21st Congress of International Council of the Aeronautical Sciences, Melbourne, Australia, 13-18 September, 1998
Paper ICAS-98-2.4.3

SELF-EXCITED OSCILLATIONS OF SUPERSONIC OPPOSING JET FLOW

Fujita M., Karashima K.*
Mitsubishi Research Institute, Inc., Japan; *Nishinippon Institute of Technology, Japan

Keywords: self-excited oscillations, supersonic opposing jet flow

The purpose of the present study is to validate quantitatively the theoretical models suggested in the previous study of one of the authors, in which the mechanism of self-excited oscillations of a supersonic opposing jet flow in a supersonic free stream was interpreted physically. Wind tunnel experiments as well as computations are conducted to obtain unsteady flow fields at several total pressure ratios of jet to free stream. The Mach number of free . Stream and jet are 2.5 and 1.5, respectively. In the experiment, a hemisphere-cylinder model with a jet nozzle at its stagnation point is employed, and unsteady surface pressure is measured by pressure-transducers which are directly embedded into the model. In the computation, a time-accurate algorithm using a viscous compressible flow model is applied to the identical configuration as the experimental model. Unsteady solutions are obtained by a finite difference method which consists of high-resolution upwind space differencing and second-order explicit time integration. The results obtained show that the frequency of oscillations depends on the total pressure ratio and the scale of model examined. The . Numerical solutions compare well with the experimental results, and the theoretical models mentioned above have been validated quantitatively.

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