Particle-laden filaments from a draining suspension

Area of Science:

• Fluid dynamics
• Soft matter physics
• Interfacial phenomena

Background:

• Hele-Shaw cells are used to study fluid instabilities.
• Suspensions of non-colloidal particles exhibit complex behaviors in confined geometries.
• Interfacial deformations are crucial in multiphase flow systems.

Purpose of the Study:

• To investigate the drainage dynamics of particle suspensions in a Hele-Shaw cell.
• To characterize the particle-scale instability and its relation to classic instabilities.
• To develop a theoretical framework for the observed phenomena.

Main Methods:

• Experimental investigation of particle suspension drainage in a vertical Hele-Shaw cell.
• Varying channel gap thickness and drainage rates.
• Analysis of interfacial deformations and pattern formation.
• Derivation of a scaling law based on force balance.

Main Results:

• Particle-laden filaments form normal to the receding interface, distinct from viscous fingering.
• At higher drainage rates, classic Saffman-Taylor instability is observed, enhanced by suspension viscosity.
• A scaling law based on single-particle force balance reasonably predicts the onset of particle-scale instability.
• The instability is confirmed to originate from individual particle dynamics.

Conclusions:

• The drainage of particle suspensions can lead to novel interfacial instabilities.
• Particle dynamics play a critical role in pattern formation at the microscale.
• The derived scaling law provides a fundamental understanding of particle-driven interfacial instabilities.