Investigation of installation effect of jet noise from turbofan engines

To quantitatively investigate the impact of installation on jet noise from modern high bypass ratio (BPR) turbofan engines, a model-scale noise experiment with a jet propulsion system and a realistic fuselage model was conducted in the anechoic wind tunnel of ONERA, CEPRA 19. Two area ratios (an area of the secondary nozzle over an area of the primary nozzle), 5 and 7, and various airframe configurations such as positions relative to the jet nozzle position and flap angles, were considered. The followings were investigated using the acoustic data acquired from the experiment: (1) impact of the presence of the airframe; (2) impact of flap angles; (3) impact of jet nozzle position relative to the wing; and (4) flight effect. Based on the observation, it could be concluded that the frequency region can be divided into two parts: the low frequencies (= 1.5 kHz) and high frequencies (> 1.5 kHz). It seems that the interaction between the jet and the pressure side of the wing contributes the noise at the low frequencies and the interaction between the jet and the flap tip contributes the noise at the high frequencies.