Collaborative Proposal: Experimental Studies of Dilute Pyroclastic Density Currents

火山碎屑密度流是火山爆发或熔岩穹顶坍塌产生的固体颗粒和气体的高温快速混合物。它们传播的距离很远，造成巨大的危险，并改变风景。控制火山碎屑密度流运动和输运的过程在数量上还没有得到很好的理解。即使是概念性模型也仍然存在争议。关于丘陵、山脊和山谷如何改变和引导火山碎屑密度流，以及空气如何混合到流中，这些基本问题仍然存在。这些关键过程控制着水流的速度、方向和向大气中注入火山灰。更好地了解火山碎屑密度流的长期结果是评估它们所造成的危害的科学基础。该项目将利用动态缩放的实验室实验，特别是它们与地形的相互作用，来了解火山碎屑密度流的动力学。这将通过成像模拟的稀薄火山碎屑密度流内的三维速度场和浓度场，并量化空气的夹带和颗粒的沉积来实现。这一理解将提高我们将野外沉积与这些洋流的动力学联系起来的能力。该实验装置被设计成允许进行大量的实验，从而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.