高空长航时(HALE)飞机结构细长、具有柔性,在常规飞行条件下可发生结构大变形、气动失速以及结构低频振动与刚体运动耦合,这些现象显著影响其静、动态特性。基于几何精确完全本征运动梁模型、ONERA动失速气动力模型和六自由度刚体运动模型,建立了考虑几何非线性、动失速和材料各向异性等因素的大展弦比柔性飞机非线性气动弹性与飞行动力学耦合模型。使用常规布局和飞翼布局两种柔性飞机算例模型,对大展弦比柔性飞机非线性气动弹性与飞行动力学耦合配平、动稳定性和时域响应特性开展了研究。研究结果表明:当机翼变形较小时,柔性飞机配平迎角小于刚性飞机配平迎角,整个翼展范围内均可能发生失速,全机升力损失显著,可导致飞行高度迅速降低;当机翼变形较大时,柔性飞机配平迎角大于刚性飞机配平迎角,失速发生于翼尖且范围有限;机翼变形增大可导致全机运动趋于不稳定,气动弹性剪裁有助于改善柔性飞机动稳定性。
High-altitude long-endurance (HALE) aircraft features slender and flexible structures, which under nominal operation conditions may result in large structural deformation, aerodynamic stall, and coupling between the low-frequency structural vibration and the rigid body motion of the aircraft. These nonlinearities and interactions affect dramatically the static and dynamic behaviors of a HALE flexible aircraft. This paper developed a coupled model of aeroelasticity and flight dynamics for high-aspect-ratio flexible aircraft based on the geometrically exact, fully intrinsic beam theory, ONERA aerodynamic stall model, and a six degree of freedom model of the rigid body motion. This model takes into consideration the geometrical nonlinearities, dynamic stall and material anisotropy, etc. Two case models of the conventional configuration and the flying-wing configuration are used to investigate the characteristics of the trim, dynamic stability and time-domain response of the high-aspect-ratio flexible aircraft with nonlinear aeroelasticity and flight dynamics coupled. The results obtained indicate that when the wing deformation is relatively small, the angle of attack required for the trim of the flexible aircraft is smaller than that for a rigid aircraft, and stall may occur along the whole wing span, which may cause altitude decrease quickly due to the dramatic reduction in the total lift of the complete aircraft. When the wing deformation is relatively large, the angle of attack required for the trim of the flexible aircraft is larger than that for a rigid aircraft, and stall occurs in a limited region near the wing tip. In addition, the motion of a flexible aircraft may become unstable due to large deformation of its wings, which can be improved by applying aeroelastic tailoring.
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