The motion of a neutrally buoyant particle of an elliptic shape in two dimensional shear flow: A numerical study
Journal
Physics of Fluids
Journal Volume
27
Journal Issue
8
Date Issued
2015
Author(s)
Abstract
In this article, we investigate the motion of a neutrally buoyant particle of an elliptic shape freely moving in two dimensional shear flow by direct numerical simulation. An elliptic shape particle in shear flow, when initially being placed at the middle between two walls, either keeps rotating or has a stationary inclination angle depending on the particle Reynolds number Re=Grra2/ν, where Gr is the shear rate, ra is the semi-long axis of the elliptic particle, and ν is the kinetic viscosity of the fluid. The critical particle Reynolds number Recr for the transition from a rotating motion to a stationary orientation depends on the aspect ratio AR = rb/ra and the confined ratio K = 2ra/H, where rb is the semi-short axis of the elliptic particle and H is the distance between two walls. Although the increasing of either parameters makes an increase in Recr, the dynamic mechanism is distinct. The AR variation causes the change of geometry shape; however, the K variation influences the wall effect. The stationary inclination angle of non-rotating slender elliptic particle with smaller confined ratio seems to depend only on the value of Re − Recr. An expected equilibrium position of the particle mass center in shear flow is the centerline between two walls. When placing the particle away from the centerline initially, it migrates either toward an equilibrium height away from the middle between two walls or back to the middle depending on the confined ratio and particle Reynolds number; but for higher particle Reynolds numbers, besides the previous two positions, the elliptic particle placed close to the middle just moves parallel to the wall with a stationary orientation.
Type
journal article