Effect of Sideslip on High-Angle-of-Attack Vortex Flow over Close-Coupled Canard Configuration

Abstract

The aerodynamic response to sideslip is crucial for an aircraft’s lateral stability, especially for configurations incorporating vortex flow, on which sideslip causes asymmetric vortex behavior and brings extra complexity. In this work, vortex flow over a close-coupled canard configuration under sideslip is simulated using delayed detached-eddy simulation, with the angle of attack varying up to the poststall regime. Sideslip-induced distinctions in both vortex dynamics and canard/wing-vortex interaction are analyzed to explain the nonlinear response of the configuration. The results reveal that the effect of sideslip differs significantly upon different angle-of-attack regimes. At a medium angle of attack, the spanwise extension of the low-pressure area due to windward vortex core expansion results in superior windward lift against the leeward side, but the relatively low pressure retained due to delay of the leeward vortex breakdown is the main motivation that leeward lift surpasses windward at a high angle of attack. The canard vortex trajectory deflected under sideslip induces asymmetric vortex interaction, enhancing the leeward side, which not only leads to an unusual rolling moment toward the higher lift side at a medium angle of attack but also causes an abrupt loss of lateral stability at the poststall angle of attack. A featured demarcation line exists on both the canard and the wing to separate the lift imbalance area, which is found useful in interpreting the nonlinear behavior.