The wake alleviation properties of wings with out board, triangular flap extensions are estimated using data from particle image velocimetry. The experiments are conducted in a towing tank at chord-based Reynolds numbers of O(10(5)). The triangular-flapped 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 flap vortices near the tip vortices causes a rapidly growing instability to occur between the vortices on either aside of the wake. The resulting nonlinear interactions between the vortices result in a wake that is highly three-dimensional and incoherent. These effects are reflected in a marked decrease in both the rolling moment and downwash on a simulated following wing. To determine the wake alleviation properties of the triangular-flapped wings, their wakes are compared to that of a conventional, rectangular wing. For all of the experimental runs, the wakes of the triangular-flapped 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-flapped wings offers a possible mechanism to reduce significantly the wake hazard problem. References: 30
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