Rarefied gas flows: hydrodynamic versus Monte Carlo modelling

A detailed comparison between the predictions of hydrodynamic and Monte Carlo modellings of rarefied gas flows is presented. The effects of velocity slip and temperature jump observed in rarefied gas flows are accounted for in a computational fluid dynamics code by modifying boundary conditions for velocity and temperature. Results predicted by this modified version of the computational fluid dynamics code are shown to be reasonably close to those predicted by the Direct Simulation Monte Carlo (DSMC) method for the Couette flow and for the molecular heat transfer between two infinite parallel plates for Knudsen numbers up to as high as about 1.5. The hydrodynamic model for rarefied gas flows can have a wide range of applications including the mathematical analysis of the processes in the planetary atmospheres and cometary mantles as an alternative to kinetic models.