大攻角高精度非定常气动力建模及动稳定性分析方法研究

Flight performance requirement for new generation of advanced aircraft is much more strict in the increasingly complicated world pattern, one of the remarkable characteristics of the aircraft is the ability to finish a varity of complex tasks with strict unsteady aerodynamic forces affected by highly maneuvering. However,for a long time, research on nonlinear aerodynamics at high angle of attack only depends on limited wind tunnel tests, large-scale and precisely systematic research can not be carried out. As a result, based on high-precision computational fluid dynamics (CFD) technique, this project adopts detached-eddy simulation (DES) to accurately calculate the unsteady flow filed at high angle of attack, with the analysis of flow characteristics on probable maneuvering motion of advanced aircraft, such as large amplitude motion of single degree and complex multi-axis coupled motion, the influencing factors of nonlinear flow filed at high angle of attack are extracted and extended, then a new high-precision and clearly physical meaning unsteady aerodynamics model can be built and further testfied. Finally, on this basis, the linear dynamic derivative concept is extended and a new general dynamic stability criterion is analogically defined, which can represent the linear stability at small angle of attack as well as nonlinear local and global stability at high angle of attack. Research of this project can provide theoretical support for dynamic aerodynamic design of new generation of advanced aircraft.

日益复杂的世界格局形式对新型先进飞行器的性能提出了更为严苛的要求，能够经受高机动运动下的非定常气动力作用，完成各种复杂任务成为该类飞行器的显著特点之一。长期以来，有关大攻角下的飞行器动态特性研究依赖有限的风洞试验，难以开展大规模、更为精确的系统性研究，因此，本项目借助高精度CFD手段，采用DES方法对大攻角时非定常运动的流场进行精确计算，通过分析单自由度大振幅以及多轴耦合的复杂运动等先进飞行器可能进行的机动形式的流场特点，提取扩充大攻角非线性流场的影响因子和特征参数，建立具有明确物理意义的新型高精度非定常气动力模型并进行仿真验证；在此基础上，将线性动导数概念进行延伸，类比定义表征小攻角线性、大攻角非线性状态局部以及全局动稳定特性的通用判据概念。本项目的研究可以为新一代先进飞行器的动态气动设计研究提供理论支撑。

新一代先进飞行器必须具有极高的机动性和稳定性。机动性决定了飞行器具备能够在复杂的流场环境中利用瞬时的高机动性完成各种复杂任务的能力，此时飞行器必然经受严峻的非定常气动力作用，出现“气动-运动”高度耦合现象。而稳定性则保证飞行器的机动动作能够迅速到位，准确地改变飞行状态，从而提高作战效能。目前针对机动性的大攻角非定常气动力建模方法存在物理含义不清晰，预测精度较差的缺陷；动稳定性评估方法也不够精细，且大攻角范围缺乏相应的判据概念。.本项目针对以上问题，创新性的开展三个方面的研究工作：1）基于CFD的先进飞行器典型构型的定常/非定常流场高效精确求解方法研究，重点筛选DES类方法开展典型三角翼的单/多自由度机动运动气动特性仿真计算；2）基于非线性流动特征的高精度大攻角非定常气动力建模，通过CFD分析提取流场影响因子，改进建立新的非线性动导数模型和状态空间方程模型，完成典型构型的验证分析；3）飞行器通用动态稳定性判据概念重建及分析，建立新的精细化动导数仿真计算方法，类比建立新的大攻角范围动态稳定性判据，完成其数值仿真辨识方法研究。.研究结果表明，SAS自适应尺度模型对于静态和动态大攻角流场的仿真计算能力与DES方法接近，对于网格的适应性更好，可以用来对各种复杂非定常流场进行分析。通过引入初始攻角、俯仰角速度、减缩频率以及振幅等流场参数后，建立的非线性气动导数模型和状态空间方程模型的预测精度和范围都得到较大提升，极大地提高了气动力建模的实用性。新建立的动导数计算方法更为精细系统化，能够快速辨识各个单独的动导数；新建立的大攻角动稳定性通用判据涵盖常规动导数和大攻角动稳定概念，提升了全攻角范围的动态表述能力。.本项目的研究方法和结论进一步明确了大攻角机动运动的“气动-运动”互相耦合的机理，丰富了高机动飞行器的非定常设计理念，为未来新型飞行器的动态气动设计提供基础理论支撑。