LES–RANS of Installed Ultra-High-Bypass-Ratio Coaxial Jet Aeroacoustics with Flight Stream

Using large-eddy simulation–Reynolds-averaged Navier–Stokes (LES–RANS), this paper studies a round coaxial nozzle with an ultra-high bypass ratio of 15, with and without a wing-flap geometry. Depending on engine placement, the nozzle can become extremely close to the wing-flap geometry, introducing strong installation effects. Two different flap deflections of 8 and 14 deg are contrasted with an isolated round nozzle. A flight stream is applied and an Ffowcs Williams-Hawkings (FWH) surface placement procedure for installed jets is proposed. Impressive agreement with available experimental data is economically achieved for far-field overall sound pressure level and spectra as well as near-field spectra. The LES provides a wider range of polar and azimuthal angles at 1 deg increments, providing one of the most detailed acoustics data sets to date. The installed cases generate up to 20 dB more noise at mid-low frequencies due to large flap trailing edge sources. Additional sources are introduced by the interaction of the flight stream with the lifting surfaces. Second-order space-time correlations reveal length and time scales in the flow. Fourth-order space-time correlations indicate increasing magnitudes of the dominant noise source components with increasing flap angle. The three-dimensional unsteady data set produced should lead to improved acoustics models.