Influence of Nonflat Plate Trailing Edge Serration on Airfoil Noise Reduction

The current study experimentally investigates the influence of nonflat plate trailing edge serrations on airfoil noise characteristics. Experiments are carried out at different flow velocities in the range of $25–40\mathrm{m}/\mathrm{s}$, corresponding to the Reynolds number range of ${2.4\times 10}^5$ to ${3.9\times 10}^5$. The wavelength ($\lambda$) of the serrations considered is in the range of 5–30 mm, and the serration height ($2h$) is in the range of 10–30 mm. The acoustic spectra show that the conventional nonflat plate trailing edge serrations generate a narrowband vortex shedding noise. The narrowband noise is observed to decrease with an increase in the wavelength; however, it is observed to increase with an increase in the serration height or root thickness by around 16 dB. Inclinations ($\theta$) provided at the root of the serrations reduce the narrowband noise up to 20 dB and the broadband noise up to 5 dB. When a perforated plate inserts the sawtooth gap of the serration, the hybrid configuration effectively eliminates the vortex shedding phenomenon at the roots with a significant reduction in the low frequency range as well as the high frequency broadband noise.

Airfoil noise poses a significant challenge in aviation, wind energy, and other sectors where aerodynamic noise reduction are crucial. When an airfoil is subjected to turbulent flow, the primary source of noise arises from the interaction of the flow with its trailing edge. The geometrical modifications made at the trailing edge helps to minimize the intensity of the noise generation. This paper presents the results of an experimental investigation on the impact of nonflat plate trailing edge serrations. The major findings of the study reveal that employing a nonflat plate trailing edge serrations can substantially mitigate airfoil trailing edge noise levels.