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Article

Temperature effects on the aerodynamic and acoustic fields of a rectangular supersonic jet

Authors: Gojon, R, Baier , F, Gutmark, E., Mihaescu, M
Document Type: Article
Pubstate: Published
Journal: 55th AIAA Aerospace Sciences Meeting
Volume: AIAA2017-0002   19
Year: 2017

Abstract

In the first part of the paper, a modified artificial dissipation mechanism permitting to perform Large-Eddy Simulations of highly compressible flows is proposed. This dissipation mechanism is evaluated using one linear 2-D test case and two non-linear 2-D test cases. In the second part, the flow and acoustic near-field of rectangular supersonic jets are explored using compressible LES based on this modified artificial dissipation mechanism. At the exit of a converging diverging rectangular nozzle of aspect ratio 2 and of design Mach number 1.5, the jets are overexpanded. Four simulations with four different temperature ratios ranging from 1 to 3 are performed in order to characterize the effect of the temperature on the aerodynamic and aeroacoustic fields of the jets. The geometry of the nozzle and the exit conditions are chosen in order to match those in the experimental study conducted at the University of Cincinnati. It is shown that the total number of cells in the shock cell structure decreases with the increase of the temperature ratio. However, the temperature does not influence the size of the first shock cell and the linear decrease of the shock cell size in the downstream direction. The Overall Sound Pressure Levels are then plotted along the minor and major axis. It is seen that the intensity of the screech feedback mechanism increases with the Temperature Ratio. Moreover, for JetTR2.5 and JetTR3, the strong flapping motion of the jet along the minor axis due to the screech feedback mechanism seems to yield to an asymmetric organization of the Mach wave radiation. The convection velocity of the turbulent structures in the jet shear layers along the minor axis is then studied. Once normalized by the jet exit velocity, the convection velocity is shown to decrease with the jet temperature ratio. In the last part of the paper, the near- and far-field acoustic are studied. In the near-field, screech tones which frequencies are consistent with both experimental data and a theoretical model are observed. In the far-field, four acoustic components typical of non-ideally supersonic jets are observed, namely the screech noise, the broadband shock-associated noise, the mixing noise and the Mach wave noise. Their directivities and frequencies are in agreement with experimental results and models.