We investigate the dynamic response of flexible aircraft in low-altitude atmospheric turbulence. To this end, three turbulence models of increasing fidelity, namely, the one-dimensional von K{a}rm{a}n model, the two-dimensional Kaimal model and full three-dimensional wind fields extracted from large-eddy simulations (LES) are used to simulate ambient turbulence near the ground. Load calculations and flight trajectory predictions are conducted for a flexible high-aspect ratio aircraft, using a fully coupled nonlinear flight dynamics/aeroelastic model, when it operates in background atmospheric turbulence generated by the aforementioned models. Comparison of load envelopes and spectral content, on vehicles of varying flexibility, shows strong dependency between the selected turbulence model and aircraft aeroelastic response (e.g. 58\% difference in the predicted magnitude of the wing root bending moment between LES and von K{a}rm{a}n models). This is mainly due to the presence of large flow structures at low altitudes that have comparable dimensions to the vehicle, and which despite the relatively small wind speeds within the Earth boundary layer, result in overall high load events. Results show that one-dimensional models that do not capture those effects provide fairly non-conservative load estimates and are unsuitable for very flexible airframe design.

中文翻译：

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评估飞机气动弹性的低空大气湍流模型

我们研究了柔性飞机在低空大气湍流中的动态响应。为此，提出了三种保真度不断提高的湍流模型，即一维von K{a}rm{a}n模型、二维Kaimal模型和从大涡模拟（LES）中提取的全三维风场) 用于模拟地面附近的环境湍流。当它在由上述模型产生的背景大气湍流中运行时，使用完全耦合的非线性飞行动力学/气动弹性模型对灵活的高纵横比飞机进行载荷计算和飞行轨迹预测。在不同灵活性的车辆上比较载荷包络和频谱内容，表明所选湍流模型与飞机气动弹性响应（例如 LES 和 von K{a}rm{a}n 模型之间机翼根部弯矩的预测幅度有 58% 的差异）。这主要是由于在低空存在大流量结构，其尺寸与飞行器相当，尽管地球边界层内的风速相对较小，但会导致整体高负载事件。结果表明，没有捕捉到这些影响的一维模型提供了相当不保守的载荷估计，不适合非常灵活的机身设计。导致整体高负载事件。结果表明，没有捕捉到这些影响的一维模型提供了相当不保守的载荷估计，不适合非常灵活的机身设计。导致整体高负载事件。结果表明，没有捕捉到这些影响的一维模型提供了相当不保守的载荷估计，不适合非常灵活的机身设计。