管间距对串联双圆柱表面压力分布特性的影响研究

对气液两相流中串联双圆柱表面压力分布特性进行了系统的实验研究 ,着重讨论了管间距的影响。实验双圆柱的间距比分别为 2 .0 ,3.0 ,4.0 ;截面含气率的范围为0～ 0 .3;来流雷诺数的范围为 3× 1 0 4 ～ 8× 1 0 4 。     

A class of parabolic hemivariational inequalities

ＩｎｔｒｏｄｕｃｔｉｏｎＬｅｔΩｂｅａｎｏｐｅｎｂｏｕｎｄｅｄｄｏｍａｉｎｏｆＲＮ,Ｑ=Ω× (0 ,Ｔ) ,0 <Ｔ<∞ ,2 ≤ｐ<∞ ,(1 /ｐ) (1 /ｐ′) =1 .Ｆｏｒｃｏｎｖｅｎｉｅｎｃｅ ,ｗｅｓｅｔＶ =Ｗ1,ｐ0 (Ω) ,Ｖ′=Ｗ- 1,ｐ′(Ω)ｉｎｔｈｅｓｅｑｕｅｌ.ＴｈｅｎＶｉｓａｒｅａｌｒｅｆｌｅｘｉｖｅＢａｎａｃｈｓｐａｃｅｄｅｎｓｅｌｙａｎｄｃｏｍｐａｃｔｌｙｉｍｂｅｄｄｅｄｉｎｔｏＬｐ(Ω) .ＴｈｅｎｏｒｍｏｆａｎｙＢａｎａｃｈｓｐａｃｅＢｉｓｄｅｎｏｔｅｄｂｙ‖·‖Ｂ.ＴｈｅｐａｉｒｉｎｇｂｅｔｗｅｅｎＢａｎ…     

环氧树脂表面金属离子注入改性层的摩擦学性能研究

以 3种剂量 (2× 10 1 5 ions/cm2 、1× 10 1 6 ions/cm2 及 1× 10 1 7ions/cm2 )分别对环氧树脂进行 Al、Ti和 Fe离子注入处理 ,采用 MM- 2 0 0型摩擦磨损试验机考察了注入改性层的摩擦学性能 ,采用傅立叶变换红外光谱仪分析离子注入前后环氧树脂表面基团及其键合方式 .结果表明 :3种金属离子注入处理后环氧树脂的耐磨性均显著提高 ,摩擦系数降低 ;其中 Al离子注入处理的摩擦学改性效果最好 ;对应于环氧树脂最小磨损体积损失的不同金属离子的注入剂量亦不同 .红外光谱分析结果表明 :经 Al离子注入后 ,环氧树脂表面保持微量的吸附水 ;同时其表面发生了脱氢及氧化等作用 ,形成了新的化学基团 ,且其立体网状交联程度提高 ,这使得离子注入处理后环氧树脂的减摩耐磨性能得以明显改善 .     

Difference scheme and numerical simulation based on mixed finite element method for natural convection problem

ntroductionLetΩ R2 beaboundeddomain .Weconsiderthefollowingnon_stationarynaturalconvectionproblem :Problem (Ⅰ )　Findu =(u1,u2 ) ,p ,andTsuchthat,foranyt1>0 ,ut- μΔu +(u· )u + p=λjT　　 ((x ,y ,t) ∈Ω× (0 ,t1) ) ,divu =0　　　　　　　　　 ((x ,y,t) ∈Ω× (0 ,t1) ) ,Tt-ΔT +λu· T =0　　 ((x,y,t) ∈Ω× (0 ,t1) ) ,u =0 ,T =0　　　　　　 ((x,y,t)∈ Ω× (0 ,t1) ) ,u(x ,y ,0 ) =0 ,　T(x,y,0 ) =f(x,y)　　 ((x,y) ∈Ω) ,whereuisthefluidvelocityvectorfield ,pthepressurefield ,Tthet…     

基于稀薄效应的微气体径向轴承稳态性能

针对微气体轴承给出参考努森数的定义,根据空气不同温度时的黏度,得到参考努森数的分布范围;考虑气体稀薄效应,给出基于Burgdorfer一阶滑移速度边界的微气体径向轴承润滑Reynolds方程的修正形式; 采用有限差分法求解修正的Reynolds方程,得到不同参考努森数$Kn_0$, 轴承数以及轴颈偏心率情况下轴承的压力分布、无量纲承载能力及偏位角. 数值分析表明:随气体稀薄程度的增强,气体径向轴承的压力明显降低,无量纲承载力降低,而轴承偏位角增大. 当偏心率小于0.6时,轴承偏位角变化平缓,受$Kn_0$数的影响不明显. 当轴承数较小时,气体稀薄程度对轴承的无量纲承载力、偏位角影响较小.      

