  Dynamics of a Brownian particle in an asymmetric micro-channel that is
subjected to an external oscillating force is numerically analyzed. In addition
to the elastic collisions with the walls that are kind of short range
interactions, the long range hydrodynamic influences of the walls have been
considered. We demonstrate how the geometrical parameters of the channel change
the rectified current of the particle. As a result of numerical calculations,
we show that long range hydrodynamic interactions with walls, decrease the
efficiency of the Brownian ratchet.
