A comprehensive survey on the methods of angle of attack measurement and estimation in UAVs

Angle of Attack (AOA) is a crucial parameter which directly affects the aerodynamic forces of an aircraft. The measurement of AOA is required to ensure a safe flight within its designed flight envelop. This paper intends to summarise a comprehensive survey on the measurement techniques and estimation methods for AOA, specifically in Unmanned Aerial Vehicle (UAV) applications. In the case of UAVs, weight constraint plays a major role as far as sensor suites are concerned. This results in selecting a suitable estimation method to extract AOA using the available data from the autopilot. The most feasible and widely employed AOA measurement technique is by using the Multi-Hole Probes (MHPs). The MHP measures the AOA regarding the pressure variations between the ports. Due to the importance of MHP in AOA measurement, the calibration methods for the MHP are also included in this paper. This paper discusses the AOA measurement using virtual AOA sensors, their importance and the operation.     

基于CFD高精度算法的雷电电磁场研究

雷电空间电磁场一直是电磁领域研究的热门，成熟的算法例如有限时域差分法（FDTD），传输线矩阵法（TLM）以及频域的矩量法（MoM）在计算雷电问题方面都有广泛的应用。由于计算流体力学（CFD）中的Euler方程与电磁学中的Maxwell方程有着相同的守恒形式，而且采用间断伽辽金方法（DG）已经在流场问题上得到广泛的尝试，因此引入了基于计算流体力学的DG方法来离散时域Maxwell方程，并采用网格分区并行技术加速计算，使用基于DG的圆球雷达散射截面积（RCS）算例进行测试，数值结果一致表明DG算法在求解电磁场问题上的可行性，之后通过计算一段近场雷电通道的电场分布并与解析解、某算法仿真解对比，数据基本吻合，说明该方法适合于雷电电磁场的计算。     

Unsteady wakes-secondary flow interactions in a high-lift low-pressure turbine cascade

Detailed experimental measurements were conducted to study the interactions between incoming wakes and endwall secondary flow in a high-lift Low-Pressure Turbine (LPT) cascade. All of the measurements were conducted in both the presence and absence of incoming wakes, and numerical analysis was performed to elucidate the flow mechanism. With increasing Reynolds number, the influence of the incoming wakes on suppressing the secondary flow gradually increased owing to the greater influence of incoming wakes on reducing the negative incidence angle at higher Reynolds numbers, leading to a lower blade loading near the leading edge and suppression of the Pressure Side (PS) leg of the horseshoe vortex. However, the effect of unsteady wakes on suppressing the profile losses gradually became weaker owing to the reduced size of the Suction Side (SS) separation bubble and increased mixing loss in the free-flow region at high Reynolds numbers. Incoming wakes clearly improved the aerodynamic performance of the low-pressure turbine cascade at low Reynolds numbers of 25,000 and 50,000. In contrast, at the high Reynolds number of 100,000, the profile loss at the midspan and mass-averaged total losses downstream of the cascade were higher in the presence of wakes than in the absence of wakes, and the unsteady wakes exerted a negative influence on the aerodynamic performance of the LPT cascade.     

流动阻力及能量损失对注射成型制件的影响

本文分析了在塑料熔体充满型腔的过程中，流动阻力及能量损失产生的形式和物理原因，进而讨论了对塑料制件成型及凝固过程中的影响。并提出降低影响的措施。     

FDI飞机舵面损伤故障全局检测的非线性数学模型

阐述了飞机在单舵面损伤故障下 ,建立故障状态下的数学模型 ,以及同样输入条件下飞机正常运动时的数学模型 ,得到飞机在相同飞行条件下损伤时的气动系数和无损伤正常时的气动系数 ,最终得到气动系数的残差。这将为以后飞机过载残差和角加速度残差奠定基础。论文中结合一定的算例给予证实推论的正确性。     

Wave-Particle-Electric Field Synergetic Auroral Electron Acceleration

Space Science Reviews - We discuss afresh the problem of the auroral electron acceleration based on the controversy reports of Bryant, D. A. et al.: 1992, Phys. Rev. Lett. 68, 37, and Borovsky, J.:...     

预测悬停旋翼跨音速流动的一种组合自由尾流/CFD方法

一种新的组合自由尾流 / CFD方法用于悬停旋翼流动的 CFD解中以考虑实际尾流的作用 .用文中描述的尾流分析方法研究了螺旋尖涡的运动 .首先从广义尾流模型开始 ,用半经验公式模化了涡核对旋翼尾流的作用 ;然后在环量收敛和尾迹收敛的条件下完成了自由尾迹计算 ;最后应用 Jameson有限体积龙格 -库塔推进格式求解了欧拉方程 .所得结果与相关文献和实验数据进行了比较     

燃烧火焰温度分布重建结果误差分析

分析了采用辐射型CT算法的燃烧火焰温度发布重建结果误差产生的原因，给出了解决方法。     

ADI方法求解完全跨声速非定常小扰动方程

本文修改了Whitlow的ADI格式,以便求解另一变形的完全跨声速小扰动方程。本文给出的NACA64A006和NACA0012翼型的非定常跨声速流动的计算结果与其它数值结果和实验结果的比较表明本文格式是合理的且便于实际应用的。     

世界贸易组织与航空产品包装

论述了我国加入世界贸易组织后，如何搞好航空产品的包装和包装标准化工作，以提高航空工业军品和民品在国际市场的竞争能力。