Using the tower fly-by method, decay meassurements were made on wake vortices generated by B-727, B-757 and B-767 aircraft. In addition to a 60-meter instrumented tower, two remote sensing systems were deployed: (1) Laser Doppler Velocimeter (LDV) (high resolution vortex profiles at ranges of 40 - 200 meters) and (2) Monostatic Acoustic Vortex Sensing System (MAVSS) (lower resolution profiles up to 500 meters beyond the tower location). Typical early morning meteorology during the test period consisted of stratified drainage flows. Because of the persistent crosswind, the MAVSS gave the most complete vortex decay information. Meteorological conditions were measured by instruments on the tower and on a tethersonde. The analysis looked for statistical relationships between vortex lifetime and several meteorological parameters, treated independently. Due to the meteorological conditions of stratification, low turbulence and wind shear, the upwind vortex lasted longer than the downwind vortex; the circulation remained above 140 m2/s for up to 125, 150 and 170 seconds for the B-727, B-757 and B-767, respectively. However, in every case, the crosswind was strong enough to sweep both wake vortices away from the generating location; in some cases the vortices traveled more than 500 meters laterally. Although these durations are much longer than the normally observed vortex lifetimes, they are related, according to the analysis, to strong crosswind shear coupled with low turbulence levels. While this long vortex migration at the observed strength levels might represent a potential vortex encounter hazard for operations on a downwind parallel runway, the drainage flow conditions which led to this unusual vortex behavior would be unlikely to occur at most airports.
Wake vortex decay near the ground under conditions of strong stratification and wind shear
Nachlaufwirbelzerfall in Erdbodennähe bei starker Schichtung und hohem Windgradient
1996
10 Seiten, 20 Bilder, 4 Tabellen, 8 Quellen
Aufsatz (Konferenz)
Englisch
Wake Vortex Decay Near the Ground Under Conditions of Strong Stratification and Wind Shear
British Library Conference Proceedings | 1996
|Wake vortex decay near the ground
AIAA | 1975
|Density stratification effects on wake vortex decay
NTRS | 1986
|Density stratification effects on wake vortex decay
AIAA | 1986
|Aircraft Control in Wake Vortex Wind Shear
NTIS | 1995
|