Aircraft Wake-Vortex Decay in Ground Proximity-Physical Mechanisms and Artificial Enhancement

Aircraft wake-vortex evolution in ground proximity is investigated numerically by means of large-eddy simulations. The simulations are performed either with a flat ground or with different modifications to the ground surface to trigger rapid vortex decay. The impact of environmental turbulence in terms of turbulent wind is taken into account, where wall-resolved and wall-modeled large-eddy simulation are performed for low- and high-Reynolds-number cases, respectively. To understand wake-vortex decay mechanisms in ground proximity, the interaction of primary and secondary vortices is carefully investigated. We find that vortex decay can be initiated at an earlier time and substantially accelerated with obstacles at the ground. We explain the fundamental vortex dynamics describing five characteristics of the phenomenon and quantify the decay. We demonstrate that similar effects can be achieved, employing relatively small plate lines as opposed to the original large block-shaped barriers. The obstacles trigger two kinds of so-called end effects: pressure disturbances propagating within the vortex cores and secondary vortex structures propagating along the outside of the vortex cores.