The effect of flap-end additions on aircraft trailing vortices

Abstract

The influence of flap-end geometry modifications on the near-field wake behind a generic high-lift wing/flap configuration is investigated experimentally with a single-tube yawmeter. It is found that flap-end additions tend to split the concentrated area of streamwise vorticity shed by the flap into two less intense regions, associated with the tips of the flap and the addition. For shorter additions, these regions tend to roll up together, resulting in a slightly more diffuse flap vortex of almost unchanged circulation. For larger additions, the outer region is captured by the tip vortex, which correspondingly gains in circulation at the expense of the flap vortex. In all cases, the vorticity centroid of the rolled-up wake is shifted outboard, and the overall circulation slightly increased. However, the associated lift increase implies a decrease in overall circulation at a given lift coefficient.

Experimental observations of the merger of co-rotating wake vortices

“…These data were numerically differentiated, using a centred-difference approximation, to estimate the streamwise vorticity, ω x . The errors associated with this process are discussed by Graham, David & Bertényi (2004), who give the maximum absolute vorticity discrepancy as 2 √ 2 v c /∆, where v c is the maximum crossflow velocity error (5% for our probe), and ∆ the grid spacing. The uncertainty in the vorticity estimate thus varies with position, and will be discussed on a case-by-case basis.…”