Digital simulation of periodic fluid flow in a bifurcation

We here describe a finite difference technique for solving a pulsatile fluid flow problem through a bifurcation.     

Computer simulation of heat,mass and fluid flows in a melt during czochralski crystal growth

A procedure to obtain steady state heat, mass and fluid flows in the melt during Czochralski crystal growth is described. This method is satisfactorily applied to the isothermal fluid flows caused by crystal rotation and to the nonisothermal fluid flows caused by combined free and forced convection. For high Reynolds number Re = a²ω_s/v, where a is the crystal radius, ω_s is the crystal rotation rate, and v is the kinematic viscosity, this method is revised so as to avoid numerical divergence.     

仿真交通流混沌转化过程研究

为分析交通流混沌转化机理,探讨了车头间距和交通流混沌之间的关系。利用Matlab软件编制皮埃莱（Bierley）模型来产生仿真交通流时间序列,在一定参数组合情况下,研究了交通流车队中前后车辆的车头间距变化过程。通过分析这种车头间距变化曲线相轨迹,可以明显地观察到交通流混沌运动和有序运动之间的转化过程;在此基础上,应用最大Lyapunov指数改进算法对仿真交通流混沌转化过程进行了理论分析,讨论了车头间距对交通流混沌转化过程的影响作用。研究表明,车头间距的变化是交通流混沌现象产生和转化的根本原因。该研究结果有助于进一步理解交通流混沌现象,并为短时交通流预测和智能交通控制提供理论依据。     

Flow patterns of oil–water two-phase flow during pressure-driven process in nanoscale fluidic chips

Unconventional oil reservoirs have great potential to become significant sources of petroleum production in the future. Many shale oil systems consist of nanoscale pores and fractures that are significantly smaller than those from conventional reservoirs, and pore sizes are only slightly more than one order of magnitude of those of the saturating fluid molecules. This difference will cause abnormal wettability effect and typical fluid flow mechanisms in unconventional oil systems. Therefore, it is increasingly important to investigate fluid flow behaviours in nanoscale porous media. In this work, a lab-on-chip approach for the direct visualization of the water–oil flow in nanoscale channels was developed by using an advanced laser microscopy system combined with a nanofluidic chip. For the micro-scale study of interface transmission during the drainage and imbibition processes, parallel linear nanofluidic chips were used. A comprehensive study of water–oil flow behaviours is presented. During the drainage process, liquids tend to have a piston-like flow in nanoscale channels; both residual phase saturation and configuration affect the flow behaviour on such small scale; during the imbibition process, a fading-out phenomenon was observed. For a macroscale study of pressure and recovery relationships, unusual entrance pressure was discovered by using network nanofluidic chips comparing to conventional results.     

信息时代的数字仿真

第一个互联网,阿帕网(ARPANET)的建成(1969-11-21)为标志,宣告人类社会进入信息时代,也可称为互联网时代.信息化席卷全球.数字仿真本身与时俱进,用现代信息技术武装自己,分清应用需求的轻重缓急,应用业已形成的理论体系,向着以数字化、虚拟化、智能化、网络化、集成化、协同化为特征的现代化方向发展,从而能在信息化中更加安全而又经济有效地完成时代赋予的使命.     

Digital simulation of parallel inverters

Previously, a model of a nonlinear inductor exhibiting hysteresis loops was proposed, and successfully applied to typical nonlinear electric circuits [1]. This model is now generalized to include the nonlinear transformer, and applied to the digital simulation of parallel inverters. Comparison of experimental results with simulated results shows that the model taking into account the hysteresis loops behaves just like a physical inverter including the unstable operations.     

烧结烟气氨法脱硫塔气液两相流数值模拟

为研究脱硫塔内的气液分布情况对脱硫效率的影响,选用FLUENT作为计算工具,以烧结烟气氨法脱硫塔作为研究对象,对塔内气相湍流采用Euler方法描述,对喷淋液滴采用Lagrange颗粒轨道模型描述,研究烟气入口倾角和入口距离浆液池液面高度对脱硫塔内气液两相流场分布的影响,并对脱硫塔的关键参数取值给出建议.     

Integrating cluster and sequential analysis to explore learners’ flow and behavioral patterns in a simulation game with situated-learning context for science courses: A video-based process exploration

Much emphasis has been placed on the research on applying digital games in science education. Among the studies, the advantages and limitations of role-playing simulation games deserve further exploration. However, existing analyses of the behavioral patterns of role-playing simulation games in science education remain substantially lacking, particularly the integration of diverse behavioral pattern analysis methods. This study thus seeks to analyze the videotaped learning process of 86 college students in game-based learning activities that utilize a role-playing simulation game. This study used the integrated method of sequential analysis and cluster analysis and explored the learners’ flow state and learning behavioral patterns. The results show that the use of integrated behavioral pattern analysis helps to explore the traits and limitations of role-playing simulation games in science education as well as learners’ reflective behavior patterns.This study identifies a wide variety of learning behavior patterns from three potential clusters of learners and then discusses the learning process of each cluster. The different levels of flow experienced by the learners affected their learning behavior patterns; learners with higher levels of flow demonstrated a more in-depth reflective process. The study further discusses the results of these analyses and makes relevant recommendations for the systems development of the games, its educational applications, and evaluation methods.     

