Numerical simulation of pyroclastic density currents using locally refined Cartesian grids
Numerical simulation of pyroclastic density currents using locally refined Cartesian grids
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DOI：
10.1016/j.compfluid.2010.12.006
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发表时间：
2011-05
影响因子：
2.8
通讯作者：
D. Doronzo;M. D. Tullio;P. Dellino;G. Pascazio
中科院分区：
文献类型：
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作者：
D. Doronzo;M. D. Tullio;P. Dellino;G. Pascazio
火山碎屑密度流是一种紧贴地面的高温气固两相流，代表着最危险的火山爆发事件。它们对建筑物的影响是动压的函数，动压表示这些水流施加在建筑物上的横向载荷。在这种流动的数值模拟中出现了几个关键问题，这涉及到一种流变性复杂的流体，它在广泛的湍流尺度上演化，并在复杂的地形上移动。在这篇文章中，我们考虑了一种数值技术，当需要在感兴趣的区域中有足够的分辨率时，该技术旨在解决在区域离散化中遇到的困难。在不采用耗时的贴体网格生成方法的情况下，我们在地表和火山喷口附近使用局部细化的笛卡尔网格来重建陡峭的速度和颗粒浓度梯度。网格生成过程由一个高效的自动工具执行，而不考虑几何复杂性。我们展示了如何将模拟实验与数值模拟相匹配，以捕捉多相流的基本物理，获得与实验测量合理一致的动压计算值。这些结果鼓励今后应用该方法在自然尺度上评估火山碎屑密度流的影响。
Pyroclastic density currents are ground hugging, hot, gas–particle flows representing the most hazardous events of explosive volcanism. Their impact on structures is a function of dynamic pressure, which expresses the lateral load that such currents exert over buildings. Several critical issues arise in the numerical simulation of such flows, which involve a rheologically complex fluid that evolves over a wide range of turbulence scales, and moves over a complex topography. In this paper we consider a numerical technique that aims to cope with the difficulties encountered in the domain discretization when an adequate resolution in the regions of interest is required. Without resorting to time-consuming body-fitted grid generation approaches, we use Cartesian grids locally refined near the ground surface and the volcanic vent in order to reconstruct the steep velocity and particle concentration gradients. The grid generation process is carried out by an efficient and automatic tool, regardless of the geometric complexity. We show how analog experiments can be matched with numerical simulations for capturing the essential physics of the multiphase flow, obtaining calculated values of dynamic pressure in reasonable agreement with the experimental measurements. These outcomes encourage future application of the method for the assessment of the impact of pyroclastic density currents at the natural scale.