However, the work by engineers has been motivated by industrial flows with liquids that have a much lower viscosity than magma (that is, the liquids flow much more easily) and they have run experiments in tubes that are much smaller than conduits in volcanoes. So it is difficult to properly apply the engineering results to volcanic flows. This project will bring together volcanologists and engineers to run experiments at conditions relevant to volcanic eruptions. In particular, we will use air and syrup as analogues for volcanic gases and melt, and will observe flow patterns and bubble geometries for a variety gas flow rates, tube sizes and syrup viscosities. This will help us to understand the origins of the different eruption styles. The second phase of the project will investigate the physics of sound generation by gas motion and bubble bursting. Sounds, mostly at frequencies below what we can hear (infrasounds), are produced by all styles of volcanic activity and are thought to be related to gas bubbles and gas flow. Basaltic volcanoes produce some of the most interesting infrasounds because bubble merging (coalescence), bubble rise, and gas separation from the surrounding liquid (segregation) are all easy because basalt has a low viscosity compared to other types of magma. This means that there is potential to figure out important information on the gas flow inside basaltic volcanoes from infrasounds. The sounds produced by the air-syrup flow experiments described above will be recorded with microphones so that we can link flow patterns and bubble properties to the volume and pitch of the sounds they generate. An additional goal is to test if we can effectively use infrasound recordings as a tool to measure how much gas is moving through volcanoes. This is important because gases drive volcanic eruptions and play a key role in controlling eruption style and intensity. Infrasonic monitoring has huge potential because it is cheap and easy to use compared to other methods for measuring gas outputs from volcanoes. Systematic understanding of how infrasonic measurements made at volcanoes are related to the gas fluxes emitted will allow the full potential of this monitoring technique to be realized. Finally, we will use the results of the experiments and theoretical work to interpret infrasounds produced by basalt eruptions at Stromboli and Etna volcanoes in Italy. We will, for instance, evaluate whether small volcanic explosions result from the bursting of large individual bubbles or whether the explosions are the bursting of clouds of bubbles. We also anticipate gaining useful information from more subtle sounds or infrasounds that we don't already know about because the experiments will tell us what to look for in the volcanic acoustic data.

火山学的最终目标是理解和预测火山喷发。对于火山学家来说，一个主要的挑战是弄清火山内发生的事情，即使我们只能在顶部观看并进行测量。实验室实验可以弥合这一差距，因为与流动引起的记录振动相同，等于通过实际火山监测测量的振动，可以在模型火山内看到和测量流量。拟议的项目采用这种方法来研究气体如何从火山中逸出，以及如何通过用麦克风测量的声信号（声音）评估火山内的气体和流动模式。火山喷发有各种各样的风格，从熔岩流倒出顶部到简短的事件，从大气泡爆发到连续的岩浆滴水到高度爆炸性的爆发，碎片在许多公里高的圆柱上向上传播。气体为火山喷发提供了主要的驱动力，并且使用工程师在实验室实验中观察到的气体流动流动模式的框架来解释了各种类型的喷发。但是，工程师的工作是由工业流动的动机，其液体的粘度比岩浆要低得多（即液体更容易流动），并且它们已经在试管中进行的试验比火山中的导管小得多。因此，很难将工程结果正确应用于火山流。该项目将召集火山学家和工程师在与火山喷发有关的条件下进行实验。特别是，我们将使用空气和糖浆作为火山气体和融化的类似物，并将观察到气体流速，管子尺寸和糖浆粘度的流动模式和气泡几何形状。这将有助于我们了解不同喷发样式的起源。该项目的第二阶段将通过气体运动和气泡破裂来调查声音发电的物理。声音大多是在我们能听到的（反向传动）以下的频率下，是由各种风格的火山活动产生的，被认为与气泡和气体流动有关。玄武岩火山产生了一些最有趣的侵蚀，因为气泡合并（结合），气泡上升和与周围液体的气体分离（种族隔离）都很容易，因为与其他类型的岩浆相比，玄武岩的粘度较低。这意味着有潜力弄清有关玄武岩内部气流的重要信息。上述空气中流动实验产生的声音将使用麦克风记录，以便我们可以将流量模式和气泡特性与它们产生的声音的音量和音高联系起来。另一个目标是测试我们是否可以有效地使用插图记录作为测量在火山中移动多少气体的工具。这很重要，因为气体驱动火山喷发并在控制喷发风格和强度中起关键作用。与其他用于测量火山气体输出的方法相比，Indrosonic监视具有巨大的潜力，因为它便宜且易于使用。系统地了解在火山上进行的界面测量与发出的气通量有关，将使该监测技术的全部潜力得到实现。最后，我们将利用实验和理论工作的结果来解释意大利Stromboli和Etna火山的玄武岩爆发产生的非传动。例如，我们将评估小火山爆炸是否是由于大型气泡破裂引起的，还是爆炸是气泡云的爆发。我们还期望从我们尚不知道的更微妙的声音或侵权声中获得有用的信息，因为这些实验会告诉我们在火山声数据中寻找什么。

项目成果

Numerical modeling of oscillating Taylor bubbles

• DOI: 10.1080/19942060.2016.1224737
• 发表时间: 2016-01
• 期刊: Engineering Applications of Computational Fluid Mechanics
• 影响因子: 6.1
• 作者: S. Ambrose;D. Hargreaves;I. Lowndes

The existence and behaviour of large diameter Taylor bubbles

• DOI: 10.1016/j.ijmultiphaseflow.2014.04.006
• 发表时间: 2015-06
• 期刊: International Journal of Multiphase Flow
• 影响因子: 3.8
• 作者: C. Pringle;S. Ambrose;B. Azzopardi;A. Rust

Numerical modelling of the rise of Taylor bubbles through a change in pipe diameter

• DOI: 10.1016/j.compfluid.2017.01.023
• 发表时间: 2017-04-22
• 期刊: COMPUTERS & FLUIDS
• 影响因子: 2.8
• 作者: Ambrose, Stephen;Lowndes, Ian S.;Azzopardi, Barry
• 通讯作者: Azzopardi, Barry

Experimental constraints on the outgassing dynamics of basaltic magmas

玄武岩浆放气动力学的实验约束

• DOI: 10.1029/2011jb008392
• 发表时间: 2012
• 期刊: Solid Earth
• 影响因子: 3.4
• 作者: Pioli L

The rise of Taylor bubbles in vertical pipes

泰勒气泡在垂直管道中的上升

• 发表时间: 2015
• 作者: Ambrose Stephen