文丘里管中空化流场的数值模拟

基于FLUENT软件,采用标准k-ε模型和空化泡动力学模型,对三种不同几何形状的文丘里管内空化流场进行数值模拟,计算了文丘里管内空化区的空化数、压力分布和汽含率分布,研究了操作条件、文丘里管的结构形式对空化效果的影响。结果表明,理论计算的空化区汽含率分布与实验拍摄的空化云雾区图像有较好的吻合性;水力空化装置的操作条件,以及文丘里管的结构形式对空化效果有着明显的影响。     

大气紊流的数字仿真

为提高大气紊流数字模拟的精度,分析Dryden紊流模型的数字仿真技术,发现仿真中采用的高斯白噪声序列的生成精度是影响大气紊流模拟精度的重要因素.在不改变随机数序列均值、方差以及概率密度特性的情况下,采用双随机交换最小化方法对高斯噪声序列进行白化处理,使得随机数序列的白化程度提高,从而使紊流模拟的精度提高,而且模拟精度受采样间隔的影响降低.采用双随机交换最小化方法对高斯白噪声序列进行改进是提高紊流模拟精度的1种直接有效的手段.     

Animated simulation of the robot process capability

This paper describes an interactive computer graphic system developed for simulating robot capability. The system determines the positioning repeatability and accuracy of a robot performing specific operations. Central to the system are three characteristics, information describing the errors of the geometric and kinematic parameters of a robot, a common function to request and display a robot moving from one position to another, and finally a family of charts showing the repeatability of the robot implementing a given task.     

Numerical simulation of the capillary flow in the meander microchannel

Pumping in microfluidic devices is an important issue in actuating fluid flow in microchannel, especially that capillary force has received more and more attractions due to the self-driven motion without external power input. However, less 2D simulation was done on the capillary flow in microchannel especially the meander microchannel which can be used for mixing and lab-on-a-chip (LOC) application. In this paper, the numerical simulation of the capillary flow in the meander microchannel has been studied using computer fluid dynamic simulation software CFD-ACE⁺. Different combinations of channel width in the X-direction denoted as W_x and Y-direction denoted as W_y were designed for simulating capillary flow behavior and pressure drop. The designed four types of meander microchannels (W_x × W_y) were 100 × 100 μm, 100 × 200 μm, 50 × 200 μm, and 50 × 400 μm. In this simulation results, it is found that the capillary pumping speed is highly depending on the channel width. The large speed change occurs at the turning angle of channel width change from W_x to W_y. The fastest pumping effect is found in the meander channel of 100 × 100 μm, which has an average pumping speed of 0.439 mm/s. The slowest average flow speed of 0.205 mm/s occurs in the meander channel of 50 × 400 μm. Changing the meander channel width may vary the capillary flow behavior including the pumping speed and the flow resistance as well as pressure drop which will be a good reference in designing the meander microchannels for microfluidic and LOC application.     

14 nm工艺下基于CUPF的数字IC低功耗物理设计

随着集成电路生产工艺的迅速发展,功耗作为芯片质量的重要衡量标准引起了国内外学者越来越多的重视和研究。当晶体管的特征尺寸减小到纳米级时,其泄露电流的增加、工作频率的提高和晶体管门数的攀升极大提高了芯片的功耗。同时,传统的基于UPF(Unified Power Format)的低功耗设计流程存在着效率低、可修复性差等缺点。针对以上问题,以14 nm工艺下数字芯片fch_sata_t模块为例,简要介绍了全新的基于CUPF(Constant UPF)的低功耗物理设计流程,利用门控电源和多电源电压等技术对芯片进行低功耗设计。最终,通过Synopsys旗下PrimetimePX提供功耗分析结果,证明了芯片功耗满足设计要求。     

Digital simulation of continuous feedback systems

Trapezoidal convolution derives general and special discrete equivalents of continuous feedback systems in a straightforward manner. A critique of two other published discretizations is presented.     

Digital simulation of polyphase induction motors

The fundamental equations of polyphase induction motors (linear simultaneous differential equations with periodic coefficients) are directly solved by finite difference methods for balanced and for unbalanced conditions.     

基于CUDA的泥石流模拟计算研究

针对泥石流仿真过程中海量数据计算问题,采用CUDA技术即结合CPU与GPU的优点研究了一种协同计算方法以提高数据计算效率和仿真性能。同时,搭建了基于GPU的泥石流仿真计算平台,对优化的CUDA并行计算方法进行验证。实验结果表明,该方法对海量数据的计算具有快速准确、低成本、低功耗的特点,能为灾害预测提供及时准确的决策支持,满足了高密集型计算的需求。     

Dynamic simulation of product process

During 90’s Nokia utilized Concurrent Engineering (CE) process in mobile phone business successfully. Strong growing of the company, more complex technologies, maturing markets and changes in competition has increased the need to develop the product process of the company to keep its position as an agile, innovative and productive product developer. Dynamic simulation approach has been one of the activities among other product process re-engineering efforts in the company.This paper describes the approach and “Product Process Decision Simulation” (PPDS) solution as the first implemented application of the approach. A dynamic model of product development has been created and applied to manage product process complex dynamic behavior on system level in order to reduce product development cycle times, slippages and costs as well as improve perceived product quality. The key contribution of the simulation solution is to provoke facilitated discussion in order to gain shared understanding of interdependencies and dynamic causes and effects in product process.The implementation and frequent simulation workshops have started in June 2006 and about 500 R&D people have already participated.     

CSTR反应系统中物料流动的随机模拟

对于器内物料微团的流动处于理想混合状态的单个或多个CSTR组成的反应系统,物料微团流出反应系统的状况具有统计特征,用示踪剂模拟物料微团在反应系统中流动特性是常用的方法。由于示踪剂微团数目和单位时间中的时间微元数目均符合大数定理,单个示踪剂微团的流出反应系统成为随机概率的统计问题。利用Excel表格、函数功能及VBA混合编程,克服了其他编程软件对处理模拟数据不太尽如人意的缺点,与理论推导十分接近的模拟了CSTR反应系统内物料的流动状况,为探索和揭示各类反应器流动特性提供了一种有效解决途径。