Potential hazard of aircraft wake vortices in ground effect with crosswind

Aircraft wake vortices, evolving close to the ground in a cross wind, are a potential hazard to aircraft landing or taking off on the same or parallel runways. The objective of this work has been to study, by means of numerical simulation, the effect of aerodynamic and environmental conditions on the generation and transport of these vortices. The approach has been to use a computer code which solves the two-dimensional, timedependent, incompressible Navier-Stokes equations expressed in stream function-vorticity form, to study wake vortices in ground effect with crosswind. The code permits the specification of arbitrary atmospheric stability and wind profiles. A mixed no-slip/free-slip lower boundary condtion has been invoked to model the interaction of the vortices with the ground. Comparisons of code output with laboratory and field data have been used to validate the code. Simulation results have shown that, even after evolution times and cross-runway transport distances on the order of 3 min and 500 m, vortices generated by large aircraft close to the ground in a crosswind can carry sufficient average circulation to be a potential hazard to smaller aircraft. Additional full-scale data need to be acquired and additional numerical comparisons need to be performed to assess the significance of these new results.