A coupling VWM/CFD/CSD method for rotor airload prediction

A coupling fluid-structure method with a combination of viscous wake model(VWM),computational fluid dynamics(CFD) and comprehensive structural dynamics(CSD) modules is developed in this paper for rotor unsteady airload prediction. The hybrid VWM/CFD solver is employed to model the nonlinear aerodynamic phenomena and complicated rotor wake dynamics;the moderate deflection beam theory is implemented to predict the blade structural deformation; the loose coupling strategy based on the ‘delt method' is used to couple the fluid and structure solvers.Several cases of Helishape 7A rotor are performed first to investigate the effect of elastic deformation on airloads. Then, two challenging forward flight conditions of UH-60 A helicopter rotor are investigated, and the simulated results of wake geometry, chordwise pressure distribution and sectional normal force show excellent agreement with available test data; a comparison with traditional CFD/CSD method is also presented to illustrate the efficiency of the developed method.     

基于纹理边界检测的航天器椭圆特征提取方法

为确定失效航天器等非合作目标的相对位姿,提出一种通过纹理边界检测的椭圆特征提取方法。该方法假设椭圆特征是航天器表面两种不同纹理的边界,利用上一时刻相对位姿信息,将对接环离散几何模型投影到像平面,并沿各离散点的法向方向通过概率方法检测纹理边界点。利用随机抽样一致(RANSAC)方法剔除边界点中的粗大误差,进而拟合出椭圆参数。纹理特征对光照变化具有鲁棒性,因此该方法能够在变光照、星体表面反光不均匀等复杂情况下快速准确地提取图像中的椭圆特征。本文以对接环图像特征提取为例进行仿真校验,分析了算法参数和噪声对提取椭圆精度和时间的影响。利用真实图像与基于梯度边缘的椭圆提取方法进行对比,结果表明,所提出的算法具有较高的精度和速度。     

绕月微卫星精确撞月轨道设计

为实现约束条件下的精准可控撞月,提出了基于Lambert问题的精确撞月轨道设计方法。通过求解Lambert问题,可得到撞月轨道轨控时刻的速度脉冲初值解,然后通过打靶法迭代得到撞月轨道的精确解。以\"龙江二号\"微卫星轨道为例,对撞月点经纬度的覆盖性,以及燃料约束下同一撞月点可行的轨控弧段进行全面分析。最后,通过月球南极水冰探测的撞月轨道设计案例,以验证本文提出的轨道设计方法的有效性。     

过程控制机

过程控制机由数据采集系统、智能控制器、控制过程量输入输出部件和标准接口等组成。数据采集系统采集测力天平和压力传感器的输出信号,它的模拟量输入通道32路,采集速度5万次/秒,系统精度0.04%。模拟量输出控制调压阀系统,频率量输出控制模型姿态角系统,标准接口 IEEE-488和上位机通讯,传送命令和数据,所有软件固化在智能控制器的 ROM 中,它分析上位机送来命令指挥各部件工作。文章还介绍过程控制机在风洞测控系统中的工作过程以及使用后取得的良好效益。     

硅烷偶联剂改性Al2 O3p/TDE-85 的力学性能

利用硅烷偶联剂对Al2O3颗粒进行表面改性,制备了Al2O3颗粒增强的TDE-85树脂基复合材料,研究了表面改性对其力学性能的影响,采用差热分析仪测定复合材料的固化反应温度,并计算了固化反应活化能。利用扫描电子显微镜分析了拉伸断口形貌。研究发现,当Al2O3用量为2wt%时,固化反应速度较快,硅烷偶联剂用量为4wt%时,冲击强度为13.2 kJ/m2;拉伸强度为65.2 MPa;弹性模量为2.66 GPa;最大伸长率为3.35%,此时对Al2O3颗粒的表面改性综合效果最好。     

一种GPS定位信息可用性的实时判定方法

基于GPS接收机输出数据,采用3级AR模型来预测下一时刻的GPS输出值,并与实际的输出值相比较,以一定的检测门限,判断当前时刻定位信息的可用性。通过仿真证明该方法的有效性,为GPS的可用性判定提供了一种方法。     

飞行器再入大气层通信黑障的消除方法

文章通过分析等离子体鞘层与电磁波的相互作用,考察了通信黑障的产生原理及其影响,详细介绍了各种通信黑障消除方法的基本原理及其优缺点,包括改变空气动力学形状、亲电子物质注入、磁开窗、引入交叉电磁场、提高发射功率和入射波频率以及采用Raman散射通信等,为进一步开展通信黑障消除方法的应用研究指明了方向。     

铝锂合金热处理及其组织性能

本文研究国产８０９０铝锂合金热处理工艺及其组织性能。研究表明：８０９０铝锂合金在５７２±３℃固溶加热、保温３０￣６０分钟,水冷,自然时效时间长达３５天以上,机械性能差;在１９０℃,１９小时人工时效,机械性能σｂ＝５１６￣５７６ＭＮｍ＾－２,δ＝６．２￣６．３％,金相组织均匀。适当延长固溶处理加热保温时间,对铝锂合金强度有益。用扫描电镜对固溶短时保温水冷的人工时效与自然时效Ａｌ－Ｌｉ合金试样进行了继     

板宽对胶焊接头应力分布影响的数值分析

采用三维弹塑性有限元方法,研究了酚醛树脂和丙烯酸树脂两种胶粘剂的胶焊接头中,板宽对应力分布的影响。结果表明,酚醛树脂胶粘剂胶焊接头中,搭接区边缘应力值高于焊点边缘应力值,导致接头从搭接区边缘起裂,板宽增大时,焊点边缘处和搭接区边缘的峰应力都减小,对于提高胶焊接头的强度有利,但不会改变接头的断裂形式;丙烯酸树脂胶粘剂的胶焊接头,焊点边缘应力远高于搭接区边缘应力,因此接头从焊点边缘起裂,板宽增大时,焊点边缘应力基本不变。因此增加板宽对提高接头强度无明显作用,接头断裂形式也不发生改变。     

Responses of ionospheric foF2 to geomagnetic activities in Hainan

Responses of low-latitude ionospheric critical frequency of F2 layer to geomagnetic activities in different seasons and under different levels of solar activity are investigated by analyzing the ionospheric foF2 data from DPS-4 Digisonde in Hainan Observatory during 2002–2005. The results are as follows: (1) the response of foF2 to geomagnetic activity in Hainan shows obvious diurnal variation except for the summer in low solar activity period. Generally, geomagnetic activity will cause foF2 to increase at daytime and decrease at nighttime. The intensity of response of foF2 is stronger at nighttime than that at daytime; (2) seasonal dependence of the response of foF2 to geomagnetic activity is very obvious. The negative ionospheric storm effect is the strongest in summer and the positive ionospheric storm effect is the strongest in winter; (3) the solar cycle has important effect on the response of foF2 to geomagnetic activity in Hainan. In high solar activity period, the diurnal variation of the response of foF2 is very pronounced in each season, and the strong ionospheric response can last several days. In low solar activity period, ionospheric response has very pronounced diurnal variation in winter only; (4) the local time of geomagnetic activities occurring also has important effect on the responses of foF2 in Hainan. Generally, geomagnetic activities occurred at nighttime can cause stronger and longer responses of foF2 in Hainan.