Analysis of Single and Dual Under-Expanded, Rarefied Jets
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A numerical study, using the Direct Simulation Monte Carlo (DSMC) approach, of the interaction effects between two identical sonic under-expanded nitrogen jets under rarefied conditions is reported. In this paper, the effects of the jet stagnation Knudsen number (Kn<sub>s</sub>), the ratio of the stagnation-to-background pressure (P<sub>s</sub>/P<sub>b</sub>), and the distance between the jet orifices (L/D) were investigated for a range of these parameters. The background pressure has a very significant effect on the physics of flow, and the interactions between the two jets affect the location of the Mach disks for both the primary and secondary jets. When P<sub>s</sub>/P<sub>b</sub> is relatively large (P<sub>s</sub>/P<sub>b</sub>>200), the separation distance L/D has only a mild effect on the location of the Mach disk in the secondary jet. A study of the rotational-translational non-equilibrium showed large deviations between the translational and rotational temperatures in the vicinity of the orifice plate.