Three-dimensional global simulation of multiple ICMEs’ interaction and propagation from the Sun to the heliosphere following the 25–28 October 2003 solar events

This study performs simulations of interplanetary coronal mass ejection (ICME) propagation in a realistic three-dimensional (3D) solar wind structure from the Sun to the Earth by using the newly developed hybrid code, HAFv.2+3DMHD. This model combines two simulation codes, Hakamada–Akasofu–Fry code version 2 (HAFv.2) and a fully 3D, time-dependent MHD simulation code. The solar wind structure is simulated out to 0.08 AU (18 Rs) from source surface maps using the HAFv.2 code. The outputs at 0.08 AU are then used to provide inputs for the lower boundary, at that location, of the 3D MHD code to calculate solar wind and its evolution to 1 AU and beyond. A dynamic disturbance, mimicking a particular flare’s energy output, is delivered to this non-uniform structure to model the evolution and interplanetary propagation of ICMEs (including their shocks). We then show the interaction between two ICMEs and the dynamic process during the overtaking of one shock by the other. The results show that both CMEs and heliosphere current sheet/plasma sheet were deformed by interacting with each other.     

直射式气动雾化喷嘴对燃烧室性能的影响

为了深入分析燃油喷嘴对燃气轮机燃烧室性能的影响，针对燃气轮机燃烧室中的直射式气动雾化喷嘴开展了数值模 拟，获得了气流流量、燃油流量和气液比对雾化性能的影响规律，喷嘴的雾化性能参数包括雾化粒径和雾化锥角。结果表明：气液 比和气流流量对该型喷嘴的雾化性能有显著影响，燃油流量对雾化性能的影响较小；气液两相间相对速度是影响该型喷嘴雾化性 能的决定因素，相对速度增大有利于减小雾化粒径，并增大雾化锥角；气流流量和气液比的增大均有利于雾化粒径的减小，燃油流 量的增加将使雾化粒径增大；增大气流流量、气液比和减小燃油流量均可使雾化锥角增大；该型喷嘴的雾化锥角变化范围为 30.12°～41.24°，雾化粒径变化范围为131.46～ 186.52 μm。喷嘴可实现在较小的雾化锥角变化范围内获得较宽的雾化粒径变化， 以此匹配燃气轮机燃烧室不同工作状态，具有较高的实用价值。     

Solar Neutrinos

The current status of solar neutrino experiments is reviewed. All the experimental measurements show deficits of solar neutrinos. Non monotonic suppression indicates that the problem may naturally be explained by neutrino oscillations, but not by modifying solar models. A new experiment shows very promising results. We hope that a definite answer to the question of whether solar neutrinos are oscillating will be obtained in the very near future. This revised version was published online in June 2006 with corrections to the Cover Date.     

Results from the study of an M7.6 flare and its associated CME

An M7.6 flare was well observed on October 24, 2003 in active region 10486 by a few instruments and satellites, including GOES, TRACE, SOHO, RHESSI and NoRH. Multi-wavelength study shows that this flare underwent two episodes. During the first episode, only a looptop source of <40 keV was observed in reconstructed RHESSI images, which showed shrinkage with a velocity of 12–14 km s⁻¹ in a period of about 12 min. During the second process, in addition to the looptop source, two footpoint sources were observed in energy channel of as high as ∼200 keV. One of them showed fast propagation along one of the two TRACE 1600 Å flare ribbons and the 195 Å loop footpoints, which could be explained by successive magnetic reconnection. The associated CME showed a mass pickup process with decreasing center-of-mass velocity. The decrease of the CME kinetic energy and the increase of its potential energy lead to an almost constant total energy during the CME propagation. Our results reveal that the flare and its associated CME have comparable energy content, and the flare is of non-thermal property.     

