Ground vortex formation between the ground plane and an aero-engine intake during ground operation and takeoff can significantly degrade engine performance and operability. Such vortices introduce strong inlet flow distortion through unsteady swirl and total pressure loss and may entrain foreign debris from the ground, increasing the risk of fan blade erosion and long-term propulsion system degradation. Accurate numerical prediction of these phenomena remains challenging due to the strong coupling among crosswind effects, ground boundary-layer development, intake aerodynamics, and rotating fan aerodynamics. As one of the participants of the 7th AIAA Propulsion Aerodynamics Workshop (PAW7), high-fidelity simulations were performed for the coupled fan-intake configuration developed within the NIFTI (Non-Intrusive Flow distortion measurements within a Turbofan Intake) program. In this study, Volcano ScaLES was used for wall-modeled Large Eddy Simulations of Cases 2 and 3 of the workshop, corresponding to a constant crosswind velocity of 12.5 knots and two distinct fan operating points characterized by different rotational speeds and mass flow rates. Near-wall turbulence effects on the intake surfaces, fan blades, and ground plane were represented using an equilibrium wall model, allowing efficient treatment of the high-Reynolds-number boundary layers while resolving the large-scale unsteady structures governing ground vortex formation and ingestion. The simulations capture the unsteady interaction between the ground vortex, intake lip flow separation, and the rotating fan. To obtain statistically converged flow fields for this highly unsteady configuration, the simulations were advanced for several hundred fan revolutions using a sequence of successively refined grids, with a PID-controlled static-pressure outlet applied at the fan duct exit to maintain the prescribed operating conditions.
On a single server equipped with eight NVIDIA L40S GPUs, the simulation on a grid exceeding one billion cells, with targeted refinement in the intake lip, fan rotor, ground-plane boundary-layer regions, and ground vortex, required approximately 1.5 wall-hours per fan revolution, demonstrating the efficiency of large-scale GPU-accelerated WMLES for complex propulsion-integration problems. The results provide detailed insight into the unsteady dynamics of ground vortex formation, ingestion, and breakdown, as well as the resulting inlet distortion patterns upstream of the fan face, supporting improved understanding and design of integrated aero-engine intake systems operating under crosswind conditions.
