Numerical Simulation of Lava Flows on Some Volcanoes in Japan
Numerical Simulation of Lava Flows on Some Volcanoes in Japan
复制标题
日本部分火山熔岩流的数值模拟
DOI：
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发表时间：
1990
期刊：
影响因子：
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通讯作者：
K. Kamo
中科院分区：
文献类型：
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作者：
K. Ishihara;M. Iguchi;K. Kamo
本章提出了一种模拟火山实际地形上熔岩流动宏观运动的数值计算方法，并对日本最近的三次喷发进行了检验。喷发前地图上所示的火山地形是使用采样间隔小于熔岩主流宽度的网格进行数字化的。根据宾汉流体在斜面上受重力作用流动的Navier-Stokes方程的定态解，计算了熔岩在网格间的通量。该计算评估了由于辐射冷却而引起的温度变化。然后利用粘度与岩浆温度和成分之间的经验关系来估计粘度。根据喷发的记录估计渗出率和挤出持续时间。对三种不同化学成分的熔岩流进行了模拟，以验证该方法的有效性：1983年宫崎岛熔岩流(SiO_2含量为53-54%)、1986年伊豆-大岛熔岩流(54-58%)和1914年樱岛熔岩流(59-62%)。模拟结果较好地反映了熔岩的流动前锋进程和实际厚度。在熔岩流的支流和干流边缘，淹没面积存在一定的差异。这在很大程度上是由于喷发前地形图的精确度不够，以及水平维度上的采样间隔相对于熔岩流的宽度较大。
The present chapter proposes a numerical calculation for simulating the macroscopic movements of lava flows on actual topography of volcanoes and tests it for three recent Japanese eruptions. The topography of the volcanoes as shown on pre-eruption maps was digitized using a grid in which the sampling interval was smaller than the width of the main stream of lava. The flux of lava among meshes is calculated from the steady-state solution of the Navier-Stokes equation for a Bingham fluid flowing due to gravity on an inclined plane. The calculation evaluates temperature change due to cooling by radiation. Viscosity is then estimated using an empirical relationship between viscosity and magma temperature and composition. The effusion rate and the duration of extrusion were estimated from the records of the eruptions. Three lava flows with different chemical compositions were simulated to check the validity of the method: the 1983 Miyakejima lava flows (53–54% SiO2), the 1986 Izu-Oshima lava flows (54–58%), and the 1914 Sakurajima lava flows (59–62%). The simulations match fairly well the progress of flow fronts and actual thickness of the lavas. Some discrepancies in inundation area were found at the branches of lava streams and at the margins of main streams. These are largely due to insufficient precision of maps of the pre-eruptive topography and to the size of the sampling interval in the horizontal dimension being large relative to the widths of lava streams.