在低维流形上掌握极端空气动力学特性
Grasping Extreme Aerodynamics on a Low-Dimensional Manifold
AI总结：
针对极端旋涡阵风下机翼空气动力学缺乏理论基础、参数空间大的问题，本研究用升力增强型自编码器将非线性旋涡流场压缩为三个变量的低维流形，为小型飞行器在极端阵风环境下稳定飞行提供支撑。
摘要：
现代飞行器执行运输、防御、监视和救援等多种任务。这类飞行器可在平静条件下飞行，但会避开在城市峡谷、山地上空及舰船尾流中遇到的阵风环境作业。随着全球变暖导致极端天气愈发频繁，预计飞行器尤其是小型飞行器会遭遇强烈大气扰动，且仍需实现稳定飞行。然而，目前几乎没有理论流体动力学基础可描述极端旋涡阵风对机翼的影响。更棘手的是，阵风-机翼相互作用的参数空间很大。尽管这类相互作用看似复杂，且每种阵风参数组合的表现都不同，但我们表明，极端空气动力学背后的基本物理原理远比传统预期的简单，且秩更低。我们揭示，借助升力增强型自编码器（lift-augmented autoencoder），随时间和参数空间变化的非线性旋涡流场可被压缩至仅三个变量，同时保留原始高维物理的核心本质。通过机器学习，极端空气动力流可被压缩到低维流形中，这能够实现极端非定常阵风流动的实时稀疏重构、动力学建模与控制。本研究结果为下一代小型飞行器在传统认为无法飞行的大气条件下实现稳定飞行提供了支撑。
英文摘要：
Modern air vehicles perform a wide range of operations, including transportation, defense, surveillance, and rescue. These aircraft can fly in calm conditions but avoid operations in gusty environments, encountered in urban canyons, over mountainous terrains, and in ship wakes. With extreme weather becoming ever more frequent due to global warming, it is anticipated that aircraft, especially those that are smaller in size, will encounter sizeable atmospheric disturbances and still be expected to achieve stable flight. However, there exists virtually no theoretical fluid-dynamic foundation to describe the influence of extreme vortical gusts on wings. To compound this difficulty, there is a large parameter space for gust-wing interactions. While such interactions are seemingly complex and different for each combination of gust parameters, we show that the fundamental physics behind extreme aerodynamics is far simpler and lower-rank than traditionally expected. We reveal that the nonlinear vortical flow field over time and parameter space can be compressed to only three variables with a lift-augmented autoencoder while holding the essence of the original high-dimensional physics. Extreme aerodynamic flows can be compressed through machine learning into a low-dimensional manifold, which can enable real-time sparse reconstruction, dynamical modeling, and control of extremely unsteady gusty flows. The present findings offer support for the stable flight of next-generation small air vehicles in atmosphere conditions traditionally considered unflyable.
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