The dispersion of aircraft emissions during the vortex phase is studied usinga 3-D LES model with Lagrangian particle tracking. The simulations start witha fully rolled-up vortex pair of a type B747/A340 airplane and the tracercentred around the vortex cores. The tracer dilution and plume extent isstudied for a variety of ambient and aircraft parameters untilaircraft-induced effects have ceased. For typical upper troposphericconditions, the impact of stratification is more dominant compared toturbulence intensity or vertical wind shear. Moreover, the sensitivity to theinitial tracer distribution was found to be weak. Along the transversedirection, the tracer concentrations can be well approximated by a Gaussiandistribution, along the vertical a superposition of three Gaussiandistributions is adequate. For the studied parameter range, the verticalplume expansion ranges from 400 m to 550 m and cross-sectional areafrom 4.0 × 10 m to 6 × 10 m after sixminutes. For validation, selected simulations were compared to an alternativeLES model and to in-situ NO-measurements.
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