Dynamics of a spherical viscoelastic shell: Implications to a criterion for fragmentation/expansion of bubbly magma
Dynamics of a spherical viscoelastic shell: Implications to a criterion for fragmentation/expansion of bubbly magma
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DOI：
10.1016/j.epsl.2007.09.033
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发表时间：
2008-01-15
影响因子：
5.3
通讯作者：
Ichihara, Mie
中科院分区：
文献类型：
--
作者：
Ichihara, Mie
本文研究了粘弹性流体包围的球形气泡的动力学。研究的目的是了解控制气泡岩浆减压膨胀和破碎的参数。我们特别关注碎片化和扩张哪个先发生。假设气泡壁破裂发生在临界应力条件下，我们计算了不同减压速率下气泡半径和气泡壁处拉应力的变化。壳中存储拉应力的条件以无量纲参数表示。结果解释如下：当岩浆粘度大于临界值，且减压时间短于粘性膨胀时间时，膨胀前先储存拉应力；当岩浆粘度小于临界值时，无论减压多快，拉应力都不会储存。尽管人们普遍接受的理论是，碎裂受到应力条件和减压时间的影响，但减压时间 (t(1)) 究竟如何影响碎裂尚不完全清楚。这项研究表明，应力条件是由减压时间的长度控制的，与粘弹性松弛时间 (t(1)/tau) 无关，而是与粘性膨胀时间 (t(1)/tau(l)(rlx)) 相关。正如最近的实验研究表明，相对于粘弹性松弛时间（t（1）/tau）的减压时间对于破碎过程本身也很重要，这表明减压时间不是通过应力条件影响破碎。然而，必须完成更多的工作才能充分理解减压时间和松弛时间之间对碎片影响的特殊关系。 (c) 2007 Elsevier B.V. 保留所有权利。
This paper investigates dynamics of a spherical bubble surrounded by a viscoelastic fluid. The purpose of the study is to understand the parameters which control expansion and fragmentation of bubbly magma by decompression. In particular, we focus on which occurs first, fragmentation or expansion. Supposing that rupture of the bubble wall occurs in a critical stress condition, we calculate the change of the bubble radius and tensile stress at the bubble wall for various decompression rates. Conditions in which tensile stress is stored in the shell are represented in terms of dimensionless parameters. The results are interpreted as follows: when magma viscosity is larger than a critical value, and the decompression time is shorter than viscous expansion time, tensile stress is stored before expansion; when magma viscosity is smaller than the critical value, tensile stress is not stored, no matter how rapid the decompression. Although it is a generally accepted theory that fragmentation is effected by stress conditions and decompression time, exactly how decompression time (t(1)) effects the fragmentation is not yet fully understood. This study demonstrates that the stress condition is controlled by the length of the decompression time not relative to the viscoelastic relaxation time (t(1)/tau), but relative to the viscous expansion time (t(1)/tau(l)(rlx)). As suggested by recent experimental studies, the decompression time relative to viscoelastic relaxation time (t(1)/tau) is also significant to the fragmentation process itself It indicates that the decompression time effects the fragmentation not through the stress condition. However more work must be completed to fully understand the particular relationship between the decompression time and relaxation time in terms of its influence on fragmentation. (c) 2007 Elsevier B.V. All rights reserved.