An Approach towards semi-empirical Slat Track Noise Prediction

Abstract

High lift wing leading edge noise is often attributed to the slats or more generally speaking to the leading edge high lift device. Except for droop noses, flow exposed mechanical systems are necessary to mount and actuate such devices. For mechanical reasons these so called tracks are typically oriented perpendicular to the wing leading edge and accordingly inclined towards the mean flow or flight direction. Mainly from wind tunnel studies and in rare cases also from flight tests these tracks are known as strong noise sources, which locally exceed slat noise levels and show up as intense noise sources in noise maps originating from phased array beamforming. This finally means that track noise cannot be omitted for the noise prediction of high lift systems and in particular not in view of new systems like Krueger flaps. Against this background track noise was investigated in the German national funded research project INTONE (Minderung von Triebwerksinstallations- und Hochauftriebslaerm). Based on parametric studies with the small scale DLR F16 high lift system in DLR s Acoustic Wind Tunnel Braunschweig track noise was isolated and characterized. In a second step a first prediction scheme was established. The scheme allows now for the prediction of slat noise and track noise and the summation of both components which contributes to the overall leading edge noise. The application of this model showed the impact and importance of track noise compared to slat noise. Furthermore, the noise generation at the D-nose cut-outs was assessed. Both results together reveal that track noise is a major contributor to the overall high lift system noise and track noise reduction is essential in order to reduce the high lift system related airframe noise contribution. The current development is meant as first step towards a more sophisticate tool chain for wing leading edge noise prediction.