title: Thermally induced gas flows in ratchet channels with diffuse and specular boundaries.
abstract: A net gas flow can be induced in the gap between periodically structured surfaces held at fixed but different temperatures when the reflection symmetry along the channel axis is broken. Such a situation arises when one surface features a ratchet structure and can be augmented by altering the boundary conditions on different parts of this surface, with some regions reflecting specularly and others diffusely. In order to investigate the physical mechanisms inducing the flow in this configuration at various Knudsen numbers and geometric configurations, direct simulation Monte Carlo (DSMC) simulations are employed using transient adaptive subcells for collision partner selection. At large Knudsen numbers the results compare favorably with analytical expressions, while for small Knudsen numbers a qualitative explanation for the flow in the strong temperature inhomogeneity at the tips of the ratchet is provided. A detailed investigation of the performance for various ratchet geometries suggests optimum working conditions for a Knudsen pump based on this mechanism.
authors.affiliation: High Performance Computing (HPC) Laboratory, Department of Mechanical Engineering, Ferdowsi University of Mashhad, 91775-1111, Mashhad, Iran.
authors.forename: Vahid
authors.initials: V
authors.lastname: Shahabi
authors.affiliation: Institute for Nano- and Microfluidics, Technische Universität Darmstadt, Alarich-Weiss-Straße 10, 64287 Darmstadt, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Baier
authors.affiliation: High Performance Computing (HPC) Laboratory, Department of Mechanical Engineering, Ferdowsi University of Mashhad, 91775-1111, Mashhad, Iran.
authors.forename: Ehsan
authors.initials: E
authors.lastname: Roohi
authors.affiliation: Institute for Nano- and Microfluidics, Technische Universität Darmstadt, Alarich-Weiss-Straße 10, 64287 Darmstadt, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Hardt