跨声速流自发凝结水滴的测量

应用基于多波长消光法原理发展的光学探针,测量了跨声速风洞中不同马赫数湿空气流自发凝结形成的水滴尺寸及浓度,并给出了实验结果     

弹道靶中超高速发射弹的流场及空气动力特性研究(英)

本文描述的是研究爆炸成型发射弹（ＥＦＰ）模型的流场及超高速空气动力特性所用的弹道试验设备;简要报导了记录全尺寸干涉图形的技术;对径向密度分布再现的方法进行了讨论;在零攻角实验时不同模型的空气动力阻力是采用简化方法来计算的;对各种不同ＥＦＰ型式的气动稳定性提出了定性估计的方法;并阐述了用于组合体超高速飞行特性研究的数值计算技术的基本原理     

收敛形进气道数值研究的验证

介绍一种新型的、具有最小喉道面积的三维高超声速进气道 (称之为收敛形进气道 )的数值和实验研究结果。表明使用这种形式的进气道 ,在整个飞行速度范围内可以降低阻力和高超声速发动机表面的热防护要求 ,通过降低外压缩表面的倾斜度和减少进气道及燃烧室壁的面积就可以做到这一点。在采用低维次流动的气体动力设计方法的基础上设计成这种形式的进气道。计算是在无粘气体模型构架内用有限体积法进行的。同时用边界层方程计算出计及粘性的气流特性和进气道特性。数值算法是通过收敛形进气道的有限宽楔形外压缩表面的计算和实验数据来验证的。进行实验研究的马赫数M=2～ 1 0 7,基于模型进气道高度的雷诺数Re=( 1～ 5) × 1 0 6。数值计算与实验结果一致性很好。这些结果也和通常的二维进气道的数据作了比较。     

Implications of X-ray Observations for Electron Acceleration and Propagation in Solar Flares

High-energy X-rays and ??-rays from solar flares were discovered just over fifty years ago. Since that time, the standard for the interpretation of spatially integrated flare X-ray spectra at energies above several tens of keV has been the collisional thick-target model. After the launch of the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) in early 2002, X-ray spectra and images have been of sufficient quality to allow a greater focus on the energetic electrons responsible for the X-ray emission, including their origin and their interactions with the flare plasma and magnetic field. The result has been new insights into the flaring process, as well as more quantitative models for both electron acceleration and propagation, and for the flare environment with which the electrons interact. In this article we review our current understanding of electron acceleration, energy loss, and propagation in flares. Implications of these new results for the collisional thick-target model, for general flare models, and for future flare studies are discussed.     

Nonclassical Transport and Particle-Field Coupling: from Laboratory Plasmas to the Solar Wind

Understanding transport of thermal and suprathermal particles is a fundamental issue in laboratory, solar-terrestrial, and astrophysical plasmas. For laboratory fusion experiments, confinement of particles and energy is essential for sustaining the plasma long enough to reach burning conditions. For solar wind and magnetospheric plasmas, transport properties determine the spatial and temporal distribution of energetic particles, which can be harmful for spacecraft functioning, as well as the entry of solar wind plasma into the magnetosphere. For astrophysical plasmas, transport properties determine the efficiency of particle acceleration processes and affect observable radiative signatures. In all cases, transport depends on the interaction of thermal and suprathermal particles with the electric and magnetic fluctuations in the plasma. Understanding transport therefore requires us to understand these interactions, which encompass a wide range of scales, from magnetohydrodynamic to kinetic scales, with larger scale structures also having a role. The wealth of transport studies during recent decades has shown the existence of a variety of regimes that differ from the classical quasilinear regime. In this paper we give an overview of nonclassical plasma transport regimes, discussing theoretical approaches to superdiffusive and subdiffusive transport, wave–particle interactions at microscopic kinetic scales, the influence of coherent structures and of avalanching transport, and the results of numerical simulations and experimental data analyses. Applications to laboratory plasmas and space plasmas are discussed.     

Volatile Trapping in Martian Clathrates

Thermodynamic conditions suggest that clathrates might exist on Mars. Despite observations which show that the dominant condensed phases on the surface of Mars are solid carbon dioxide and water ice, clathrates have been repeatedly proposed to play an important role in the distribution and total inventory of the planet’s volatiles. Here we review the potential consequences of the presence of clathrates on Mars. We investigate how clathrates could be a potential source for the claimed existence of atmospheric methane. In this context, plausible clathrate formation processes, either in the close subsurface or at the base of the cryosphere, are reviewed. Mechanisms that would allow for methane release into the atmosphere from an existing clathrate layer are addressed as well. We also discuss the proposed relationship between clathrate formation/dissociation cycles and how potential seasonal variations influence the atmospheric abundances of argon, krypton and xenon. Moreover, we examine several Martian geomorphologic features that could have been generated by the dissociation of extended subsurface clathrate layers. Finally we investigate the future in situ measurements, as well as the theoretical and experimental improvements that will be needed to better understand the influence of clathrates on the evolution of Mars and its atmosphere.     

Numerical study of intrachamber processes dynamics at nozzleless solid propellant rocket engine actuation

The results of the comprehensive numerical analysis for dynamics of intrachamber processes that appear at nozzleless solid propellant rocket engine (SPRE) actuation are presented. A complete cycle of rocket engine operation is analyzed. We solve a conjugate problem involving the igniter actuation; heating, ignition and following combustion of a solid propellant charge; a combustion product flow in the combustion chamber; depressurization of the combustion chamber, and the subsequent motion of the rocket engine blank; variation of the combustion surface geometry at the expense of the gradual and nonuniform burnout of solid propellant web.     

Nanofillers modification of Epocast 50-A1/946 epoxy for bonded joints

Epocast 50-A1/946 epoxy was primarily developed for joining and repairing of composite aircraft structural components. The objective of the present work is to modify the Epocast epoxy resin by different nanofillers infusion. The used nanofillers include multi-walled carbon nanotubes（MWCNTs）, SiC and Al2O3 nanoparticles. The nanofillers with different weight percentages are ultrasonically dispersed in the epoxy resin. The sonication time and amplitude for MWCNTs are reduced compared to Al2O3 and SiC nanoparticles to avoid the damage of MWCNTs during sonication processes. The fabricated neat epoxy and twelve nanocomposite panels were characterized via standard tension and in-plane shear tests. The experimental results show that the nanocomposites materials with 0.5wt% MWCNTs, 1.5wt% SiC and 1.5wt% Al2O3 nanoparticles have the highest improvement in the tensile properties compared to the other nanofiller loading percentages.The improvements in the shear properties of these nanocomposite materials were respectively equal to 5.5%, 4.9%, and 6.3% for shear strengths, and 10.3%, 16.0%, and 8.1% for shear moduli. The optimum nanofiller loading percentages will be used in the following papers concerning their effect on the bonded joints/repairs of carbon fiber reinforced composites.