Molecular dynamics simulation of the role of dislocations in microcrack healing

The molecular dynamics method is used to simulate microcrack healing during heating or/and under compressive stress. A centre microcrack in Cu crystal would be sealed under compressive stress or by heating. The role of compressive stress and heating in crack healing was additive. During microcrack healing, dislocation generation and motion occurred. When there were pre-existing dislocations around the microcrack, the critical temperature or compressive stress necessary for microcrack healing would decrease, and, the higher the number of dislocations, the lower the critical temperature or compressive stress. The critical temperature necessary for microcrack healing depended upon the orientation of the crack plane. For example, the critical temperature for the crack along the (001) plane was the lowest, i.e. 770K.

智能微系统力学中的几个问题

微电子机械系统ＭＥＭＳ）和集成微电子机械系统（ＩＭＥＭＳ）近年来的蓬勃发展将为力学学科注入新的活力并为其提供难得的发展机遇。智能微系统力学是研究智能化微系统（包括ＭＥＭＳ、ＩＭＥＭＳ和ＭＯＥＭＳ等）中涉及到的力学问题，所研究的尺度一般μｍ／Ｓｕｂμｍ或以下，是微尺度力学和微电子学、物理学、自动控制、精密机械学，摩擦学等的交叉学科，从力学的角度综述了智能微系统力学的特点、所涉及的主要研究领域和目前的…

Application of enthalpy method for moving boundary problem in laser surface melting

A numerical analysis was carried out to study the moving boundary problem in the physical process of pulsed Nd-YAG laser surface melting prior to vaporization. The enthalpy method was applied to solve this two-phase axisymmetrical melting problem Computational results of temperature fields were obtained, which provide useful information to practical laser treatment processing. The validity of enthalpy method in solving such problems is presented.

燃烧气脉冲除灰技术的试验研究

中科院力学研究所研制成功的燃烧气脉冲除灰技术是电站锅炉新一代的除灰技术。该技术的原理是可燃气体与空气混合后，在燃烧室中快速燃烧，产生的冲击波作用在空预器的波纹板上，使积灰清除。技术可降低排烟温度，提高锅炉热效率和运行安全性。它已成功地用于电厂燃煤和燃油锅炉上。较详细地介绍了气脉冲除灰技术的研究及其结果，并描述了气脉冲除灰技术的先进性。

Direct Numerical Simulation of a Spatially Evolving Supersonic Turbulent Boundary Layer at Ma=6

Direct numerical simulation is carried out for a spatially evolving supersonic turbulent boundary layer at free-stream Mach number 6. To overcome numerical instability, the seventh-order WENO scheme is used for the convection terms of Navier-Stokes equations, and fine mesh is adopted to minimize numerical dissipation. Compressibilty effects on the near-wall turbulent kinetic energy budget are studied. The cross-stream extended self-similarity and scaling exponents including the near-wall region are studied. In high Mach number flows, the coherence vortex structures are arranged to be smoother and streamwised, and the hair-pin vortices are less likely to occur.

Structural Failure Analysis and Numerical Simulation of Micro-Accelerometers under Impulsive Loading

Micromachined accelerometer is a kind of inertial MEMS devices, which usually operate under intensive impact loading. The reliability of micromachined accelerometers is one of the most important performance indices for their design, manufacture and commer

关于热传导测温中动态测温响应与误差估计

从理论上给出了关于热传导测温中动态测温响应与误差估计。温度测量敏感元件的温度滞后于外界温度的变化，其滞后时间不超过敏感元件的半个特征时间L2/α,所以温度测量误差不超过βL2 /2α，也就是说，在热传导动态温度测量中，温度测量敏感元件的热响应时间可估为 L2/2α，最大温度测量误差可估为βL2 /2α。

An experimental study on turbulent coherent structures near a sheared air-water interface

The turbulence structures near a sheared air-water interface were experimentally investigated with the hydrogen bubble visualization technique. Surface shear was imposed by an airflow over the water flow which was kept free from surface waves. Results show that the wind shear has the main influence on coherent structures under air-water interfaces. Low- and high- speed streaks form in the region close to the interface as a result of the imposed shear stress. When a certain airflow velocity is reached, "turbulent spots" appear randomly at low-speed streaks with some characteristics of hairpin vortices. At even higher shear rates, the flow near the interface is dominated primarily by intermittent bursting events. The coherent structures observed neat sheared air-water interfaces show qualitative similarities with those occurring in near-wall turbulence. However, a few distinctive phenomena were also observed, including the fluctuating thickness of the instantaneous boundary layer and vertical vortices in bursting processes, which appear to be associated with the characteristics of air-water interfaces.

