  Suspensions of rodlike objects in a liquid are encountered in many areas of
science and technology and the need to orientate them is extremely important to
enhance or inhibit certain chemical reactions between them, other chemicals or
with the walls of vessels holding the flowing suspension. Orientation control
is feasible by altering velocity and nature of the liquid, its flow and the
geometry of the channel containing the flow. In this work we consider the
simplest possibility of orientation control with flow in two dimensions on the
basis of the orientation distribution of rodlike objects. The simple
differential equation satisfied by the orientation probability density function
is derived and its solution discussed. In addition, we show how birefringence
and dichroism ("Maxwell effect") of the suspension provide a direct
experimental test of orientation control.
