Interdependencies of Aerodynamic Test Conditions and High Lift System Noise Generation and Measurement

Abstract

During the last decade three ONERA and DLR common research projects1,2 were conducted with focus on the measurement and numerical simulation of high lift system noise in general and slat noise in particular. The measurements were conducted with the DLR F16 high lift system in different configurations and carried out in DLR’s Acoustic Wind Tunnel (AWB), ONERA’s F2 low speed wind tunnel and in DNW’s low speed wind tunnel in Braunschweig (DNW-NWB). F2 is a closed test section wind tunnel equipped with a wall mounted phased microphone array. AWB and NWB feature an open jet in an anechoic room at much different size. The studies aimed at the measurement and the subsequent numerical prediction of slat noise. Furthermore, the achieved database served for the present study which aimed at the identification of correlations between the aerodynamic conditions in the different test facilities and the measured acoustic data. It turned out that slat noise was captured well in all facilities while low frequency flap noise showed systematically lower levels in the small open jet AWB. By means of numerical flow simulations the aerodynamic difference was identified and the respective acoustic correction determined. The investigation proved the need for detailed and potentially CFD supported aerodynamic assessments of measurements that target not only one single high lift system related noise source but the noise generation and source ranking of the entire system.