主翼是多段翼构型的主要升力部件，其背风面边界层受到前缘缝翼尾迹中复杂旋涡结构的干扰，此类涡-边界层干扰问题与飞行器的气动力特性密切相关。采用时间解析的粒子图像测速技术对低雷诺数范围内30P30N多段翼构型在不同迎角下的主翼背风面流动开展精细实验测量，结合傅里叶模态分解和有限时间的李亚普诺夫指数流场诊断方法，从时均统计和涡动力学2个角度研究了前缘缝翼尾迹涡与主翼边界层之间的干扰特性并总结了迎角的影响规律。在实验雷诺数下，随着迎角增大，主翼背风面边界层由附着状态转变为大分离状态，前缘缝翼尾迹与主翼边界层之间的混合效应逐渐减弱。涡动力学研究表明，前缘缝翼尾迹涡产生的多频扰动能“浸入”主翼边界层并影响其内部流动结构演化，其中基频和二次谐波扰动激发的“双二次涡”结构在此过程中占据主导。二次涡在涡-边界层干扰中扮演重要角色：一方面，二次涡能将更多尾迹涡扰动注入边界层，促进尾迹与边界层的混合；另一方面，二次涡能将边界层外区的高速流体注入近壁区进而增强边界层抵抗流动分离的能力。随着迎角增大，二次涡的产生位置逐渐沿弦向后移，对主翼前缘附近混合效应的促进作用以及流动分离的抑制作用逐渐降低，最终导致尾迹与边界层之间的混合逐渐减弱、主翼背风面边界层发生大分离。

The main element is the main contributor to the lift generation of a multi-element airfoil. However， the boundary layer over the suction surface of the main element is inherently disturbed by the complex vortices in the slat wake. Therefore， the vortex/boundary-layer interactions over the main element are closely related to the aerodynamic performance of an aircraft. This study uses time-resolved particle image velocimetry to investigate the effects of angle of attack on the vortex/boundary-layer interactions over a 30P30N multi-element airfoil at a low Reynolds number， with the aid of Fourier mode decomposition and finite-time Lyapunov exponents. The results of both mean statistics and vortex dynamics are obtained. For the mean statistics， the attached boundary layer above the main element changes into a separated one as the angle of attack increases. Meanwhile， the mixing between the slat wake and the boundary layer is gradually limited with the increasing angle of attack. For the vortex dynamics， the disturbances of different frequencies， originating from the complex vortices in the slat wake， are found to penetrate the boundary layer and subsequently affect the vortex dynamics in the boundary layer. The “double-secondary vortices” topology， triggered by the wake disturbances of fundamental frequency and second harmonic， dominates the vortex dynamics in the boundary layer. These secondary vortices are vital to the vortex/boundary-layer interactions in that they inject the fluid in the slat wake into the boundary layer to promote the mixing between the slat wake and the boundary layer， while injecting the high-speed fluid around the boundary layer edge into the near-wall region and therefore enhancing the ability of the boundary layer to resist flow separation. As the angle of attack increases， the formation of secondary vortices moves downstream. As a result， the effects of secondary vortices on the wake/boundary-layer mixing and the flow separation suppression around the leading edge of the main element decrease， leading to the reduced wake/boundary-layer mixing with an increasing angle of attack and the flow separation at the largest angle of attack.