Investigating Rayleigh–Bénard convection, its onset, and its effect on mass transfer are crucial for understanding the effective dissolution processes between carbon-dioxide (CO)-saturated and CO-free brines in CO geological storage. However, most previous investigations on the onset of convection and mass transfer properties were conducted by 2D and 3D numerical simulations. Only a few 3D experimental studies of Rayleigh–Bénard convection were reported. In this study, we proposed a non-destructive experimental approach to visualize the three-dimensional (3D) fingering structure of Rayleigh–Bénard convection using a micro-focused X-ray computed tomography (X-ray CT) scanner. The experimental conditions covered the Rayleigh number () range between 3400 and 23000, which also includes the value of the actual condition of gas reservoir field. Results show that fingers and coalescence dynamics significantly developed upon increasing . At higher , the finger concentration experienced greater dilution due to the combined effects of unsteady finger motion and enhanced dispersion strength. The maximum finger extension velocity is linearly proportional to . The convective mass flux () correlated with by a power-law relationship. The findings in this study provide a better understanding of the influence of on mass transport properties and can be used as a reference for developing the convective mass transfer model of Rayleigh–Bénard convection in 3D porous media.

中文翻译：

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多孔介质中瑞利-贝纳德对流的三维可视化

研究瑞利-贝纳德对流、其发生及其对传质的影响对于了解 CO 地质封存中二氧化碳 (CO) 饱和盐水和不含 CO 的盐水之间的有效溶解过程至关重要。然而，之前大多数对对流和传质特性的研究都是通过 2D 和 3D 数值模拟进行的。仅报道了少数瑞利-贝纳德对流的 3D 实验研究。在这项研究中，我们提出了一种无损实验方法，使用微聚焦 X 射线计算机断层扫描 (X 射线 CT) 扫描仪来可视化瑞利-贝纳德对流的三维 (3D) 指法结构。实验条件涵盖瑞利数()范围3400～23000，其中也包括气藏田实际条件的值。结果表明，随着 的增加，手指和聚结动力学显着发展。在较高的值下，由于不稳定的手指运动和增强的分散强度的综合影响，手指浓度经历了更大的稀释。最大手指伸展速度与 成线性比例。对流质量通量 () 与幂律关系相关。本研究的结果使人们更好地理解了对传质特性的影响，可以作为开发3D多孔介质中瑞利-贝纳德对流的对流传质模型的参考。