Growth kinetics of interfacial patterns formed by the radial displacement of an aging viscoelastic suspension

When a soft glassy colloidal suspension is displaced by a Newtonian fluid in a radial Hele-Shaw geometry, the pattern morphology that develops at the interface is determined by the complex rheology of the former. We had reported in an earlier work [Palak, V. R. S. Parmar, D. Saha and R. Bandyopadhyay, JCIS Open, 6 (2022) 100047] that a range of pattern morphologies characterised by distinctive structural features can be formed by controlling the elasticity of the displaced suspension, the flow rate of the displacing fluid and the interfacial tension of the fluid pair. Interestingly, all the different morphological features can be distinguished in terms of their areal ratios, defined as the ratio of the areas occupied by the fully-developed pattern and the smallest circle enclosing it. In a significant advance to this earlier work, we show here that a systematic study of spatio-temporal pattern growth can reveal important information about pattern selection mechanisms. We analyse the time-evolution of the patterns to reveal interesting correlations between their growth mechanisms and fully-developed morphologies. We believe that such systematic identification of the unique temporal features characterising pattern growth at the interface between an aging viscoelastic clay suspension and a Newtonian fluid can be useful in pre-empting and suppressing the onset and evolution of interfacial instabilities in the displacement of mud and cement slurries.