  Rod shaped objects suspended in a flowing liquid might be orientated by the
velocity, nature of the liquid, the flow and the geometry of the channel
containing the flow. Orientation settings might enhance or inhibit certain
chemical reactions between the objects, other chemicals or with the walls of
vessels holding the flowing suspension. The probability density function (PDF)
describing the orientations of rod shaped objects in a flowing liquid satisfies
a Fokker-Planck equation whose solution is obtained analytically as well as
numerically from Langevin simulations for different flow parameters. The
analytical and numerical methods developed in the present work enable us to
calculate accurately the PDF for a range of the Peclet number $\alpha$ covering
several orders of magnitude, $10^{-4} \le \alpha \le 10^{8}$. We apply these
results to the experimental determination of dichroism and birefringence of the
suspension as a function of $\alpha$.
