Molecular-dynamics simulation of two-dimensional thermophoresis

A numerical technique is presented for the thermal force exerted on a solid particle by a gaseous medium between two flat plates at different temperat ures, in the free molecular or transition flow. This is a two-dimensional m olecular-dynamics simulation of hard disks in a inhomogeneous thermal envir onment. All steady state features exhibited by the compressible hard-disk g as are shown to be consistent with the expected behaviors. Moreover the the rmal force experienced by a large solid disk is investigated, and compared to the analytical case of cylinders moving perpendicularly to the constant temperature gradient for an infinite Knudsen number and in an infinite medi um. We show precise examples of how this technique can be used simply to in vestigate more difficult practical problems, in particular the influence of nonlinear gradients for large applied differences of temperature, of proxi mity of the walls, and of smaller Knudsen numbers.