Multi-Phased Flow Modeling of Vulcanian Explosions with Fountain Collapse on Montserrat

1997年8月、9月和10月，西印度群岛蒙特塞拉特岛苏弗里埃山火山发生了多次短时间爆炸。这些喷发伴随着喷发柱重部分的重力塌陷，产生浮石和火山灰流（火山碎屑流）和“火山灰飓风”，向侧面移动，进入邻近的农田和以前的人口稠密地区。 这些火山喷发中有许多是预测到的，我们和蒙特塞拉特火山观测站的其他工作人员通过连续的地震监测、对火山喷发云的测量、摄影和录像，密切记录了火山喷发。这样的数据是罕见的，在这个项目中，我们的目标是量化这些喷发，包括爆炸云的速度和轨迹，然后将这些基于现场的数据与复杂的喷发模型进行比较。在我们的模拟中，我们将试图确定爆炸前的岩浆和气体的比例在喷发管道，和压力分布。然后，我们将使用此信息作为“多相”爆炸模型的起始条件，在该模型中，分离的固相和气相被允许在从导管释放时动态地膨胀。我们可以追踪从管道中喷出的粒子的速度和轨迹，以及喷出的粒子和气体云的粒子密度。我们希望通过这项研究来确定管道中的主要条件，这些条件控制着云层是否会继续垂直上升，或者是否会坍塌形成危险的火山碎屑流。火山碎屑流是全世界爆炸性喷发造成生命损失的主要原因，从这一项目中获得的更好的认识应有助于减少本国和国外一些地点的危险。

VoightEAR-0073761Numerous short-duration explosions occurred during August, September and October 1997, at the Soufriere Hills Volcano, Montserrat, West Indies. These eruptions were accompanied by gravity collapse of heavy parts of the eruption column, that produced pumice and ash flows (pyroclastic flows) and "ash hurricanes" that moved sideways, into adjacent farmlands and formerly populated areas. Many of these eruptions were predicted, and we and other staff of Montserrat Volcano Observatory closely documented the eruptions by continuous seismic monitoring, measured surveys of the eruption clouds,photography, and video. Such data are rare, and in this project, we aim to quantify these eruptions, including the speed and trajectory of the explosion clouds, and then to compare these field-based data to sophisticated models of the eruptions. In our modeling, we will attempt to identify the magma and gas ratios in the eruption conduit before the explosion, and the pressure distribution. Then we will use this information as the starting condition for a "multi-phase" explosion model, in which separated solid and gas phases are allowed to expand dynamically upon release from the conduit tube. We can track the speeds and trajectories of the particles emitted from the conduit, and the particle densities of theerupting particle-and-gas cloud. We hope from this study to establish the main conditions in the conduit that control whether the clouds will continue to rise vertically, or will collapse to form dangerous pyroclastic flows. Pyroclastic flows are the major cause of loss of life in explosive eruptions worldwide, and the improved understanding obtained from this project should help to reduce hazards at a number of locations in this country and abroad.