Abstract:

This paper presents the results of an experimental investigation to study the effect of a porous airfoil Trailing-Edge (TE) with different open-area ratios at Reynolds number by 2.9 x 10e5 <= Rec <= 4.06 x 10e5 (based on the chord length) and the zero angle of attack (alpha=0) on the flow-induced noise generation mechanism. Acoustic pressure measurements were taken in an Anechoic Wind Tunnel (AWT) using a spiral array of 31 microphones. Five different TE configurations were considered; these are airfoil with a porous TE modelled by 15, 36, 45 and 72 slits and a reference non-porous plate. A comparison of the Power Spectral Density (PSD) graphs of a porous TE with that obtained due to reference non-porous plate indicates up to 5 dB reduction (on an average) in the noise levels between the frequency range given by 2500 Hz to 8000 Hz due to the use of porous TE. The results obtained from the cross-spectral Conventional Beamforming (CB) algorithm indicate that the noise generation source is closer to the TE at these frequencies. However, in the mid-frequency range between 2000 Hz to 2500 Hz, the noise from the Leading-Edge (LE) is comparable to that observed at the TE. This is hypothesised to be due to the interaction between the LE and the boundary-layer exiting the contraction-outlet.