数值虚拟飞行一体化模拟方法研究、软件开发及风洞实验验证

Practically every fighter program since 1960 has had costly nonlinear aerodynamic or fluid-structure interaction issues discovered in flight test. The main reason for these ‘failures’ by traditional design tool is that the predictive methods used were not able to reveal the onset and nature of the problems early in the design phase. Unfortunately, in future aircraft design, the problems will become more complex as thrust vectoring, active aeroelastic structures, and other related technologies are implemented for stability and control (S&C) augmentation. In order to reduce the risk during testing and the costs incurred by extensive wing tunnel and flight tests, it would be helpful to have a tool which enabled engineers and designers to analyze and evaluate the nonlinear, flight dynamic behavior and the S&C performance of the aircraft both early in the design phase and throughout sustainment. This tool is a CFD-based software system, named as ‘virtual flight simulation system (VFSS)’. In this project, we will try to develop this kind of VFSS, based on our unsteady RANS flow solver and dynamic hybrid grid generator. In order to simulate the flow-structure interaction, nonlinear flight dynamics, and to evaluate the S&C performance, the modules of the solution of 6DOF equations, typical control rules will be integrated into the platform. In order to enhance the robustness of moving grid generation, the dynamic hybrid grid generator will be improved by coupling other techniques. In order to improve the accuracy in temporal direction for complex unsteady flow simulations, the second-order unsteady flow solver will be developed on the moving hybrid grids. More importantly, several coupling algorithms for RANS and 6DOF equations will be developed in a unified framework, including the so-called ‘loose coupling’ and ‘fully implicit coupling’ with different temporal accuracy. The design philosophy of modularity will be adopted to the coding of VFSS. And the software will be validated by the experimental data from wind tunnel. The purposes of this project are to propose and/or improve the fundamental numerical methods related to virtual flight simulation, and furthermore, to develop a CFD-based platform for virtual flight simulation.

随着空中对抗的日趋激烈，人们对飞行器的机动性和敏捷性的要求越来越高。对于飞行器的机动飞行，传统方法是首先进行静动态气动特性分析，然后在气动数据库的基础上进行控制系统设计与仿真。这种设计模式不仅耗资大、周期长，而且无法充分考虑非定常气动特性和气动/运动耦合作用，因此最好的研究方法是耦合控制律的“数值虚拟飞行”技术。本项目拟在以往非定常计算方法和动态混合网格技术研究的基础上，通过有机集成各种动态混合网格生成技术、构造与动态混合网格相适应的时空二阶高效非定常计算方法、在统一的框架下发展非定常NS方程和飞行力学方程的多种松耦合和紧耦合计算方法，建立耦合非定常流场计算、六自由度运动方程求解、动态混合网格生成和飞行控制律的一体化数值虚拟飞行计算方法。基于面向对象软件开发技术，研制大规模并行数值虚拟飞行软件系统，并利用典型风洞实验进行验证与确认，为气动/运动/控制多学科耦合研究提供有效的研究手段和工具。

现代飞行器对机动性和敏捷性的要求越来越高。对于飞行器的高机动飞行的仿真分析，传统方法是首先进行静动态气动特性分析，然后在气动数据库的基础上进行控制系统设计与仿真。这种设计模式不仅耗资大、周期长，而且无法充分考虑非定常气动特性和气动/运动耦合作用。为了解决气动/运动/控制等多学科耦合问题，发展CFD/飞行力学/控制律耦合的数值虚拟飞行模拟技术具有重要意义。. 本项目通过开展动态混合网格技术、高效非定常计算方法、一体化耦合模拟方法、多学科耦合模拟软件体系结构、风洞虚拟飞行试验验证等方面的研究，研制大规模并行数值虚拟飞行一体化软件系统，为空气动力学、飞行力学和飞行控制多学科交叉领域研究提供有效的研究手段和工具。同时，针对典型飞行器的机动飞行动作，利用数值虚拟飞行一体化软件系统，开展深入的动态气动特性分析，探寻非定常流动及其控制机理。. 项目提出了基于网格分区和运动分解的动网格生成策略，构建了适应复杂外形的变形/重构/重叠耦合的并行动态混合网格技术，大幅提升了动态混合网格对复杂飞行器机动飞行模拟的适应能力和生成效率；将现有的满足几何守恒律的算法归纳为“面限制”和“体限制”两类，给出了更为简便的几何守恒算法，建立了精度好效率高的非定常计算方法；通过耦合求解RANS方程、刚体动力学方程、飞行控制律，并结合动态混合网格生成技术，在统一的理论框架下建立了气动/运动/控制耦合的一体化数值模拟算法；采用面向对象的思想设计了各功能模块及模块之间的接口，完成了数值虚拟飞行一体化模拟软件框架研究及平台的开发；开展了高机动弹单自由度和俯仰/滚转两自由度机动风洞虚拟飞行试验，验证了软件平台的可靠性；将该平台应用于典型战斗机的准眼镜蛇机动过程和鱼游过程数值模拟，结合传统控制方法和人工智能控制方法，研究了非定常流动特性和控制机理，并推广应用于众多复杂多体分离工程问题的模拟，在重大工程和重点型号研制中发挥良好作用。