Study on decay characteristics of vertical four-vortex system for increasing airport capacity

The wake vortices of an aircraft descend by self-induction that enables a pilot to identify approximate wake location based on the preceding aircraft path. A pilot taking off an aircraft can avoid a wake vortex encounter by performing early rotation and flying at or above the climb path of the preceding aircraft. Such operation results in a situation in which two wake vortices are present in the air simultaneously in close proximity. In this study, the transport and decay characteristic processes involving interactions between the wake vortex pairs formed by the preceding and the following aircraft have been analyzed. The high altitude of the following aircraft was included as initial conditions, and atmospheric turbulence conditions were applied to large eddy simulations to account for the vortex core instability and nonlinear transport and decay. The obtained results were used to identify the decay processes that induce the rapid dissipation of wake vortices such as merging into a single counter-rotating pair, rapid dissipation, and formation of a vortex ring with or without deformation of the lower vortex pair. The third process could be effectively used to adjust the take-off separation time for increasing the capacity at airports. (C) 2020 The Authors. Published by Elsevier Masson SAS.