DSMC-Based Shear-Stress/Velocity-Slip Boundary Condition for Navier-Stokes Couette-Flow Simulations

摘要

Direct Simulation Monte Carlo (DSMC) simulations are used to develop a shear-stress/velocity-slip boundary condition for Navier-Stokes (NS) simulations of low-speed isothermal Couette flow. In this boundary condition, the wall shear stress equals the product of the difference between the gas and wall velocities and a momentum transfer coefficient. This momentum transfer coefficient depends on two dimensionless parameters that determine its behavior in the near-continuum and transitional regimes, respectively. For a given gas, these parameters are determined by comparing the NS Couette-flow shear-stress expression to DSMC shear-stress values for free-molecular to near-continuum pressures with three values of the accommodation coefficient. The parameter values for argon, helium, nitrogen, air, and inverse-power-law (IPL) interactions from hard-sphere to Maxwell lie within narrow ranges. For the hard-sphere interaction, the DSMC-based results are in excellent agreement with previously published analytical approximations.