Dynamics of multiphase plumes in sheared stratified crossflows: implications for managing the environmental impacts of volcanic eruptions (Ref: 4659)

剪切分层横流中多相羽流的动力学：对管理火山喷发环境影响的影响（参考文献：4659）

• 批准号: 2859346
• 金额: --
• 依托单位: UNIVERSITY OF EXETER
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2859346
• 关键词: Dynamics; multiphase; plumes; sheared; stratified

Volcanic ash and gas clouds pose significant hazards to human life, infrastructure, and aircraft. Understanding the relationship between the height of a volcanic plume, the intensity of an eruption (i.e. its mass flux) and atmospheric conditions (e.g. wind speed) at the volcano is key to managing eruptive crises, reconstructing past eruption dynamics, and preparing for future eruptions. However, estimates of eruption intensity can be uncertain by over an order of magnitude which undermines our understanding of volcanic plume dynamics.An alternative approach is to use small-scale laboratory experiments analogue to volcanic plumes in which measurement uncertainties are small, but an intrinsic limitation is the simplification of conditions occurring in real-world plumes. For example, only a handful of analogue experiments have accounted for the strong influences of wind on plume dynamics, and all of them used a uniform crossflow which critically undermines their analogy with wind profiles which are commonly strongly sheared vertically. Beyond volcanology, very little experimental work has been carried out in fundamental fluid dynamics to investigate the dynamics of multiphase plumes in sheared stratified crossflow, despite such plumes being common in many environmental and industrial problems.To make a breakthrough in our understanding of the dynamics of volcanic plumes, this doctoral project will aim to combine three approaches:i) Using satellite observations, a database of eruption intensity derived from the growth rate of volcanic umbrella cloud will be built. Combined with the novel Independent Volcanic Eruption Source Parameter Archive (IVESPA) database that contains eruption intensity derived from field deposit, this will result in an unprecedented dataset with large number of well-observed volcanic events with two independent constraints on intensity.ii) A novel laboratory experiment on multiphase buoyant plumes rising in a stratified crossflow will be designed and, for the first time, include vertically sheared crossflow. A coloured saltwater plume with silicate sand particles will be injected into a water tank with a salinity gradient to reproduce atmospheric stratification. A non-uniform crossflow, created via an array of pumps, to reproduce realistic atmospheric wind profiles. Key regime parameters will be scaled to match the dynamical regimes in which volcanic plumes occur. The macroscopic properties of the plume (e.g., top height and plume width) will be monitored using video cameras.iii) The observations from natural eruptions (i) and laboratory experiments (ii) will be used to evaluate and develop numerical volcanic plume models of various complexity, ranging from one-dimensional (1D) plume models with parameterized turbulent entrainment to 3D volcanic plume models based on the OpenFOAM computational fluid dynamics software.

火山灰和气云对人类生命、基础设施和飞机构成重大危险。了解火山羽流的高度、喷发的强度(即其质量流量)和火山的大气条件(例如风速)之间的关系，对于管理喷发危机、重建过去的喷发动力学和为未来的喷发做好准备至关重要。然而，喷发强度的估计可能不确定超过一个数量级，这破坏了我们对火山羽流动力学的理解。另一种方法是使用类似于火山羽流的小规模实验室实验，其中测量不确定度很小，但固有的局限性是简化了真实世界羽流中发生的条件。例如，只有几个模拟实验考虑了风对羽流动力学的强烈影响，所有这些实验都使用了均匀的横流，这严重破坏了它们与通常垂直强烈切变的风廓线的类比。除了火山学之外，尽管多相羽流在许多环境和工业问题中很常见，但在基本流体动力学方面研究剪切分层横流中的多相羽流动力学的实验工作很少。为了突破我们对火山羽流动力学的理解，这个博士项目将致力于结合三种方法：i)利用卫星观测，将建立一个由火山伞状云的增长率得出的喷发强度数据库。与包含来自现场沉积的喷发强度的新型独立火山喷发源参数档案(IVESPA)数据库相结合，这将产生一个史无前例的数据集，其中包含大量观测良好的火山事件，并对强度有两个独立的约束。ii)将设计一种关于多相浮羽在分层横流中上升的新颖实验室实验，并首次包括垂直剪切横流。含有硅酸盐沙粒的彩色海水羽流将被注入具有盐度梯度的水箱中，以重现大气层结。通过一组泵创建的非均匀横流，以再现真实的大气风廓线。将对关键的体制参数进行调整，以匹配火山羽流发生的动力体制。将使用摄像机监测羽流的宏观性质(如顶部高度和羽流宽度)。iii)将利用来自自然喷发的观测结果(I)和实验室实验(Ii)来评估和开发各种复杂性的火山羽流数值模型，从带有参数化湍流卷吸的一维(1D)羽流模型到基于OpenFOAM计算流体力学软件的三维火山羽流模型。