  We study the rectification of a two-dimensional thermal gas in a channel of
asymmetric dissipative walls. For an ensemble of smooth Lennard-Jones
particles, our numerical simulations reveal a non-monotonic dependence of the
flux on the thermostat temperature, channel asymmetry, and particle density,
with three distinct regimes. Theoretical arguments are developed to shed light
on the functional dependence of the flux on the model parameters.
