Multiscale Analysis of Suspension Flow in Confined Systems: from liquid-air interfaces to narrowing channels
- Jeong, Deok-Hoon
- Advisor(s): Sauret, Alban
Abstract
The flow of suspensions of particles in confined systems is ubiquitous in both natural and industrial contexts, ranging from extrusion-based additive manufacturing to water infiltration in soil. However, characterizing and modeling the underlying physics, especially when the size of a constriction is similar to that of the suspended particles, remains a challenge. This PhD work has considered the interplay of particles with two distinct types of confinements featuring: soft and hard.
Soft confinements refer to deformable liquid-air interfaces, such as the ones involved in coating processes. Two processes sharing common features are considered: withdrawing a suspension from a capillary tube, leaving a thin film on the inner wall, and dip-coating, which consists of pulling a solid substrate out of a suspension bath to deposit a thin coating film on the surface. It is demonstrated that the stagnation point at the liquid-air meniscus acts as a tunable "filter" that governs the thickness of the coating film. The local thickness controls whether particles of a certain size will be deposited in the film or repelled back to the suspension bath. The deposition threshold of single spherical and anisotropic particles is investigated, and based on these findings, a filtration method for sorting particles of various sizes and guidelines for controlling the composition of the suspension film are proposed.
The discussion then shifts to the flow of suspension through hard confinements in millifluidic channels, where particles are confined within solid walls. The research focuses on the clogging mechanism known as bridging, where particles of a size comparable to the constriction form a stable arch, blocking the channel and prevent further particle transport. Through experimental investigations, the influence of the geometry of the constriction, including its size and angle, on the particle throughput before the formation of a clog is characterized. Additionally, unique clogging phenomena observed in three-dimensional systems are explored.