  We study the orientational dynamics of heavy silica microrods flowing through
a microfluidic channel. Comparing experiments and Brownian dynamics simulations
we identify different particle orbits, in particular in-plane tumbling
behavior, which cannot be explained by classical Jeffery theory, and we relate
this behavior to the rotational diffusion of the rods. By constructing the
full, three-dimensional, orientation distribution, we describe the rod
trajectories and quantify the persistence of Jeffery orbits using temporal
correlation functions of the Jeffery constant. We find that our colloidal rods
lose memory of their initial configuration in about a second, corresponding to
half a Jeffery period.
