Numerical Study of Nozzle Exit Condition Effects on Jet Development

Abstract

Numerical predictions of the ine uence of nozzle exit conditions on the development of an ideally expanded supersonic rectangular jet areperformed. The effects of theseconditions on the jet’ s development have been found to be signie cant in experimental investigations. A model for the initial conditions is developed. A higher-order accurate e nite difference algorithm for the solution of the full three-dimensional Navier ‐Stokes equations is used to generate results that isolate the impacts of excitation amplitude, modal excitation, and corner vortices on the jet character. Time-averaged, cross-correlation, and cross-spectral data are gathered from the simulation and compared to experimental data. The results indicate that, over the range of operating conditions considered here, the excitation amplitude does not signie cantly alter the jet development. The corner vortices, although prescribed ina sensethatshouldanticipateaxisswitching (asdeterminedby experimentalsubsonicresults ), arefound to delay it. This appears to be caused by the dominance of e ow instabilities in supersonic jets and the observed tendency of the corner vortices to reduce the mixing associated with this instability. Finally, independent of modal excitation, the lowest-order modes (of the large-scale turbulence structure ) are found to consist of a combination of e apping in the minor axis plane with varicose motion in the major axis plane.