Analysis of Thermal Slip in Oscillating Rarefied Flow Using Dsmc

In this study, the nonequilibrium effects at the stagnation wall in one-dimensional unsteady micro ow responding to the external sinusoidal oscillation are investigated. The  uctuating behavior of the rareŽ ed medium is simulated by employing the unsteady DSMC method under various conditions with different acoustic Reynolds and Knudsen numbers. As a result, it is found that the nonequilibrium effect exists at the stagnation wall, especially when the gas density number is small. Due to such a nonequilibrium effect found in a  uctuating medium, the Knudsen number representing system size becomes a more important system parameter than the acoustic Reynolds number even for the constant excitation frequency. Also, the validity of the well-known Maxwell–Smoluchowski relation and its higher-order modiŽ cations are tested by comparing the heat  uxes from these relations with the direct DSMC result.