Shock interactions in the outer heliosphere

Observations of plasma and magnetic fields by Pioneer 10 and 11 and Voyager 1 and 2 reveal that MHD shocks are an important component of the large-scale solar wind structures in the outer heliosphere. This review discusses recent progress in simulation studies of the nonlinear evolution of the solar wind structures, and in particular concentrates on the theoretical development and applications of the shock interactions model. Various stream propagation models, which do not use the Rankine-Hugoniot relations to calculate the jump conditions at shock crossings, have been used to simulate the essential evolution process of isolated streams and the formation and propagation of corotating and transient shocks. They produce fairly good results in the region up to a few AU. In 1984, the shock interactions model was introduced to study the evolution of large-scale solar wind structures in the region outside 1 AU up to several tens of AU. The model uses the exact Rankine-Hugoniot relations to calculate the shock speed and shock strength at all shock crossings. So that the model can more accurately calculate the shock speeds and the accumulated irreversible shock heating of plasma at several tens of AU. The applications of the shock interactions model are presented in three groups. (a) The first group covers the basic interaction of a shock with the ambient solar wind, the formation and propagation of shock pairs, and the collision and merging of shocks. (b) The second group covers the use of the shock interactions model to simulate the nonlinear evolution of large-scale solar wind structures in the outer heliosphere. These simulation results can provide the detailed evolution process for large-scale solar wind structures in the vast region not directly observed. Two selected studies are reported. (c) Finally, the shock interactions model is applied to studying the heating of the solar wind in the outer heliosphere. The model calculations support shocks being chiefly responsible for the heating of the solar wind plasma in the outer heliosphere at least up to 30 AU.     

Terminal control monitor for ATC using knowledge-based system

A knowledge-based system for air traffic control (ATC) in terminal control regions is designed for improving service and operation. Domain knowledge is established following rules, regulations, and comments from controllers. An expert system is adopted for approach control and airport control in the terminal control region. The proposed system was implemented in PC-AT with Turbo Prolog. The air terminal control monitor was checked with regard to flight information input, real-time data refreshment, air traffic rescheduling, constraint violation double checking, emergency responses, and normal monitoring. Simulation results are given     

Scanning Spaceborne Synthetic Aperture Radar with Integrated Radiometer

Spaceborne synthetic aperture radar systems are severely constrained to a narrow swath by ambiguity limitations. Here a vertically scanned-beam synthetic aperture system (SCANSAR) is proposed as a solution to this problem. The potential length of synthetic aperture must be shared between beam positions, so the along-track resolution is poorer; a direct tradeoff exists between resolution and swath width. The length of the real aperture is independently traded against the number of scanning positions. Design curves and equations are presented for spaceborne SCANSARs for altitudes between 400 and 1400 km and inner angles of incidence between 20° and 40°. When the real antenna is approximately square, it may also be used for a microwave radiometer. The combined radiometer and synthetic-aperture (RADISAR) should be useful for those applications where the poorer resolution of the radiometer is useful for some purposes, but the finer resolution of the radar is needed for others.     

一种外环水平结构双轴光纤惯导系统旋转方案设计方法

目前国内外长航时高精度自主惯导系统多采用双轴旋转调制自动补偿技术,而旋转方案设计对系统导航精度影响至关重要.双轴惯导系统按结构可分为外环水平结构和外环航向结构两类.分析了外环水平结构双轴惯导系统在旋转方案设计中的局限性,考虑到光纤陀螺输出特性,指出外环水平结构双轴光纤惯导系统不宜采用传统旋转方案,并提出了一种该类双轴光纤惯导系统的旋转方案设计方法,最后对所设计旋转方案与十六位置旋转方案进行试验对比,试验表明此设计方案导航精度提升了71％.     

氢气添加对RP-3航空煤油着火特性的影响

为了揭示可燃小分子气体H2添加对RP-3航空煤油着火特性的影响,采用激波管实验装置对RP-3航空煤油的着火特性进行了实验测量,获得了多工况下RP-3航空煤油的着火延迟时间。以RP-3航空煤油的正癸烷、甲苯和丙基环己烷三组分模拟替代燃料的燃烧反应机理为基础,构建了RP-3/H2混合燃料的Zeng-Jachimowski燃烧反应机理,并对该机理进行了验证。采用该机理对RP-3/H2混合燃料多工况下的着火延迟时间进行计算与分析,结果表明:Zeng-Jachimowski机理可以较好预测高温条件下RP-3/H2混合气着火特性;当H2添加比小于70%时,着火延迟时间随H2添加缓慢减小,当H2添加比大于90%时,RP-3航空煤油/氢气混合气活性显著提升,着火延迟时间随H2添加急剧减小;通过对H,OH和O活性自由基的浓度及H自由基生成速率ROP分析解释了H2添加对RP-3航空煤油着火延迟时间的非线性影响。     

