Development of a Slat Cover Liner

Kurzfassung

Slat noise reduction is one major challenges in the attempt to reduce high lift system generated airframe noise. The particularity of the slat is the strong governance of the low speed aerodynamic performance, which at the end depends also on small details like e.g. an optimized the slat gap size. Even though it is well known that the gap size has high influence on the noise generation, its modification for the sake of a quick and cheap noise reduction is nearly impossible as it would require the complete aerodynamic re-assessment of the aircraft. Against this background a passive liner solution to be installed in the slat cove was investigated in the German national funded research project MOVE.ON (Multi-Optimierung und Verifizierung von Entwuerfen durch Performance Tests und Simulationen ). Based on parametric studies with the small scale DLR F16 high lift system in DLR’s Acoustic Wind Tunnel Braunschweig a first and non-optimized prototype of a slat cove liner was developed. The effect on slat noise was a 3 dB reduction without meaningful aerodynamic penalties. Based on these results an improved version of this liner was manufactured to be tested with the large scale DLR F15LS high lift system. This quasi full-scale version of the slat cove liner proofed the aforementioned findings of a 3 dB noise reduction without aerodynamic penalties. In parallel to the experimental studies numerical acoustic simulations were carried out. The scope of these simulations was to recompute the liner configuration in view of a future numerical design of such technologies.