Wake Alleviation Properties of Triangular-Flapped Wings

The wake alleviation properties of wings with outboard, triangular ap extensions are estimated using data from particle image velocimetry. The experiments are conducted in a towing tank at chord-based Reynolds numbers of O (105). The triangular- apped wings generate two unequal strength, counter-rotating vortex pairs that have circulation strength ratios ranging from ¡ 0.4 to ¡ 0.7. Introducing the oppositely signed ap vortices near the tip vortices causes a rapidly growing instability to occur between the vortices on either side of the wake. The resulting nonlinear interactions between the vortices result in a wake that is highly three-dimensional and incoherent. These effects are re ected in amarked decrease in both the rolling moment and downwash on a simulated following wing. To determine the wake alleviation properties of the triangular- apped wings, their wakes are compared to that of a conventional, rectangular wing. For all of the experimental runs, the wakes of the triangular- apped wings have maximum rolling moments and downwashes that are substantially less than those of the rectangular wing. The results indicate that the instability in the wake of the triangular- apped wings offers a possible mechanism to reduce signi cantly the wake hazard problem. I.