The Complexity of Nonlinear Flow and non‐Fickian Transport in Fractures Driven by Three‐Dimensional Recirculation Zones
The Complexity of Nonlinear Flow and non‐Fickian Transport in Fractures Driven by Three‐Dimensional Recirculation Zones
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DOI：
10.1029/2020jb020028
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发表时间：
2020-08
期刊：
影响因子：
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通讯作者：
Lichun Wang;M. Cardenas;Jia‐Qing Zhou;R. Ketcham
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文献类型：
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作者：
Lichun Wang;M. Cardenas;Jia‐Qing Zhou;R. Ketcham
尽管非线性裂缝流和非菲克输运在自然环境中很常见，但驱动和控制这些相互交织的现象的机制很少被一起仔细研究。在这里，我们通过三维真实裂缝内的数值模拟实验研究了再循环区（RZ）在控制非线性流动和非菲克输运方面的关键作用。 RZ 是从完全解析的流场中定量绘制的，直接模拟增加的雷诺数 (Re)。 RZ的发展和生长与孔径的扩张和收缩有关，决定了流动的非线性程度。此外，扩大的 RZ 具有更大的捕获溶质并随后将溶质释放回主流的能力。这总是会导致具有双峰、有时是多峰突破曲线（BTC）的非菲克运输。 BTC 模式之间的时间间隔通过幂律相关。 Re 和 RZ 体积足以表征双峰 BTC。
Although nonlinear fracture flow and non‐Fickian transport are common in natural settings, the mechanisms driving and controlling these intertwined phenomena are seldom scrutinized together. Here we investigated the critical role of recirculation zones (RZs) in controlling both nonlinear flow and non‐Fickian transport through numerical simulation experiments within three‐dimensional real fractures. RZs were quantitatively mapped from fully resolved flow fields directly simulated across increasing Reynolds number (Re). The development and growth of RZs, which are related to aperture expansion and contraction, determine the degree of flow nonlinearity. Moreover, expanding RZs have more capacity to capture and later release solutes back to the main flow. This always results in non‐Fickian transport with bimodal and sometimes multimodal breakthrough curves (BTCs). The time interval between the BTC modes is related via a power law. The Re and RZ volume are sufficient for characterizing the bimodal BTC.