多孔介质中高Rayleigh数溶质对流的Rayleigh分馏
Rayleigh fractionation in high-Rayleigh-number solutal convection in porous media
摘要：
本文研究了两组分在混合气体和饱和对流多孔层之间的分馏。地质二氧化碳（CO $_2$）存储的动机，我们假设对流仅由第一个组件的溶解浓度驱动，而第二个作为示踪剂与扩散性增加。在高瑞利数对流的直接数值模拟表明，分区的组件，在一般情况下，不遵循瑞利分馏的趋势，因为通常假设。最初，示踪剂扩散率的增加也会增加其通量，因为扩散性边界层更深地渗透到流动中。然而，对于$D_2\geq 10\, D_1$，其中$D_1$和$D_2$分别是CO $_2$和示踪剂在水中的扩散系数，示踪剂在上升和下降羽流之间的横向泄漏降低了示踪剂通量。组分之间的瑞利分馏仅在两种气体的溶解度和气体中的初始浓度差异非常大的情况下实现。
英文摘要：
We study the fractionation of two components between a well-mixed gas and a saturated convecting porous layer. Motivated by geological carbon dioxide (CO$_2$) storage we assume that convection is driven only by the dissolved concentration of the first component, while the second acts as a tracer with increased diffusivity. Direct numerical simulations for convection at high Rayleigh numbers reveal that the partitioning of the components, in general, does not follow a Rayleigh fractionation trend, as commonly assumed. Initially, increases in tracer diffusivity also increase its flux, because the diffusive boundary layer penetrates deeper into the flow. However, for $D_2\geq 10\, D_1$, where $D_1$ and $D_2$ are, respectively, the diffusion coefficients of CO$_2$ and the tracer in water, the transverse leakage of tracer between up- and down-welling plumes reduces the tracer flux. Rayleigh fractionation between components is only realized in the limit of two gases with very large differences in solubility and initial concentration in the gas.
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