正交正放类网架结构固有频率及屈曲分析的样条Galerkin法

本文根据考虑剪切变形的具有３个广州位移的平板弯曲理论，把正交正放类平板网架假设为由三层不同性质材料组成的各向正交异性夹层析。文中双５次Ｂ样条函数中的一组基底作为试函数，用加权残值法中的离散型Ｇａｌｅｒｋｉｎ法，导出了这类网架的频率方程屈曲方程。数值算例表明，这种方法是方便而精确的。     

网架结构拟夹层板法的有限元验证

用拟夹层板法和有限元法对网架结构进行分析,对三类屋面网架（正放四角锥网架、两向正交正放网架和正放抽空四角锥网架）进行了均布荷载、局部荷载（半跨均布荷载）作用下的静力分析以及固有振动分析,对三类竖向承重网架墙体进行了稳定性分析。通过与有限元法分析结果的对比,表明了拟夹层板法作为一种简化的计算方法,其精度是比较高的,绝大多数的误差都小于5％,是可以直接用于工程结构设计的一种有效方法。此外,拟夹层板法还可作为一种在宏观上检验有限元建模正确与否的实用方法。     

基于刚度分解法的输电铁塔结构杆件力分析

提出了输电铁塔应用刚度分解法的分析过程,利用刚度分解法分别建立了铁塔各段等效抗弯刚度矩阵和等效抗剪刚度矩阵代替空间桁架分析法中的总刚度矩阵,求得各段铁塔杆件受力。采用迭代方法求得全塔结构受力,使计算过程简化,实例计算结果与计算机计算结果吻合很好,可为输电铁塔结构设计提供参考。     

正交正放类网架结构固有频率及屈曲分析的样条Galerkin法

本文根据考虑剪切变形的具有３个广义位移的平板弯曲理论，把正交正放类平板网架假设为由三层不同性质材料组成的各向正交异性夹层板。文中以双５次Ｂ样条函数中的一组基底作为试函数，用加权残值法中的离散型Ｇａｌｅｒｋｉｎ法，导出了这类网架的频率方程和屈曲方程。数值算例表明，这种方法是方便而精确的。     

平板网架结构分析的超级有限元法

本文给出一种二维矩形超级单元，用以分析平板网架结构、其做法是将大型平板网架结构离散成一系列矩形超级单元，考虑弯曲，剪切、挤压、拉压、翘曲等多种非经典变形效应，采用构件自由度向超级元自由度的转换把大型多构件问题的求解变为二维问题的求解，可大大减少未知量，又能保证精度，并可方便地与一般有限元软件连接。     

桁架网架结构分析的一种非经典综合离散法

本文提出一种基于非经典变形理论的综合离散法，并用于网架结构的力学分析。文末给出了平面桁架稳定分析和平板网架静力分析的数值算例。表明了本文所提出的新方法的有效性和简捷性。     

桁架网架结构分析的一种非经典综合离散法

本文提出一种基于非经典变形理论的综合离散法，并用于网架结构的力学分析．文末给出了平面桁架稳定分析和平板网架静力分析的数值算例．表明了本文所提出的新方法的有效性和简捷性．     

平板网架结构分析的超级条元法

本文针对复杂杆系结构提出一种超级有限条的分析方法。这种方法基于半连续半离散思想将各杆件结点自由度归结为整体结构自由度；进一步又将整体自由度简化为少数结线自由度上机计算。这将为复杂结构体系开拓一条简便、实用的工程分析途径。     

基于SMSA算法的网架结构优化设计

提出了应用SMSA(simulated simplex-annealing, 单纯形模拟退火)算法对网架结构进行优化设计,并对算法中参数的选 择进行了探讨,算例分析表明了单纯形模拟退火算法应用在网架结构优化中的可行性和有效 性.     

Relationship between space charge and effective pore size of nanoporous electrode in electric double-layer capacitor

The space-charge distributions of electric double-layer capacitors (EDLCs), which are energy storage devices, were examined with the pulsed electroacoustic (PEA) method. It was found that the experimental results could be influenced by the reflection and penetration of sound waves when the space-charge distributions of EDLCs were measured with the PEA method. This is because EDLCs have a five-layer structure consisting of three materials (aluminum, cellulose, and activated carbon). We calculated the reflect...     

A nodal Godunov method for Lagrangian shock hydrodynamics on unstructured tetrahedral grids

We present a nodal Godunov method for Lagrangian shock hydrodynamics. The method is designed to operate on three‐dimensional unstructured grids composed of tetrahedral cells. A node‐centered finite element formulation avoids mesh stiffness, and an approximate Riemann solver in the fluid reference frame ensures a stable, upwind formulation. This choice leads to a non‐zero mass flux between control volumes, even though the mesh moves at the fluid velocity, but eliminates volume errors that arise due to the difference between the fluid velocity and the contact wave speed. A monotone piecewise linear reconstruction of primitive variables is used to compute interface unknowns and recover second‐order accuracy. The scheme has been tested on a variety of standard test problems and exhibits first‐order accuracy on shock problems and second‐order accuracy on smooth flows using meshes of up to O(10⁶) tetrahedra. Copyright © 2014 John Wiley & Sons, Ltd.     

