Department of Geosciences and Engineering, Delft University of Technology, Delft, The Netherlands.
Department of Chemical Engineering, Delft University of Technology, Delft, The Netherlands.
Soft Matter. 2017 Jan 25;13(4):765-775. doi: 10.1039/c6sm02199a.
We experimentally investigate the flow of hydrolyzed polyacrylamide (HPAM) solution with and without salt in model porous media at high Weissenberg numbers (Wi > 1.0). The effect of pore shapes on the flow pattern and pressure drop is explored by using periodic arrays of circular and square pillars in aligned and staggered layouts. In the apparent shear-thinning regime, we observe stationary dead zones upstream of the pillars. In addition, we confirm that the size of stationary dead zones correlates with the level of shear-thinning, by varying the amount of salt in HPAM solution. At higher shear rates (or Wi), these dead zones are periodically washed away. We present the mechanism of this elastic instability and characterize it based on the pressure drop fluctuation spectral density.
我们在高威森贝数（Wi>1.0）下实验研究了有无盐的水解聚丙烯酰胺（HPAM）溶液在模型多孔介质中的流动。通过使用圆形和方形支柱的周期性阵列以对齐和交错的方式排列，探索了孔隙形状对流动模式和压降的影响。在明显的剪切变稀区域，我们观察到支柱上游的固定死区。此外，我们通过改变 HPAM 溶液中的盐量，证实固定死区的大小与剪切变稀的程度相关。在较高的剪切速率（或 Wi）下，这些死区会被周期性地冲走。我们提出了这种弹性不稳定性的机制，并根据压降波动谱密度对其进行了表征。
