The NASA-Langley wake vortex modelling effort in support of an operational aircraft spacing system

Abstract

Two numerical modelling efforts, one using a large eddy simulation model and the other a numerical weather prediction model, are underway in support of NASA's Terminal Area Productivity program. The large-eddy simulation model (LES) has a meteorological framework and permits the interaction of wake vortices with environments characterized by crosswind shear, stratification, humidity, and atmospheric turbulence. Results from the numerical simulations are being used to assist in the development of algorithms for an operational wake-vortex aircraft spacing system. A mesoscale weather forecast model is being adapted for providing operational forecast of winds, temperature, and turbulence parameters to be used in the terminal area.This paper describes the goals and modelling approach, as well as achievements obtained to date. Simulation results will be presented from the LES model for both two and three dimensions. The 2-D model is found to be generally valid for studying wake vortex transport, while the 3-D approach is necessary for realistic treatment of decay via interaction of wake vortices and atmospheric boundary layer turbulence. Meteorology is shown to have an important affect on vortex transport and decay. Presented are results showing that wake vortex transport is unaffected by uniform fog or rain, but wake vortex transport can be strongly affected by nonlinear vertical change in the ambient crosswind. Both simulation and observations show that atmospheric vortices decay from the outside with minimal expansion of the core. Vortex decay and the onset three-dimensional instabilities are found to be enhanced by the presence of ambient turbulence. Nomenclature

Multimodel Ensemble Methods for Prediction of Wake-Vortex Transport and Decay

“…In general, the fast-time wake-vortex models are empirical algorithms used for fast predictions of wake transport and decay, based on aircraft parameters and ambient weather conditions. The models used in this study include the Aircraft Vortex Spacing System (AVOSS) Prediction Algorithm (APA) [32][33][34][35][36], Terminal Area Simulation System (TASS) Derived Algorithms for Wake Prediction (TDP) [14,37], and the deterministic two-phase wake-vortex decay and transport model (D2P) [12,13]. The APA and TDP models have been developed by NASA, whereas D2P has been developed by DLR.…”

NASA aircraft vortex spacing system development status

“…Numerical wake modeling with Langley's Terminal Area Simulation System (TASS) Large-Eddy Simulation model 12,15 are focused on providing the needed sensitivity studies and relationships between wake motion and decay behavior and specific atmospheric parameters.…”

Energy decay of vortices in viscous fluids: an applied mathematics view

“…The topic of this paper, the slow energy decay, causes problems when wingtip vortices remain on the runway for a long time, see Proctor (1998), Kantha (2010), Gerz et al (2002), Breitsamter (2011), Spalart (1998). Vortices are also important when explaining several flow phenomena.…”