Splitting method for two-dimensional phreatic flow equation

ＳＰＬＩＴＴＩＮＧＭＥＴＨＯＤＦＯＲＴＷＯ－ＤＩＭＥＮＳＩＯＮＡＬＰＨＲＥＡＴＩＣＦＬＯＷＥＱＵＡＴＩＯＮＸｕＳｈａｏｈｕｉ（徐绍辉）ＺｈｕＸｕｅｙｕ（朱学愚）ＺｈｕＧｕｏｒｏｎｇ（朱国荣）（ＲｅｃｅｉｖｅｄＭａｙ１１,１９９５;Ｃｏｍｍｕｎｉｃａｔ...     

多自由度参激系统稳定性分析的数值解法

现有参激系统的动力稳定性问题研究主要集中在主不稳定区域上。为获得组合不稳定区域,基于Floquet方法,采用Bolotin方法在不同周期数下设解形式,结合特征值分析法得到确定多自由度参激系统动力不稳定区域的数值解法。对一个两自由度受周期轴向力的旋转轴系算例的稳定性分析,发现通过增加设解近似项数可获得高阶不稳定区域,且各阶不稳定区域边界随近似次数的增加逐渐趋于稳定,此外,增大阻尼可使各不稳定区域边界变得更加平滑。本文方法可用于一般多自由度周期参激阻尼系统,是一种简明易操作的直接数值解法。     

变截面悬臂梁的刚度叠加法

利用梁的弯曲刚度与位移成反比的关系, 可较为方便地计算变截面悬臂梁端截面的位移．该 方法是区别于载荷叠加法和逐段变形效应叠加法的叠加方法．     

空间杆系与叠层板组合结构的非线性稳定分析

本文用非线性有限元法研究一种空间杆系与复合材料叠层板组合结构的非线性稳定问题。将杆系离散成空间梁柱单元，将复合材料叠层板离散成复合材料叠层板单元，并考虑了几何非线性和板的成层正交各向异性性质。为了获得较高的计算效率并顺利通过稳定临界点，求解非线性平衡方程采用了变增量步长和柱面弧长法迭代策略。在考证了程序的正确性之后，具体分析了几个工程模型，得出了于工程设计有益的结论。     

基于谱元法的空间刚架动力学特性分析

以空间刚架结构为研究对象,应用谱元法研究其动力学特性,依次推导出杆、轴和铁木辛柯梁的动力学刚度阵,进而得到空间刚架的动力学刚度阵和频域响应的理论方程,拓展了谱元法应用范围。编程计算获得空间刚架的固有频率和点的谐响应曲线,与有限元分析相比较,进一步得到载荷下的瞬态响应。研究表明,谱元法在刚架结构的动力学特性分析中,比有限元方法高效高精度,更适宜解决中高频振动问题。     

A geometry‐based level set method for curvilinear overset grids with application to ship hydrodynamics

In a previous work (Int. J. Numer. Meth. Fluids 2007; 55 :867–897), we presented a two‐phase level set method to simulate air/water turbulent flows using curvilinear body‐fitted grids for ship hydrodynamics problems. This two‐phase level set method explicitly enforces jump conditions across the interface, thus resulting in a fully coupled representation of the air/water flow. Though the method works well with multiblock curvilinear grids, severe robustness problems were found when attempting to use it with overset grids. The problem was tracked to small unphysical level set discontinuities across the overset grids with large differences in curvature. Though negligible for single‐phase approaches, the problem magnifies with large density differences between the phases, causing computation failures. In this paper, we present a geometry‐based level set method for curvilinear overset grids that overcomes these difficulties. The level set transport and reinitialization equations are not discretized along grid coordinates, but along the upwind streamline and level set gradient directions, respectively. The method is essentially an unstructured approach that is transparent to the differences between overset grids, but still the discretization is under the framework of a finite differences approach. As a result, significant improvements in robustness and to a less extent in accuracy are achieved for the level set function interpolation between overset grids, especially with big differences in grid curvature. Example tests are shown for the case of bow breaking waves around the surface combatant model David Taylor Model Basin (DTMB) 5415 and for the steady‐state ONR Tumblehome DTMB 5613 with superstructure. In the first case, the results are compared against experimental data available and in the second against results of a semi‐coupled method. Copyright © 2011 John Wiley & Sons, Ltd.