LES-RANS of installed ultra-high bypass-ratio coaxial jet aeroacoustics with a finite span wing-flap geometry and flight stream-part 1: Round nozzle

The jet noise produced by aeroengines is a critical topic in engine design. Large-Eddy Simulation (LES) and hybrid LES-Reynolds-Averaged Navier-Stokes (LES-RANS), provides a method to increase understanding of influences on the noise produced. Installed jet noise modelling has received less attention than isolated jet noise yet is becoming more important for design. Here, using LES-RANS, a coaxial nozzle with an ultra-high bypass-ratio of 15 is studied with and without a wing-flap geometry. The bypass ratio leads the nozzle to become extremely close to the wing-flap geometry introducing strong installation effects. Two different flap deflections of 8 and 14 degrees are contrasted with an isolated round nozzle. A flight stream is applied and an FWH surface placement procedure for installed jets is proposed. The installed cases generate more directional noise at mid-low frequencies as the presence of the flap trailing edge produces a strong dipole source. 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 in increasing flap angle and may lead to improved acoustics models