Lift-generated vortex wakes of subsonic transport aircraft

The flow fields of vortices. whether buoyancy-driven or lift-generated, are fascinating fluid-dynamic phenomena which often possess intense swirl velo cities and complex time-dependent behavior. As parr of the on-going study o f vortex behavior, this paper presents a historical overview of research co nducted on the structure and modification of the vortices generated by the lilting surfaces of subsonic transport aircraft. Although primarily present ed from an experimental point of view, the derivation and use of relatively compact theoretical formulations and concepts are included. Experience wit h lift-generated wakes has shown that they are so complex that progress req uires application of a combined theoretical and experimental research progr am, because either alone often leads to incorrect conclusions. The primary purpose of the research to be described is to find a way to reduce the haza rd potential of lift-generated vortices shed by subsonic transport aircraft in the vicinity of airports during landing and takeoff operations. The inf ormation presented points out that the characteristics of lift-generated vo rtices are related to the aerodynamic shapes that produce them and that var ious arrangements of surfaces can be used to produce quite different vortex structures. It is concluded that a satisfactory aerodynamic solution to th e wake-vortex problem at airports has not yet been found, but a reduction i n the impact of the wake-vortex hazard on airport capacity may soon become available through wake-vortex avoidance concepts currently under study. Pub lished by Elsevier Science Ltd.