Dynamic three-dimensional computed tomography (CT) imaging of liquid transport in porous media has primarily been conducted at high brilliance synchrotrons thus allowing fast, sometimes sub-second, temporal resolution to be obtained. University laboratory CT instruments lack the photon flux available at synchrotrons, limiting the obtainable spatiotemporal resolution. Here, we discuss our experiences with instrumentation and software methods to conduct time-resolved micro-computed tomography (4D-CT) experiments of flow in porous media, based on a conventional CT instrument operated with a highly undersampled number of projections. An experimental stage outfitted with syringe pumps placed on a slip ring allowed two-phase flow experiments to be carried out with continuous unidirectional rotation and without obstruction of the liquid supply lines. An iterative reconstruction algorithm based on a priori information was used to provide high image quality and ∼30 s time resolution despite the few and low-exposed projections compared to standard protocols. The experimental technique was demonstrated with imbibition and drainage in glass bead-pack and Bentheimer sandstone samples with sub-minute temporal resolution, allowing the liquid configurations just before and after fast dynamic phenomena such as cooperative pore-filling events and Haines jumps to be captured. Power law scaling exponents for burst volumes associated with imbibition and drainage were estimated and compared with the literature. That 4D-CT experiments can be carried out using conventional CT instruments to challenge contemporary permeability models is of high importance for many geo-, bio- and environmental physics challenges.

中文翻译：

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使用基于实验室的微型计算机断层扫描对多孔介质中的两相流进行 4D 成像

多孔介质中液体传输的动态三维计算机断层扫描 (CT) 成像主要在高亮度同步加速器上进行，因此可以获得快速（有时是亚秒级）的时间分辨率。大学实验室 CT 仪器缺乏同步加速器可用的光子通量，限制了可获得的时空分辨率。在这里，我们讨论了我们使用仪器和软件方法进行多孔介质流动时间分辨微计算机断层扫描 (4D-CT) 实验的经验，这些实验基于使用高度欠采样投影数量操作的传统 CT 仪器。配备有放置在滑环上的注射泵的实验台允许在连续单向旋转且不阻塞液体供应管线的情况下进行两相流实验。尽管与标准协议相比，投影很少且曝光度低，但使用基于先验信息的迭代重建算法来提供高图像质量和约 30 秒的时间分辨率。该实验技术通过玻璃珠填充和本泰默砂岩样品的吸胀和排水进行了亚分钟时间分辨率的演示，从而可以捕获快速动态现象（例如协同孔隙填充事件和海恩斯跳跃）之前和之后的液体构型。估计了与吸入和排水相关的爆破体积的幂律标度指数，并与文献进行了比较。可以使用传统 CT 仪器进行 4D-CT 实验来挑战当代渗透率模型，这对于许多地质、生物和环境物理挑战非常重要。