Flow of foams is studied in a model porous medium, in a large range of capillary numbers Ca and relative gas flow rates $f_g$. From pressure measurements, we find that the effective viscosity is a decreasing power-law function of Ca, with the exponent ranging from $-1$ to $-0.75$. Direct observation reveals that the flow is heterogeneous. The fraction of preferential paths increases with both $f_g$ and Ca. In a straight channel of varying cross section, a bubble train behaves as a shear-thinning yield stress fluid. This feature accounts quantitatively for the effective viscosity in the micromodel.

中文翻译：

---

多孔介质中泡沫的屈服应力流体行为

在模型多孔介质中，大范围的毛细管数Ca和相对气体流速下研究泡沫的流动 $F_G$。通过压力测量，我们发现有效粘度是Ca的递减幂律函数，指数范围为$-\mathrm{1个}$ 至 $-0.75$。直接观察发现流量是非均质的。优先路径的比例随着$F_G$和钙。在横截面变化的直通道中，气泡序列表现为剪切稀化的屈服应力流体。此功能定量说明了微模型中的有效粘度。