Miscible viscous fingering involving production of gel by chemical reactions

We have experimentally investigated miscible viscous fingering with chemical reactions producing gel. Here, two systems were employed. In one system, sodium polyacrylate (SPA) solution and aluminum ion (Al3$+)$ solution were used as the more and less viscous liquids, respectively. In another system, SPA solution and ferric ion (Fe3$+)$ solution were used as the more and less viscous liquids, respectively. In the case of Al3$+$, displacement efficiency was smaller than that in the non-reactive case, whereas in the case of Fe3$+$, the displacement efficiency was larger. We consider that the difference in change of the patterns in the two systems will be caused by the difference in the properties of the gels. Therefore, we have measured the rheological properties of the gels by means of a rheometer. We discuss relationship between the VF patterns and the rheological measurement.