摘要：Mitigation of sonic boom to an acceptable stage is a key point for the next generation of supersonic transports. Meanwhile, designing a supersonic aircraft with an ideal ground signature is always the focus of research on sonic boom reduction. This paper presents an inverse design approach to optimize the near-field signature of an aircraft, making it close to the shaped ideal ground signature after the propagation in the atmosphere. Using the Proper Orthogonal Decomposition(POD) method, a guessed input of augmented Burgers equation is inversely achieved. By multiple POD iterations, the guessed ground signatures successively approach the target ground signature until the convergence criteria is reached. Finally, the corresponding equivalent area distribution is calculated from the optimal near-field signature through the classical Whitham F-function theory. To validate this method, an optimization example of Lockheed Martin 1021 is demonstrated. The modified configuration has a fully shaped ground signature and achieves a drop of perceived loudness by 7.94 PLdB. This improvement is achieved via shaping the original near-field signature into wiggles and damping it by atmospheric attenuation. At last, a nonphysical ground signature is set as the target to test the robustness of this inverse design method and shows that this method is robust enough for various inputs.

摘要：飞行器的边界特性决定了其安全性和飞行性能,是飞行器设计的难点和重点。引入迎风格式伴随方程和不同的通量限制器处理形式,提高复杂流动问题的伴随方程求解精度、效率和鲁棒性,拓展伴随优化方法在飞行器边界特性设计的应用范围。介绍了离散伴随求解梯度的基本原理,在此基础上推导了伴随方程的无黏项及其边界条件的变分形式,根据通量限制器的处理方式,形成一阶精度、二阶精度和混合精度的伴随方程。对伴随方程的边界处理措施进行了研究。通过ONERA M6机翼梯度精度和鲁棒性验证算例,对比迎风格式和中心格式的伴随方程求解性能,分析限制器和边界处理措施对伴随方程的收敛性和梯度精度的影响。通过CRM翼身组合体巡航气动优化设计和边界特性优化设计算例,验证了求解器对飞行器巡航性能设计和边界特性设计的有效性。计算和设计结果表明,建立的迎风格式伴随方程求解方法鲁棒和梯度精度高,能够适用于飞行器边界特性设计难题的求解。

摘要：随着现代飞行器性能需求的不断提高,飞行器精细化气动优化设计要求更高可信度的CFD数值分析及更多的独立设计变量,使得基于代理模型的全局优化算法在超过一定的设计变量后显著降低了效率,难以满足复杂工程的设计需求。而目前的高维代理模型过程复杂、时间花费高,缺乏对工程问题的广泛适应性。针对以上难题,提出了利用监督式非线性降维代理建模方法来缓解代理优化过程中的高维变量设计难题。该方法将核主成分分析(非线性)降维与高斯回归过程模型统一训练,自适应构建新型高维代理模型,并随着优化过程不断学习改进模型,建立了从高维输入到输出的准确映射,有效解决了传统高维代理模型训练时间花费高和适应性差等难题。然后基于该新型代理模型发展了适用于飞行器复杂气动设计的高维全局优化设计方法,并将其应用到美国航空航天学会(AIAA)优化小组发布的2个复杂跨声速优化算例中。通过与传统代理优化方法全面比较,验证了所提的方法能大幅提高飞行器高维变量全局优化效率和全局寻优能力。

摘要：相对于常规直升机,基于前行桨叶方案(ABC)速度更高的刚性共轴双旋翼直升机对旋翼翼型的气动性能要求更加苛刻,包括更高马赫数下的低阻和高阻力发散特性,并维持良好的中、低马赫数下的升阻特性以及所有状态下的力矩特性等10余项指标要求,面临高维多目标优化难题。针对该类问题,首先发展了基于核主成分分析(KPCA)的非线性目标降维技术,然后建立了基于新型多可信度多项式混沌-Kriging(AMF-PCK)代理模型的高效多目标稳健优化方法,并提出了变可信度伪期望改进矩阵(VF-PEIM)并行样本填充方法,使多目标优化设计效率和能力显著提高。利用所建立的基于新型多可信度代理模型的多目标优化方法对高速直升机7%厚度旋翼翼型进行了优化设计。设计翼型的气动表现分别与经典的OA407翼型在高、中、低马赫数下进行了全面比较,对比结果验证了提出的新型多目标优化设计方法的有效性,设计翼型高速气动特性得到了显著提升。

摘要：两级入轨航天器(TSTO)级间分离过程中对轨道级、助推级的姿态精确控制尤为重要。数值模拟可以较为准确地预测级间分离这种飞行器多体分离问题,运用非结构嵌套网格技术及双时间步法耦合流动控制方程、刚体运动方程求解TSTO在攻角-2°、马赫数6、海拔高度30 km的级间分离过程,发展了一种优化轨道级、助推级在级间分离过程的运动姿态的技术。该技术通过松弛迭代法提取轨道级、助推级的无舵偏气动力数据,基于无舵偏气动力数据设计气动舵面、燃气舵所需要提供的俯仰力矩,使得轨道级、助推级的运动姿态更加接近设计目标。数值模拟结果表明,TSTO在分离过程中两级之间会存在强烈的气动干扰,严重影响两级的姿态控制,发展的技术可为TSTO分离过程中轨道级、助推级的舵面运动、燃气舵工作状态设计提供参考,提高TSTO级间分离的效率、安全性。

