Numerical Study of a Supersonic Jet Impinging on a Flat Plate in a Vacuum

摘要

Impingement of an axially symmetric free jet into a vacuum from a supersonic nozzle (M_e = 5) on a flat plate was studied based upon the Direct Simulation Monte Carlo method. Numerical simulations were carried out for hard-sphere molecules (for γ = 5/3) to examine the rarefaction effects of plume impingement in a vacuum environment. The distance from nozzle exit to the plate was four times the nozzle diameter. Results show that (1) a concaved plate shock is formed adjacent to the plate, (2) the compressed gas behind the plate shock expands and a supersonic plate jet is formed, and (3) the primary jet is then enveloped by the plate jet. The maximum value of the stagnation pressure on the plate is about 4.2% of the stagnation pressure of the primary jet. The maximum shear stress on the flat plate was found at R/H ≈ 0.17 for the case of Kn_D = 0.00625. This value may be slightly dependent on the Knudsen number. Present results showed a good agreement with the previous results of continuum theory and the results of experiments except for the rarefaction effects.