Formation and Destabilization of the Particle Band on the Fluid-Fluid Interface

Area of Science:

• Fluid dynamics
• Interfacial phenomena
• Particle-laden flows

Background:

• Particle inclusion in Newtonian liquids alters interfacial dynamics.
• Viscous fingering typically requires a destabilizing viscosity ratio, but can occur with particle addition.
• Particle band formation and breakup are observed when particle diameter (d) approaches channel gap thickness (h).

Purpose of the Study:

• To experimentally characterize fluid-fluid interface evolution in particle-laden flows.
• To investigate the new physical regime where particle size is comparable to channel gap thickness.
• To develop a model for particle band formation and predict fingering onset.

Main Methods:

• Experimental investigation of fluid-fluid interface dynamics.
• Utilizing Hele-Show cells for flow configuration.
• Developing a model based on particle concentration and the ratio h/d.

Main Results:

• Observed formation and breakup of dense particle bands at the interface.
• Demonstrated viscous fingering in the absence of a destabilizing viscosity ratio due to particle inclusion.
• Successfully modeled fingering onset as a function of particle concentration and h/d.

Conclusions:

• Particle inclusion fundamentally changes interfacial dynamics, leading to instabilities.
• A new physical regime for viscous fingering is identified when particle size is comparable to channel gap thickness.
• The proposed model accurately captures fingering onset in this regime.