Passive control method in attenuating self-induced roll oscillations of low-aspect-ratio wings using oblique slot bleed

The purpose of this paper is to introduce an effective near tip slot configuration for low-aspect-ratio rectangular wings, to attenuate its self-induced roll oscillations at large angle of attack. A series wind tunnel tests were conducted on 9 different test models, each with a narrow near tip slot (3mm) orientated differently, at the wind speed of 10m/s, with the angle of attack ranging from 0 ^◦ to 30 ^◦ . Among all the models tested, the model with slot orientation angle of β = 45 ^◦ have demonstrated the best effect on attenuating the oscillation. At α = 26 ^◦ , the RMS roll angles was suppressed by ∆Φ _rms,max = 47 ^◦ . The effect to lessen roll frequency has also been observed. For other tested models, the β = 30 ^◦ model and the β = 120 ^◦ model have also shown attenuation effect in general. PIV measurements showed that the bleed results from wing tip slot may have affected the generation and reattachment of wing tip vortex, and thus result in attenuation or enhancement of self-induced roll oscillations.