Development and validation of new simulation method for wake-vortex decay in ground proximity with artificial enhancements

Abstract

The aviation industry is undergoing a tremendous growth and is expected to continue in the decades ahead. One of the main factors affecting this growth is the airport capacity, which is limited by the frequency of landings and takeoffs. Aircrafts need to be separated since each aircraft is producing a pair of vortices in its wake that pose a danger to following aircraft. Even though a few concepts for reduced separation under certain conditions are being implemented at selected airports worldwide, it still persists to be a hurdle due to the limited knowledge of aircraft wake vortex decay. A clear understanding of wake-vortices and a precise prediction and avoidance system is required to establish an efficient operational method without jeopardising the safety of the aircrafts. The goal of this project is to study aircraft wake vortex decay and to reduce the impact of wake-vortices on the runway throughput. Hence, the wake-vortex dynamics at various atmospheric and wing span-loading conditions, in ground proximity is of primary focus for the current research. In this dissertation, the simulation software Jetcode, which was developed for combustion research at Stanford University, is adapted and validated for the wake-vortex research. Throughout the research, Lamb-Oseen vortex model is used to initialise the velocity fields of the shed wake-vortices. Large Eddy Simulations(LES) with dynamic Smagorinsky model is used to solve the unsteady, incompressible and viscous Navier-Stokes equation. The Temporal LES methodology is used for studying the atmospheric effects on wake-vortices. The effect of crosswind and turbulence intensity on the formation of secondary vortical structures in ground proximity are analysed in detail. The lateral transport of the primary vortex pair is investigated with two new parameters. Postprocessing codes to track the vortices and to determine the circulation of the vortices individually are developed. After performing the preliminary analysis on the wake vortex evolution, it is concluded that enhancing the secondary vortices interaction with the primary vortices result in an accelerated decay of the primary vortex pair. VII A new Prandtl Vorticity Distribution (PVD) method is introduced to initialise vortices, including those originating from the flaps, for any given lift distribution using Temporal LES methodology. This method is based on Prandtl Lifting-Line Theory and is effective in simulating the vortices shedding behind any type of aircraft with any high-lift configuration. The available measurements of B747 aircraft is considered for rest of the study. LIDAR measurements of landing 'Heavy' category aircrafts are used to validate the results of the new method. It has been found that the landing configuration of B747 results in a two pair wake-vortex system. The additional pair of vortices is due to the extension inboard flap. These inboard flap vortices greatly reduce the strength of the primary vortex pair. Using this method, the possibility of reducing the strength of the vortices by...