Fan-intake aerodynamic interactions under crosswind conditions

The aerodynamics of an aero-engine intake under off-design conditions is characterized by a range of steady and unsteady mechanisms that can adversely affect the fan operability. A hierarchical computational fluid dynamics approach was used for an initial assessment of the primary aerodynamic interactions between the fan and the intake design. These approaches included steady computations with a lower order fan model as well as full unsteady computations. For a powered intake in crosswind, the direction of the wind determines the direction of rotation of the ground vortex relative to the fan. For the full unsteady analyses, the threshold crosswind speed reduced by 12kts and 22kts relative to the steady analysis for the counter-rotating and co-rotating configuration respectively. Overall, this work identified and assessed for the first time a fan-intake unsteady aerodynamic interactions that may affect the design of short intakes in association with fan systems.