Pattern Formation in Suspension Flows

Sungyon Lee
Mechanical Engineering, University of Minnesota

Lee focuses on two complementary flow configurations in which the presence of suspended particles may drastically alter the dynamics of the fluid-fluid interface and lead to pattern formation. First, Lee reports a particle-induced fingering instability when a mixture of particles and viscous oil is injected radially into an air-filled Hele-Shaw cell. Experimental results show that the onset and characteristics of fingering are most directly affected by the particle volume fraction but also depend on the ratio of the particle diameter to gap size. The physical mechanism and reduced model are also discussed. In the second part of the talk, Lee discusses the result of injecting air into a packing of soft hydrogel beads that are saturated in water. This new combination of buoyancy, capillarity, and elasticity under confinement leads to complex morphologies of air migration, as well as nontrivial dynamics in the amount of trapped air in the system.

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