Abstract: Flap side-edge noise is a significant noise source for airplane at takeoff and landing stages.The noise generation mechanism from flap side-edge noise is analyzed by numerical simulation of unsteady flow field using Very Large Eddy Simulation(VLES).Two kinds of flap side-edge shape modifications are proposed on the basis,and their frequency spectrum and directivity of far-field noise are compared with the baseline configuration using permeable integral surface Ffowcs Williams and Hawkings(FW-H)acoustic analogy method to investigate their effects on noise reduction.Via the numerical simulation of flow field and acoustic field,it proves that the flap side-edge noise is broadband noise in nature.The different shapes of flap side-edge change the pattern of flow field,vortex structures and the developing process of vortex,thus having influences on noise source distributions and characteristics of far-field noise.The result shows that at the given 5° angle of attack,the proposed flap side-edge shape modifications can achieve reduction of the overall sound pressure level(OASPL)ranging from 1 to 2 dB without decreasing the lift and drag aerodynamic performances too mach.