Wake Vortex Far-Field of a Generic Transport Aircraft Affected by Oscillating Flaps

The influence of oscillating trailing-edge flaps of a generic transport aircraft on the middle and far fields of the wake vortex system is investigated. The aim is to be able to reduce separation distances between aircraft during approach in order to increase capacity at airports. By introducing a certain disturbance by means of oscillating flaps in the near field, the long-wavelength Crow instability should be excited in the further downstream development. The evolution of the wake vortex system is investigated using a large-eddy simulation approach. The wake vortex system is examined up to 133 spans downstream for two high-lift configurations. A nonactuated configuration with statically deflected flaps is compared to a configuration with actuated flaps. The results show that the long-wavelength Crow instability cannot be excited by actuated trailing-edge flaps. However, a faster decrease of the dimensionless circulation over the downstream position can be observed for the actuated configuration compared to the nonactuated configuration, due to a faster diffusion of the rolled-up vortex pair. Furthermore, the averaged induced rolling moment on an aircraft [with the International Civil Aviation Organization's (ICAO's) classification of "light"] encountering the wake vortex of the actuated configuration (ICAO's classification of "heavy") is up to 32.5% lower than for a follower aircraft, which is entering the wake vortex of the nonactuated configuration.