An algebraic factorisation scheme for spectral element solution of incompressible flow and scalar transport

A spectral element algorithm for solution of the unsteady incompressible Navier–Stokes and scalar (species/heat) transport equations is developed using the algebraic factorisation scheme. The new algorithm utilises Nth order Gauss–Lobatto–Legendre points for velocity and the scalar, while (N-2)th order Gauss–Legendre points are used for pressure. As a result, the algorithm does not require inter-element continuity for pressure and pressure boundary conditions on solid surfaces. Implementations of the algorithm are performed for conforming and non-conforming grids. The latter is accomplished using both the point-wise matching and integral projection methods, and applied for grids with both polynomial and geometric non-conformities. Code validation cases include the unsteady scalar convection equation, and Kovasznay flow in two- and three-dimensional domains. Using cases with analytical solutions, the algorithm is shown to achieve spectral accuracy in space and second-order accuracy in time. The results for the Boussinesq approximation for buoyancy-driven flows, and the species mixing in a continuous flow micro-mixer are also included as examples of applications that require long-time integration of the scalar transport equations.     

EXPERIMENTAL RESEARCH OF THE WHOLE TENSILE CURVE FOR BITUMINOUS MORTAR

细观尺度上, 沥青混合料是由沥青胶浆、粗骨料和孔隙等构成的多相复合材料, 而沥青胶浆的力学参数为沥青混合料进行细观尺度研究的重要部分, 对抗拉强度有着决定性的影响. 本文通过设计制作加载夹具针对不同温度和不同加载速率的条件, 对9 组试件进行拉伸试验, 得到沥青胶浆拉伸全曲线. 通过对沥青胶浆拉伸全曲线的研究和计算, 确定了沥青胶浆的最大破坏应力σ_max、刚度K_nn 和破坏位移U, 这些参数为采用粘聚带本构模型模拟沥青混合料的开裂行为提供了力学参数.     

内衬涂塑预应力钢筒混凝土管应力分析

传统预应力钢筒混凝土管(prestressed concrete cylinder pipe,PCCP)容易开裂、预应力丝锈蚀而爆管失效.提出了耐腐蚀内衬涂塑钢筒预应力混凝土管(prestressed concrete cylinder pipe with plastic,PCCP-P),建立了PCCP-P线弹性轴对称分层圆筒平面应变模型,考虑预应力引起的内部径向压力,针对喷射砂浆保护层在管道预制阶段不受力以及缠丝、运行阶段混凝土弹性模量不同的特点,对PCCP-P分阶段进行分析,得到各结构层的应力解析解,并建立有限元模型进行验证.本研究可为PCCP-P和传统PCCP设计提供依据.     

基于半主动激光末制导的迫击炮弹

半主动激光制导技术在军事上有着广泛的应用。在分析半主动激光工作原理的基础上,着重对国外半主动激光末制导迫击炮弹进行了深入的分析,指出了研究的现状及存在的不足,对迫击炮弹的研究具有一定的指导意义。     

爆炸衬砌试验研究

给出了爆炸衬砌的定义。介绍了爆炸衬砌技术的施工工艺和衬砌机理。推导出爆扩料仓半径的计算公式。分析了爆炸对周围土壤物理、力学性质的影响。指出装药药量及其在料仓中的位置是影响衬砌效果的重要因素。研究结果表明 ,砂浆衬砌外侧存在一个抗剪强度明显高于原状土体的土质外衬。爆炸衬砌在地下土层中形成的是一个砂浆与土体的复合衬砌。     

不可压N-S方程的基于粘接元的区域分裂解法

首先,简单介绍了基于粘接元的无重叠区域分裂方法.这种方法利用变分原理,非常适合有限元近似.然后,着重讨论了这种区域分裂方法在求解不可压Navier-Stokes方程中的应用,具体包括等价变分公式的建立、通过算子分裂的时间离散、区域分裂情形下广义Stokes问题的共轭梯度迭代求解方法、空间的有限元离散.最后,以数值实验结果验证了这种区域分裂方法应用于不可压Navier-Stokes方程求解时的可靠性.     

水泥砂浆的率型本构方程

水泥砂浆的动态力学行为具有应变率敏感的非线性粘弹特性,并伴随着微损伤的率型演化,给出的水泥砂浆计及损伤演化的率型本构方程,与实验结果吻合良好。     

稀土离子与伴清蛋白结合的紫外差光谱研究

在ｐＨ７．４ ,２５ ℃的条件下, 使用紫外吸收差光谱进行了Ｅｕ３＋ ,Ｔｂ３＋ ,Ｌｕ３＋ 对脱铁伴清蛋白的滴定。结果表明, 稀土离子与脱铁伴清蛋白结合后其差光谱均在２４４ 和２９４ ｎｍ 处给出吸收峰, 在２４４ ｎｍ 处, 稀土离子脱铁伴清蛋白络合物的摩尔吸光系数相近, 约为（２．１ ±０．１） ×１０４ ｃｍ －１·ｍｏｌ－ １·Ｌ;稀土离子可占据脱铁伴清蛋白的两个金属离子结合部位, 但优先占据脱铁伴清蛋白的Ｎ端结合部位。Ｃ端结合部位与稀土离子的结合量受ＣＯ２ －３ 浓度及离子半径的影响, 离子半径越大、ＣＯ２－３ 浓度越高,稀土离子在该部位的结合量越少。     

MULTIGRID FOR THE MORTAR ELEMENT METHOD WITH LOCALLY P_1 NONCONFORMING ELEMENTS

In this paper we study the theoretical properties of multigrid algorithm for discretization of the Poisson equation in 2D using a mortar element method under the assumption that the triangulations on every subdomain are uniform. We prove the convergence of the W-cycle with a sufficiently large number of smoothing steps. The     

A mortar element method for elliptic problems with discontinuous coefficients

This paper proposes a mortar finite element method for solvingthe two-dimensional second-order elliptic problem with jumpsin coefficients across the interface between two subregions.Non-matching finite element grids are allowed on the interface,so independent triangulations can be used in different subregions.Explicitly realizable mortar conditions are introduced to couplethe individual discretizations. The same optimal L²-norm andenergy-norm error estimates as for regular problems are achievedwhen the interface is of arbitrary shape but smooth, thoughthe regularity of the true solution is low in the whole physicaldomain.