耦合运动非定常气动模型对飞机飞行特性仿真的影响

 在大振幅偏航滚转单自由度强迫振荡和耦合强迫振荡运动风洞试验的基础上,分别运用准定常气动力建模方法和非定常气动力建模方法,获取飞机的气动力模型;运用两种不同的气动力模型,对飞机的纵向正弦振荡机动飞行进行了仿真。结果表明,准定常模型在小迎角下的仿真结果与非定常模型的结果基本一致;在较大迎角时,准定常模型仿真结果趋于稳定,而非定常模型仿真结果使飞机进入横航向振荡飞行状态,这一现象与F-16XL的试飞结果类似,其主要原因是耦合运动的非定常模型与准定常模型所产生的阻尼特性不一致。这也表明,分析大迎角飞行特性时应考虑耦合运动下的非定常气动特性。     

Improvement of Baldwin-Lomax turbulence model for supersonic complex flows

Entropy represents the dissipation rate of energy. Through direct numerical simulation (DNS) of supersonic compression ramp flow, we find the value of entropy is monotonously decreasing along the wall-normal direction no matter in the attached or the separated region. Based on this feature, a new version of Baldwin-Lomax turbulence model (BL-entropy) is proposed in this paper. The supersonic compression ramp and cavity-ramp flows in which the original Baldwin-Lomax model fails to get convergent solutions are chosen to evaluate the performance of this model. Results from one-equation Spalart-Allmaras model (SA) and two-equation Wilcox k-x model are also included to compare with available experimental and DNS data. It is shown that BLentropy could conquer the essential deficiency of the original version by providing a more physically meaningful length scale in the complex flows. Moreover, this method is simple, computationally efficient and general, making it applicable to other models related with the supersonic boundary layer.     

超长航时太阳能无人机关键技术综述

超长航时太阳能无人机（UAV）以其高效节能、原理上可实现无限巡航的特点受到广泛关注，而其独特的设计指标与任务特性也对各项关键技术提出了较高要求。多设计要素的高度耦合意味着不同于常规飞行器的总体设计方法，低密度、低速度的飞行条件使其具有明显的低雷诺数气动特性，柔性超大展弦比机翼带来了复杂的气动弹性问题，低翼载荷特性与较大的风场扰动增加了控制难度，极端的飞行环境与苛刻的任务指标对能源、动力系统带来了新挑战，飞行性能对能源系统的高度依赖开辟了飞行轨迹优化的研究方向。本文梳理了超长航时太阳能无人机关键技术的研究现状，在此基础上对各项技术中的难点问题进行了阐释，并对超长航时太阳能无人机未来发展趋势进行了展望。     

Airfoil Aeroelastic Flutter Analysis Based on Modified Leishman-Beddoes Model at Low Mach Number

Based on modified Leishman-Beddoes (L-B) state space model at low Mach number (lower than 0.3), the airfoil aeroelastic system is presented in this paper. The main modifications for L-B model include a new dynamic stall criterion and revisions of normal force and pitching moment coefficient. The bifurcation diagrams, the limit cycle oscillation (LCO) phase plane plots and the time domain response figures are applied to investigating the stall flutter bifurcation behavior of airfoil aeroelastic systems with symmetry or asymmetry. It is shown that the symmetric periodical oscillation happens after subcritical bifurcation caused by dynamic stall, and the asymmetric periodical oscillation, which is caused by the interaction of dynamic stall and static divergence, only happens in the airfoil aeroelastic system with asymmetry. Validations of the modified L-B model and the airfoil aeroelastic system are presented with the experimental airload data of NACA0012 and OA207 and experimental stall flutter data of NACA0012 respectively. Results demonstrate that the airfoil aeroelastic system presented in this paper is effective and accurate, which can be applied to the investigation of airfoil stall flutter at low Mach number.     

三维机翼的气动优化设计

将机翼外形参数化的思想和气动分析有效结合,在ISIGHT软件集成平台中同时实现三维外形建模、气动分析及其优化的全过程.探讨了机翼三维模型的自动化建模方法和解决方案,实现了机翼外形建模的完全自动化,并对实现机翼气动优化的相关算法进行了分析和研究.通过对机翼三维外形的自动调整和修改,在集成优化框架内,实现了气动性能的最优化...     

A short history of the European Transonic Wind Tunnel ETW

This paper is written as a contribution to the celebration of 50 years of Progress in Aerospace Sciences and of the centenary of the birth of its founder, Dietrich Küchemann. It reviews the evolution of the European Transonic Wind Tunnel, ETW, from early conceptual studies to its entry into service and its current capabilities and achievements. It traces the development, from the earliest days, of experimental aerodynamics and of the basic aerodynamic understanding that gave rise to the main periods of wind tunnel building before and after World War II. By about 1960, this activity appeared to have come to a natural halt. The paper gives an account of the role of Küchemann in arguing the need in 1968 for a further step in wind tunnel capability, to provide transonic testing at high Reynolds numbers. It describes his leading role in gaining acceptance of the concept, formulating the specification and promoting studies of alternative, radical design options for the co-operative European project that became ETW. The progress of ETW through design, construction, commissioning and into full operation is recorded. The paper discusses the many technical innovations that have been introduced in order to meet customer requirements in the challenging field of aerodynamic testing in a cryogenic environment and, finally, looks to the future and the further technical challenges that it holds.     

带阻力元铰链力矩四分力天平研制

介绍了带阻力元铰链力矩天平研制的情况。实验证明,用两台带阻力元的铰链力矩天平同时测量导弹左、右舵面气动载荷是成功的,天平研制也是成功的。     

非平衡电弧加热射流光谱学诊断方法：第二部分：氩,氮混合射流

本文是非平衡电弧加热射流光谱学诊断方法实验研究工作的第二部分，给出了氩、氮混合射流的结果，证明亚声速射流中确有非平衡囊兜现象存在。     

一种建立非定常气动力频域模型的简单方法

本文给出的方法,线化了非定常气动力的karpel近似式的非线性部分,并吸取了Roger近似式中同一矩阵各元素独立确定以得到较高精度的特点。它不仅简化了拟合中的计算,改善了拟合精度,还保持了Karpel方法所引入的最小阶次。     

Progress in helicopter infrared signature suppression

Due to their low-attitude and relatively low-speed fight profiles, helicopters are subjected to serious threats from radio, infrared(IR), visual, and aural detection and tracking. Among these threats, infrared detection and tracking are regarded as more crucial for the survivability of helicopters. In order to meet the requirements of infrared stealth, several different types of infrared suppressor(IRS) for helicopters have been developed. This paper reviews contemporary developments in this discipline, with particular emphasis on infrared signature suppression, advances in mixer-ejectors and prediction for helicopters. In addition, several remaining challenges, such as advanced IRS, emissivity optimization technique, helicopter infrared characterization, etc., are proposed, as an initial guide and stimulation for future research. In the future, the comprehensive infrared suppression in the 3–5 lm and 8–14 lm bands will doubtfully become the emphasis of helicopter stealth. Multidisciplinary optimization of a complete infrared suppression system deserves further investigation.