The impact of sedimentary anisotropy on solute mixing in stacked scour‐pool structures
The impact of sedimentary anisotropy on solute mixing in stacked scour‐pool structures
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DOI：
10.1002/2016wr019665
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发表时间：
2017-04
影响因子：
5.4
通讯作者：
J. Bennett;C. Haslauer;O. Cirpka
中科院分区：
文献类型：
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作者：
J. Bennett;C. Haslauer;O. Cirpka
水力传导系数的空间变异性对溶质扩散和混合有很强的影响。在大多数研究中，其局部各向异性被忽略。最近的研究表明，沉积各向异性的空间变化方向可以导致扭曲流增强横向混合，但大多数这些研究使用地质学上难以置信的几何形状。我们使用基于对象的方法来生成具有各向同性或各向异性填充的堆叠冲刷池结构，这些结构通常在冰川沉积物中报告。我们分析了如何在这些功能的空间变化的各向同性导电性和内部各向异性的变化影响横向羽流变形和纵向和横向的传播和混合。在五个测试案例中，电导率的标量值或其各向异性的空间方向在冲刷池结构之间变化。基于100种随机配置，我们比较了速度分量、拉伸和折叠指标、平流旅行时间分布、平流弥散输送中的一个和两个粒子统计以及稳态平流弥散输送的通量相关稀释指数的变化性。五个测试案例。内部各向异性取向的变化引起横向速度分量的强烈变化，这导致横向方向上的变形并增强横向混合，而它几乎不影响纵向速度分量的变化，从而影响纵向扩散和混合。后者由水力传导系数标量值的空间变异性控制。我们的研究结果表明，沉积各向异性是横向混合的重要，而它可能被忽略时，考虑纵向扩展和混合。
The spatial variability of hydraulic conductivity is known to have a strong impact on solute spreading and mixing. In most investigations, its local anisotropy has been neglected. Recent studies have shown that spatially varying orientation in sedimentary anisotropy can lead to twisting flow enhancing transverse mixing, but most of these studies used geologically implausible geometries. We use an object‐based approach to generate stacked scour‐pool structures with either isotropic or anisotropic filling which are typically reported in glacial outwash deposits. We analyze how spatially variable isotropic conductivity and variation of internal anisotropy in these features impacts transverse plume deformation and both longitudinal and transverse spreading and mixing. In five test cases, either the scalar values of conductivity or the spatial orientation of its anisotropy is varied between the scour‐pool structures. Based on 100 random configurations, we compare the variability of velocity components, stretching and folding metrics, advective travel‐time distributions, one and two‐particle statistics in advective‐dispersive transport, and the flux‐related dilution indices for steady state advective‐dispersive transport among the five test cases. Variation in the orientation of internal anisotropy causes strong variability in the lateral velocity components, which leads to deformation in transverse directions and enhances transverse mixing, whereas it hardly affects the variability of the longitudinal velocity component and thus longitudinal spreading and mixing. The latter is controlled by the spatial variability in the scalar values of hydraulic conductivity. Our results demonstrate that sedimentary anisotropy is important for transverse mixing, whereas it may be neglected when considering longitudinal spreading and mixing.