Onset of particle-induced miscible fingering

We experimentally investigate particle-induced miscible fingering by systematically injecting silicone oil into the mixture of oil and non-colloidal particles in a Hele-Shaw cell. In the case of miscible fingering in pure liquids, the viscosity ratio between the fluids has been shown to set the fingering onset in the large Peclet number limit. By contrast, the onset of particle-induced miscible fingering is observed to have a strong dependence on the relative particle size and cannot be simply explained by the viscosity ratio. We will experimentally quantify the onset of miscible fingering in suspensions and discuss what differentiates this particle-induced phenomenon from the pure liquid counterpart.