21st Congress of International Council of the Aeronautical Sciences, Melbourne, Australia, 13-18 September, 1998
Paper ICAS-98-2.10.5

SUPERSONIC UNDEREXPANDED RECTANGULAR JET OSCILLATIONS: A COMPUTATIONAL STUDY

Han S., Taghavi R. R.
The University of Kansas, USA

Keywords: supersonic, underexpanded, rectangular, jet oscillations, computational study

A computational study on the effects of nozzle exit geometry on the underexpanded supersonic jet evolution and comparison with experimental data is presented in this paper. The purpose of this study was to answer the following questions: (1) Can reasonable information about the unsteady flapping oscillations of underexpanded rectangular-supersonic jets be calculated by using the three-dimensional Proteus computer code? (2) What are the effects of nozzle exit geometry on mixing characteristics of supersonic jets? In this study, the supersonic jets emerging from the rectangular and notched nozzles are investigated for their mixing characteristics. The aspect ratio of these nozzles was 5.0. The computational analysis was conducted by running the three-dimensional Proteus code developed at NASA Lewis Research Center. The code solves the three-dimensional, Reynolds averaged, unsteady, compressible Navier-Stokes equations in strong conservation law form. A structured grid system and. An improved grid system produced by shock adaptive grid method was used for this study. The structured grid was used first and based on the results of calculations, the shock adaptive grid was generated and the code was run again with this new grid. The centerline distributions of axial velocity, static pressure, and mass flow rate are plotted and compared with experimental data along with the axial velocity and static pressure contour maps at the center planes. It is concluded that the three-dimensional Proteus code can be used to analyze the underexpanded supersonic rectangular jet mixing and flapping characteristics. It is also shown that the change of nozzle exit geometry strongly affects the jet mixing.

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