Computational Study of a Contoured Plug-Nozzle as a Supersonic Jet NoiseSuppressor

摘要

The report summarizes a computational jet noise study of an ideal contoured plug-nozzle (CPN). The gas dynamics of the jet flows have been predicted using the CFD code, NPARC with k-epsilon turbulence model; these data are then used as inputs to perform the noise computations based on the modified version of General Electric MGB code. The study covers a range of operating pressure ratio, 2.0 less than xi less than 5.0 (shockless flow at design pressure ratio, xi(d) = 3.62). The computational results indicate consistent noise reduction effectiveness of the CPN at all operating pressure ratios. At the design pressure ratio (shockless), the codes predict overall sound pressure levels within +3.O dB of the experimental data. But the theory overpredicts the OASPL's at all pressure ratios except at lower angles to the jet axis in overexpanded mode (xi less than xi(d)), the deviations being within 4.5 dB. The mechanism of shock formations in the CPN jet flows is noted to be basically different from those in the convergent-divergent nozzle jet flows.