Frictional Fluid Dynamics and Plug Formation in Multiphase Millifluidic Flow.

Area of Science:

• Physics
• Fluid Dynamics
• Materials Science

Background:

• Granular suspensions exhibit complex flow behaviors when subjected to external forces.
• The displacement of liquids by gases in porous media is crucial in various industrial and natural processes.

Purpose of the Study:

• To experimentally investigate the flow and patterning of granular suspensions displaced by air in confined geometries.
• To understand the mechanisms of plug formation, clogging, and subsequent gas percolation.
• To identify the conditions for fluidization and complete evacuation of the suspension.

Main Methods:

• Experimental study of granular suspension displacement by air in a narrow tube.
• Observation of interface dynamics, plug formation, and gas percolation.
• Development of an analytical model for granular accumulation stability.

Main Results:

• The invading air-liquid interface forms granular plugs that clog the tube due to wall friction.
• Gas percolates through static plugs once pressure exceeds capillary entry pressure, reestablishing flow.
• The process leads to a trail of plugs, and a critical withdrawal rate induces fluidization and complete evacuation.
• An analytical model accurately predicts the observed flow regimes based on stability conditions.

Conclusions:

• The study elucidates the clogging and unclogging dynamics of granular suspensions during air displacement.
• A critical liquid withdrawal rate governs the transition to a fluidization regime, enabling complete suspension evacuation.
• The developed model provides a predictive tool for understanding and controlling granular flow in confined systems.