Analyse der Zerfallsmechanismen von Wirbelschleppen in der Atmosphäre

Results of high-resolution numerical simulations of aircraft wake vortex evolution and decay in different regimes and atmospheric conditions are presented. The different cases comprise (i) the near field interaction of a trailing vortex with an exhaust jet, (ii) the evolution of single vortices and counter-rotating vortex pairs in homogeneous isotropic turbulence, as well as (iii) the decay of wake vortices in a turbulent stably stratified atmosphere, and (iv) in a weakly turbulent sheared environment. The different cases are used to analyse common aspects of vortex dynamics and decay mechanisms. In all scenarios the formation of coherent secondary vorticity structures that enclose the primary vortices is observed. These secondary vorticity structures deform and weaken the primary vortices and in some cases lead to rapid vortex decay. It is shown that the mean swirling flow effectively rearranges and intensifies any secondary vorticity by tilting and stretching. The secondary vorticity may either originate from the turbine jet, ambient turbulence or may be produced baroclinically. Based on the observed phenomena, eleven postulates are established that pinpoint fundamental aspects of the observed decay mechanisms. 2003 Éditions scientifiques et médicales Elsevier SAS. All rights reserved. Zusammenfassung Mittels hochauflösender numerischer Simulationen wird die Entwicklung und der Zerfall von Flugzeug-Wirbelschleppen unter ver-schiedenen atmosphärischen Bedingungen untersucht. Die betrachteten Szenarien umfassen (i) die Wechselwirkung eines Triebwerksstrahls mit einem Nachlaufwirbel, (ii) die Entwicklung von Einzelwirbeln und gegensinnig rotierenden Wirbelpaaren in homogener isotrope