考虑粘性相互作用的跨音速机翼分析

本文将一些已有的三维全位势方程计算方法和一种三维积分边界层方法作了弱相互作用的耦合计算。计算了三种机翼并与已有的试验数据作了比较。     

Alfvénic Electron Acceleration in Aurora Occurs in Global Alfvén Resonosphere Region

Auroral emission caused by electron precipitation (Hardy et al., 1987, J. Geophys. Res. 92, 12275–12294) is powered by magnetospheric driving processes. It is not yet fully understood how the energy transfer mechanisms are responsible for the electron precipitation. It has been proposed (Hasegawa, 1976, J. Geophys. Res. 81, 5083–5090) that Alfvén waves coming from the magnetosphere play some role in powering the aurora (Wygant et al., 2000, J. Geophys. Res. 105, 18675–18692, Keiling et al., 2003, Science 299, 383–386). Alfvén-wave-induced electron acceleration is shown to be confined in a rather narrow radial distance range of 4–5 R _E (Earth radii) and its importance, relative to other electron acceleration mechanisms, depends strongly on the magnetic disturbance level so that it represents 10% of all electron precipitation power during quiet conditions and increased to 40% during disturbed conditions. Our observations suggest that an electron Landau resonance mechanism operating in the “Alfvén resonosphere” is responsible for the energy transfer.     

Dynamics of Coronal Loop Oscillations Recent Improvements and Computational Aspects

We will discuss the observed, heavily damped transversal oscillations of coronal loops. These oscillations are often modeled as transversal kink oscillations in a cylinder. Several features are added to the classical cylindrical model. In our models we include loop curvature, longitudinal density stratification, and highly inhomogeneous radial density profiles. In this paper, we will first give an overview of recently obtained results, both analytically and numerically. After that, we shed a light on the computational aspects of the modeling process. In particular, we will focus on the parallellization of the numerical codes.     

高速铁路隧道初始压缩波一维流动模型的数值分析方法

基于隧道内空气流通截面是时间和距离的二元函数条件与一维流动理论,提出了高速列车驶入设有缓冲结构隧道端口时产生初始压缩波的数值分析方法。一维流动理论采用考虑摩擦、传热以及空气质交换等因素的一维可压缩非定常不等熵流动模型。数值分析方法采用广义黎曼变量特征线法。与国外有关未设缓冲结构、开孔型与未开孔型缓冲结构的隧道端口三种情况的现车试验结果进行了比较,表明本文所建方法正确、合理,能够模拟计算多种类型缓冲结构条件下的压缩波波动规律。     

Relativistic MHD Simulations of Jets with Toroidal Magnetic Fields

This paper presents an application of the recent relativistic HLLC approximate Riemann solver by Mignone & Bodo to magnetized flows with vanishing normal component of the magnetic field. The numerical scheme is validated in two dimensions by investigating the propagation of axisymmetric jets with toroidal magnetic fields. The selected jet models show that the HLLC solver yields sharper resolution of contact and shear waves and better convergence properties over the traditional HLL approach.     

Assessment of Two Turbulence Models and Some Compressibility Corrections for Hypersonic Compression Comers by High-order Difference Schemes

The Spalart-Allmaras (S-A) turbulence model,the shear-stress transport (SST) turbulenee model and their compressibility corrections are revaluated for hypersonic compression corner flows by using high-...     

基于磁流体控制的高超声速进气道黏性效应

建立引入电磁源项的二维低磁雷诺数磁流体动力学(MHD)方程组,对高超声速二维前体/进气道黏性流场进行了数值模拟.在给出了进气道高于设计马赫数的非设计工况下黏性流场的基本特征基础上,进一步分析了施加MHD控制对进气道黏性效应的影响.结果表明:施加MHD控制可以有效抑制非设计工况下内进气道表面的附面层分离,改善上壁面的热状况,平衡上、下壁面之间的热负担;黏性作用下,进气道流场及性能参数随磁感强度的变化规律与无黏模型计算结果存在较大差别,对磁流体控制的高超声速进气道研究不可忽略黏性的影响.      

高超声速等截面磁流体发电机性能研究

采用三维低磁雷诺数磁流体动力学五方程模型,对等截面管道法拉第型分段电极磁流体发电机内的流动进行数值模拟,研究了负载系数、磁场强度、电极-绝缘壁宽度比对发电通道性能的影响.结果表明:当负载系数为0.50时电功率密度达到最大,并且随着负载系数的增大发生器的减速能力降低;当磁场强度为8T时,500mm的管道长度即可将来流马赫数从6降低到3以下,温度保持在800K以下,并且每立方米的管道发电量能够达到兆瓦级的水平.      

突跃型与平滑型斜爆震波起爆机制数值模拟

采用带有化学反应的Euler方程,对突跃型与平滑型2种形态的斜爆震波(ODW)在起爆机制和结构特点等方面的差异进行了研究.结果表明:斜激波(OSW)后是否存在亚声速区是判定斜爆震形态的依据.当波后火焰抬升斜激波面使得亚声速区存在时,横向激波与三波点结构就会出现并形成突跃型斜爆震.当波后所有区域皆为超声速区时,波后火焰燃烧无法影响到上游激波面,则会形成平滑型斜爆震.通过斜激波关系式给出了横向激波形成所需的临界斜激波角度,只有当斜激波角度大于此临界角度时才能形成突跃型斜爆震波,反之则形成平滑型斜爆震波.      

Type II Solar Radio Bursts: Theory and Space Weather Implications

Recent data and theory for type II solar radio bursts are reviewed, focusing on a recent analytic quantitative theory for interplanetary type II bursts. The theory addresses electron reflection and acceleration at the type II shock, formation of electron beams in the foreshock, and generation of Langmuir waves and the type II radiation there. The theory's predictions as functions of the shock and plasma parameters are summarized and discussed in terms of space weather events. The theory is consistent with available data, has explanations for radio-loud/quiet coronal mass ejections (CMEs) and why type IIs are bursty, and can account for empirical correlations between type IIs, CMEs, and interplanetary disturbances. This revised version was published online in August 2006 with corrections to the Cover Date.