D4.2.5 Noise reduction potential through spoiler edge modifications or a fractal design

Abstract

This report presents an overview on the results obtained during the spoiler noise wind tunnel test conducted in the Acoustic Wind Tunnel Braunschweig1. The scope of this test was to identify and rank order the effectiveness of different techniques for spoiler noise reduction such as e.g. spoiler side edge fences or fractal spoilers. Noise tests were conducted on a scaled high lift system with one spoiler deployed. The results presented in this report indicate that the most effective device in terms of noise reduction is a splitter plate that retains the original fixed wing trailing edge and therefore shields the spoiler generated noise with respect to noise radiation towards the ground. The noise reduction potential of spoiler side edge fences was determined to be in the order of 2 dB while fractal spoilers provide a noise reduction potential of about 1 dB. From the aerodynamic point of view all tested spoiler configurations without splitter plate provide a lift degradation of about 0.5*CL and a drag increase of about 0.10 to 0.12*CD. By application of a splitter plate the lift decrease is reduced to about 0.4*CL while the drag increase remains in the order of 0.10*CD. This in fact means that a splitter plate is able to provide a better lift over drag ratio.