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首页> 外文会议>International Conference on Computational Science - ICCS 2003 Pt.3 Jun 2-4, 2003 Melbourne, Australia and St. Petersburg, Russia >Anisotropic Convection Model for the Earth's Mantle
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Anisotropic Convection Model for the Earth's Mantle

机译：地幔各向异性对流模型

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The paper presents a theory for modeling flow in anisotropic, viscous rock. This theory has originally been developed for the simulation of large deformation processes including the folding and kinking of multi-layered visco-elastic rock (Miihlhaus et al. [1,2]). The orientation of slip planes in the context of crystal-lographic slip is determined by the normal vector ― the director ― of these surfaces. The model is applied to simulate anisotropic mantle convection. We compare the evolution of flow patterns, Nusselt number and director orientations for isotropic and anisotropic rheologies. In the simulations we utilize two different finite element methodologies: The Lagrangian Integration Point Method Moresi et al [8] and an Eulerian formulation, which we implemented into the finite element based pde solver Fastflo (www.cmis.csiro.au/Fastflo/). The reason for utilizing two different finite element codes was firstly to study the influence of an anisotropic power law rheology which currently is not implemented into the Lagrangian Integration point scheme and secondly to study the numerical performance of Eulerian (Fastflo)- and Lagrangian integration schemes. It turned out that whereas in the Lagrangian method the Nusselt number vs time plot reached only a quasi steady state where the Nusselt number oscillates around a steady state value the Eulerian scheme reaches exact steady states and produces a high degree of alignment (director orientation locally orthogonal to velocity vector almost everywhere in the computational domain). In the simulations emergent anisotropy was strongest in terms of modulus contrast in the up and down-welling plumes. Mechanisms for anisotropic material behavior in the mantle dynamics context are discussed by Christensen. The dominant mineral phases in the mantle generally do not exhibit strong elastic anisotropy but they still may be oriented by the convective flow. Thus viscous anisotropy (the main focus of this paper) may or may not correlate with elastic or seismic anisotropy.
机译：本文提出了一种用于模拟各向异性粘性岩石中流动的理论。该理论最初是为模拟大型变形过程而开发的，包括多层粘弹性岩石的折叠和扭结（Miihlhaus等人，[1,2]）。滑移平面在晶体学滑移背景下的方向由这些表面的法向矢量“指向矢”确定。该模型用于模拟各向异性地幔对流。我们比较了各向同性和各向异性流变的流型，努塞尔数和指向矢方向的演变。在仿真中，我们使用两种不同的有限元方法：拉格朗日积分点方法Moresi等[8]和欧拉公式，我们将其实施到基于有限元的pde求解器Fastflo（www.cmis.csiro.au/Fastflo/）中。 。使用两种不同的有限元代码的原因是，首先研究了各向异性幂律流变学的影响，该流变学目前尚未在Lagrangian积分点方案中实现，其次是研究Eulerian（Fastflo）-和Lagrangian积分方案的数值性能。事实证明，在拉格朗日方法中，努塞尔特数与时间图仅达到准稳态，其中努塞尔特数围绕稳态值振荡，而欧拉方案达到精确​​的稳态并产生高度对齐（方向定向器局部正交）。到计算域中几乎所有位置的速度向量）。在模拟中，在上升羽流和下降羽流中，模量对比方面出现的各向异性最强。克里斯滕森（Christensen）讨论了地幔动力学背景下各向异性材料行为的机理。地幔中的主要矿物相通常不表现出强弹性各向异性，但它们仍可以通过对流流动定向。因此，粘性各向异性（本文的主要重点）可能与弹性各向异性或地震各向异性无关。

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