Effects of Detailed Aircraft Geometry on Wake Vortex Dynamics During Landing

The final approach and touchdown of a landing aircraft is studied numerically with different hybrid Reynolds-averaged Navier-Stokes (RANS)/large-eddy simulations (LES) approaches. Particular emphasis is put on the ground effect and the wake vortex evolution before and after touchdown. Additionally, the effect of the landing gear on the aircraft's aerodynamics during landing is analyzed. The near field around the landing aircraft is generated using two different RANS methods. In a number of steady-state simulations the altitude of the aircraft above ground was varied in fixed steps. Furthermore, a simplified continuous landing maneuver was simulated by applying unsteady RANS simulations. The resulting RANS fields are then coupled with an LES simulation using three different approaches. The computed vortex circulation is compared with aircraft measurements. As a result it can be seen that the new transient hybrid approach provides physically reasonable results. The landing gears have a notable effect on the aircraft's drag, as well as on the wake footprint. However, the effect on the wake vortex circulation evolution is moderate. Remarkably, the simulations with landing gear show a strong coherent vortex, merging late with the main vortex. A particular emphasis is put on the comparison with light detection and ranging (LIDAR) measurement data collected in a recent campaign at Vienna airport. The vortex structures predicted by the simulations are clearly visible in those measurements. Simulated tangential velocity profiles are compared with vortex model profiles. It is observed that standard vortex models fail to capture the complex vortex structures emerging during the landing process but can be improved including mirror vortices.