Algorithm for Prediction of Trailing Vortex Evolution

Abstract

We describe an algorithm that predicts the trajectories and circulation decay of aircraft trailing vortices. We e rst presentthemethodology used by the algorithm to simulatetrailing vortex behavior, including 1 )thedescent of the vortices through a realistic atmosphere dee ned by crosswind, turbulence, and stratie cation proe les and 2 ) the interaction of the vortices with the ground. Examples are presented to demonstrate the algorithm’ s capability. We then describea database approach forquantifying comparisons between algorithm predictions and measurements of wake vortex transport and decay. The use of databases to optimize the constant factor k in the term governing the effect of turbulence on vortex decay is reported, with the result that k appears to depend on the intensity of ambient turbulence. Using selected groupings of cases from the database, we have determined that vortices not interacting with the ground decay about a factor of two faster in high-intensity ambient turbulence than in low-intensity ambient turbulence. We also show that the circulation decay for vortices in the ground effect appears to be independent of the ambient turbulence level.