摘要：宽速域高超声速飞行器是航空航天领域新的战略制高点,其飞行速域与空域极大化特点导致亚/跨/超/高超声速气动性能难以兼顾。为了缓解高低速气动设计的矛盾,以典型宽速域乘波-机翼布局为研究对象,结合基于代理模型的全局优化方法和基于伴随梯度的局部优化方法,对该宽速域构型的布局参数和剖面形状进行了从全局到局部的多目标分步优化。结果表明,在约束亚声速升力系数、高超声速阻力系数的情况下,基于代理模型的布局参数优化方法能够在维持高超声速气动性能的同时,将亚声速的升阻比提升9.5%。进一步选取布局参数优化结果 Pareto面上亚声速气动特性最优的构型,利用基于伴随梯度的优化方法,对机翼剖面进行梯度优化。优化结果表明,梯度优化能够有效地改善飞行器亚/高超声速状态下的阻力特性,并将翼型在几何上优化为兼顾亚/高超声速气动特性的双S翼型。通过上述从布局参数到剖面参数的优化,乘波-机翼构型的亚声速升阻比相比初始构型提升了12.4%,高超声速升阻比相比原始构型提升了6.2%。

摘要：Advanced engineering systems, like aircraft, are defined by tens or even hundreds of design variables. Building an accurate surrogate model for use in such high-dimensional optimization problems is a difficult task owing to the curse of dimensionality. This paper presents a new algorithm to reduce the size of a design space to a smaller region of interest allowing a more accurate surrogate model to be generated. The framework requires a set of models of different physical or numerical fidelities. The low-fidelity （LF） model provides physics-based approximation of the high-fidelity （HF） model at a fraction of the computational cost. It is also instrumental in identifying the small region of interest in the design space that encloses the high-fidelity optimum. A surrogate model is then constructed to match the low-fidelity model to the high-fidelity model in the identified region of interest. The optimization process is managed by an update strategy to prevent convergence to false optima. The algorithm is applied on mathematical problems and a two-dimen-sional aerodynamic shape optimization problem in a variable-fidelity context. Results obtained are in excellent agreement with high-fidelity results, even with lower-fidelity flow solvers, while showing up to 39% time savings.

摘要：反隐身技术的发展对军用飞行器的隐身性能提出更高要求,针对考虑吸波材料的飞行器低雷达散射截面(RCS)设计问题,结合阻抗边界条件,建立了考虑吸波材料的麦克斯韦方程离散伴随方程,推导了伴随方程的多层快速多极子展开形式,实现了RCS关于外形、材料电参数、涂覆厚度等参数的高效、高精度梯度求解。提出一种基于开关函数的吸波材料涂覆位置优化方法,采用进气道等典型外形对几何外形、材料涂覆位置、涂敷厚度、电磁参数等设计变量开展优化设计。设计结果表明,考虑吸波材料特性的伴随优化方法可以在理想导体外形设计和材料涂敷的基础上进一步减缩散射强度,同时能够实现对材料参数、涂覆厚度的优化设计,为吸波材料的选择和涂覆提供指导;基于开关函数的涂覆位置优化能够在材料总重量的约束下,实现吸波材料的最优分配。提出的吸波材料的RCS伴随优化方法可以为吸波材料高效涂敷方案设计提供参考和技术支撑。

摘要：Constructing metamodel with global high-fidelity in design space is significant in engineering design. In this paper, a double-stage metamodel （DSM） which integrates advantages of both interpolation metamodel and regression metamodel is constructed. It takes regression model as the first stage to fit overall distribution of the original model, and then interpolation model of regression model approximation error is used as the second stage to improve accuracy. Under the same conditions and with the same samples, DSM expresses higher fidelity and represents physical characteristics of original model better. Besides, in order to validate DSM characteristics, three examples including Ackley function, airfoil aerodynamic analysis and wing aerodynamic analysis are investigated, In the end, airfoil and wing aerodynamic design optimizations using genetic algorithm are presented to verify the engineering applicability of DSM.

摘要：The arbitrary space-shape free form deformation （FFD） method developed in this paper is based on non-uniform rational B-splines （NURBS） basis function and used for the integral parameterization of nacelle-pylon geometry. The multi-block structured grid deformation technique is established by Delaunay graph mapping method. The optimization objects of aerodynamic characteristics are evaluated by solving NavierStokes equations on the basis of multi-block structured grid. The advanced particle swarm optimization （PSO） is utilized as search algorithm, which com-bines the Kriging model as surrogate model during optimization. The optimization system is used for optimizing the nacelle location of DLR-F6 wing-body-pylon-nacelle. The results indicate that the aerodynamic interference between the parts is significantly reduced. The optimization design system established in this paper has extensive applications and engineering value.