Stall Behaviour of the EUROLIFT High Lift Configurations

Kurzfassung

Based on a previous analysis of the high lift performance of a commercial aircraft-type high lift configuration in terms of lift curves and drag polars and their Reynolds-number dependency a detailed study of the corresponding stall behavior is carried out. It is part of extensive experimental research activities on the aerodynamics of high lift configurations within the European projects EUROLIFT (I) and II. The investigations are conducted using the KH3Y wind tunnel model (DLR F11), which is representative for a wide-body twin-jet commercial aircraft. The model is designed for a step by step complexity increase up to a complete high lift configuration including pylon, nacelle, and nacelle strake. The wind tunnel data have been gathered in the European Transonic Windtunnel ETW in two different test campaigns. The Reynolds-number range extends from Re ~ 2.3 x 106 up to Re ~ 25 x 106. To analyze the stall behavior spanwise pressure distributions at maximum lift and at lift breakdown are compared for two limiting Reynolds-numbers for each of the four complexity stages of the KH3Y configuration. The investigation reveals that for the clean high lift wing without nacelle stall is triggered at the outboard sections of the fixed wing. When the nacelles are added the lift breakdown starts on the fixed wing inboards of the nacelle. Adding a nacelle strake alleviates the lift breakdown inboards of the nacelle, while lift breakdown still occurs around the spanwise position of the nacelle on the fixed wing. For none of the four configurations a significant change of the stall type is observed for the considered Reynolds-number conditions. Yet, the investigation of the most complex configuration with strake reveals, that the effectiveness of the strake and its interaction with the flow on the fixed wing is subject to Reynolds-number influences.