The Roll Dynamic Instability Mechanism and Deformed Wing Improvement

In recent years, the un-commanded lateral motions at high subsonic and transonic speeds, which are able to induce the mishap of the aircraft, has become a popular research issue. However, dynamic instability mechanism and control or alleviate methods are still a key issues for the resolve of the un-commanded lateral motions. This exploratory research performed to investigate the cause of non-linearity and the destabilizing mechanism due to the presence of asymmetric body vortex or wing/body bound vortex breakdown phenomenon. The focus of the effort is on developing the free oscillation test techniques and a nonlinear dynamic analysis method for identifying the non-linear aerodynamic, combined laser vapor screen flow visualization technique for observing the flow structures and building the vortex control or alleviate methods. The results of free oscillation experiment and laser vapor screen flow observation discovered that the subcritical type asymmetric wing/body bound vortex breakdown gives rise to a key effect on the non-linearity and dynamic instability of roll motion, and proved that the innovative morphing wing could adjust the unstable roll motion of the baseline wing and delay the wing/body bound vortex breakdown by increasing wing bound vortex strength and suppressing body vortex evolvement.