分子动力学模拟技术在有机蒙脱石研究中的应用

综述了现阶段分子动力学模拟技术在有机蒙脱石研究领域的进展情况,指出了现有研究中存在的问题并对其应用前景进行了展望。通过总结发现当前研究所存在的问题主要是建立的蒙脱石模型较为理想化,没有充分考虑外界环境因素以及蒙脱石类质同象取代位等晶体化学特征对有机蒙脱石层间结构和性能的影响,但随着模拟细节的逐步完善和计算机运算能力的提高,相信分子动力学模拟技术必然会更加广泛、更加深入地应用于有机蒙脱石的研究当中。

基于分子动力学模拟的超低温SiO_(2)材料开裂影响因素分析

本研究针对岩石主要成分SiO_(2)的常见分子结构,运用LAMMPS分子动力学软件构建了SiO_(2)预制裂纹试样微观尺度下裂纹扩展分析数值模拟模型,分析了不同加载速率、力加载方式、不同温度下力加载及模型厚度条件下的裂纹扩展规律,揭示了超低温下固体材料裂纹起裂扩展的微观影响因素及其规律。研究发现:加载速率变化会引起裂纹扩展路径变化,但不同加载速率下总体势能、动能、区域平均应力以及总体温度的变化规律基本相似;不同温度下力加载,裂纹总长和裂纹平均扩展速率随温度的增加而增加。分子动力学模拟技术能有效反映微观环境对固体介质裂纹扩展的影响规律,为探究岩石类等建筑材料的脆性破坏机理研究提供了新途径。

金属钚表面氦释放的分子动力学模拟

钚因放射性衰变而出现自辐照老化效应，氦行为和氦泡行为是这种老化效应的集中体现，也是理解这种老化效应的重要途径。运用分子动力学模拟技术，研究了氦泡的释放过程。钚-钚、钚-氦和氦-氦相互作用势分别采用嵌入原子多体势（Embedded Atom Method，EAM）、Morse对势和Lennard．Jones对势，计算体系采用表面平板模型。研究结果表明：距离表面一定距离的氦泡中的氦原子发生释放，释放过程受距离表面的距离、温度、氦泡大小以及氦原子密度等因素的影响；

基于CFD模拟的混合式住宅小区布局对风环境改良的研究

文章旨在探讨衡阳市住宅小区的风环境问题,并提出优化方案。通过对该市不同季节的气象数据和现存建筑的模拟分析,研究发现建筑布局和围合形式对风环境有着显著的影响。因此,作者提出了针对冬季和夏季不同风向的方案,以改善住宅小区内部的风环境。本研究采用计算流体动力学CFD(Computational Fluid Dynamics)模拟技术模拟住宅小区周边的风环境,并控制改良后的模拟方案中的变量,以验证所提出的优化方案的可行性,同时对比分析不同方案的效果。结果表明,合理的调整建筑布局能显著优化其周围的风环境,改善通风并缓解局部风速过快的问题。证明CFD技术在未来住宅小区的规划上能提供更科学合理的方案。希望本研究能为未来同类型研究提供参考。

单晶铜表面划擦过程模拟

应用分子动力学模拟技术模拟刚性针尖在单晶铜表面的划擦过程,探讨在微观领域材料的摩擦磨损特性,为进一步探讨纳米摩擦模拟技术及微观领域材料特性奠定基础.模拟结果表明,在材料微观划擦机理中,针尖的摩擦阻力来自于基体表面位错的堆积,同时,位错在基体中的传播速度对摩擦阻力也有影响.

上海应物所等研究揭示锂离子嵌入碳纳米管束的精细过程

中科院上海应用物理研究所物理生物学实验室宋波和方海平采用最新的量子分子动力学模拟技术，研究了锂离子嵌入碳纳米管束及其在碳纳米管束中扩散的动态行为。

Simulation and Analysis on the Two-Phase Flow Fields in a Rotating-Stream-Tray Absorber by Using Computational Fluid Dynamics

The flow field of gas and liquid in a φ150mm rotating-stream-tray (RST) scrubber is simulated by using computational fluid dynamic (CFD) method. The sismulation is based on the two-equation RNG κ-ε turbulence model, Eulerian multiphase model, and a real-shape 3D model with a huge number of meshes. The simulation results include detailed information about velocity, pressure, volume fraction and so on. Some features of the flow field are obtained: liquid is atomized in a thin annular zone; a high velocity air zone prevents water drops at the bottom from flying towards the wall; the pressure varies sharply at the end of blades and so on. The results will be helpful for structure optimization and engineering design.

