飞机积冰后若干飞行力学问题综述

回顾飞机积冰后若干飞行力学问题研究的历史与现状,着重介绍了积冰飞机气动数据的获取途径、积冰飞机飞行力学建模与飞行仿真、积冰对飞机稳定性和操纵性的影响以及积冰对飞机飞行性能的影响.在已有飞机积冰后飞行力学问题研究的基础上,提出了飞机积冰后飞行力学问题研究领域需要解决和关注的若干问题,包括通过数值模拟方法获取积冰飞机的气动数据、完善积冰对飞机气动导数影响的计算模型以及加强平尾失速方面的研究.今后需要进一步对模拟冰风洞、数值模拟方法和平尾失速进行研究,并获取更多实验数据.     

机翼结冰过程的数值模拟

为预测飞机机翼结冰的形状,建立了一套采用时间步进法进行结冰过程数值模拟的方法.开发了一个软件框架用于使结冰模拟和网格更新全自动化.基于Messinger的质量和能量守恒方程建立了结冰热力学模型.采用了基于Spalart-Allmaras湍流模型在粗糙壁面的扩展模型来计算表面传热系数.提出了一种新的结冰生长方式.能预测霜...     

尾部可调的发动机进口支板结冰数值模拟研究

基于模块化思想,在FLUENT软件基础之上开发了发动机进口支板的结冰计算程序,针对尾部可调支板的结冰问题进行了计算研究。通过分析发动机进口支板结冰的物理过程,将支板结冰计算分成四个模块,分别为两相流流场计算、水滴收集计算、热力学分析和表面结冰量计算、动网格计算。首先将各模块单独进行研究,通过FLUENT提供的UDF函数及宏函数逐一实现各模块功能,最后将各模块整合,实现了发动机进口支板的结冰计算。通过计算获得了调整角度为30°时,支板的液态水含量分布、不同时间下支板结冰的区域以及不同温度下支板结冰的特点,给出了可调支板应重点防冰区域。数值模拟方法为工程应用提供了一条可选的途径。     

Alfvén waves in the context of solar-like star formation: accretion columns and disks

In this work we examine the damping of Alfvén waves as a source of plasma heating in disks and magnetic funnels of young solar like stars, the T Tauri stars. We apply four different damping mechanisms in this study: viscous-resistive, collisional, nonlinear and turbulent, exploring a wide range of wave frequencies, from 10⁻⁵Ω_i to 10⁻¹Ω_i (where Ω_i is the ion-cyclotron frequency). The results show that Alfvénic heating can increase the ionization rate of accretion disks and elevate the temperature of magnetic funnels of T Tauri stars opening possibilities to explain some observational features of these objects. This revised version was published online in August 2006 with corrections to the Cover Date.     

Black-hole transients: From QPOs to relativistic jets

Due to the impressive amount of new data provided by the RXTE satellite in the past decade, our knowledge of the phenomenology of accretion onto black holes has increased considerably. In particular, it has been possible to schematize the outburst evolution of transient systems on the basis of their spectral and timing properties, and link them to the ejection of relativistic jets as observed in the radio. Here, I present this scheme, concentrating on the properties of the quasi-periodic oscillations observed in the light curves and on the link with jet ejection.     

Fluid instabilities around accreting X-ray sources

Some aspects of fluid instabilities occurring in the magnetospheres of accreting neutron stars are discussed. It is pointed out that (i) in the absence of strong differential rotation, the accreting plasma should be drawn out into spiralling, sheet-like structures, resulting in efficient mixing between the two media; (ii) the Rayleigh-Taylor instability also acts to limit the X-ray luminosity in super-critical sources; and (iii) magnetic shear has a strong stabilizing influence on Kelvin-Helmholtz modes, and its presence may allow substantial amounts of material to be supported around the magnetosphere.     

Energy release in stellar magnetospheres

The interaction of a stellar magnetosphere with a thin accretion disk is considered. Specifically, I consider a model in which (1) the accretion disk is magnetically linked to the star over a large range of radii and (2) the magnetic diffusivity of the disk is sufficiently small that there is little slippage of field lines within the disk on the rotation time scale. In this case the magnetic energy built up as a result of differential rotation between the star and the disk is released in quasi-periodic reconnection events occuring in the magnetosphere (Aly and Kuijpers 1990). The radial transport of magnetic flux in such an accretion disk is considered. It is show that the magnetic flux distribution is stationary on the accretion time scale, provided the time average of the radial component of the field just above the disk vanishes. A simple model of the time-dependent structure of the magnetosphere is presented. It is shown that energy release in the magnetosphere must take place for (differential) rotation angles less than about 3 radians. The magnetic flux distribution in the disk depends on the precise value of the rotation angle.     

月壤含水特性原位快速预判传感器设计与验证

基于月壤和水冰对不同谱段近红外激光存在吸收/反射差异性的特点,提出了采用多模近红外激光光强差异反演月壤含水特性的水冰原位快速预判方法。通过发射/接收光路同轴设计及多模激光光路分时复用设计,实现了多模激光光学系统轻小型化设计,研制出基于多模近红外激光的月壤水冰原位快速预判传感器工程样机,并开展了针对低含水率极区模拟月壤的含水特性原位预判试验。试验结果表明：该传感器水冰检测限可达0.39%,单次预判时间可优于1 s,光斑直径@检测距离为5 cm@500 mm,传感器具备对地面模拟月壤含水特性进行原位快速预判的能力。     

Black hole accretion and X-ray spectra of QSOS

Changes in Eddington accretion ratios are thought to result in X-ray spectral index changes in Galactic binary black hole systems. Objects with higher Eddington ratios have softer X-ray spectra. Can we apply this result to much more massive black hole systems such as QSOs? If so, X-ray observations will give us valuable insight into the physics of QSOs. Among QSOs, X-ray spectral index is part of a large set of correlated optical and UV observational properties, especially optical Fe II and [O III] strengths in the Hβ region. To investigate whether this set of correlations is related to Eddington ratio, we use as probes, BALQSOs that have been suggested to be youthful super-accretors. We conducted infrared spectroscopy of the Hβ rest wavelength region for a sample of BALQSOs and compared line measurements with those for high and low redshift non-BAL QSOs. Hβ line widths and bolometric luminosity are used to calculate QSO black hole masses and Eddington ratios. Our results support the hypothesis that optical Fe II and [O III] line strengths are Eddington ratio indicators in QSO central engines. A possible explanation is that strong Fe II and weak [O III] indicate abundant cold gas that could fuel near Eddington accretion.     

基于光强反射和压电振动的混合式结冰探测系统

为解决目前飞机结冰探测存在测点单一,测量不准确、探测位置不匹配的问题,基于光强反射方法研制了光纤结冰传感器,基于压电振动方法研制了平膜结冰传感器,将两者进行组合嵌入至NACA0012翼型,研制了一种适合飞机翼面、多点分布测量的混合式结冰探测系统,并在低温冷库、结冰风洞中进行了测试.研究表明:多点分布测量的混合式结冰探测...