Load alleviation of plunging swept and unswept wings with spoilers

The effectiveness of mini-spoilers for loads alleviation of both plunging unswept and swept wings with leading edge and trailing edge spoilers was investigated experimentally in a water tunnel. For unswept wings, both leading-edge and trailing-edge spoilers exhibit similar frequency responses at pre-stall angles of attack, with their effectiveness dependent on the reduced frequency of the plunging motion. The study reveals that taller spoilers provide better load alleviation performance than shorter ones, particularly at low reduced frequencies, although the spoiler height’s influence diminishes as the reduced frequency increases. Under highly unsteady conditions, the leading-edge spoiler shows minimal impact on the formation of the leading-edge vortex, whereas the trailing-edge spoiler tends to be engulfed in separated flow, thus limiting their capabilities in loads alleviation. At stall and post-stall angles of attack, the trailing-edge spoiler offers limited load alleviation benefits, whereas the leading-edge spoiler demonstrates improved performance. As the sweep angle increases, the trailing-edge spoiler's effectiveness diminishes due to intensified spanwise flow, thereby restricting its ability to control wing circulation. Similarly, the effectiveness of the leading-edge spoiler placement also declines, as a tip vortex forms at its inboard edge, moving outboard and reattaching the flow behind the spoiler.