Study on a reacting viscous fingering with gel production based on interfacial LAOS rheological measurement

We experimentally investigate the influence of flow rate on viscous fingering (VF) involving production of gel by chemical reactions. Three solution systems are used. As the more viscous fluid, 0.4 wt% sodium polyacrylate (SPA) solution is used in the first system, while 0.35 wt% xanthan gum (XG) solution is used in the second system. For both the systems, 20 wt% glycerol solution containing 0.1 M ferric ion is used as the less viscous fluids. In the third system, 2.5 wt% sodium alginate (SA) solution is used as the more viscous fluid, while 20 wt% glycerol solution containing 0.05 M calcium ion is used as the less viscous fluid. In VF experiment, the fracture pattern is observed for lower flow rate in SPA system, whereas for higher flow rate in XG system, and it is not confirmed for SA system. We consider the difference originates from the viscoelastic properties of the gels depending on deformation rate. Therefore, we analyze such influences by performing large amplitude oscillatory shear (LAOS) measurement of gel formed at the reactive liquid – liquid interface. Based on analysis of interfacial LAOS measurement, we propose that both yield of gel and a certain magnitude of gel’s elasticity are necessary for the fracture formation.