Influence of trailing-edge flaps on the flow field and noise generation characteristics of airfoils

High-lift flow control devices are widely used in the aerospace field. Currently, most research on high-lift devices focuses on the impact of flaps on the aerodynamic characteristics of modified wing profiles, while studies on the mechanisms and characteristics of noise generation caused by the addition of high-lift flow control devices are relatively scarce. This study employs delayed detachment edy simulation and the Ffowcs Williams–Hawkings acoustic analogy method to numerically simulate the flow field around the National Advisory Committee for Aeronautics (NACA) 0021 airfoil at an angle of attack of 15°, systematically investigating the effects of trailing edge flaps (TEFs)—a high-lift device—on energy distribution, flow field structure, and noise generation and characteristics. The results indicate that compared to the original airfoil, the flow field around the airfoil with a TEF exhibits a reduction in noise at medium and low frequencies, with a maximum reduction of 21.51 dB. However, broadband noise increases in the medium and high-frequency ranges, with a maximum increase of 19.12 dB, and the average total sound pressure level increases by 3.83 dB. By integrating the analysis of time-averaged pressure pulsation distribution and boundary enstrophy flux (BEF)analysis for different airfoils, it was revealed that the periodic trailing edge separation vortices and their interactions, along with the increased vorticity generated by the wall, leading to an increase in vortex structures, are the primary causes of the increased noise in the TEF airfoil. The results of this study not only provide new insights into the noise mechanisms of high-lift wing profiles but also offer important references for noise reduction designs based on flow control.