Large Eddy Simulations of Hot Supersonic Jets for Aeroacoustics

The noise from the turbulent, hot, supersonic jets at take-offs and landings as well as high-Mach cruise at altitude dominates noise emanating from other powerplant components and has significant safety implications for launch personnel, as well as environmental impacts of noise pollution around military installation. Noise generation mechanisms of supersonic jets are complex and different than those of subsonic jets typically encountered in the exhausts of transport aircraft, with the large-scale turbulence structures being dominant in supersonic jets. Intense Eddy Mach wave radiation from regions along the jet shear layer is produced by the large-scale turbulence structures convected supersonically relative to the ambient medium. Additionally, oblique shock cell quasi-periodic structures, the result of imperfectly expanded supersonic jets, are noise radiation sources and contribute to discrete tone screech and broadband frequency noise. In Phase I, CRAFT Tech and Purdue University demonstrated and validated an innovative high-fidelity, hybrid RANS-LES method to characterize the noise sources in the near-field and mid-field of these hot, supersonic jets, with the farfield noise emissions obtained using the Ffowcs Williams-Hawkings technique. During Phase II, the model will be upgraded and applied to the analysis of noise attenuation concepts under consideration for military aircrafts under realistic scenarios.