Influence of inertia on the rotation of axisymmetric particles in shear flow*

We experimentally investigate the rotational dynamics of a neutrally-buoyant axisymmetric particle in a viscous shearing flow. A custom-built shearing cell and a multi-view shape reconstruction method are used to obtain direct measurement of the period and the angular phase of the Jeffery orbits (Jeffery, 1922), focusing on oblate and prolate shapes (both ideal objects such as ellipsoids but also objects of practical interest such as cylinders). By systematically changing the viscosity of the fluid, we examine the effect of inertia on the dynamical behaviour of the suspended particle. While the measurements of the period of rotation are in good agreement with the results found in the Stokes regime, we report a systematic drift among several rotations toward limiting orbits for both fibers and disks. This is compared to the most recent small-inertia theories (Einarsson et al., 2015; Dabade et al., 2016).