Suppression of airfoil-leading-edge turbulence interaction noise using detached micro-perforated fairings

Abstract

This study investigates the use of detached micro-perforated fairings for reducing turbulence interaction noise generated by the wake impingement of a solid/perforated rod onto the leading edge (LE) of a downstream NACA0012 airfoil in an anechoic wind tunnel. The fairings, which have the same profile as the airfoil LE, are positioned upstream of the airfoil and in close proximity to the LE. The efficiency of noise control is evaluated by varying the porosity σ, windward width A, and gap distance G between the fairing and airfoil LE, and assessed using near- and far-field microphone arrays. The acoustic measurements indicated that micro-perforated fairings can significantly reduce airfoil LE turbulence interaction noise with a reduction of overΔLp_LE = 12 dB when using a fairing with σ = 28.4% and A/tmax = 1 at the gap distance G/c = 0.133 (where tmax and c represent the maximum thickness and chord length of the airfoil, respectively). Additionally, it was observed that changes in porosity σ had less sensitivity in noise control compared to A and G parameters, with nearly similar noise reductions under the range of porosity tested (16.9% ∼ 31.9%). Observations made using wall-pressure sensors on the LE surface and particle image velocimetry (PIV) demonstrated that the applied noise reduction mechanism prevented turbulence from impinging upon the airfoil LE area in the chord range of 0 ∼ 0.04.