The work presented herein examines the interaction of aircraft wake vortices with nonuniform ambient shear in close proximity of the ground. The investigation is based on two- and three-dimensional numerical simulations using a grid-based Reynolds-averaged Navier-Stokes solver. The simulations are tailored to establish the extent of simplifications in mathematical modeling that can be realized while maintaining acceptable accuracy. The results are intended to provide the ground work for the development of real-time algorithms that may be used at airports in dynamic spacing of aircraft during landing and take-off. Through comparison with field data as well as simulations based on a one-equation turbulence model, the assumption of a constant eddy viscosity is shown to be adequate for modeling the turbulent diffusion of wake vortices in low-turbulence ambient conditions. Nonlinear interactions are demonstrated in the instance of simultaneous influence of ambient shear and ground proximity on the wake-vortex dynamics. Furthermore, neither axial motion within the core of the wake vortices nor nonuniform headwind shear are shown to have significant influence on the kinematics of the wake / crosswind-shear interaction, lending support for twodimensional modeling of this flow if three-dimensional instability effects are accounted for separately. Finally, the results help to establish the levels of accuracy and resolution of wind measurements that are required for reliable prediction of wake-vortex dynamics in nonunifonnly sheared ambient conditions.

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Conference 40th AIAA Aerospace Sciences Meeting and Exhibit 2002
Yaras, M. (2002). Numerical simulations of aircraft wake-vortex dynamics in nonuniform windshear and ground proximity. Presented at the 40th AIAA Aerospace Sciences Meeting and Exhibit 2002.