Briefing: Interaction of a counter-rotating vortex pair with the ground Available to Purchase

The counter-rotating pair of vortices formed from aircraft wingtips in flight presents a potential hazard to other aircraft in the form of a sustained rolling moment. Such a trailing vortex pair travels downwards with a self-induced velocity, and may interact with the ground plane at airports. The ground affects both the trajectories of the original vortex pair as well as the development of three-dimensional instabilities in the pair. As the vortex pair approaches the ground plane, it generates a boundary layer on the ground that separates to form opposite-sign, secondary vortices. These secondary vortices impact the trajectories and development of the original vortex pair. The focus of the current paper is not simply the 2D behaviour of the vorticity, but also the development of 3D instabilities. A novel technique has been developed using laser-induced fluorescence to visualise this secondary vorticity in unprecedented detail, revealing new flow phenomena.