UNcovering the role of Pyroclasts on volcanIc jet Noise – UNPIN

在火山爆发时，岩浆被粉碎，并以火山灰的形式喷射出来。驱动一次爆炸性喷发所需的能量取决于内部过程（例如，岩浆中溶解的挥发物的释放）和外部过程（例如，外部水的蒸发）的可变组合。大气中的高温可对社会和基础设施造成重大和各种危害。火山喷发的时间和强度是无法预测的，或者只是无法充分预测，但提前预测对于评估和减轻火山危害至关重要。火山活动既可以直接在现场监测，也可以远程监测，例如通过天基系统或地面地震和声学网络。特别是，声波信号越来越多地用于监测偏远地区的活火山。火山发出的声信号在可听和次声光谱范围内。声波监测的目的是将测量到的声波信号与具体的喷发过程联系起来。然而，对这些信号的解释仍然很困难，因为为纯净空气流动而开发的基础物理学忽略了火山环境的复杂现实。迄今为止，还没有全面的数据集来解释火山相关条件对声波信号的影响。该项目的目的是确定火山特有的动态条件对可测量的声波信号的影响，特别是：-（火山）颗粒的存在及其体积分数和大小；-爆炸驱动气体的体积、压力和温度；-火山口的几何形状（“喷嘴形状”）；以及整个火山大厦的形态。为此目的，将进行规模的、专门设计的激波管实验来模拟冲动性火山喷发（“启动射流”）。这些实验室实验的声学记录将揭示这些参数对相关声学信号的影响，从而为颗粒负载射流的动力学及其声学特性提供独特的见解。然后将按比例和可重复的实验室实验与火山爆发的分析进行比较。该结果将为我们解释爆炸性火山喷发期间产生的声波信号的能力打开新的大门，为改进火山喷发特征和随后的风险评估以及人类和社会对活火山的相关恢复力做出重大贡献。

During explosive volcanic eruptions, magma is fragmented and ejected as tephra. The energy required for driving an explosive eruption depends on a variable combination of intrinsic (e.g., outgassing of volatiles dissolved in magma) and extrinsic (e.g., evaporation of external water) processes. Tephra in the atmosphere can pose significant and varied hazards to society and infrastructures. The timing and the intensity of an eruption are not, or only insufficiently, foreseeable, and yet predictions ahead of time are essential to assess and mitigate volcanic hazards.Volcanic activity can be monitored directly on site as well as remotely, e.g. via space-based systems or earth-based seismic and acoustic networks. In particular, acoustic signals are increasingly used for monitoring active volcanoes in remote areas. Volcanoes emit acoustic signals in both the audible and the infrasonic spectral range. The goal of acoustic monitoring is to relate a measured acoustic signal with the specific eruption process. However, the interpretation of these signals is still difficult, because the underlying physics, developed for the flow of pure air, ignore the complex reality of volcanic environments. To date, there are no comprehensive datasets explaining the influence of volcano-relevant conditions on the acoustic signals.The aim of this project is to determine the influence of volcano-specific dynamic conditions on the measurable acoustic signals, in particular:- the presence of (volcanic) particles, and their volume fraction and size;- the volume, pressure, and temperature of the explosion-driving gas;- the geometry of the volcanic vent ("nozzle shape"); and- the morphology of the entire volcanic edifice.For this purpose, scaled, specially designed shock-tube experiments will be performed to simulate impulsive volcanic eruptions ("starting jets"). Acoustic recording of these laboratory experiments will uncover the influence of these parameters on the associated acoustic signals, thus providing unique insights into the dynamics of particle-laden jets and their acoustic properties. The scaled and reproducible laboratory experiments will then be compared with the analysis of volcanic eruptions. The results will open new doors to our capacity to interpret the acoustic signals generated during explosive volcanic eruptions, contributing significantly to an improved eruption characterization and ensuing risk assessment and the related resilience of people and society to active volcanoes.