油管的疲劳强度分析

疲劳断裂是油管失效的一种形式 ,本文针对抽油机井常用油管 (J5 5 ,2 1/ 2″)在循环载荷作用下的疲劳断裂问题进行了理论与实验研究。在实测油管载荷谱与应变谱的基础上应用弹塑性有限元法计算油管螺纹内的应力应变场 ,并进行了有关的疲劳实验 ,以得到油管的疲劳强度。油管内第一啮合齿齿根处应力应变最大 ,应力已经达到屈服阶段 ,油管是在高应力应变水平和低应力应变幅状态下工作。当油管内的应力应变进入强化段εeq >1 0 - 2 ε,塑性应变幅超过 4× 1 0 - 5ε时 ,油管就会发生疲劳断裂     

BLOCK H-MATRICES AND SPECTRUM OF BLOCK MATRICES

ＩｎｔｒｏｄｕｃｔｉｏｎＬｅｔＡ ∈Ｃｎ ,ｎ,ａｎｄｂｅｐａｒｔｉｔｉｏｎｅｄａｓｆｏｌｌｏｗｓ:Ａ =Ａ11Ａ12 …Ａ1ｋＡ2 1Ａ2 2 …Ａ2ｋ…………Ａｋ1Ａｋ2 …Ａｋｋ,( 1 )ｗｈｅｒｅＡｉｉ∈Ｃｎｉ,ｎｉ,1 ≤ｉ≤ｋ ,∑ｋｉ=1ｎｉ=ｎ ,Ａｉｉ( 1 ≤ｉ≤ｋ)ａｒｅｎｏｎｓｉｎｇｕｌａｒ.Ｉｎｍｏｓｔｐｒａｃｔｉｃａｌａｐｐｌｉｃａｔｉｏｎｓ,ｔｈｅｍａｔｒｉｃｅｓＡｉｊａｒｅｓｐａｒｓｅａｎｄｍａｎｙｏｆｔｈｅｂｌｏｃｋｍａｔｒｉｃｅｓａｒｅｚｅｒｏ .Ｄｅｆｉｎｉｔｉｏｎ 1　ＩｆＢ =(ｂｉｊ) =(‖Ａｉｊ‖ ) ｋ×…     

偏心迷宫密封动静特性研究

建立了不同偏心状态下迷宫密封三维数值分析模型,应用基于微元理论的密封动力特性系数识别方法计算密封静态和动态特性. 结果表明:转子偏心会降低密封抑制流体泄漏的效果;密封腔内周向压力高点随偏心率增大逐渐偏离最小间隙处. 低偏心率(≤ 0.5)下,静态直接刚度K与静态交叉刚度k变化较小,高偏心率(> 0.5)下K和k的绝对值减小. 随着偏心率的增大,密封小间隙侧流动黏性效应增强是产生负静态直接刚度的主要原因. 密封偏心涡动时,低偏心率(< 0.6)下刚度和阻尼系数变化较小,随偏心率和涡动频率的升高直接刚度逐渐变为负值;随偏心率的增大,交叉刚度在正交两个方向上大小不再相等,有效阻尼降低,高偏心率(≥ 0.6)下有效阻尼受偏心率影响更显著.      

The Space-Time Finite Element Method for Parabolic Problems

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｅｑｕａｔｉｏｎｓｗｅｃｏｎｓｉｄｅｒｅｄａｒｅａｓｆｏｌｌｏｗｓｕｔ-Δｕ =ｆ(ｕ) ,　　Ω× [0 ,Ｔ] ,ｕ｜ Ω =0 ,　　　　　 Ω× [0 ,Ｔ] ,ｕ( · ,0 ) =ｕ0 ,Ω ,( 1 )ｗｈｅｒｅΩ ∈Ｒ2 ,ｔｈｅｆｕｎｃｔｉｏｎｆ(ｕ)ｓａｔｉｓｆｉｅｓ｜ｆ(ｕ)｜≤ｃ｜ｕ｜ ,　　 ｕ∈Ｃ(Ω) . ( 2 )Ａｎｄｆ(ｕ)ｉｓＬｉｐｓｃｈｉｔｚｃｏｎｔｉｎｕｏｕｓ,ｉ.ｅ.ｉｔｓａｔｉｓｆｉｅｓ｜ｆ(ｕ) -ｆ(ｖ) ｜≤Ｌ｜ｕ-ｖ｜ ,　　 ｕ ,ｖ∈Ｃ(Ω) ,( 3 )ｗｈｅｒｅＬｉｓＬｉｐｓｃｈｉｔｚｃｏｎｓｔａ…     

微尺度圆管内气体流量的实验测量

以氮气和氦气为工作介质,研究了微尺度(φ=17.6μm,17.9μm)圆管内压力驱动的气体流动,测量了在不同进出口压力下的流量,并与计算值进行了比较.结果表明,即使对于极低Mach数(M=0.003～0.03)流动,其可压缩性仍十分明显,它来源于微尺度效应.在本文的实验参数下,Kundsen数范围为3×10-3～7×10-3,表面滑移不明显,稀薄气体效应可以忽略.     

