Effects of the wavy leading-edge wavelength on the reduction in the noise of the rod–airfoil configuration

Rod-airfoil interaction noise becomes a major issue in some aeronautical applications. The design of four wavy leading edges (WLEs) with varying wavelengths, bioinspired by the tubercles on humpback whales’ flippers, aims to mitigate far-field noise. Among these cases, a reduction in the wavelength is found to be advantageous for noise suppression, with the smallest wavelength case achieving a maximum noise reduction of 1.9 dB. Furthermore, the noise radiation induced by WLEs is suppressed mainly at medium frequencies. The theory of multiprocess aeroacoustics is applied to reveal their underlying mechanisms. The dominant factor is the source cutoff effect, which significantly decreases the source strength on hills. Additionally, spanwise decoherence with phase interference serves as another crucial mechanism, particularly for reducing mid-frequency noise.