Inertial migration of a neutrally buoyant finite sized sphere in a pipe with streamwise periodic corrugations

Abstract

A finite sized neutrally buoyant object migrates radially under the action of inertial lift in a smooth circular pipe due to the hydrodynamic coupling between the object and the surrounding fluid. Decorating the pipe walls with periodic corrugations alters the deformation of the fluid locally, thereby modifies the object’s migration pattern. This study investigates inertial migration of a finite sized neutrally buoyant sphere in a pipe with streamwise periodic corrugations of a size comparable to the sphere diameter. Fully resolved simulations are performed using smoothed particle hydrodynamics (SPH) to investigate the effect of Reynolds number, streamwise arrangement of corrugations as well as the corrugation topology on the inertial coupling of fluid and solid domains and long-time dynamics of suspended particles. The results show that periodicity in corrugation arrangement causes near wall fluid to deform periodically, this is reflected on the migrating sphere as oscillating linear and radial accelerations. These oscillations result in the object to spin around an axis perpendicular to its primary rotation axis. This secondary rotation permits the object to escape locally active flow regions and results in it to follow an oscillatory path. The rate and strength of such oscillations, thus its migratory behavior can be orchestrated by controlling the corrugation arrangement and/or topology.