NUMERICAL SIMULATION FOR THE MOTION OF A SPHERICAL PARTICLE IN LAMINAR SQUARE DUCT FLOWS

摘要

The motion of a neutrally buoyant spherical particle suspended in laminar square duct flows was investigated numerically. The obtained trajectories of the particle indicated that the particle migrates laterally towards several points over the duct cross section, depending on the Reynolds number (Re) and the size ratio of the particle and the duct. It was found that these asymptotic positions agree with the points where the lateral forces exerted on the particle vanish, confirming that the particle asymptotic positions represent equilibrium positions. At low Re, they are located near the centers of the duct wall, which correspond to the so-called channel face equilibrium position observed experimentally. At relatively high Re, four additional equilibrium positions emerge on the diagonal in the duct cross section near the corners, corresponding to the channel corner equilibrium position. For Re between these two cases, the intermediate equilibrium positions are raised, and their locations were found to approach the diagonal with increasing Re. These migration properties account well for the observations of experiments, using micro-, submillimeter-, and macro-scale tubes.