Gas-liquid flows through packed bed reactors (PBRs) are challenging to predict due to the tortuous flow paths that fluid interfaces must traverse. Experiments at the International Space Station showed that bubble and pulse flows are predominately observed under microgravity conditions, while trickle and spray flows observed under terrestrial conditions, are not present in microgravity. Toward understanding the physics behind the latter experiments, we simulate bubble flow through a PBR for different packing-particle-diameter-based Weber numbers and under different gravity conditions. We demonstrate different pore-scale mechanisms such as capillary entrapment, buoyancy entrapment, and inertia-induced bubble displacement. Then, we perform a quantitative analysis by introducing a new dynamic length scale, dependent upon the evolving gas-liquid interfacial area, to understand the dynamic trade-offs between the inertia, capillary, and buoyancy forces on a bubble passing through a PBR. This analysis leads us to define new dimensionless Weber-like numbers that delineate bubble entrapment from bubble displacement.

翻译：通过填充床反应器（PBR）的气液两相流因流体界面需穿越曲折的流动路径而难以预测。国际空间站的实验表明，在微重力条件下主要观察到气泡流和脉动流，而在地面条件下观察到的滴流和喷雾流在微重力环境中并不存在。为理解后述实验背后的物理机制，我们模拟了不同颗粒直径韦伯数及不同重力条件下气泡流经PBR的过程。我们展示了毛细滞留、浮力滞留及惯性诱导气泡位移等不同孔隙尺度机制。随后，通过引入一个依赖于气液界面动态演化的新动态长度尺度进行定量分析，以理解气泡穿过PBR时惯性力、毛细力和浮力之间的动态权衡。该分析引导我们定义了新的类韦伯无量纲数，用以区分气泡滞留与气泡位移。