混凝土水力劈裂的数值模拟

针对混凝土坝越来越高,越来越容易产生水力劈裂的问题,总结已有混凝土水力劈裂问题的研究成果,结合水力劈裂的发生条件、在水压作用下混凝土裂缝的开展以及影响水力劈裂作用的因素,探讨水力劈裂数值模拟的方法.比较有限元法、扩展有限元法和无单元法在水力劈裂数值模拟问题应用上的优点与不足,并分析数值模拟模型建立过程中参数设置的差别.结果表明,必须从坝材料、施工和水压等多方面考虑才能确保水力劈裂数值模拟结果的可靠性.     

高混凝土重力坝孔口应力非线性数值模拟

为准确描述重力坝孔口应力分布,提出高混凝土重力坝孔口应力的非线性数值计算分析整体方案．首先对坝体进行线性计算获得孔口应力分布规律及峰值以便于配筋,然后基于损伤塑性模型对孔口剖面作非线性应力应变分析,考察钢筋应力及其止裂效果．以某钢筋混凝土重力坝工程为背景,依据规范简化混凝土单轴应力一应变曲线,在Abaqus平台上对中孔的3个剖面进行非线性有限元分析,考察中孔在坝体自重和内水压力作用下的结构特性和损伤分布规律等,并重点探讨损伤区域的演化及钢筋应力等问题．结果表明数值模拟结果与模型试验有较好的一致性,可为同类型工程的数值计算和设计提供一定借鉴．     

Computational model of mesoscopic structure of concrete for simulation of fracture processes

This paper describes mathematical modelling and computational tool for simulation of fracture processes of cementitious composites at the mesoscopic level. The tool relies on highly realistic 3D- and 2D-representations of the heterogeneous internal structure of concrete for understanding the micromechanics of aggregate–matrix interactions. The generation mechanism allows control of aggregate volume content, shape and size distribution. The allocation procedure proved capable to produce numerical concrete with aggregate distributions comparable to real concrete. The continuum was discretised into lattices of linear elements, for structural analyses. Compression, direct tension and wedge-splitting tests were simulated. Parametrical study was carried out to investigate effects of different material properties and proportions in concrete admixtures.     

A numerical simulation of the greenhouse microclimate

A numerical one-dimensional model was designed to simulate the diurnal changes of the greenhouse environment. The model takes into consideration a soil layer, a vegetation layer, an air layer and a cover. The thermal radiative, sensible, latent and conductive heat fluxes were modeled in each layer in terms of its unknown temperature and vapor pressure. The model was applied to the coastal region of Israel during the winter and summer seasons in order to assess the heating/cooling requirements of glass and polyethylene covered greenhouses.     

Investigating fracture strength of poly-silicon membranes using microscopic loading tests and numerical simulation

The fracture strength of poly-silicon as widely used membrane material in micro electro mechanical system applications has a critical impact in respect to design, function and reliability of e.g. pressure sensors or microphones. This circumstance necessitates the investigation of the fracture strength of these poly-silicon membranes. In this study the strength was investigated by experimental tests and numerical simulations. A new fracture test has been developed that applies a well-defined and almost constant stress within a certain region of the membrane and prevent a cracking of the membrane at the edge. The brittle behavior of poly-silicon needs a statistical evaluation of the results. To this end, a set of 45 membranes was tested at each of the three positions on the wafer in order to assure statistical accuracy and to evaluate the strength distribution across the wafer. The experimental loading tests were attended by scanning electron microscopy to examine the microstructure and the crack path. Using finite element simulation, the non-linear deformation behavior during membrane loading was analyzed and the fracture stresses were calculated. In the final step the obtained results were statistically evaluated by means of a two-parametric Weibull distribution. High values were found for the characteristic fracture stresses. They are in the range of 5400–6000 MPa.     

