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

火山灰和气体云对人类生命、基础设施和飞机构成重大危险。了解火山羽流高度、喷发强度（即质量通量）和火山大气条件（如风速）之间的关系是管理喷发危机、重建过去喷发动力学和为未来喷发做准备的关键。然而，喷发强度的估计可能是不确定的，超过一个数量级，这破坏了我们对火山羽动态的理解，另一种方法是使用类似于火山羽的小规模实验室实验，其中测量的不确定性很小，但内在的限制是简化了现实世界羽的条件。例如，只有少数模拟实验说明了风对羽流动力学的强烈影响，而且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强烈垂直剪切的风廓线的类比。除了火山学之外，在基本流体动力学方面，很少有实验工作来研究剪切分层横流中多相羽流的动力学，尽管这种羽流在许多环境和工业问题中很常见。为了突破我们对火山羽流动力学的理解，这个博士项目旨在联合收割机三种方法：利用卫星观测，将建立一个根据火山伞云增长率得出的喷发强度数据库。结合新的独立火山喷发源参数档案（IVESPA）数据库，该数据库包含从现场存款得出的喷发强度，这将产生一个前所未有的数据集，其中包含大量观测良好的火山事件，对强度有两个独立的限制。包括垂直剪切横流。将带有硅酸盐砂颗粒的彩色盐水羽状物注入具有盐度梯度的水箱中，以再现大气分层。通过一系列泵产生的非均匀横流，以再现真实的大气风廓线。关键的状态参数将按比例调整，以符合火山羽流发生的动力学状态。羽流的宏观性质（例如，㈢将利用自然喷发的观测和实验室实验评估和开发各种复杂的火山羽流数值模型，从参数化湍流卷吸的一维羽流模型到基于OpenFOAM计算流体动力学软件的三维火山羽流模型。

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.