Design Criteria for Low-Noise Trailing-Edges

Abstract

This paper summarizes the results of an experimental study on flow-permeable trailing-edge noise reduction means. Basic design rules are presented with respect to a future employment at current high-lift devices of passenger aircraft. The main focus is directed at the identification of the major design parameters of comb-type or slit edge-modifications. The achievable noise reduction capability was quantified by directional microphone measurements on a flat plate and on a two-dimensional NACA0012-like airfoil in the open-jet Aeroacoustic Wind Tunnel Braunschweig. It was found that flexibility of the comb material is beneficial, but not essential to achieve a noise reduction. Apart from a minimum device length the slit width was identified as the decisive design parameter. An almost zero-spacing of the comb fibers revealed the best results, leading to the assumption that the obtained noise reduction is mainly due to a viscous damping of turbulent flow pressure amplitudes in the comb area.