Accelerated destruction of aircraft wake vortices

All aircraft shed a wake of vorticity which typically rolls up to form a trailing counter-rotating vortex pair. When encountered by following aircraft, these vortices can cause a substantial loss of altitude which is especially hazardous during takeoff and landing. Since avoiding this wake vortex hazard currently determines the spacing between aircraft on approach to land, accelerating the destruction of these vortices could lead to greater safety and increased airport utilization.;In practice, an aircraft's vortex wake often breaks down via the Crow instability. No other instability has been found which is more rapidly growing or shows a greater ability to mix vorticity of opposite sign. Thus, the objective of this research is to investigate alleviation schemes by which perturbations, applied to the wake at the wing, survive the roll-up process, excite the Crow instability at large amplitude and lead to accelerated destruction of the wake vortices.;To carry out this research, a new numerical method has been developed which solves the incompressible Navier-Stokes equations in vorticity form in a domain which is periodic in one direction and unbounded in the other two. For problems requiring high accuracy, this method has been shown to be orders of magnitude more efficient than existing schemes. A code using this method has been used to fully characterize the Crow instability as it exists in a 3D, viscous environment and validate the analytical models of this instability. Other simulations have studied the evolution of the Crow instability in perturbed wakes shed by elliptically loaded and high-lift wings. Finally, a new mechanism to be used in accelerating the destruction of aircraft wake vortices is proposed. Its behavior is investigated using both Navier-Stokes and vortex filament methods. The results indicate that the time required for vortex linking can be reduced by as much as a factor of seven when compared to the time required for equivalent growth via the linear Crow instability. This mechanism shows significant potential for use in a wake vortex hazard alleviation scheme.