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：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：A robust optimization design approach of natural laminar airfoils is developed in this paper. First, the non-uniform rational B-splines （NURBS） free form deformation method based on NURBS basis function is introduced to the airfoil parameterization. Second, aerodynamic characteristics are evaluated by solving Navier-Stokes equations, and theγ-Reθt transition model coupling with shear-stress transport （SST） turbulent model is introduced to simulate boundary layer transition. A numerical simulation of transition flow around NLF0416 airfoil is conducted to test the code. The comparison between numerical simulation results and wind tunnel test data approves the validity and applicability of the present transition model. Third, the optimization system is set up, which uses the separated particle swarm optimization （SPSO） as search algorithm and combines the Kriging models as surrogate model during optimization. The system is applied to carry out robust design about the uncertainty of lift coefficient and Mach number for NASA NLF-0115 airfoil. The data of optimized airfoil aerodynamic characteristics indicates that the optimized airfoil can maintain laminar flow stably in an uncertain range and has a wider range of low drag.

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.

摘要：Experiment design method is a key to construct a highly reliable surrogate model for numerical optimization in large-scale project. Within the method, the experimental design criterion directly affects the accuracy of the surrogate model and the optimization efficient. According to the shortcomings of the traditional experimental design, an improved adaptive sampling method is proposed in this paper. The surrogate model is firstly constructed by basic sparse samples. Then the supplementary sampling position is detected according to the specified criteria, which introduces the energy function and curvature sampling criteria based on radial basis function （RBF） network. Sampling detection criteria considers both the uniformity of sample distribution and the description of hypersurface curvature so as to significantly improve the prediction accuracy of the surrogate model with much less samples. For the surrogate model constructed with sparse samples, the sample uniformity is an important factor to the interpolation accuracy in the initial stage of adaptive sam- pling and surrogate model training. Along with the improvement of uniformity, the curvature description of objective function surface gradually becomes more important. In consideration of these issues, crowdness enhance function and root mean square error （RMSE） feedback function are introduced in C criterion expression. Thus, a new sampling method called RMSE and crowd- ness enhance （RCE） adaptive sampling is established. The validity of RCE adaptive sampling method is studied through typical test function firstly and then the airfoil/wing aerodynamic opti- mization design problem, which has high-dimensional design space. The results show that RCE adaptive sampling method not only reduces the requirement for the number of samples, but also effectively improves the prediction accuracy of the surrogate model, which has a broad prospects for applications.

摘要：对基于Kriging模型气动优化的加点方法和设计空间的构建问题进行了研究。首先,针对高效全局优化(EGO)方法收敛缓慢的问题,提出了一种混合加点方法,该方法通过引入期望提高(EI)阈值控制EI和最小预测值(MP)加点准则,利用先全局再局部的优化思想,提高了EGO方法在确定设计空间内的收敛性。其次,针对设计空间的构建问题,对比了扩大设计变量范围和多轮优化两种不同的设计空间构建方法,分析了设计变量范围对设计空间大小和样本密度的影响,进而提出了自适应设计空间扩展的代理模型优化方法。相对于传统固定设计空间的方法,自适应设计空间扩展的方法在动态的设计空间中进行优化搜索,只在有潜力的维度扩展设计变量范围,通过构建自适应设计空间,实现了样本的高效配置。最后,通过ADODG标准翼型优化算例证实,自适应设计空间优化方法可以大幅提高气动优化设计效率。

摘要：双后掠前缘飞翼布局具有较好的气动隐身特性,是近年的一项研究热点。其纵向气动特性设计的主要难点是如何在小俯仰力矩的约束下实现高升阻比设计。本文从平面形状选择、重心位置选择、翼型选择/优化与配置等方面提出了一些设计思路,设计了一种双后掠前缘飞翼布局,并通过数值模拟和风洞试验两种手段,验证了设计思路的合理性。CFD计算表明该布局在亚声速设计点具有较高升阻比和较小的俯仰力矩系数。

摘要：飞翼布局由于在气动、隐身和结构等方面的综合优势,是未来最有潜力的飞行器气动布局形式。关于飞翼布局的气动设计研究,学术界开展了大量的设计分析,研究发现低速起降性能和操控是飞翼布局性能和安全的主要难点。对于飞翼布局无人机和作战飞机,由于隐身设计的影响,使得其低速起降性能、操控特性更加严苛,以往的研究主要集中在高速巡航的设计,关于低速设计研究很少,因此基于高性能离散伴随优化设计平台,开展了某飞翼布局无人机的高低速综合设计研究,分析对比了不同低速设计模型对飞机低速特性的影响,在此基础上,建立了高低综合设计模型,全面提升了飞机的高低速性能,经过对结果的分析,总结了高低速一体化设计的要点和规律,为飞翼布局的气动设计提供了有力的设计模型和参考。

摘要：声爆抑制是发展新一代超声速民机必须突破的关键技术。飞行器总体布局参数对其声爆特性有重要影响。数据挖掘(DM)可以从大量的数据中通过算法搜索隐藏的信息,是飞行器设计知识提取的有力工具。选取后掠角、展弦比、梢根比、上反角、机身长细比5个总体布局参数作为设计变量,目标函数定义为远场感知噪声级,同时计算升、阻力系数作为气动力衡量指标。基于总变差分析(ANOVA)、决策树算法、自组织映射(SOM)网络组成的数据挖掘体系提取低声爆设计知识库。获得所选设计变量与声爆/气动力的相关度,并实现对设计变量的分层与降维。后掠角有最高设计优先级,长细比、上反角重要程度次之,展弦比与梢根比为低敏感变量。对于算例中的飞行器,在合理区间内选择较大的后掠角、上反角能够使声爆最小化的同时,设计适于超声速巡航的小展弦比布局。