Flow mechanisms of lateral–directional control by an all-moving wingtip on a tailless configuration

All-moving wingtips (AMTs) are attractive for tailless configurations as they provide yawing and rolling moments while preserving low-observable characteristics. However, previous studies have mainly focused on the overall aerodynamic forces and moments under AMT deflections, whereas the underlying flow mechanisms, especially the interaction between the AMT and the adjacent wing, remain insufficiently understood. To establish a fundamental understanding of AMT-induced lateral–directional control mechanisms, this study employs numerical simulations and wind tunnel tests to investigate unilateral AMT deflection, a basic control case in which only the left all-moving wingtip (LAMT) is deflected. The results reveal a distinct transition in the moment-generation mechanism with increasing angle of attack (AoA): at low AoAs, where the flow remains largely attached, LAMT deflection mainly acts as a local aerodynamic blockage and produces yawing and rolling moments on the LAMT itself, with little influence on the adjacent left-wing flow. As the AoA increases and the left-wing leading-edge vortex (LEV) develops, the yawing moment remains dominated by the LAMT contribution, whereas the rolling moment becomes primarily governed by the interaction between LAMT-induced flow structures and the left-wing LEV. The LAMT deflection modifies the breakdown behavior of the left-wing LEV and influences the upper-surface suction on the adjacent wing, thereby generating rolling moment contributions from both the LAMT and the left wing. Depending on AoA, deflection direction, and deflection amplitudes, LAMT-induced interactions can either delay or advance the breakdown of the left-wing LEV.