Among the several noise-generation mechanisms of airfoil self-noise, trailing-edge bluntness noise is an important noise source, which is caused by the vortex shedding at blunt trailing edges. A numerical study on airfoil trailing-edge bluntness noise control using the bio-inspired wavy leading edges is presented in this paper. The high-fidelity, improved, delayed, detached eddy simulation (IDDES) method was used to calculate the flow field, and the acoustic analogy method was used for noise prediction. For both the blunt-trailing-edge airfoils, a baseline airfoil with a straight leading edge and a bio-inspired airfoil with a wavy leading edge were used in this study. The chord-based Reynolds number was 400,000, and there was no angle of attack. The numerical results show that the trailing-edge bluntness noise of the baseline airfoil was significantly reduced by the wavy leading edges. The sound pressure level reduction was about 3.7 dB at the characteristic frequency, and the maximum sound pressure level reduction was as high as 35 dB. The trailing-edge bluntness noise was decreased at all directional angles. The maximum overall sound pressure level reduction was 6.3 dB at 0°. In addition, by analyzing the pressure fluctuations, wake characteristics, turbulent vortex structures and spanwise correlation and coherence of the flow field, the noise-reduction mechanisms of the bio-inspired airfoil are deeply revealed.

Aerodynamic noise produced by the rotating blade is an important hindrance for the rapid development of modern wind turbines. Among the various noise sources, the airfoil trailing edge noise contributes a lot to the wind turbine noise. The control of wind turbine airfoil trailing edge self-noise by bio-inspired sinusoidal wavy leading edges is experimentally studied in a semi-anechoic chamber. The noise radiated by the baseline NACA 0012 airfoil and various wavy airfoils is measured using a planar microphone array consisting of fifty-two microphones. The noise source identifications are achieved by using the CLEAN-SC method. The effects of velocity and angle of attack on noise radiation of the baseline airfoil are analyzed in detail. The noise control law of the wavy amplitude and wavelength on airfoil trailing edge noise is explored. Based on the acoustic beamforming results, the noise control effects of the wavy leading edges are intuitively demonstrated. In general, the wavy leading edge with a larger amplitude and smaller wavelength has a better effect on the airfoil trailing edge noise reduction. The maximum sound pressure level reduction can be up to 33.9 dB. The results of this study are expected to provide important information for wind turbine aerodynamic noise control.

This paper presents numerical studies on the effects of upstream porous treatments on the hydrodynamic and hydroacoustic performances of a hydrofoil. The inflow velocity is 5 m/s and the chord-based Reynolds number is 2.5 × 10⁷. A rapid turbulent boundary layer (TBL) noise prediction method is proposed by coupling the Reynolds-averaged Navier–Stokes (RANS) flow simulations, the Lee’s empirical wall pressure spectrum (WPS) model and the Howe’s trailing-edge noise model. This hybrid model is well validated against the experimental data. Using the developed noise prediction method, the effects of upstream porous treatments on the hydrodynamic and hydroacoustic performances are systematically studied, focusing on key parameters such as porous coverage area, porosity, pore diameter and half-porous configurations. The results generally indicate that the porous treatments can significantly reduce the mid-to-high-frequency noise, whilst slightly increasing the low-frequency noise. Within this parametric range, a larger porous coverage area yields more pronounced mid-to-high frequency noise reduction. Specifically, when the porous coverage accounts for 10% of the chord length, the mid-to-high frequency noise reduction reaches 14.3 dB; as the coverage expands to 25% of the chord, the noise reduction in this frequency band further increases to 35.2 dB. While smaller porosity and pore diameter enhance noise reduction, they incur greater hydrodynamic penalties. Within the scope of this study, the minimum porosity (φ = 0.55) and the minimum pore diameter (d = 0.1 mm) achieved mid-to-high frequency noise reductions of 19.1% and 17.3%, respectively, while the drag coefficient increased by 8.9% and 17.3%, respectively. Furthermore, the noise reduction is found to deteriorate with increasing angles of attack (AOAs). The wall shear stress and boundary layer thickness are also significantly affected by the porous treatments. This work provides rapid evaluations and can also be used for the optimization of porous treatments.