Simulation of the Clustering Phenomenon in a Fast Fluidized Bed: The Importance of Drag Correlation

Drag force is a key parameter in the numerical modeling of gas-particle flow in circulating fluidized beds. The reliability of current drag force correlations over the regime of fast fluidization has, however, not been thoroughly investigated. In this article, a drag force correlation accounting for the clustering effects for Geldart A particles is used to simulate the behaviors typical of fast fluidization, including dynamic evolution of clusters as well as time- averaged axial and lateral voidage profiles. Diverse images of clusters are captured and the time-averaged profiles of voidage are shown to be in quantitative agreement with the present empirical correlation. The results based on different constitutive correlations of drag force show the importance of the choice of drag force in modeling fast-fluidized beds. This drag force correlation, based on a simple averaging assumption, could give some basic insights about the magnitude of the drag reduction.

Numerical Simulation of Dynamic Performance of the Molten Carbonate Fuel Cell

A three dimension of dynamic mathematical model of the molten carbonate fuel cell is established,in which the heat generation, mass transfer and electrochemical characteristics are described. The performance of the fuel cell including the distributions of the temperature and the velocity is predicted numerically. Then the experimental data including the output performance of the fuel cell generation system and the temperature distributions are compared. The numerical results are in agreement with the experiment results.

Dissipative Particle Dynamics Simulations of Domain Growth and Phase Separation in Binary Immiscible Fluids

It was investigated that the domain growth processes of spinodal decomposition with different quenching depth in two and three dimensional binary immiscible fluids by using parallel dissipative particle dynamics simulations. In two dimensions, the dynamic scaling exponent 1/2 for coalescence and 2/3 for inertial regimes in the shallow quench and strong finite size effects in the cases of deep quenching were obtained. In three dimensions, it was used that the diffusive regime with exponent n=l/3 in the shallow quench and the inertial hydrodynamic regime with n=2/3 for different quenches. The viscous effects are not clearly reflected, showing n=1/2 in both shallow and deep quenches in this time period, due to the soft nature of interaction potential adopted in dissipative particle dynamics.

Flux Limiter Lattice Boltzmann for Compressible Flows

In this paper, a new flux limiter scheme with the splitting technique is successfully incorporated into a multiple-relaxation-time lattice Boltzmann （LB） model for shacked compressible flows. The proposed flux limiter scheme is efficient in decreasing the artificial oscillations and numerical diffusion around the interface. Due to the kinetic nature, some interface problems being difficult to handle at the macroscopic level can be modeled more naturally through the LB method. Numerical simulations for the Richtmyer-Meshkov instability show that with the new model the computed interfaces are smoother and more consistent with physical analysis. The growth rates of bubble and spike present a satisfying agreement with the theoretical predictions and other numerical simulations.

Development and application of simulation technique for hydrokinetic hammer

The computer simulation is an important method for hydrokinetic hammer design. Various kinds of simulation measures with their technical characters and applications being taken during the computer aided design are enumerated. Computer simulation supports plenty of valuable references to the designer. Each type of simulation process is used to explore the exact aspect of the performance of hydrokinetic hammer and each type of simulation method has its own excellences and deficiencies. Thus the integrative simulation methods based on modem computational technology are brought forward to obtain the perfect capability of the whole product. Along with the development of computer hardware and software, various kinds of platforms have been provided to different simulation methods that can be carried out with distinct working flows. The jet flow element is the core part of the hydrokinetic hammer. We can build the ideal simulation model of it by means of CFD （ computational fluid dynamics） technology. On the other hand, to set up the digital model of piston and hammer, the best way is to build the virtual prototype using automatic dynamic analysis of mechanical system. As a result of the argumentation, we think the technique of Virtual Prototype and CFD are the prime way to process the combined computer simulation for hydrokinetic hammer,

Simulating ion clustering in potassium thiocyanate aqueous solutions with various ion-water models

Using a molecular dynamics simulation technique,we compared several commonly used ion-water models to describe the microscopic structures and dynamics in KSCN aqueous solutions.Results are compared with observations of femtosecond infrared vibrational-energy transfer and anisotropy measurements.The Jorgensen/TIP4P model is found to provide the best reproduction of clustering properties such as percentage of clustered ions,cluster-size distribution,concentration dependence of the water,and ion-rotation time constants.