Unsteady Analysis of Aeroengine Intake Distortion Mechanisms: Vortex Dynamics in Crosswind Conditions

The formation of a ground vortex and its ingestion into an aero-engine intake under crosswind conditions play a significant role in the aerodynamic excitation of the fan. Using steady and unsteady numerical simulations, an analysis of the dynamics of several distortion features is presented. For a simplified intake at high crosswind velocities, there is a substantial movement of the ingested ground vortex at the aerodynamic interface plane (AIP). The ingested ground vortex follows a specific trajectory while varying both in size and strength. The transition from a periodic to an aperiodic regime of the intake distortion at the AIP occurs as the crosswind velocity is increased. Circumferential mode decomposition shows that the largest amplitude of the distortion occurs at the first circumferential mode, and the amplitudes of the higher modes decrease monotonically. Furthermore, the amplitude of the spatial harmonics is time-dependent, which may be an influential feature at the time of assessing fan forced response.