Unsteady flow interactions and ground plane proximity in a coupled compact intake-fan in crosswind

The assessment of the crosswind flow separation mechanisms and resulting distortion for compact intakes can be a key contributor for the design of viable large civil aeroengines. Under crosswind conditions, the intake aerodynamics are strongly influenced by both the fan and the ground plane. However, the impact of key design parameters, such as ground clearance, on the intake flow distortion is not fully understood. This study investigates the effects of a large variation in ground clearance on the intake-fan unsteady aerodynamics using an Unsteady Reynolds-Averaged Navier-Stokes fully coupled with a rotating fan stage. The work includes an assessment of the unsteady swirl distortion and the unsteady peak distortion events. The findings show that increased ground clearance can have adverse effects for the considered compact intake design. Gross separation can occur at lower crosswind velocities and arise at the intake lower section due to mass flow redistribution. When the ground clearance is increased, the gross separation on the windward side of the intake occurs at a greater crosswind velocity but exhibits greater levels of unsteady intake flow distortion. Overall, intake designs should be assessed at the expected ground clearance as the distortion and the onset of separation can vary substantially.