Figure 14—Surfactant induced fingering stability.
Ostwald ripening also occurred in the high viscosity case
(polymer-induced) where surfactant- induced fingers were consumed by the
larger-sized polymer fingers as the surfactant induced fingers lost
their hydrodynamic stability (Figure 15 ). Polymer-induced
hydrodynamic stability then dominated the overall finger morphology
rendering the number of droplets zero. Polymer-induced fingers are also
observed to follow the original finger patterns of the
surfactant-induced fingers however, as they consumed and developed into
new morphologies. In our previous study (Lee et al. 2020), polymeric
nanofluid (cellulose nanocrystals) was also observed to demonstrate a
similar behavior and such effect became more pronounced as the viscosity
of the solution increased over time (increase in hydrostatic stability).