Denis Semwogerere, Jeffrey F. Morris, and Eric R. Weeks, J. Fluid Mech.

An experimental investigation of the influence of
Brownian motion on shear-induced particle migration of
monodisperse suspensions of micron-sized colloidal particles
is presented. The suspension is pumped through a 50 micron x
500 micron rectangular cross-section glass channel. The
experiments are characterized chiefly by the sample volume
fraction (*phi* = 0.1 - 0.4), and the flow rate expressed as
the nondimensional Peclet number (*Pe* = 10 - 400). For each
experiment we measure the entrance length, which is the distance
from the inlet of the channel required for the concentration
profile to develop to its nonuniform steady state. The entrance
length increases strongly with increasing *Pe* for *Pe*
<< 100, in marked contrast to non-Brownian flows for which the
entrance length is flow rate independent. For larger *Pe*
the entrance length reaches a constant value which depends on
the other experimental parameters. Additionally, the entrance
length decreases with increasing *phi*; this effect is strongest
for low *phi*. Modeling of the migration based on spatial
variation of the normal stresses due to the particles captures
the primary features observed in the axial evolution over a
range of *Pe* and *phi*.