液–固脉冲流化床中浓度波传播与衰减

采用数值计算和实验验证相结合的方法研究液一固脉冲流化床中浓度波的传播和衰减。当脉仲开半周期乃和闭半周期乃都远大于颗粒弛豫时间吊时,两相的惯性力之差在一个周期的绝大部分时间中相对于重力很小,可忽略,这时由双流体模型的动量方程可推导出推广的Richardson-Zaki公式,双流体模型简化为局部平衡模型。采用五阶精度WENO格式求解浓度波传播方程,得到了脉冲流化过程中浓度波传播与衰减的规律,与实验结果符合良好。

Net-like Ferromagnetic Mnsb Film Deposited on Porous Silicon Substrates

MnSb films were deposited on porous silicon substrates by physical vapor deposition (PVD) technique. Modulation effects due to the substrate on microstructure and magnetic properties of the MnSb film's were studied by scanning electron microscope (SEM), X-ray diffraction (XRD) and measurements of hysteresis loops. SEM images of the MnSb films indicate that net-like structures were obtained because of the special morphology of the substrates. The net-like MnSb films exhibit some novel magnetic properties different from the unpatterned referenced samples. For example, in the case of net-like morphology, the coercive field is as low as 60 Oe.

障碍物管道中湍流火焰发展的数值模拟

应用湍流马赫数修正的非稳态可压缩性K-ε-f-gr四方程湍流模型，模拟了半开口狭长管道中重复布置的障碍物引起的湍流火焰加速现象。结果表明，障碍物产生的扰动对加强燃烧和湍流输运的影响很大。随着火焰向前传播，火焰穿过障碍物时发生变形，反应区越来越长，且火焰速度逐渐上升。同时，火焰速度和管内压力的计算结果与实验测量值吻合良好，修正后的湍流模型能较真实地模拟障碍物管内预混火焰的发展过程。

表面具有流向微槽叶片的传热性能分析

在综合考虑了流向微槽表面强化的传热特性和流向微槽表面减阻机理研究结果垢基础上，分析了表面具有流向微槽的叶片的传热性能，提出了与已有的叶片冷却技术完全不同的，全新的叶片冷却技术－叶片外部冷却技术。

圆域内双柱整流现象的数值模拟

基于Reyleigh整流定律，利用ψ－ε形式的定常不可压N-S方程，数值模拟了双柱在圆域内 作高频小振幅振动时所产生的定常整流流动。揭示了流动随整流雷诺数的演化特性。此外就求解ψ－ε形式的N-S方程所涉及的定解边界条件问题，亦进行了必要的讨论。

LEVEL SET输运方程的求解方法及其对气-液两相流运动界面数值模拟的影响

用数值模拟方法来研究气-液两相流动与传热现象是当今多相流领域的一个热门课题.由于两相流固有的复杂性,气-液两相流界面迁移现象的数值模拟一直是两相流研究中的一大难点.本文介绍了捕捉气-液两相流相界面运动的水平集方法(Level Set)及其研究进展,介绍了求解Level Set输运方程的3种方法,即一般差分格式、Superbee-TVD格式和Runge-Kutta法-5阶WENO组合格式.结合主流场的求解,分别用这3种方法对4种典型相界面在5种流场中的迁移特性进行了模拟计算,并对计算结果进行了比较和分析.结果表明,Runge-Kutta法-5阶WENO组合格式求解Level Set输运方程的效果最好,在以后的计算中将主要采用这种组合格式来进行气-液相界面输运方程的求解.