Modification of broadband trailing edge noise through hairy coating: Proceedings of the 26th International Congress on Sound and Vibration, ICSV 2019

An experimental study on the effect of artificial hairy coating on the broadband trailing edge noise of a flat plate was conducted and presented in this paper. The study was inspired by the hairy feather structure of quiet-flying owls. The experiment was conducted at the HKUST low speed anechoic wind tunnel, UNITED, at chord-based Reynolds number ranging between 160,000 to 300,000 at zero angle of attack. Turbulent strips were applied at 12-20% of the chord to suppress the instability noise. Three different hairy coatings with varying lengths and diameters were tested. A 56-channel microphone array was used to acquire the induced noise, as well as to investigate the effect of hairy coating on the source distribution. It was observed that the presence of hairy coating significantly reduces the trailing edge noise above a critical chord-based Strouhal number, which depends on the hair length. However, the hairy coating also produces an apparent low frequency hump in the noise spectrum below that Strouhal number. Interestingly, at flow speed close to the owl's flight speed (below 10 m/s), the critical frequency corresponding to the critical Strouhal number is well below 2 kHz, which is the lower hearing bound of owls' prey © Proceedings of the 26th International Congress on Sound and Vibration, ICSV 2019. All rights reserved.