Simulation of nonequilibrium outflow in vacuum from steady source

The investigation of monatomic gas (helium) steady outflow from the axially-symmetric sonic source in vacuum has been carried out. The source had uniform profiles of the parameters in its exit plane. The Direct Simulation Monte-Carlo method was used for the simulation. The research was done forthe range of Knudsen numbers from $10^4$ to infinity.
The influence of the Knudsen numbers on the flowfield and its parameters angular variations is analyzed. The special attention is paid to the flow on high deflection angles, including the region of the backflow. It is shown that the breakdown of the continuum flow leads to qualitatively different laws of variations of the flow parameters in comparison with the known continuum models.