Hybrid symbolic and numerical simulation studies of time-fractional order wave-diffusion systems

Boundary control of time-fractional order diffusion-wave systems is becoming an active research area. However, there is no readily available simulation tool till now for researchers to analyze and design controllers. In this paper, a simulation method for some typical boundary control problems, combining symbolic mathematics and numerical method, is presented with two application examples. In the intermediate steps of the simulation, an important by-product, the transfer function of the controlled system, can be obtained, which makes the design of more advanced boundary controllers possible and much easier.     

Life-cycle studies of a concrete structure using simulation on a microcomputer

This paper describes a means of exploiting the combination of microcomputers and Monte Carlo simulation to perform a systematic life-expectancy and financial analysis. The use of the program Venturer, is illustrated using an example of a footbridge. The service life of the structure is modelled using the times taken for carbonation and visible corrosion. The possible prolongation of the life expectancy due to the application of a coating is considered. The results of sensitivity analyses which indicate the relative importance of the factors considered are also shown.     

glsim: A general library for numerical simulation

We describe glsim, a C++ library designed to provide routines to perform basic housekeeping tasks common to a very wide range of simulation programs, such as reading simulation parameters or reading and writing self-describing binary files with simulation data. The design also provides a framework to add features to the library while preserving its structure and interfaces.     

Damage analysis and numerical simulation for failure process of a reinforced concrete arch structure

This work focuses on the implementation of damage mechanics model to explain and understand failure mechanisms of the concrete structures. A tensorial damage theory and an isotropic application to the arch ribs of a real bridge are presented. Two reinforced concrete arch ribs of a 28 year old bridge has been removed from the field to the laboratory. They were loaded up to failure in order to study the remaining strength of the structure. The damage model involves three independent parameters for simulating the damage behaviors of the concrete material. The damage theory—additional load—finite element method is developed to simulate numerically the failure process of the RC structures based on the proposed damage model. The predicted displacements, strains and failure mode of the RC arch are good agreement with the experimental results. The values of the three material parameters that describe the damage characteristics of concrete were obtained. The numerical calculations revealed the interested behaviors of concrete in a damaging process. The proposed damage model can be used effectively to describe the damage and fracture behaviors of concrete.     

混凝土湿热耦合模拟分析程序软件的开发与应用

为了利用计算机技术时混凝土湿热耦合传输及变形进行数值模拟分析,并在实际工程结构变形预测中有效应用,根据提出的基于Visual Basic调用Matlab及ANSYS的软件开发策略,通过混合编程开发了混凝土湿热耦合数值模拟计算程序软件(CTMSoft).利用CTMSofl对实际工程结构中混凝土的湿热传输及变形进行了数值模拟,模拟分析结果与现场实际试验及结构监测结果一致,证实该方法和程序软件是正确有效的.     

基于AM1量子化学方法的醇胺类缓蚀剂在模拟混凝土孔溶液中对钢筋缓蚀作用研究

用电化学极化曲线的方法评价了几种醇胺化合物在混凝土模拟孔溶液中对钢筋的缓蚀效果,用Gaussian03程序中的AM1方法计算了这几种醇胺化合物的量子化学参数,并采用最小二乘法,分别将它们的前线分子轨道能级、氮氧原子上的净电荷、分子偶极距以及热力学参数与相对缓蚀效率进行拟合.用所拟合的方程预测了这些醇胺的缓蚀效率,预测结果与实验结果基本相符.     

A numerical simulation of inertial waves in a rotating fluid

Inertial waves in a fluid-filled rotating cylinder are studied using a numerical simulation. A perturbation applied along the centerline at the midplane of a right circular cylinder is used to excite these internal waves. A primitive variable, time-marching finite difference solution of the linearized axisymmetric governing equations is used to obtain the flow and pressure fields. Results compare well with theoretical predictions and are displayed graphically.     

