大迎角气动弹性分析是现代飞行器设计中非常引人瞩目并且复杂的研究课题。采用Navier-Stokes方程求解非定常流场,耦合结构运动方程,在状态空间内实现了70°削尖三角翼涡破裂前后的气动弹性时域模拟。研究显示,前缘分离涡破裂后,流动的非定常脉动特性非常明显,这种非定常效应对机翼气动弹性特性的影响不可忽略。涡破裂前,气动弹性失稳表现为单纯的颤振问题。涡破裂后,破裂漩涡运动引起的外激载荷作用在翼面上引起抖振效应,这时的气动弹性问题可能既不是单纯的颤振问题,也不是单纯的抖振问题,而是颤振和抖振伴生的复杂问题。随着迎角增加,涡破裂点位置前移,破裂漩涡产生的外激载荷增强,抖振效应增强,气动弹性特性呈现明显的颤振与抖振伴生的现象。经功率谱密度分析发现,随着迎角增加,作用在翼面上的脉动载荷增加,对应的峰值频率有降低的趋势。
Aeroelastic analysis at high angles of attack is an attractive and complicated research subject in modern aircraft design. By using the Navier-Stokes(N-S) equations coupled with structural motion equations, an aeroelastic analysis of a 70° cropped delta wing before and after vortex breakdown in the time-domain is performed in a state-space. It is shown that the unsteady fluctuation characteristics of the flow become highly obvious after the vortex breakdown,which exert a significant impact on the aeroelastic characteristics of the wing. Before the vortex breakdown, the aeroelastic instability presents itself as just a simple flutter. However, after the vortex breakdown, the aeroelastic phenomenon may be neither a simple flutter, nor a simple buffet induced by the external excitation loads on the wing, but a complex state including both flutter and buffet. As the angle of attack increases, the vortex breakdown location moves forward, and the external excitation loads due to the vortex breakdown rise. The influence of buffet thus increases, and the aeroelastic characteristics become a more obvious phenomenon involving flutter and buffet. Besides, from the analysis of the power spectra density (PSD), it is also found that the fluctuating loads on the wing rise and the frequency of the peak on the PSD decreases as the angle of attack increases.
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