Cross‐stream migration of nonspherical particles in second‐order fluid flows: Effect of flow profiles
Cheng‐Wei Tai, Shiyan Wang, Vivek Narsimhan
Abstract
Abstract We investigate the cross‐stream migration of spheroidal particles in a weakly viscoelastic fluid under various unbound parabolic flows (circular and elliptic tube flow, as well as 2D slit flow). The viscoelastic fluid investigated is a second‐order fluid under the co‐rotational limit. Our theory finds that the different flow profiles do not significantly alter the migration speed of particles toward the flow centerline, but drastically alter their orientation dynamics. At long times, prolate particles align along the flow direction in a circular tube flow, but undergo log‐rolling in a 2D slit flow. We explain the origin of these orientation dynamics, and explain why such behavior can give rise to a similar cross‐stream migration velocity. We lastly examine particle motion in an unbound elliptic tube flow with unequal velocity curvature in the two lateral directions. We quantify the conditions under which the long‐time particle orientation changes from log‐rolling to flow‐alignment.