基于特征值方法的旋翼尾迹稳定性分析

Analysis of Rotor Wake Stability by Eigenvalue Method

给出一个旋翼尾迹线性化稳定性分析的方法.在该方法中,尾迹涡线被离散为直线涡段,尾迹的扰动归结为涡元端点的扰动,考虑了桨尖涡的自诱导和涡线的互诱导以及桨尖涡与桨叶的实际干扰.使用该方法,分别以UH-1H和AH-1G模型旋翼为例,对悬停和前飞状态的旋翼尾迹的稳定性进行计算和分析.结果表明:旋翼尾迹运动存在大于0的特征值,是内在不稳定的,且最大发散率随波数变化呈现出一定规律性;前飞与悬停状态不同,其最大发散率减小,不稳定性减弱.

A linearized analytical method for stability analysis of the helicopter rotor wake is given. The wake vortex filaments are discretized into a number of straight-line vortex segments and perturbations of the vortex filaments are described by the end-position change of vortex segments. Self-induced and mutually-induced effects of the tip vortices as well as the interaction between rotor blade and tip vortex are considered. Taking UH-1H and AH-1G model rotors as numerical examples, stability of the rotor wakes in both hover and forward flight is analyzed. It is shown that there is a positive eigenvalue in rotor wake motion and the Wake is intrinsically unstable. Furthermore, a regular change of the maximum divergence rate with wave number is observed. The maximum wake divergence rate is smaller and the instability is weaker in forward flight compared with that in hovering flight.