SUMMARY

Inlet nacelles of commercial aircraft propulsion systems are optimized for cruise but must also be designed to accommodate flight during takeoff/landing which can suffer from significantly impeded performance in the presence of crosswind. As the speed of the crosswind relative to the speed of the inlet flow reaches a critical magnitude, the flow over the nacelle’s inlet surface can undergo separation leading to distortion which can hinder the engine thrust. Furthermore, the engine’s performance and safety may be compromised by its proximity to the ground due to the formation of a ground vortex that is drawn into the engine and can lead to the ingestion of ground debris which may damage the fan blades. The first primary objective of this research is the elucidation and characterization of the fundamental mechanisms of the inlet flow and the onset of separation with incident crosswind and the formation and evolution of a ground vortex due to a ground plane. Of particular interest are the effects of these flow phenomena on the performance of the inlet as measured by flow distortion. The second objective is to investigate different approaches for control and mitigation of the adverse effects of flow separation and the ground vortex with specific emphasis on any possible coupling between the two. Approaches for controlling separation are based on earlier work at Georgia Tech and elsewhere by using fluidic actuation near the surface to alter the structure of the inlet boundary layer. These approaches are based on either distributed, surface-integrated actuation jet arrays or by exploiting autonomous bleed of air across the nacelle’s surface. It is expected that indirect control of the ground vortex formation will be more challenging since the vortex is highly unsteady. It is anticipated that the proposed investigations will demonstrate how flow control within the nacelle can be used to suppress the formation of the ground vortex or prevent its ingestion into the inlet.