锥柱组合体抖振载荷不确定度的精细量化方法

Buffeting fluctuating loads have important influence on the structure stability, structural fatigue failure and capabilities of precision avionics of cone-cylinder type spacecraft such as launch-vehicle and missile. Computational Fluid Dynamics(CFD) Simulation is an important way to predict the buffeting fluctuating loads of aircraft. While, the Buffeting fluctuating loads predicted by CFD have marked dispersity or uncertainty because they are strongly impacted by the uncertainties introduced by the parameters of flight status, computational mesh, fluid physics model and numerical algorithm. Nowadays, the uncertainty quantification of the predicted buffet loads is still a challenge topic and lack of systematic study. This proposal will use automatic difference based unsteady adjoint method to analyse the sensitive derivatives of buffeting loads to different kinds of input parameters with uncertainty. Furthermore, the propagation feature of uncertainty introduced by different input parameter will be investigated individually to clarify their influence on the buffeting loads. The input parameters have key influence on the uncertainty of buffeting load will be identified. Finally, the probabilistic collocation method under the polynomial chaos framework will be used to realize the uncertainty quantification of the buffeting loads in statistical solution form considering with the uncertainty influence of several key input parameters. The planned research work in this proposal will further improve the basic theory of uncertainty quantification in CFD. The expected research results of this project can directly serve the integrated aerodynamic/structural design work of cone-cylinder type spacecraft.

抖振载荷对锥柱组合体类飞行器(运载火箭和导弹)的结构稳定性、结构疲劳破坏和机载精密仪器的正常工作有重要影响。计算流体力学(CFD)分析是获取抖振载荷的重要技术手段，但其计算过程受到飞行状态、计算网格、物理模型、数值格式等多种输入参数的不确定性影响，导致抖振载荷的预测结果呈现很大的分散性。目前国内外对抖振载荷预测结果的不确定度精细量化问题尚未系统地开展研究。本项目计划采用基于自动微分的非定常伴随方法精确分析抖振载荷对各种不确定性输入因素的敏感性，分类揭示不确定性的传播规律和影响权重，筛选出对抖振载荷计算结果影响最显著的关键不确定性输入参数，最后运用基于多项式混沌的概率配置方法，在考虑多个关键不确定性输入参数影响的情况下，实现抖振载荷预测结果不确定度的统计学精细量化。本项目拟开展的研究工作可以完善CFD的不确定性量化分析理论，预期成果在航天运载飞行器的气动/结构精细化设计中具备很好的应用价值。

本项目当前已经按照计划书中的安排顺利完成。主要开展了以下三方面的研究工作：其一，在锥柱组合体抖振载荷的数值预测方法研究方面，发展了非阻塞通讯模式的并行算法、熵相容格式和微分雷诺应力框架下的IDDES方法，有效提升了计算流体力学分析平台对锥柱组合体抖振载荷预测能力和计算效率；其二，在不确定性量化分析方法方面，根据不确定性输入的类别选取合适的不确定性量化方法，发展了集成子系统不确定度的综合量化方法，并结合敏感度分析方法，实现CFD预测结果的整体不确定性量化；其三，运用前面发展的不确定性量化分析理论和数值工具，对锥柱组合体抖振载荷问题进行了不确定性量化研究，考察了来流条件、几何外形、数值格式和湍流模型等因素对抖振载荷预测结果不确定性的具体影响。通过开展以上的研究工作，本项目发展和完善了抖振载荷数值预测不确定性的量化分析理论，揭示了各类不确定性因素在锥柱体抖振脉动载荷数值计算过程中的影响机制和规律。数值算例表明：本项目所发展的理论方法和计算程序可以在多种不确定因素影响效应共同存在的情况下精细量化锥柱体抖振脉动载荷不确定性，进而以更准确、更全面、更可信的统计解来描述航天运载器在真实工况下的抖振载荷CFD预测结果。