Control of Vent Geometry on the Fluid Dynamics of Volcanic Plumes: Insights From Numerical Simulations
Control of Vent Geometry on the Fluid Dynamics of Volcanic Plumes: Insights From Numerical Simulations
复制标题
喷口几何形状对火山羽流流体动力学的控制：数值模拟的见解
DOI：
10.1029/2020gl087038
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发表时间：
2020
影响因子：
5.2
通讯作者：
Koyaguchi T.
中科院分区：
文献类型：
--
作者：
Suzuki Y. J.;Costa A.;Koyaguchi T.
用三维数值模拟方法模拟了从圆形到线状裂隙喷口的喷发云团，研究了喷口形状对喷发过程中火山羽流高度和稳定性的控制作用。我们的结果表明，从圆形或低长宽比(接近正方形)的裂隙喷口喷出的云可以与急流区顶部的径向悬浮流(RSF)联系在一起，而从窄裂隙喷口喷出的云则与之无关。非RSF羽流比与RSF相关的羽流更稳定，因为喷出的混合物中高度浓缩的部分很容易消散，并与通风口附近的空气混合。即使在岩浆流量固定的情况下，RSF区域的羽流高度也随着长径比的增加而减小，而非RSF区域的羽流高度则增加。这些观测表明，空气卷吸的效率受到喷口形状的影响，而喷口形状反过来又控制着喷发羽流的动态。
We present three‐dimensional numerical simulations of eruption clouds from circular to linear fissure vents to investigate the control of vent shape on the height and stability of volcanic plumes during large explosive eruptions. Our results show that clouds ejected from circular or low‐aspect‐ratio (nearly square‐like) fissure vents can be associated with radially suspended flow (RSF) at the top of the jet region, whereas those emitted from narrow‐fissure vents are not. Non‐RSF plumes are more stable than those associated with RSF because the highly concentrated parts of the ejected mixture are easily dissipated and mixed with air near the vent. Plume height in the RSF regime decreases while that in the non‐RSF regime increases with increasing aspect ratio, even for a fixed magma flow rate. These observations suggest that the efficiency of air entrainment is influenced by the vent shape, which in turn controls the dynamics of eruption plumes.