Wave-Particle-Electric Field Synergetic Auroral Electron Acceleration

Space Science Reviews - We discuss afresh the problem of the auroral electron acceleration based on the controversy reports of Bryant, D. A. et al.: 1992, Phys. Rev. Lett. 68, 37, and Borovsky, J.:...     

Phase coherence of MHD waves in the solar wind

Large amplitude MHD waves are commonly found in the solar wind. Nonlinear interactions between the MHD waves are likely to produce finite correlation among the wave phases. For discussions of various transport processes of energetic particles, it is fundamentally important to determine whether the wave phases are randomly distributed (as assumed in quasi-linear theories) or they have a finite coherence. Using a method based on a surrogate data technique and a fractal analysis, we analyzed Geotail magnetic field data (provided by S. Kokubun and T. Nagai through DARTS at the Institute of Space and Astronautical Science) to evaluate the phase coherence among the MHD waves in the earth's foreshock region. The correlation of wave phases does exist, indicating that the nonlinear interactions between the waves is in progress. This revised version was published online in August 2006 with corrections to the Cover Date.     

二维通道内湍流边界层分离的实验研究

用激光多普勒技术测量了二维扩压器中不可压湍流边界层分离流动，得到了时均速度和雷诺剪应力分布。实验结果分析表明：以Ｃｏｌｅｓ速度律发展的Ｂａｒｄｉｎａ速度分布可以描述瞬时间歇分离点以前和瞬时间歇再附点以后的时均速度分布，但无法描述分离区的边界层速度型。Ｃｒｏｓｓ速度分布可描述分离区的边界层速度分布。Ｃｅｂｅｃｉ＆Ｓｍｉｔｈ涡粘性代数模型难以正确地描述分离边界层的雷诺剪应力。     

轴对称降落伞稳定下降阶段的流场特性

文章根据降落伞的特点,通过3点假设(伞衣的薄膜假设、降落伞的轴对称假设和流场的定常 假设),将三维复杂流动问题,转化成二维轴对称问题,以节约计算时间。然后,建立轴对称降落伞的流体力 学计算模型,利用数值模拟手段,求解RNG(Renormalization Group)k-epsilon湍流模型下的N—S方程组,获 得与有关单位试验相吻合的计算结果。分析发现带顶孔的轴对称降落伞绕流和亚临界状态下带中心孔的 圆球绕流,在尾流区拓扑结构上几乎完全一致。结果表明建立的轴对称降落伞模型,能够揭示降落伞流场 的本质特性,为进一步研究降落伞流场的流动机理和流固耦合问题打下基础。     

轴对称湍流射流的相似解

本文在相似性条件下,得到了用k-ε模式的轴对称湍流射流的相似方程。利用动量相似方程的近似求解结果作为初值,同时引入变量变换,进行迭代求解。本文的方法收敛速度快,计算简便。     

Phase Space Density Analysis of Energy Transport in the Earth’s Magnetotail

Two energetic events in the Earth’s magnetotail detected by Geotail are examined with detailed analysis of three-dimensional velocity phase space density. It is found that the occurrence of multiple ion components is high during these dynamic episodes. Different populations evolve independently of each other, suggesting particles from multiple activity sites contributing to the observed phase space density. The transport properties with consideration of multiple components are evaluated, with the result showing significant differences from those based on a single fluid approach. This comparison indicates that precise evaluation of the energy and magnetic flux transport of energetic events in the magnetotail requires resolving individual populations in the phase space density.     

街道峡谷湍流流动的风洞试验与数值计算

在１：２５０的风洞模型上,测量街道峡谷的平均流速,湍流度等参数,分析了街道峡谷内的湍流流动状态,探讨了屋顶来流风在街道峡谷内产生复杂流场的主要特征,并用三维湍流流模型对风洞试验模型进行了数值计算,试验和计算结果为研究街道峡谷风环境以及街道峡谷的传热传质过程提供了基础。     

湍流附面层壁面摩擦应力的测量方法

 本文讨论了不可压和可压湍流附面层壁面摩擦应力的测量方法,对Presto管、Stanton管、底层隔板、表面热膜和计算Preston管法进行了校准和测量比较。     

风洞模拟近地面大气边界层

本文通过大气边界层风洞的模拟实验，介绍一种在风洞中模拟近地面大气边界层的方法。根据大风地区的现场实测资料，对大气的风剖面及湍流度等有关参数，提出了一些特殊的要求。常规的模拟方法难以保证与实际风环境的相似，为此专门研制了一种在保证平均风剖面相似的前提下，可使气流产生大湍流度的装置，简称湍流度调节器。通过对模拟边界层的平均风速，湍流度及风速谱的测量分析，证明与实际风区大风环境的风结构相当一致。为解决实     

多卜勒湍流检测

对湍流目标进行检测,是多卜勒效应在现代机载气象雷达中的应用。鉴于目前在新型机载气象雷达中普遍装备了湍流信号处理电路,本文就有关的湍流目标及其检测原理和方法作简要介绍。