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 the trickle and spray flows observed under terrestrial conditions are not present in microgravity. To understand the physics behind the former 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 new dynamic scales, 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：填充床反应器中的气液流动由于流体界面必须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冲流，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。为理解前述实验背后的物理机理，我们基于不同填料粒径韦伯数和重力条件模拟了气泡流经填充床反应器的过程。我们展示了不同孔隙尺度的机制，如毛细捕获、浮力捕获和惯性诱导气泡位移。随后，通过引入依赖于气液界面面积演化的新动态标度进行定量分析，以理解惯性力、毛细力和浮力在气泡通过填充床反应器时的动态权衡。该分析使我们定义了新的无量纲类韦伯数，用于区分气泡捕获与气泡位移。