采用主动流动控制方法加快翼尖涡衰减破碎是提升机场起降频率、保证飞机飞行安全的最具潜力的技术之一。由于翼尖涡不稳定性认识的不足，已有的主动控制方法常常不能获得最优的控制效果。为了揭示翼尖涡不稳定模态的演化规律，采用体视粒子图像测速技术和线性稳定性分析方法对孤立翼尖涡的不稳定模态演化特征进行研究，结果表明：孤立翼尖涡的扰动模态可以根据其在特征值谱的位置分成主扰动模态、P族次级扰动模态、A族次级扰动模态、S族次级扰动模态4种；其中主扰动模态和P族扰动模态具有两瓣式的结构特征，决定了翼尖涡摇摆的各向异性特征，A族次级扰动模态具有流向速度波动大于横向速度波动的特征，S族次级扰动模态则具有更高的切向波数和作用范围。不同族扰动模态的流向演化规律不同，翼尖涡的主扰动模态和P族扰动模态沿流向发生旋转，并且扰动幅值随着流向逐渐放大，A族次级扰动模态随着流向发展会逐渐增大扰动幅值；S族次级扰动模态随着流向会逐渐覆盖住整个涡核，这种穿透涡核的扰动会随着流向进一步放大。描述了不同翼尖涡扰动模态的扰动能量随流向的演化规律，发现S族次级扰动模态有更高的切向波数特征，也同时具有较高的扰动能量增长，意味着利用S族次级扰动模态指导翼尖涡主动控制是最具潜力的一种策略。

Using the active flow control method to accelerate the attenuation and fragmentation of the wing tip vortex is one of the most potential technologies to improve the take-off and landing frequency of the airport and ensure the flight safety of aircraft. Due to the lack of understanding of wingtip vortex instability， the existing active control methods often cannot achieve the optimal control effect. To reveal the evolution law of the unstable modes of the wingtip vortex， the evolution characteristics of the unstable modes of the isolated wingtip vortex are studied using the SPIV technique and the linear stability analysis method. The results show that： the perturbation modes of the isolated wingtip vortex can be divided into four types according to its position in the eigenvalue spectrum： main perturbation mode， P secondary perturbation mode， A secondary perturbation mode and S secondary perturbation mode. Among them， the main perturbation mode and P-group perturbation mode have two-lobe structural characteristics， which determine the anisotropic characteristics of wingtip vortex wandering. The secondary perturbation mode of group A has the characteristic that the fluctuation of flow velocity is larger than that of transverse velocity， while the secondary perturbation mode of group S has a higher tangential wavenumber and range of action. The flow direction evolution law of different perturbation modes is different. The main perturbation mode and P group perturbation mode of the wing tip vortex rotate along the flow direction， with the perturbation amplitude gradually magnified with the flow direction. Group A secondary perturbation mode will slowly increase the perturbation amplitude with the development of the flow direction. Group S secondary perturbation mode will gradually cover the whole vortex core with the flow direction， and the perturbation passing through the vortex core will be further magnified with the flow direction. The evolution law of perturbation energy of different wing tip vortex perturbation modes with flow direction is described. S secondary perturbation modes have higher tangential wavenumber characteristics and meanwhile higher perturbation energy growth， meaning that using S-group secondary perturbation modes to guide the active control of the wing tip vortex is the most potential strategy.