Analysis of lift enhancement, drag and noise reduction characteristics of oscillating jets on aircraft figh-lift devices

This paper addresses the aerodynamic and noise issues caused by flap flow separation at moderate angles of attack during aircraft high-lift device takeoff and landing. Using the canonical 30P30N three-element airfoil as the research object, under conditions of Reynolds number 1.7×10⁶, Mach number 0.17, and angle of attack 5.5°, a multi-parameter optimization framework based on Bayesian optimization algorithm is established. An oscillating jet method for lift enhancement, drag reduction, and noise suppression is developed. The improved delayed detached-eddy simulation (IDDES) method is coupled with the Ffowcs Williams-Hawkings (FW-H) equation to numerically simulate the hybrid aerodynamic and aeroacoustic characteristics. Flow field properties with and without oscillating jet actuation are compared. Results indicate that oscillating jets with a frequency equal to the characteristic frequency and momentum coefficients of 1.897% and 0.006% significantly reduce the separation vortex on the trailing edge flap. Lift increases by approximately 8.24%, while drag decreases by about 8.00%. The overall sound pressure level (OASPL) of aerodynamic noise is reduced by 1.27 dB, with the maximum reduction of 2.88 dB observed at the 30° direction. At the far-field monitoring point directly beneath the wing at a distance of five chord lengths (270°, 5C), low-frequency noise decreases by 4.28 dB. The tonal peak caused by shed vortices exhibits the most substantial reduction of 14.05 dB, whereas high-frequency noise remains nearly unchanged. Beyond directly injecting energy into the flow field, the jet introduces disturbances that generate spanwise vortices, promoting energy exchange between low-momentum fluid within the shear layer and high-momentum fluid in the main stream. This process effectively weakens the boundary enstrophy flux at the flap trailing edge. Consequently, the interaction region of positive and negative Lamb vector divergence is significantly reduced, leading to suppressed acoustic source intensity in that zone. This study provides theoretical foundations for lift enhancement, drag reduction, and noise control design of aircraft high-lift devices.