A composite numerical scheme for the numerical simulation of coupled Burgers’ equation

In this work, a composite numerical scheme based on finite difference and Haar wavelets is proposed to solve time dependent coupled Burgers’ equation with appropriate initial and boundary conditions. Time derivative is discretized by forward difference and then quasilinearization technique is used to linearize the coupled Burgers’ equation. Space derivatives discretization with Haar wavelets leads to a system of linear equations and is solved using Matlab7.0. Convergence analysis of proposed scheme exhibits that the error bound is inversely proportional to the resolution level of the Haar wavelet. Finally, the adaptability of proposed scheme is demonstrated by numerical experiments and shows that the present composite scheme offers better accuracy in comparison with other existing numerical methods.     

一种新型离心风机的气动噪声数值仿真

以一种新型离心风机为例,运用Lighthill声比拟理论和计算流体动力学技术对离心风机的非定常流场和气动噪声进行数值模拟。首先以风机内部静压脉动随时间的波动判断离心风机的主要噪声源的位置,然后,以噪声频谱图和1／3倍频程图分析离心风机的噪声组成,判断离心风机噪声的产生机理。并以实验结果作为根据,验证仿真结果的正确性。结果表明：在非定常流场中,离心风机的噪声源主要分布在叶片与蜗壳之间的狭窄区域,在气动噪声成分中涡流噪声所占的比例最大,其产生的主要原因是由于叶片尾缘漩涡脱落造成的压力脉动形成的。     

一种面向数值模拟软件的持续集成平台

随着软件复杂度的增加和交付需求的变化,快速集成和自动部署成为高性能数值模拟软件推广应用的瓶颈。为满足软件构建和发布的差异化需求,简化从用户需求到软件发布的工作流程,基于Jenkins设计持续集成平台,实现软件静态审查、编译、测试和发布流程的自动化,全面记录软件构建日志和测试结果。利用Docker技术将构建环境容器化,实现环境的快速搭建和配置管理,满足多样化目标环境需求。该平台的实际应用效果显示,基于该平台的产品发布周期相比之前缩短约75%,可极大简化软件安装和部署难度。     

Reducing numerical dissipation in smoke simulation

Numerical dissipation acts as artificial viscosity to make smoke viscous. Reducing numerical dissipation is able to recover visual details smeared out by the numerical dissipation. Great efforts have been devoted to suppress the numerical dissipation in smoke simulation in the past few years. In this paper we investigate methods of combating the numerical dissipation. We describe visual consequences of the numerical dissipation and explore sources that introduce the numerical dissipation into course of smoke simulation. Methods are investigated from various aspects including grid variation, high-order advection, sub-grid compensation, invariant conservation, and particle-based improvement, followed by discussion and comparison in terms of visual quality, computational overhead, ease of implementation, adaptivity, and scalability, which leads to their different applicability to various application scenarios.     

A numerical simulation for the blow-up of semi-linear diffusion equations

Many mathematical models have the property of developing singularities at a finite time; in particular, the solution u(x, t) of the semi-linear parabolic Equation (1) may blow up at a finite time T. In this paper, we consider the numerical solution with blow-up. We discretize the space variables with a spectral method and the discrete method used to advance in time is an exponential time differencing scheme. This numerical simulation confirms the theoretical results of Herrero and Velzquez [M.A. Herrero and J.J.L. Velzquez, Blow-up behavior of one-dimensional semilinear parabolic equations, Ann. Inst. Henri Poincare 10 (1993), pp. 131–189.] in the one-dimensional problem. Later, we use this method as an experimental approach to describe the various possible asymptotic behaviours with two-space variables.     

GLANUSIT: A software toolbox for the numerical simulation of large ice masses evolution

The here presented GLAciology NUmerical SImulation Toolbox (GLANUSIT) is a software application which provides a user friendly environment for the numerical simulation of large ice masses evolution. The graphical user interface has been developed in MATLAB while the core of GLANUSIT contains the original FORTRAN codes, which develop the specific numerical methods for the solution of the complex shallow ice model. This highly nonlinear model governs the coupled thermodynamical and hydrodynamical processes. The global algorithm mainly consists on a fixed point iteration between the different subproblems. The numerical solution of each subproblem requires specific techniques, which are not common in present software packages, as for example the part of moving boundaries solvers included in the code. Finally, a practical case study with real data is presented.