The influence of heating and velocity on the unsteady nature of jet mixing layers is investigated by solving the time-dependent compressible Navier-Stokes equations using MacCormack’s explicit finite difference algorithm. The computations are performed for jet Mach numbers of 0.3 and 0.8 with flow total temperatures up to 800K. The Reynolds number ranges from 3 × 105 to 1.3 × 106. Excitation is accomplished by imposing an acoustic pressure signal inside the jet duct. The objective of this effort is to compare the response of heated and unheated jets with acoustic excitation at high and low subsonic Mach Numbers. The preliminary results indicate that without acoustic excitation the mixing in the heated jet is greater than in the unheated case. It has also been found that for the low speed heated jets (M= 0.3, Tt = 672K) acoustic excitation causes the production of large scale vortex structures to occur in a regular periodic manner with organized periodic pairing at some Strouhal numbers. These results are in agreement with experimental data.

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