Discontinuity-capturing finite element computation of unsteady flow with adaptive unstructured mesh

A discontinuity-capturing scheme of finite element method (FEM) is proposed. The unstructured-grid technique combined with a new type of adaptive mesh approach is developed for both compressible and incompressible unsteady flows, which exhibits the capability of capturing the shock waves and/or thin shear layers accurately in an unsteady viscous flow at high Reynolds number. In particular, a new testing variable, i.e., the disturbed kinetic energyE, is suggested and used in the adaptive mesh computation, which is universally applicable to the capturing of both shock waves and shear layers in the inviscid flow and viscous flow at high Reynolds number. Based on several calculated examples, this approach has been proved to be effective and efficient for the calculations of compressible and incompressible flows. The project supported by the National Natural Science Foundation of China (10125210), the Hundred-Talent Programme of the Chinese Academy of Sciences and the Innovation Project of the Chinese Academy of Sciences (KJCX-SW-L04, KJCX2-SW-L2)     

考虑约束扭转的薄壁梁单元刚度矩阵

推导了薄壁空间梁单元刚度矩阵 ,考虑了双向弯曲及截面约束扭转对杆件轴向变形的影响 ;计算了截面的翘曲变形 ,以及二次剪应力对翘曲变形的影响 ,可适用于任意截面 (包括开口、闭口和混合剖面 )的薄壁杆件。计算结果表明 ,考虑约束扭转的薄壁梁单元刚度矩阵有相当好的精确度 ,可以用于薄壁杆件的静动力分析。     

关于测试物体转动惯量方法的探讨

<正> 复杂形体转动惯量的测定法一般有:落体法;复摆法;扭振法.它们都以时间为测定量,再由理论公式求出转动惯量.落体法受阻尼影响较大,实验表明,测量误差>>5%.复摆法要求小摆幅(≤5°),给测试带来不便;如摆幅太大(60°),测量误差也>>5%(46%).扭振法测试转动惯量,阻尼影响很小,振幅影响也远不如复摆法,只要参数选择得当,可保证误差≤5%.     

新月形尾鳍推进的流体力学分析

本文运用三维波动柔板位流模型与最佳游动方式理论,继续分析了新月形鱼尾的推进性能,从而实现了对鱼类三种主要推进模式的较为系统的研究。理论分析表明,高速海洋动物所具有的大展弦比、尖叶梢、中等后掠的新月形尾能获得接近于最佳的推进性能。对海豚游动特性的理论估算也给出了令人满意的结果。     

均匀来流中横向振动圆柱近迹涡结构的数值模拟

从涡量流函数形式的N-S方程出发,在不同的振动频率、振幅及Re数下数值研究了均匀来流中横向振动圆柱粘性统流的涡脱泻现象。着重探讨了近迹复杂的涡结构及其非定常演化过程,以及它们对物体受力特性的影响,并首次成功地模拟了近年来实验研究中所发现的一些重要的流动现象,如相位“开关”现象(phase switch phenomena)及复杂涡结构(complex vortex structure),等等。通过数值模拟,不仅能够再现实验研究中所发现的一些重要的流动现象,还可进一步预示某些新的流动现象,使数值计算起到与实验研究相辅相成的作用。     

旋转圆管湍流的大涡模拟数值研究

采用大涡模拟（LES）方法,并结合动力学亚格子尺度应力（SGS）模型,通过数值求解柱坐标系下的滤波Navier-Stokes方程,研究了绕管轴旋转圆管内的湍流流动特性.为验证计算的可靠性,以及动力学SGS模型对于旋转湍流的适用性,将大涡模拟计算所得的结果,与相应的直接模拟（DNS）结果和实验数据进行了对比验证,吻合良好.进一步对旋转圆管湍流的物理机理进行了探讨,研究了湍流特性随旋转速率的变化规律.当旋转速率增加时,湍流流动有层流化的发展趋势.基于湍动能变化的关系,分析了旋转效应对湍流脉动生成的抑制作用.     

基于三联苯-2,2′,4,4′-四羧酸的二维双层锌(Ⅱ)配位聚合物的水热合成、晶体结构及荧光性质(英文)

采用水热法合成了一个配合物[Zn2(tpta)0.5(H2tpta)(dpe)(H2O)2]n(1)(H4tpta=三联苯-2,2′,4,4′-四羧酸,dpe=1,2-二(4-吡啶基)乙烯),并用元素分析、红外光谱、X-射线单晶衍射、热重分析和荧光分析对其进行了表征。晶体结构分析表明:该配合物属于三斜晶系,空间群为P1,a=1.017 4(2)nm,b=1.034 1(2)nm,c=1.883 1(4)nm,α=96.147(4)°,β=96.866(4)°,γ=98.023(4)°,V=1.932 2(7)nm3,Z=2,Dc=1.640 g·cm-3,μ=1.320 mm-1,F(000)=974,R1=0.066 9,wR2=0.133 2(I2σ(I));具有环状双核锌(Ⅱ)连接的二维双层结构,双层之间又进一步通过O-H…O氢键组装成三维超分子结构。此外,该配合物具有较好的热稳定性和发光性能。     

共沉淀-连续微反应法制备Fe_3O_4纳米粒子

采用共沉淀-连续微反应法制备了Fe3O4纳米粒子(1),其结构和形貌经XRD和TEM表征。1具有很好的尖晶石结构,形貌均一,分散性好,尺寸分布窄,粒径15 nm~20 nm。磁性测量结果表明,1具有超顺磁性,饱和磁化强度为62.24 emu·g-1。     

Synthesis and Characterization of a New 2D Ca(Ⅱ) Coordination Polymer Containing 1D Calcium-oxygen Chains

A new 2D Ca(Ⅱ) coordination polymer, [Ca(H2btc)(H2O)2]n(1, H4 btc = biphenyl-3,3',5,5'-tetracarboxylic acid), has been synthesized using the hydrothermal method and characterized by single-crystal X-ray diffraction, elemental analysis, IR, thermogravimetric analysis, and photoluminescent analysis. Complex 1 crystallizes in the monoclinic system, space group C2/c with a = 17.5676(15), b = 11.4496(8), c = 7.6197(8)A, β = 102.787(2)o, V = 1494.6(2) A3, Z = 4, D3 c = 1.797 Mg·m-, μ = 0.483 mm-1, F(000) = 832, the final R = 0.0348 and wR = 0.0915 for 1521 observed reflections with I 2σ(I). Complex 1 has a 2D network containing 1D calcium-oxygen chains. These 2D networks are further connected by O–H···O hydrogen bonding interactions to generate a 3D supramolecular structure.