Impact of short-span strip on oscillating-wing tip vortex

The impact of 12 spoiler–tab configurations, of different heights and widths, on the tip vortex generated by an oscillating NACA 0015 wing was investigated experimentally. For an oscillating wing equipped with a spoiler, the peak tangential velocity and core and total circulation were greatly reduced compared to a tab, regardless of its width, while the core radius remained largely unaffected with its center displaced vertically above the baseline wing. The most noticeable impact of a spoiler with a reduced height was its potential in alleviating the blade–vortex interaction (BVI) strength. Meanwhile, the largest favorable impact on the critical vortex flow parameters was achieved via a 25%-span spoiler–tab combination with a height of 5 and 2.5% chord, respectively. A contrary effect on the BVI suppression, especially during pitch-up, was, however, observed. The impact on the BVI can be improved by reducing the height of the spoiler at the expense of unfavorable change in the vortex strength and displacement.