The 7th International Conference on Fluid Mechanics May 24-27,2015,Qingdao,China

正http://www.icfm7.org First Announcement and Call for PapersThe objective of International Conference on Fluid Mechanics(ICFM)is to provide a forum for researchers to exchange new ideas and recent advances in the fields of theoretical,experimental,computational Fluid Mechanics as well as interdisciplinary subjects.It was successfully convened by the Chinese Society of Theoretical and Applied Mechanics(CSTAM)in Beijing(1987,     

INFORMATION FOR CONTRIBUTORS

Contributions： The Journal, Acta Mechanica Solida Sinica, is pleased to receive papers from engineers and scientists working in various aspects of solid mechanics. All contributions are subject to critical review prior to acceptance and publication.     

Preface

This special issue of PARTICUOLOGY is devoted to the first UK-China Particle Technology Forum taking place in Leeds, UK, on 1-3 April 2007. The forum was initiated by a number of UK and Chinese leading academics and organised by the University of Leeds in collaboration with Chinese Society of Particuology, Particle Technology Subject Group （PTSG） of the Institution of Chemical Engineers （IChemE）, Particle Characterisation Interest Group （PCIG） of the Royal Society of Chemistry （RSC） and International Fine Particle Research Institute （IFPRI）. The forum was supported financially by the Engineering and Physics Sciences Research Council （EPSRC） of United Kingdom,     

基于鲁棒滤波的捷联导引头视线角速度估计方法

针对捷联导引头无法直接获取视线角速度等信息的问题,研究了鲁棒滤波在大气层外飞行器捷联导引头视线角速度估计中的应用。为了建立非线性滤波估计模型,考虑目标视线角速度的慢变特性,采用一阶马尔科夫模型建立了状态方程;推导了视线角速度的解耦模型,并建立了量测方程;考虑到实际应用中存在系统噪声统计特性失准的问题,基于Huber-Based鲁棒滤波方法,设计了视线角速度滤波器,并完成了基于Huber-Based滤波方法和扩展卡尔曼滤波方法的数学仿真。仿真结果表明Huber-Based滤波方法的视线角、视线角速度及视线角加速度估计精度分别达到0.1140'、0.1423'/s、0.0203'/s2,而扩展卡尔曼滤波方法的视线角、视线角速度及视线角加速度估计精度仅分别为0.6577'、0.6415'/s、0.0979'/s~2。仿真结果证明了该方法可以有效地估计出相对视线角速度等信息,并且在非高斯噪声的条件下,依然可获得较高的估计精度,具有一定的鲁棒性。     

Guide for authors

正Each of the sections below provides essential information for authors.We recommend that you take the time to read them before submitting a contribution to Acta Mechanica Sinica.We hope our guide to authors may help you navigate to the appropriate section.How to prepare a submission This document provides an outline of the editorial process involved in publishing a scientific paper in Acta Mechanica     

Use specification of multiscale materials for life spanned over macro-, micro-, nano-, and pico-scale

Multiscale material intends to enhance the strength and life of mechanical systems by matching the transmitted spatiotemporal energy distribution to the constituents at the different scale, say—macro, micro, nano, and pico,—, depending on the needs. Lower scale entities are, particularly, critical to small size systems. Large structures are less sensitive to microscopic effects. Scale shifting laws will be developed for relating test data from nano-, micro-, and macro-specimens. The benefit of reinforcement at the lower scale constituents needs to be justified at the macroscopic scale. Filling the void and space in regions of high energy density is considered.Material inhomogeneity interacts with specimen size. Their combined effect is non-equilibrium. Energy exchange between the environment and specimen becomes increasingly more significant as the specimen size is reduced. Perturbation of the operational conditions can further aggravate the situation. Scale transitional functions and/or f_j/j+1 are introduced to quantify these characteristics. They are represented, respectively, by , and (f_mi/ma,f_na/mi,f_pi/na). The abbreviations pi, na, mi, and ma refer to pico, nano, micro and macro.Local damage is assumed to initiate at a small scale, grows to a larger scale, and terminate at an even larger scale. The mechanism of energy absorption and dissipation will be introduced to develop a consistent book keeping system. Compaction of mass density for constituents of size 10⁻¹², 10⁻⁹, 10⁻⁶, 10⁻³ m, will be considered. Energy dissipation at all scales must be accounted for. Dissipations at the smaller scale must not only be included but they must abide by the same physical and mathematical interpretation, in order to avoid inconsistencies when making connections with those at the larger scale where dissipations are eminent.Three fundamental Problems I, II, and III are stated. They correspond to the commonly used service conditions. Reference is made to a Representative Tip (RT), the location where energy absorption and dissipation takes place. The RT can be a crack tip or a particle. At the larger size scales, RT can refer to a region. Scale shifting of results from the very small to the very large is needed to identify the benefit of using multiscale materials.