非定常流弯肘型尾水管不规则压力脉动预测

尾水管内螺旋状涡带引起的压力脉动是造成混流式水轮机机组振动的主要原因之一,直接威胁机组的安全运行。为此,提出一种基于CFD数值计算的水轮机尾水管压力脉动数字化预测法,并利用此法对一大型混流式水轮机偏工况下尾水管内水流流动进行了长时间非定常流计算,讨论该工况下尾水管内死水域与涡带的运动规律,预测了尾水管的不规则压力脉动,压力脉动分析结果表明,其波形、频率、相位与实际基本一致。     

系统动力学在水资源管理中的应用

系统动力学是以反馈控制理论为基础,以仿真技术为手段,研究复杂社会经济系统的定量方法,目前已广泛地应用于可持续发展研究、水资源开发利用及承载力方面、水资源规划、城市水环境和环境经济中等方面的研究．文中在对系统动力学应用有关文献阅读的基础之上,对系统动力学应用的领域和方法进行了分类、归纳和整理,为系统动力学的进一步应用提供信息。     

NUMERICAL ANALYSIS OF LEAKAGE FLOW THROUGH TWO LABYRINTH SEALS

The leakage flow through two labyrinth seals, e.g the interlocking seal and the stepped seal, was numerically investigated. Preliminary calculation of the seal-cavity averaged pressure by using the one-dimensional control volume method showed favorable agreement with the experimental measurements. Subsequently, in-depth understanding of the fluid flow through the labyrinth seals was obtained by employing Computational Fluid Dynamics (CFD) and k ?ε turbulence model, which resulted in a potential wealth of information like the streamline pattern, velocity vector field, and distribution of turbulent kinetic energy and static pressure. At the clearance of the seal the turbulent kinetic energy reached the peak value, while in the bulk region of the cavities it decayed fast. The static pressure rapidly dropped as the fluid flow went through the clearance; no distinct difference of the static pressure was inspected in the cavities. Also noted from the numerical results was that the stepped seal showed better sealing performance than the interlocking seal.     

Effects of landscape structure on vegetation and some animal groups after agriculture abandonment

This research was carried out on the montane belt of a south-exposed watershed in the Intermediary Alps which have been hit by agriculture abandonment. The aim of the study was to study the relationships between vegetation, landscape mosaic, and two kinds of animals using this space at different scales: roe deer (Capreolus capreolus) and earthworms (lumbricids). Landscape dynamics (post-cultural recolonisation) and landscape structure have been approached by means of the Arc/Info geographical information system (GIS). Several methods used to study on one hand roe deer distribution, and, on the other, earthworm abundance and diversity are developed. Of these, in particular, GIS processing is used to sample earthworms according to vegetation dynamics, and roe deer distribution is related to landscape heterogeneity. Earthworms are more abundant and diversified in the key steps of vegetation dynamics. These lumbricids can be considered as functional indicators of these dynamics. Results also demonstrate that both the vegetation type and the landscape heterogeneity have a direct influence on the use of the space by the roe deer. They show themselves to be structural indicators of the landscape.     

柔性机器人的协调操作及其逆动力学控制算法

柔性协调机器人系统是一个含柔性机器人内部各杆之间,运动协调约束条件和动力协调约束条件之间,柔性机器人与负载之间,以及柔性机器人之间高度耦合的复杂非线性系统,无论在动力学建模,还是控制算法方面都要比刚性协调机器人困难得多。通过对刚、柔性机器人协调操作系统本质特性的比较,利用有限元法和Lagrange方程建立了柔性协调机器人系统的动力学模型,并以系统逆动力学任务为目标,提出了通过校正机器人名义刚性运动来达到提高系统位姿控制精度的预测校正控制算法,成功给出了平面两3R柔性臂机器人协调操作刚性负载的仿真算例。     

带式输送机的动力学设计及理论计算

从带式输送机的动力学入手，研究了输送机在使用传动力设备和使用软起设备时的动力学设计与理论计算方法。     

水下推动器作用下氧化沟流场的数值模拟

该文通过建立推动器三维数学模型,采用MRF模型定义其转动、RNG k-ε模型模拟流场湍流变化的方法对水下推动器作用下的氧化沟流场进行了三维数值模拟,并用充足的实测数据对模拟结果进行验证.模拟值与实测数据吻合良好,表明该数学模型能较为准确有效地模拟出推动器作用下氧化沟流速的分布及三维流场的沿程变化情况.     

Influence of high-porosity mesh stent on hemodynamics of intracranial aneu- rysm： A computational study

This paper studies the influence of a High-Porosity Mesh （HPM） stent on the hemodynamic characteristics in the intracranial aneurysm based on the Computational Fluid Dynamics （CFD）. An idealized basilar tip aneurysm model and a HPM stent model are built. The pulsating blood flow in a cardiac cycle is computationally simulated for non-stented and stented models, to provide a wealth of information of the spatio-temporally varying blood flow field. The influence of the stent placement on the hemodynamic characteristics is analyzed in terms of distributions of velocity, pressure, Wall Shear Stress （WSS） and Energy Loss （EL）, which are believed to play an important role in the development and rupture of the aneurysm. The numerical results clearly show that the velocity, pressure, WSS and EL of the blood flow in the aneurysm are reduced by 30%-40% when the HPM stent is implanted. These computational results may provide valuable hemodynamic information for clinical neurosurgeon.     

基于多体系统运动学理论的坐标测量机误差自动建模

研究分析了运用多体系统运动学理论对复杂机械如坐标测量机进行误差建模的基本原理,介绍了误差自动建模过程。以FXYZ型立式三坐标测量机为例进行了误差建模,给出了空间误差模型具体数学表达式。理论分析和实际应用显示所述方法很好地解决了误差建模的通用性问题,为精度分析和误差补偿等提供了一个理想的误差建模方式。     

低浓度煤层气流态化燃烧技术的研究进展

低浓度煤层气由于热值低、流量变化大,利用较困难,大部分都未经处理就直接被排放,不仅浪费资源,而且还污染环境,引起了国内外的密切关注。较之常规的煤层气利用技术,以惰性颗粒和催化颗粒为床料的流态化燃烧技术具有热容量大、燃料适应性广的特点,在低浓度煤层气燃烧利用方面表现出巨大的潜力。为此,综述了该技术的研究现状,分析了惰性颗粒和催化颗粒作用下,床层温度、进气浓度、流化风速及气固两相流对其燃烧特性的影响,介绍了在流化床中催化燃烧反应的模型及其动力学特性,探讨了杂质性气体对气固催化反应的作用机制,明确了SO_2作用下硫酸铜的生成是催化剂硫中毒的根本原因,提出了相应的抗硫中毒措施,讨论了水蒸气对低浓度甲烷催化燃烧的影响。最后,就该技术的未来发展进行了分析与展望,得出的认识如下:①后续的研究应该侧重颗粒尺寸变化对流态化燃烧带来的影响;②应寻找更加廉价、催化活性更优的催化剂替代;③对惰性颗粒下低浓度甲烷流态化燃烧,缺乏燃烧机理分析,需要进一步从理论角度进行深度挖掘。