Shear induced lift and rotation on MicroFiber deposition in low Reynolds number flows

Abstract

Lateral migration is of significant importance to fiber deposition in wall-bounded flows, especially when other active external physical transport mechanisms are absent. Due to great technical difficulty, investigation on this phenomenon is limited to fundamental derivations, and the implication to particle deposition has not been fully explored. To fill the gap, this study investigated the shear-induced lift and rotation on microfiber transport and deposition in low Reynolds number flows. Transport and deposition of non-neutrally buoyant ellipsoidal fibers in Poiseuille flow in horizontal and vertical channels is systematically examined, and various lateral migration scenarios are carefully investigated. It was found out that, in absence of the sideway gravity, shear-induced lift and rotation cause the fibers to drift across main streamlines in the vertical channel. This lateral movement is either the driving force for fiber deposition in a downward flow or pushes the particles toward channel center in an upward flow configuration. Lateral migration velocity in the vertical channel is found to correlate positively with fiber length and shear rate. Lateral migration is negligible in a horizontal channel where the sideway gravity is dominant. Current study clearly identified the presence of fiber transport scenarios where lateral migration driven by the shear-induced lift and rotation is the major contributor for fiber deposition in wall-bounded flows. The finding is of particular significance to practical applications, as frequently, they involve a combination of these transport scenarios either actively or passively. The study also provided additional insights to examine the equivalency of spheres to fiber dynamics.