Collaborative Proposal: Experimental Studies of Dilute Pyroclastic Density Currents

火山碎屑密度流是由火山爆发或熔岩穹丘坍塌产生的固体颗粒和气体的高温快速移动的混合物。它们传播很远，造成巨大的危害，并改变景观。火山碎屑密度流的运动和输运过程在定量上还没有得到很好的理解。甚至概念模型也存在争议。基本的问题仍然是关于山丘、山脊和山谷如何改变和引导火山碎屑密度流，以及空气如何混入流中。这些关键过程控制着水流的速度、方向以及火山灰向大气中的喷射。更好地了解火山碎屑密度流的长期结果是评估其危害的科学基础，本项目将使用动态缩放的实验室实验，特别是它们与地形的相互作用，以了解火山碎屑密度流动力学。这将通过成像的三维速度和浓度场内建模稀火山碎屑密度流，并量化夹带的空气和颗粒的沉降。这一认识将提高我们将场沉积物与这些电流的动力学联系起来的能力。实验装置的设计允许大量的实验，因此，探索参数和过程之间的关系。

Pyroclastic density currents are hot and fast-moving mixtures of solid particles and gas produced by explosive volcanic eruptions or the collapse of lava domes. They travel great distances, pose substantial hazards, and alter landscapes. The processes governing the movement of, and transport in, pyroclastic density currents are not well understood quantitatively. Even conceptual models remain controversial. Basic questions remain about how hills, ridges, and valleys alter and direct pyroclastic density currents and about how air mixes into the currents. These key processes control current speed, direction, and injection of ash into the atmosphere. The long term outcome of better understanding pyroclastic density currents is a scientific foundation for assessing the hazards they pose.This project will use dynamically scaled laboratory experiments, in particular their interaction with topography, to understand pyroclastic density current dynamics. This will be accomplished by imaging the three-dimensional velocity and concentration fields inside modeled dilute pyroclastic density currents, and quantifying the entrainment of air and sedimentation of particles. This understanding will improve our ability to relate field deposits to the dynamics of these currents. The experimental setup is designed to permit a large number of experiments and hence to explore relationships between parameters and processes.