Numerical and Experimental Investigation of the Origin of a Rarefied Jet

摘要

We investigate the flow region close to a cylindrical nozzle from which a free rarefied jet is issuing. Analytical,nnumerical, and experimental procedures are used to completely describe the aerodynamic flowfield from thenupstream stagnation chamber, through the nozzle, and, finally, to the downstream ambient region. The combinedntheoretical–experimental investigation addresses the shortage of results in the literature concerning rarefied flownthrough finite length tubes, particularly in the region close to the jet origin.We also investigate the sensitivity of the jetncharacteristics to the velocity profile at the nozzle exit. Attention is paid to the physical differences between ancontinuumflow and a rarefied gas flow operating in the same geometrical conditions. The analytical expressions arenderived fromfreemolecular kinetics, the computational code is based on the direct simulationMonte Carlomethod,nand the experimental investigation uses measurements from a Patterson impact pressure probe. The broadernimplications of the results are discussed.