Numerical studies on convective stability and flow pattern in three-dimensional spherical mantle of terrestrial planets
Numerical studies on convective stability and flow pattern in three-dimensional spherical mantle of terrestrial planets
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类地行星三维球形地幔对流稳定性和流态的数值研究
DOI：
10.1093/gji/ggw226
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发表时间：
2016
影响因子：
2.8
通讯作者：
and Masaki Ogawa
中科院分区：
文献类型：
--
作者：
Takatoshi Yanagisawa;Masanori Kameyama;and Masaki Ogawa
我们利用线性稳定性分析和数值实验探讨了具有温度依赖粘度的流体在基本加热的三维球壳中的热对流，同时考虑了我们的结果在类地行星上的应用。在线性稳定性分析中，壳的内外半径比在0.11-0.88之间。当粘度敏感地依赖于温度时，热对流发生的临界瑞利数从0.11增加到0.88，降低了两个数量级。在off= 0.11-0.55范围内进行的数值模拟表明，当f_ = 0.33或更大时，沿地表和底部边界均形成热边界层（TBL），分别诱发冷羽流和热羽流。然而，对于较小的值，TBL只在底部边界上发展。对流发生在滞盖状态，当表面边界的均方根速度小于其深度最大值的1%时，当表面边界的粘度与底部边界的粘度之比超过取决于的阈值时。阈值从106.5atf= 0.11降低到104atf= 0.55。如果对流地幔底部的黏度为1020-1021Pa s，那么火星、金星和地球的瑞利数就超过了src，但月球和水星就没有；除非地幔粘度远低于1020Pa s和/或地幔含有强大的内部热源，否则后一类行星不太可能发生对流。
We explore thermal convection of a fluid with a temperature-dependent viscosity in a basally heated 3-D spherical shell using linear stability analyses and numerical experiments, while considering the application of our results to terrestrial planets. The inner to outer radius ratio of the shellfassumed in the linear stability analyses is in the range of 0.11–0.88. The critical Rayleigh numberRcfor the onset of thermal convection decreases by two orders of magnitude asfincreases from 0.11 to 0.88, when the viscosity depends sensitively on the temperature, as is the case for real mantle materials. Numerical simulations carried out in the range off= 0.11–0.55 show that a thermal boundary layer (TBL) develops both along the surface and bottom boundaries to induce cold and hot plumes, respectively, whenfis 0.33 or larger. However, for smallerfvalues, a TBL develops only on the bottom boundary. Convection occurs in the stagnant-lid regime where the root mean square velocity on the surface boundary is less than 1 per cent of its maximum at depth, when the ratio of the viscosity at the surface boundary to that at the bottom boundary exceeds a threshold that depends onf. The threshold decreases from 106.5atf= 0.11 to 104atf= 0.55. If the viscosity at the base of the convecting mantle is 1020–1021Pa s, the Rayleigh number exceedsRcfor Mars, Venus and the Earth, but does not for the Moon and Mercury; convection is unlikely to occur in the latter planets unless the mantle viscosity is much lower than 1020Pa s and/or the mantle contains a strong internal heat source.