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Collective dynamics of arrays of confined rigid spheres and deformable drops

kevin Shen (caltech), Michael Loewenberg (Yale university), Jerzy Blawzdziewicz (Texas Tech University), Pieter Janssen (Sabic Innovative Plastics), Eligiusz Wajnryb (polish academy of science), Patrick Anderson (Eindhoven University), Matthew Baron (Princeton University)

Complex Fluids: Suspensions, Emulsions, and Gels

Tue 4:20 - 5:40

Barus-Holley 160

The evolution of linear and two-dimensional arrays and clusters of rigid spheres and deformable drops in Poiseuille and shear flow between parallel walls is investigated with boundary integral simulations to determine the effect of particle deformation on the collective dynamics in confined particulate flows. We show that linear arrays of rigid spheres aligned in the flow direction undergo a particle-pairing instability and are unstable to lateral perturbations. In comparison, linear arrays of deformable drops exhibit additional dynamical features, including formation of transient triplets, cascades of pair-switching events, and formation of pairs with equal interparticle spacing. Deformation also stabilizes linear arrays of drops to lateral perturbations. These pairing and alignment phenomena are qualitatively explained in terms of hydrodynamic far-field dipole interactions (insensitive to particle deformation) and quadrupole interactions (deformation induced). A simplified model, based on this analysis, is presented and used to explore the collective dynamics of two-dimensional arrays of particles and drops in Poiseuille and shear flow. Our results demonstrate the quadrupolar interactions between deformable drops leads to the spontaneous formation of droplet strings in confined emulsions under shear as seen in experiments [Phys. Rev. Lett., 2001, v86, p1023].