海洋重力仪采样质量悬挂系统分析

针对轴对称型海洋重力仪采样质量悬挂系统的刚度设计问题,运用材料力学和最小势能原理重点对水平和垂直方向的等效刚度进行理论分析,分析结果表明:系统在水平面内各方向的刚度相等,与拉丝材料的弹性模量和横截面积成正比,与拉丝的初始长度成反比;系统竖直方向等效刚度与绷紧弹簧的张力成正比,与拉丝的初始长度成反比.对仪器工程应用中,因拉丝弯曲而产生的干扰阻力进行了评估分析,结果表明在正确选择拉丝的材料和几何尺寸的条件下,由干扰阻力所引起的误差可以忽略不计.     

涡轮叶片前缘气膜冷却换热实验

针对某型涡轮叶片放大模型的前缘冷却结构气膜冷却效果开展了细致的实验研究,利用红外热像仪测量了叶片表面的温度场分布,分析了前缘的气膜孔倾角、吹风比、主流雷诺数等参数对绝热冷却效率和压力损失的影响.实验中前缘的3排气膜孔倾角变化范围是35°~90°,主流雷诺数变化范围是76112~142624,吹风比变化范围是0.44~2.64.结果表明:气膜孔倾角越小,前缘驻点附近的气膜覆盖效果越好;气膜孔倾角为45°的叶片压力损失系数最小,气膜孔倾角为75°的叶片压力损失系数最大;主流雷诺数增大,绝热冷却效率下降,压力损失系数增加;吹风比增大到1.32时,绝热冷却效率达到最大,吹风比再增大绝热冷却效率反而下降.      

Z-pin增强树脂基复合材料单搭接连接性能

为提高复合材料单搭接头的连接性能,制备了不同参数的Z-pin增强单搭接头,通过拉伸试验,研究了Z-pin体积分数、直径以及植入角度对单搭接头连接性能的影响规律,分析了Z-pin对单搭接头性能的增强机理。结果表明Z-pin能明显提高复合材料单搭接头的连接性能：植入角度为90°、Z-pin直径为0.5 mm时,在0%~3.0%体积分数范围内,单搭接头强度随着Z-pin体积分数的增加呈线性增加,含3.0% Z-pin的接头剪切强度为16.76 MPa,比无Z-pin的接头强度提高了33.2%;Z-pin体积分数为1.5%、植入角度为90°时,Z-pin直径变化对单搭接头强度影响不大;含Z-pin体积分数为1.5%、直径为0.5 mm时,随着Z-pin植入角度（背离搭接末端）的增加,单搭接头强度先增加后下降,失效模式从Z-pin拔出失效转变为Z-pin剪断失效;在植入角度为40°时,剪切强度最大（21.04 MPa）,比无Z-pin的接头剪切强度提高了67.1%。Z-pin植入角度（倾向于搭接末端）对单搭接头强度无影响。     

导弹地效区飞行空气动力和飞行力学特性研究

采用CFD和风洞试验技术,研究了导弹地效区飞行的空气动力和飞行力学相关特性。研究结果表明,导弹地效区飞行,由于受到地面效应的作用,其空气动力和飞行力学特性同常规自由空间飞行相比,发生了较大变化,常规导弹气动布局很难实现地效区飞行。由于地效区飞行运动响应十分复杂,加之飞行高度很低,这使现有飞行控制技术难以适应。这要求在气动布局设计中,必须将气动力、飞行力学和控制响应一体化考虑,气动布局技术是协调解决运动响应和动力学耦合的核心。     

旋转盘腔去旋系统数值模拟

对带有管式减涡器的盘腔内流动特性进行数值模拟,研究了减涡管的长度、管径和引气鼓筒孔的外形及尺寸,对盘腔内压力损失、流动结构的影响。计算结果表明:管式减涡器对于降低引气气流的压力损失有显著作用,存在最佳的减涡管长度使得引气的压力损失最小;减涡管管径、鼓筒孔面积增大都会减少流动损失;在鼓筒孔面积一定的情况下,长圆形鼓筒孔的性能比圆形鼓筒孔的更优。