轴对称坐标系下含曲率的水平集方程在非结构网格上的数值方法

为了在三角形和四边形网格上采用水平集方法模拟轴对称爆轰波阵面与曲率相关的运动,假设爆轰波阵面的法向速度是曲率的线性函数,通过坐标变换得到了轴对称坐标系下的水平集方程。水平集方程的曲率无关项采用正格式离散,曲率项采用伽辽金等参有限元方法空间离散,时间离散采用半隐格式。算例表明,在轴对称三角形网格和四边形网格上,含曲率的水平集方程的离散格式为强一阶精度。给出了三角形和四边形混合网格上不光滑界面以曲率收缩的运动过程,收缩过程未出现不稳定现象。多个爆轰波阵面相互作用的算例说明本文的格式可有效地模拟曲率相关的爆轰波的相互作用问题     

前向多翼叶轮流动分析及出口滑移的计算

本文分析了离心风机前向多翼叶轮内的流动特性,计算了跨叶片面内的理想流场和湍流边界层.用三次样条平滑和旋转坐标变换方法解决了用流线曲率法数值解大曲率流场时的收敛问题;用考虑旋转和曲率对流动结构影响的Richardson数修正理想流场.提出了一种予测叶片边界层分离及流动滑移的方法.     

弹性板边界元中计算边界高阶导数的渐近收敛积分方程

本文针对板弯曲边界元方法中计算边界曲率等高阶导数项时边界积分方程中出现的高阶奇异积分项,通过对未知挠曲函数作渐近展开并加以适当摄动,获得了渐近收敛的边界积分方程。采用这一方法计算板边界上的曲率分布,获得了满意的数值结果。     

基于SPH方法的表面张力修正算法及其应用

针对传统SPEI方法中基于CSF模型的表面张力算法,在计算边界、尖角等粒子缺失部位的曲率时存在偏差较大,且粒子秩序较差,对大变形问题表面张力计算精度较低的问题,在Morris提出的表面张力SPH方法基础上,通过引入CSPM方法对边界法向的计算和曲率的计算进行修正,得到了表面张力修正方程组.应用本文方法模拟了水溶液中初始...     

用白光光源获得斜率和曲率的干涉法

本文介绍了用白光光源和衍射光栅作为基本光学元件,在滤波光路中获得物面斜率和曲率条纹的实验原理和方法.讨论了该方法的一些基本性质的和特点.     

曲率和旋转对离心叶轮叶片上湍流边界层的影响

本文将曲率和旋转项引入二维湍流边界层动量方程中,导出动量损失厚度的积分关系式。分析了曲率和旋转对湍流结构的直接影响,并提出壁面速度分布律的修正表达式。     

含裂纹一维欧拉梁的裂纹无效位置分析

基于集中柔度模型,建立了含裂纹一维欧拉梁的频率方程,以此为基础探讨了裂纹无效位置的求解方法。数值计算结果显示,裂纹无效位置和位移振型节点并不一致。进一步的理论推导证明裂纹无效位置就是曲率模态振型的零点位置,从曲率和力学性能基本参数的关系分析,这一结论是合理的。本文结论对于实验、测试方案设计有指导意义。     

磁场力及膜曲率对磁敏感薄膜-基底界面黏附性能的影响与调控

界面黏附和脱黏的可调控在攀爬装置、黏附开关、机械抓手等方面具有重要的应用需求. 针对磁敏感薄膜-基底界面, 开展了薄膜初始曲率及外加磁场对界面黏附性能影响机制的研究. 首先实验制备了具有初始曲率的磁敏感薄膜, 分别开展了具有初始曲率的磁敏感薄膜-基底界面撕脱实验及理论研究, 研究了薄膜初始曲率、弯曲刚度和外加磁场强度对界面黏附性能的影响规律. 实验和理论结果一致表明: 具有初始曲率的磁敏感薄膜-基底界面黏附力随薄膜初始曲率的增大而减小, 而外加磁场能够有效提高界面黏附力;相比于初始零曲率薄膜-基底界面稳态撕脱力与薄膜弯曲刚度无关, 薄膜弯曲刚度减弱了具有初始曲率薄膜-基底界面的稳态撕脱力. 进一步从能量角度分析了界面等效黏附性能, 揭示了薄膜弯曲能、磁场势能、界面黏附能的相互竞争机制. 最后, 基于本文的实验及理论结果, 提出了一种磁场和薄膜初始曲率协同调控的简易机械抓手, 可连续实现物体的拾取、搬运和释放功能. 本文结果不仅有助于理解多场调控的界面可逆黏附机制, 对界面黏附可控的功能器件设计亦提供了一种新方法.      

振型归一化对梁结构柔度曲率损伤指标的影响

结构柔度矩阵需由质量矩阵归一化振型获得,而质量矩阵归一化振型难以直接测得,限制了柔度曲率类损伤指标的应用。为分析振型归一化方法对梁结构柔度曲率类损伤指标的影响,根据梁结构的刚度、弯矩和位移曲率的关系,建立了均布荷载作用下结构损伤前后位移曲率与损伤程度的理论表达式,实现定量分析均匀荷载面曲率结构损伤程度。提出P-范数振型归一化方法,通过均匀荷载面曲率指标推导了振型质量矩阵归一化系数差x_α与损伤程度的关系。以三跨连续梁算例对理论进行了验证,结果表明,损伤程度定量指标效果良好,不同P-范数振型归一化方法下,损伤程度的偏差可由2x_α估算;2-范数振型归一化方法的损伤识别结果与质量矩阵振型归一化结果最接近,故当无法获得质量矩阵归一化振型时,可采用2-范数归一化振型代替。     

波形弹簧的非线性计算模型

本文应用Ritz法导出了波形弹簧的载荷与变形之间的非线性关系。在推导过程中,同时考虑了弹簧周向曲率、波形曲率、附加弯曲的影响。经过验证,本文计算结果与实测结果相当接近。     

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.