充液容器流固耦合模态仿真分析研究

主要介绍目前容器类流固耦合模态分析最常用的两种计算方法:声固耦合法及虚拟质量法。从理论上分别对这两种方法进行分析,并指出它们之间的联系与区别:虚拟质量法采用了声固耦合法在不可压缩流体情况下的形式,并有所改进,即流体的作用完全由虚拟质量阵来体现,而流体的虚拟质量阵则通过具有解析解性质的边界元法获得。最后,通过开口方槽干状态、湿状态的无阻尼模态仿真分析研究,揭示出流体对结构模态特性影响的变化规律,同时指出了两种方法(虚拟质量法、声固耦合法)对结构湿模态计算结果有规律性的差异:随着振动频率的升高,不仅容器内流体对结构模态特性的影响在减小,分析湿模态的两种方法所得到的计算结果之间的差别也在逐渐减小。     

转动载荷对卫星姿态的影响与控制研究

研究带有转动载荷和挠性附件的卫星姿态控制问题.基于具有广义坐标形式的牛顿 欧拉方法建立了卫星姿态动力学模型和转动载荷力矩模型,研究载荷产生的动不平衡力矩和静不平衡力矩的机理和特点.分析载荷干扰对卫星姿态的影响特性,给出基于传递函数进行拉氏变换以估算姿态抖动量的方法.分析卫星姿态控制系统设计干扰补偿控制器的条件,给出了控制器的工程设计方法.验证结果表明该方法有效且能提高卫星姿态精度.     

空气节流对超燃发动机燃烧性能的影响

为优化隔离段及燃烧室内的流场结构,减小流动速度,提高流道压力,在凹槽稳焰器下游布置空气节流装置,向燃烧室内喷入高压空气,目的是在隔离段建立合适的激波串,以利于点火和火焰稳定.采用CFD方法,对比了无/有空气节流时的冷流流场、燃烧流场,结果表明:节流激波串扩大了低动量区域,激波引起的流动扭曲和较长的驻留时间使得分离流内的空气/燃料混合程度得到显著增强,混合效率由无节流时的40%提高到85%,燃烧效率由无节流时的10%提高到60%.对节流位置和节流量进行了参数化研究,以隔离段入口为坐标原点,分别考察了785,1000,1100mm三个流向节流位置,以及10%,15%,30%三种节流量的影响,结果表明:距离凹槽较近的节流位置对燃烧的影响更为显著,所需节流量更少.30%的节流量将使燃烧室背压急剧提高,引起流动壅塞.研究表明在785mm的流向节流位置采用15%的节流量可获得最好的燃烧性能.      

体积激励法测量液体推进剂量的地面模拟试验

针对大贮箱推进剂量测量精度不高问题,研究一种测量精度较高、重复性强的液体推进剂量测量方法。首先介绍体积激励法测量推进剂量的测量原理,重点分析地面模拟试验装置组成,包括体积激励装置、编码电机控制、数据采集及数据处理分系统。其次阐述试验方案,试验在常温常压下进行,采用不同激励频率改变体积。最后,以水作为模拟推进剂开展地面模拟试验,结果表明在不同填充水平下液体推进剂量测量误差都控制在贮箱总体积的1%以内,为未来高精度测量推进剂量飞行试验及空间应用提供可靠支持。     

测量液体推进剂剩余量的体积激励法

首先给出了以贮箱内气体为对象的一般热力学测量控制方程,完成气体及液体体积的计算; 以贮箱系统为研究对象,建立了系统处于等温、绝热及非等温条件下的热力学模型,考虑了气体与液体、贮箱壁的传热传质等因素,得出了比较理想的测量模型。其次,对影响测量的系统误差进行了分析,建立了各种影响因素的误差模型,并提出了相应的修正措施。然后,给出了在现有技术水平下测量的最大误差,结果表明测量误差在贮箱总体积的1%以内。最后,对激励频率、体积改变量大小及测量设备等相关应用技术问题进行了分析讨论与合理设计。体积激励法是一种可满足测量精度和耗能要求的良好方法。     

软隔板双脉冲发动机二级点火延迟试验分析

在进行软隔板双脉冲发动机的试验研究时发现,二级脉冲出现远远超过指标要求的点火延迟.为了改进这种状况,从点火药量和隔板厚度两方面进行试验研究.结果表明单纯增加点火药量使得隔板破裂太快,能量过早地释放;而单纯增加隔板厚度使得隔板不能按预定位置和方式破裂,影响工作性能.最终结合软隔板双脉冲发动机的工作特点,从两方面同时改进,达到了比较合理的点火延迟.