  The pressure-driven flow of a suspension of spinning particles in a
rectangular channel is studied using an acoustic method. The suspension is made
of insulating particles (PMMA) dispersed in a slightly conducting oil (Ugilec +
Dielec) and is subjected to a DC electric field. In such a case, the particles
are polarized in the direction opposite to that of the electric field and begin
to rotate in order to flip their dipoles in the field direction. Such a
rotation of the particles is known as Quincke rotation and is responsible for
an important decrease of the effective viscosity of the suspension. Indeed, due
to the electric torque exerted on the particles, the stress tensor in the
suspension is not symmetric anymore and a driving effect arises from the
anti-symmetric part. When such a suspension flows through a rectangular
channel, the velocity profile is expected to deviate from the usual Poiseuille
flow. In this paper, the velocity profiles are measured using Pulsed Ultrasound
Doppler Velocimetry technique. They compare well with those that are computed
from the otherwise measured rheological law.
