近日，
该研究团队成功利用频闪X射线微断层扫描技术，实现了对原位捕获固结多孔介质中多相流的四维（4D，即3D+时间）观察。在总持续时间为6.5秒、帧率高达2kHz的实验条件下，研究人员获取了前所未有的多尺度液体动力学数据。该研究的断层扫描策略基于一个重要事实：尽管海恩斯跳跃在时间上间隔不规则，但其发生几乎是确定的，并且在吸水-排水循环中可以重复。利用这一特性，研究人员深入研究了由烧结玻璃碎片构成的多孔介质中随时间变化的流动模式。
通过这种方法的可重复性，研究人员能够将不同角度下连续周期中记录的射线投影组合成3D电影。这使得他们能够以前所未有的时空分辨率（比现有技术高出两个数量级）重建孔隙尺度的事件，如海恩斯跳跃。这种高分辨率使他们能够详细探索排水过程中的界面动力学，包括流体前缘的位移和速度。该研究的实验方法不仅揭示了多孔介质中多相流的复杂行为，而且为研究快速而确定的介观过程开辟了新的道路。
据悉，多孔介质中的缓慢多相流现象非常有趣，其潜在动力学具有高度的确定性，但受到时空过程层次结构的影响。虽然实验研究在多相流动方面取得了显著的进展，但在孔隙尺度上以毫秒级分辨率探测流体动力学的三维显微镜方法仍然相对稀缺。 然而，在这些特定的长度和时间尺度上，发生了一种被称为“海恩斯跳跃”的关键孔隙填充事件。
附：英文原文
Title: Multiscale drainage dynamics with Haines jumps monitored by stroboscopic 4D X-ray microscopy
Author: Tekseth, Kim Robert, Mirzaei, Fazel, Lukic, Bratislav, Chattopadhyay, Basab, Breiby, Dag Werner
Issue&Volume: 2023-12-26
Abstract: Slow multiphase flow in porous media is intriguing because its underlying dynamics is almost deterministic, yet depends on a hierarchy of spatiotemporal processes. There has been great progress in the experimental study of such multiphase flows, but three-dimensional (3D) microscopy methods probing the pore-scale fluid dynamics with millisecond resolution have been lacking. Yet, it is precisely at these length and time scales that the crucial pore-filling events known as Haines jumps take place. Here, we report four-dimensional (4D) (3D + time) observations of multiphase flow in a consolidated porous medium as captured in situ by stroboscopic X-ray micro-tomography. With a total duration of 6.5 s and 2 kHz frame rate, our experiments provide unprecedented access to the multiscale liquid dynamics. Our tomography strategy relies on the fact that Haines jumps, although irregularly spaced in time, are almost deterministic, and therefore repeatable during imbibition-drainage cycling. We studied the time-dependent flow pattern in a porous medium consisting of sintered glass shards. Exploiting the repeatability, we could combine the radiographic projections recorded under different angles during successive cycles into a 3D movie, allowing us to reconstruct pore-scale events, such as Haines jumps, with a spatiotemporal resolution that is two orders of magnitude higher than was hitherto possible. This high resolution allows us to explore the detailed interfacial dynamics during drainage, including fluid-front displacements and velocities. Our experimental approach opens the way to the study of fast, yet deterministic mesoscopic processes also other than flow in porous media.
DOI: 10.1073/pnas.2305890120
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2305890120