Aeronautical engineering: A continuing bibliography with indexes (supplement 296)

This bibliography lists 592 reports, articles, and other documents introduced into the NASA scientific and technical information system in Oct. 1993. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Flow structure in a model of aircraft trailing vortices

We consider a model of incompressible trailing vortices consisting of an array of counter-rotating structures in a doubly periodic domain, infinite in the vertical direction. The two-dimensional vortex array of Mallier and Maslowe is combined with an axial velocity profile chosen proportional to the initial axial vorticity to provide an initial condition for the vortex wake. This base flow is a weak solution of the steady Euler equations with three velocity components that are functions of two spatial coordinates, thus allowing its linear stability properties to be investigated. These are used to interpret several stages in the development of vortex structure observed in fully three-dimensional direct numerical simulation (DNS) at Reynolds numbers Gamma/(2pinu)=[script O](1000). For sufficiently high axial velocity, its effect can be seen, in that each vortex in the linear array first develops helical structures before undergoing a period of relaminarization. At later times the more slowly growing cooperative elliptical instabilities become apparent, but the helical structure persists and the observed vortical structures remain coherent for longer periods than in the absence of axial velocity. Using the stretched-vortex subgrid model, large-eddy simulation runs are performed at large Reynolds numbers and a mixing transition identified at about Re=1–2×10^4. Similar phenomena are observed in these simulations as are seen in the DNS

SIMULATION OF WAKE VORTEX AIRCRAFT IN GROUND EFFECT

The problem developed in this paper is encountered in airplane aerodynamics and concernsthe influence of long life longitudinal wake vortices generated by wing tips or by external obstaclessuch as reactors or landing gears. More generally it concerns 3D bodies of finite extension in crossflow. At the edge of such obstacles, longitudinal vortices are created by pressure differences inside theboundary layers and rotate in opposite senses. It can constitute a danger to another aircraft that fliesin this wake, especially during takeoff and landing. In this case the wake vortex trajectories andstrengths are altered by ground interactions. This study presents the results of a Large EddySimulation of wake vortex in ground effect providing the vorticity flux behavior

Aeronautical engineering: A continuing bibliography with indexes (supplement 279)

This bibliography lists 759 reports, articles, and other documents introduced into the NASA scientific and technical information system in May 1992. Subject coverage includes: design, construction, and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics