COMPUTATIONS OF HIGH-SPEED, HIGH KNUDSEN NUMBER MICROCHANNEL FLOWS

The effect of varying the Knudsen number Kn in microchannel flows was simulated using the direct simulation Monte Carlo method (DSMC) combin ed with the monotonic Lagrangian grid (MLG). The DSMC-MLG, a method th at provides automatic grid refinement according to number density, has been optimized for massively parallel computation and provides a fast , highly resolved description of the flow. New outflow boundary condit ions, consistent with the DSMC-MLG algorithm, were developed to allow the user to specify the outflow pressures. The effect of varying Kn wa s examined for three different values of Kn (0.07, 0.14, and 0.19) for a high-speed inflow by varying the channel height. A Navier-Stokes co mputation was also performed to show continuum regime flow. The comput ations provide contours of pressure, temperature, and Mach number to s how complex interactions among oblique shocks and boundary layers, and how these change with the Kn. Temperature jumps and slip velocities a s functions of position along the wall are compared for all cases. The computations show that the velocity slip is approximately constant be hind the shock, while the temperature jump is reduced.