Insights into volcanic conduit flow from an open‐source numerical model
Insights into volcanic conduit flow from an open‐source numerical model
复制标题
从开源数值模型深入了解火山管道流
DOI：
10.1029/2001gc000192
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发表时间：
2002
期刊：
影响因子：
3.7
通讯作者：
L. Mastin
中科院分区：
文献类型：
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作者：
L. Mastin
计算火山爆发的流体动力学的数值模型已越来越多地用于了解火山过程和评估火山灾害。然而，开发这些模型的人很少公开这些模型，以便其他科学家可以验证、使用和可能改进它们。在本文中，我提出了一个可视化的，交互式的，开源的数值模型，计算垂直喷发管道中岩浆和气体的稳态流动，并包含用户友好的实用程序，用于快速确定硅酸盐熔体，H2O气体和熔体-气体-晶体混合物的物理，热力学和传输特性。该模型通过结合含水硅酸盐熔体的非Arbian粘度关系、取决于毛细管数的气体的粘度和体积分数之间的关系以及分别使用熔体和H2O气体的热力学关系在混合物中的绝热温度变化，代表了对先前发表的导管模型的进步。没有管道模型的火山学家经常使用不可压缩、层流、牛顿管流的分析方程来近似管道流，该方程预测质量通量与管道半径的四次方成正比，与混合物粘度成反比。这里提出的模型并不比包络线后计算更难使用，表明管流近似显著高估了质量通量对管道半径和混合物粘度的敏感性。从模型的结果还表明，粘性加热在较低的管道，这是不考虑在大多数其他模型，可能会增加几个百分点的大规模喷发的质量流量和降低的粘度的混合物在破碎深度的百分之几十。
Numerical models that calculate the fluid dynamics of explosive volcanic eruptions have been used with increasing frequency to understand volcanic processes and evaluate volcanic hazards. Yet those who develop such models rarely make them publicly available so that they can be verified, used, and possibly improved by other scientists. In this paper I present a visual, interactive, open‐source numerical model that calculates steady state flow of magma and gas in vertical eruptive conduits and contains user‐friendly utilities for quickly determining physical, thermodynamic, and transport properties of silicate melts, H2O gases, and melt‐gas‐crystal mixtures. The model represents an advance over previously published conduit models by incorporating a non‐Arrhenian viscosity relation for hydrous silicate melts, a relation between viscosity and volume fraction of gas that depends on Capillary number, and adiabatic temperature changes in the mixture using established thermodynamic relations for melts and H2O gas, respectively. Volcanologists who have not had access to conduit models have frequently approximated conduit flow using an analytical equation for incompressible, laminar, Newtonian pipe flow, which predicts that the mass flux is proportional to the fourth power of conduit radius and inversely proportional to mixture viscosity. The model presented here, which is not much more difficult to use than a back‐of‐the‐envelope calculation, shows that the pipe‐flow approximation significantly overestimates the sensitivity of mass flux to both conduit radius and mixture viscosity. Results from the model also show that viscous heating in the lower conduit, which is not considered in most other models, may increase the mass flux of large silicic eruptions by several percent and decrease the viscosity of the mixture at the fragmentation depth by a few tens of percent.