Effect of Noise Reducing Modifications of the Slat on Aerodynamic Properties of the High-Lift System

To minimize slat noise according to the guidelines of "A Vision for 2020" brush-like devices were installed on a slat trailing edge to "soften" it. In experiments slat noise was considerably reduced by such devices. But their effect on aerodynamics is yet unknown. This study shows that the investigated brush-like devices on slat trailing edges influence the aerodynamic properties of high-lift systems adversely. Because of increasing boundary layer thickness with length and diameter of the brushes the suction peaks are reduced so that C_L decreases. These are preliminary results. An optimization of slat chord length and brush length should be conducted to minimize C_L reduction