NEW APPROACH TO OBTAIN SPACE-TIME CONSERVATION SCHEMES

Inordertoovercometheseverallimitationsofthetraditionalmetheds,anewnumericalmethodofspace-timeconservationelementandsolutionelement(CE/SE)forsolvingconser-vationlawswasdevelopedbyChang['j.Thismethoddifferssubstantiallyinbothconceptandmethedologyfromthewell-establishedmethodslsuchasfinitedifference,finiteelement,etc.,andithasmanynontraditionalfeatures.First,spaceandtimeareunifiedandtreatedonthesamefooting,andbytheintroductionofconservationelementandsolutionelement,bothlocalandglobalfluxconserv…     

基于声波有限元分析法的发动机进排气系统噪声的研究

汽车发动机进排气系统的噪声在发动机总噪声中占有重要分量，因此需要积极采取降噪措施。通过建立发动机进排气系统的理论模型，利用声波有限元分析法对发动机进排气系统的噪声特性作出预测，并将实际计算结果与实测值进行比较，结果表明声波有限元分析法能有效地预测不同结构的进排气系统的噪声特性。     

Simulations of pickup-ion acceleration at quasi-perpendicular shocks

We present results from hybrid simulations (kinetic ion/fluid electron) of the interaction of interstellar pickup ions with collisionless shocks. Since cross-field transport is unphysically suppressed in the one-dimensional geometry used here, an ad hoc scattering algorithm is used to model this effect. This is a necessary step to accelerate the pickup ions from their initial low energies at quasi-perpendicular shocks to the high energies which are often observed associated with traveling interplanetary shocks by Ulysses.     

Composition of anomalous cosmic rays and implications for the heliosphere

We use energy spectra of anomalous cosmic rays (ACRs) measured with the Cosmic Ray instrument on the Voyager 1 and 2 spacecraft during the period 1994/157-313 to determine several parameters of interest to heliospheric studies. We estimate that the strength of the solar wind termination shock is 2.42 (–0.08, +0.04). We determine the composition of ACRs by estimating their differential energy spectra at the shock and find the following abundance ratios: H/He = 5.6 (–0.5, ⁺0.6), C/He = 0.00048 ± 0.00011, N/He = 0.011 ± 0.001, O/He = 0.075 ± 0.006, and Ne/He = 0.0050 ± 0.0004. We correlate our observations with those of pickup ions to deduce that the long-term ionization rate of neutral nitrogen at 1 AU is 8.3 × 10^–7 s^–1 and that the charge-exchange cross section for neutral N and solar wind protons is 1.0 × 10^–15 cm² at 1.1 keV. We estimate that the neutral C/He ratio in the outer heliosphere is 1.8(–0.7, +0.9) × 10^–5. We also find that heavy ions are preferentially injected into the acceleration process at the termination shock.     

转动壳体行波振动的有限元分析方法

转动壳体由于离心力与哥氏力的影响 ,其振动频率随转速变化 ,并且同一振型对应两个不同频率的前、后行波。本文给出了用有限元法计算转动壳体的有限元公式 ,用 MSC/ NASTRAN的 DMAP语言编制了形成哥氏力矩阵与离心刚度矩阵的程序 ,并将计算结果与实验进行了对比     

跨声速翼型激波／边界层干扰被动控制的数值模拟计算

本文应用数值计算的方法着重研究了跨声速翼型开孔壁的减阻效果。计算采用了边界层与位流相互作用的模型,藉以了解开孔壁对激波强度及结构的影响和对边界层控制的效果。通过对NACA0012翼型的计算表明,本文采用的自然吹吸的开孔模型能够显著地削弱激波的强度,改善激波的结构,但会使粘性损失增加。在马赫数较小时,翼型开孔后总阻力会增加,而在大马赫数时,开孔翼型的减阻效果才表现出来。这种趋势是与实验结果相吻合的。     

不断发展的毫米波对抗技术

介绍了毫米波（MMW）技术在电子对抗中的应用，指出了毫米波技术的优势，分析了毫米波技术固有的抗干扰特点，叙述毫米波技术在应用中存在的问题和今后需采取的措施以及发展方向。     

双重加权实质无波动激波捕捉格式

本文构造了一种新的加权激波捕捉格式，命名为双重加权实质无波动(Double Weighted Essentially Non—Oscillatory，简称DWENO)格式。DWENO格式不需要引进最优权值，并且可以递推地达到任意高阶精度。文中给出了典型算例的计算结果，这些结果表明DWENO格式具有高于WENO格式的间断分辨率。     

楔—后掠柱激波干扰流场和热流的工程算法

本文针对航天飞机机翼前缘的简化模型,即楔-后掠柱模型,在大后掠、高超声速条件下,提供了一种计算柱体前缘激波干扰流场和热流的工程计算方法。在中国科技大学流体力学实验室的激波风洞中取得了激波干扰的流场显示结果。计算的结果与国内外实验数据的比较表明,这是一种有效的方法。     

低电离层中的行星波扰动及其垂直传播

根据武昌电离层观象台接收的罗兰－Ｃ ＬＦ无线电波的传播资料，利用小波分析方法，研究了１９８５年和１９８６年冬季的低电离层中的行星波扰动及其垂直传播。结果表明：（１）两个冬季中，在７５ｋｍ和９５ｋｍ高度上，均存在明显的行星波扰动，主要成分是５－１０天和１０－２０天周期的波动，扰动幅度随高度增长，但增长值小于理论增长值；（２）在７５ｋｍ高度上的扰动和９５ｋｍ高度上的扰动，具有十分相似的扰动形态。根据行