NUMERICAL STUDY OF TWO INTERFACE METHODS FOR COMPRESSIBLE MULTI-FLUID FLOWS

INTRODUCTIONThe direct numerical simulation of com-pressible multi- fluid flows is an important re-search topic with various key applications.Therelatively dominant difficulty of simulation lies intreatment of the moving material interface. Ingeneral,there are two basic approaches to treatcontact discontinuities.The first,front trackingmethod[1,2 ] ,explicitly characterize the interfacemotion by the motion of individual points on theinterface. The other approach is front capturingmethod[3…     

双组元姿控发动机喷管化学反应流场数值模拟

本文对混合比为０．９、１．０、１．１三种状态下工作的双组元自然推进剂（肼／四氧化二氮）姿控发动机喷管内化学反应流动进行了数值模拟。数值模拟时采用了弱耦合点隐式方法的数值方法及肼／四氧化二氮的十二组分、十三个基元反应的有限速率化学反应模型。得到了三种混合比下反应流及混合比为１．０时冻结流发动机的推力和比推力、喷管中的流动参数及各组分的质量分数。分析表明，数值模拟的结果与理论分析一致，结果可靠。本文工作为姿控发动机的喷管设计提供了理论依据。     

GRACE gravity field modeling with an investigation on correlation between nuisance parameters and gravity field coefficients

The GRACE (Gravity Recovery And Climate Experiment) monthly gravity models have been independently produced and published by several research institutions, such as Center for Space Research (CSR), GeoForschungsZentrum (GFZ), Jet Propulsion Laboratory (JPL), Centre National d’Etudes Spatiales (CNES) and Delft Institute of Earth Observation and Space Systems (DEOS). According to their processing standards, above institutions use the traditional variational approach except that the DEOS exploits the acceleration approach. The background force models employed are rather similar. The produced gravity field models generally agree with one another in the spatial pattern. However, there are some discrepancies in the gravity signal amplitude between solutions produced by different institutions. In particular, 10%–30% signal amplitude differences in some river basins can be observed. In this paper, we implemented a variant of the traditional variational approach and computed two sets of monthly gravity field solutions using the data from January 2005 to December 2006. The input data are K-band range-rates (KBRR) and kinematic orbits of GRACE satellites. The main difference in the production of our two types of models is how to deal with nuisance parameters. This type of parameters is necessary to absorb low-frequency errors in the data, which are mainly the aliasing and instrument errors. One way is to remove the nuisance parameters before estimating the geopotential coefficients, called NPARB approach in the paper. The other way is to estimate the nuisance parameters and geopotential coefficients simultaneously, called NPESS approach. These two types of solutions mainly differ in geopotential coefficients from degree 2 to 5. This can be explained by the fact that the nuisance parameters and the gravity field coefficients are highly correlated, particularly at low degrees. We compare these solutions with the official and published ones by means of spectral analysis. It is found that our solutions are, in general, consistent with others in the spatial pattern. The water storage variations of the Amazon, Chari and Ganges river basins have also been computed. The variations computed with the NPARB approach are closer to those produced by JPL and DEOS solutions, while the variations produced with the NPESS approach are in good agreement with those produced by the CSR and GFZ solutions. A simulation study is implemented with considering realistic noise and low-frequency error. The two approaches are used to recover the true model. The NPESS solution appears closer to the true one. Therefore we are inclined to estimate the nuisance parameters simultaneously with the geopential coefficients.     

基于连续损伤模型的复合材料波纹梁压溃分析

复合材料的耐撞性受到了广泛重视,而波纹梁因其优异的抗屈曲构型被广泛应用于飞机翼梁和直升机底板等经常发生碰撞的结构中。进行了复合材料波纹梁的屈曲分析,研究了高度对波纹梁破坏模式的影响。建立复合材料波纹梁的连续损伤单波模型,层内基于Hashin判据建立含损伤因子的损伤刚度矩阵,层间根据二次名义应力准则和B-K准则模拟损伤演化,并通过典型复合材料波纹梁压溃试验验证了所建立模型的正确性。基于单波分析模型,通过施加周期性边界条件和反对称边界条件,研究了多波结构的吸能特性。     

分布式光纤测温系统及高速数据采集与处理

分布式光纤测温系统是一种用于实时测量空间温度场分布的光纤传感系统 ,在系统中 ,光纤本身既是传输媒体也是传感媒体。讨论了系统的工作原理、设计思想、系统构成、高速数据采集以及瞬态采样平均技术 ,该系统已应用于石油测井。     

防空导弹武器系统故障诊断技术探究

对主要的故障诊断技术进行了系统地归纳和分类,并重点讨论了基于知识处理的智能故障诊断方法,对专家系统故障诊断方法、故障树故障诊断方法、模糊故障诊断方法、神经网络故障诊断方法以及基于支持向量机的故障诊断方法进行了详细介绍。     

太阳电池阵枪式微型电阻焊接系统设计与分析

太阳电池阵枪式微型电阻焊接系统,采用电阻点焊的方法,辅以自动化操作,控制系统设有机器视觉监控可实时监控焊接情况。焊后对焊点进行金相分析,焊点界面结合紧密,无局部未焊合或虚焊、微裂纹、孔洞等明显缺陷,焊点综合性能佳。该焊接系统的研制对实现太阳电池阵的高效自动化组装和焊接,提高太阳电池阵焊点的承载能力、极端温度下的力学性能、可靠性、导电性等具有重要意义。     

重力空射稳定伞阻力特征自动化设计

为进行重力空射稳定伞的初步设计,文章以多体动力学软件(ADAMS)为二次开发平台,构建了重力空射箭-伞系统的动力学仿真模型;推导了火箭和稳定伞的气动模型,并利用动态链接子程序实现了气动力的加载;通过ADAMS命令语言建立了参数化模型和用户界面。在此基础上,自编可行方向优化算法实现了稳定伞阻力特征的自动化设计。最后,根据仿真计算结果对试验火箭出舱时间、安全通道、回收方式等问题进行了分析,为后续空射稳定伞的细节设计以及空射总体方案的确定提供了参考。     

无线电陆空通话英语交际能力模型研究

民航无线电陆空通话语言是以英语为载体的一种空地交流的特殊语言。本文在应用语言学的研究成果之上,提出了该语言的交际能力模型,该模型包括语言能力、策略能力、背景知识和心理生理机制四个部分。笔者结合民航陆空通话实际,对模型各个部分进行了分析,重点解析了策略能力在模型中的核心功能。     

薄壁梁系的可靠性优化设计

以结构系统的可靠度作为薄壁梁系结构的优化控制参数。用改进的分枝眼界法判从主要失效模式。用PNET法计算结构系统的可靠度。导出了两种梁系结构可靠度的灵敏度分析表达式。提出最佳矢量型算法的选代公式,有效地求解了Ⅰ型截面梁系结构在系统可靠度约束下的最小重量设计问题;且在其中通过设计变量连接来满足薄壁梁的稳定性要求。算例的结果说明了方法的有效性。