Grants and Contributions:

Grant or Award spanning more than one fiscal year (2017-2018 to 2018-2019).

The intake of aircraft engines is constructed to provide a steady and uniform flow over a wide range ofx000D
operating conditions. Nacelles are designed to optimize cruise efficiency while meeting the stringentx000D
operational requirements at off-design conditions. One of the most critical operating points occurs on thex000D
ground with severe crosswinds when the aircraft is at rest. In this setup, the crosswind causes a stagnation pointx000D
to occur on the outer nacelle, the flow then accelerates and transitions around the lip before entering the enginex000D
at a near-sonic speed. The negative pressure gradient at the engine inlet results in flow separation, whichx000D
distorts the incoming flow stream; at sufficiently large distortion levels, stall or aerodynamic instabilities of thex000D
fan blades may arise. The accurate prediction of the engine inflow distortion is extremely difficult as it involvesx000D
laminar-to-turbulent transition, complex geometry and pressure gradients and flow separation. This projectx000D
seeks to improve on existing transitional models to accurately determine the onset of transition on a complexx000D
three-dimensional nacelle, and thus improve the prediction accuracy of inflow distortion at these criticalx000D
off-design conditions.