Assessment of noise control on flap side edge using VLES simulation

With the continuing development of civil aviation, aircraft noise has been a major factor to be considered in aircraft design. The application of high bypass ratio turbofan engine has largely reduced engine noise, airframe noise is of comparable dominant, especially during landing approach. Noise radiation from flap side edge is known to be a major component of airframe-generated noise, the present work focuses on the noise control on flap side edge. Very large eddy simulation (VLES) combined with Ffowcs Williams and Hawkings (FW-H) equation is used to investigate and assess the flap side-edge shape modification treatment as a passive means for flap noise reduction. VLES is intended to infer effects of the different side-edge shapes on acoustically relevant features of the unsteady-state flow near the flap side edge, providing reliable sound source input for FW-H equation to predict the far-field noise propagation and radiation. The potential noise source of flap side edge is the pressure fluctuations of complex vortex structures and their interaction with side-edge surface. The modified flap side-edge shapes result in different vortex structures aiming at weakening the strength of vortex at initiation and roll-up processes. Computations confirm that noise reduction has been obtained without compromising the aerodynamic performance of the high lift device, even enhancing. Several flap side-edge configurations with lower rounded side edge and serrated side edge are investigated in this paper. The numerical simulation shows the difference of flow field and far-field noise between modified flap side-edge configurations and baseline configuration, revealing the mechanisms of the noise generation and assessing the passive noise control approaches on flap side edge.