河道一维非恒定流数值模拟深化研究

传统的河道一维非恒定流数值计算一般采用特征线法和以Preissmann方法为代表的有限差分法.特征线法计算精度比较高,但受时间步长的限制,用于河道一维非恒定流计算时计算效率却不太高.而Preissmann方法相比特征线法计算效率有所提高,但在求解过程中特征量的守恒性却没有做出相应要求.为了兼顾数值计算的效率和特征量的守恒,建立了基于有限体积法的河道一维非恒定流数值计算方法,并分别选取淮河干流洪水和史灌河洪水进行了验证计算,验证计算成果表明所采用的方法特征量守恒性较好,洪峰水位计算值与实测值吻合也较好,可用于河道一维非恒定流计算.     

楔形流道内单气泡动力学行为特性研究

楔形流道是一个具有复杂物理边界的流场,对其内部气液两相流动特性的研究具有现实意义.该文首先对孔板流量计内掺混气泡的两相流体建立了数学模型,采用贴体坐标系同位网格下的SIMPLE算法解决了速度与压力的耦合问题,改进了贴体坐标下Level Set方法,并利用其对楔形孔板流量计内单气泡两相流场进行了模拟.针对不同Re数和不同We数时其内部流场的模拟结果进行了分析,得出流场内气泡形态及其流动特性的变化规律.     

基于SIP/SIMPLE协议实现在席服务

本文提出了如何利用SIMPLE／SIP协议实现未来的在席和即时消息服务，通过分析SIP技术的优势和SIMPLE实现的机理，提出了较为健壮、安全、灵活的在席服务程序模型。     

压水堆上腔室模拟体三维流场分析

本文以秦山核电厂压水堆为例，对其上腔室模拟体内的紊流强迫流动进行了三维稳态研究。采用Ｌａｕｎｄｅｒ和Ｓｐａｌｄｉｎｇ提出的Ｋ－ε两方程模型，并结合壁面函数法，对模拟体内的紊流强迫流动进行了数值模拟，得到了三维流速分布以及最大横向流速所在区域。在上腔室模拟体上，以水为介质进行了流场的可视化实验研究，采用激光测速仪测得了纵向流速分布，并用流线显示了流场，数值计算与流场试验结果符合较好。     

二维稳态传热问题的计算机仿真

热量传输现象在工程技术领域中广泛存在，对二维稳态传热情形下温度场分布的研究有重要现实意义。对于复杂几何形状的物体和非线性的边界条件，分析解法显得无能为力；相比之下，建立在有限元基础上的数值计算是有效和准确的。在传热和流体流动问题的数值计算方面，SIMPLE算法被广泛采用。通过VC和Matlab的混合编程用SIMPLE算法实现了对二维稳态传热问题的计算仿真，描述了温度场的分布。     

A bridge between projection methods and SIMPLE type methods for incompressible Navier–Stokes equations

A bridge is built between projection methods and SIMPLE type methods (Semi‐Implicit Method for Pressure‐Linked Equation). A general second‐order accurate projection method is developed for the simulation of incompressible unsteady flows by employing a non‐linear update of pressure term as Θⁿ?pⁿ⁺¹+(I?Θⁿ)?pⁿ, where Θⁿ is a coefficient matrix, which may depend on the grid size, time step and even velocity. It includes three‐ and four‐step projection methods. The standard SIMPLE method is written in a concise formula for steady and unsteady flows. It is proven that SIMPLE type methods have second‐order temporal accuracy for unsteady flows. The classical second‐order projection method and SIMPLE type methods are united within the framework of the general second‐order projection formula. Two iteration algorithms of SIMPLE type methods for unsteady flows are described and discussed. In addition, detailed formulae are provided for general projection methods by using the Runge–Kutta technique to update the convective term and Crank–Nicholson scheme for the diffusion term. Copyright © 2007 John Wiley & Sons, Ltd.     

Development of a remote fault diagnosis system applicable to autonomous mobile robots

In this paper, the novel idea of using an autonomous mobile robot as a virtual local network is proposed as a system for the remote diagnosis of faults of a mobile robot. There are two primary points in this research. First, an objective of the research is to achieve a system with good expandability, i.e. one in which the diagnosis can be achieved whether there are many or few mobile robots to be diagnosed. To accomplish this goal by simply changing some system settings, a simple network management protocol (SNMP) structure is utilized. Within the developed diagnosis system, a mobile robot is taken as one of the management objects of the network management system (NMS). The SNMP, which is widely used in the NMS, is applied and adapted to the developed system as the communication protocol for exchanging diagnosis information. Moreover, by taking advantage of the active moving and sensing ability of autonomous mobile robots, an effective method of fault inference called a 'run-test' is discussed. By using this method, the accuracy of the diagnoses is improved. In the best-case scenario, the certainty of an accurate diagnosis increased from 20% (without using the 'run-test') to 93%. On the other hand, in some cases, the accuracy of the diagnosis results barely improved. On average, among the cases discussed in this paper, the accuracy of the diagnosis results improved about 2.1 times by the proposed method.     

Two-dimensional modeling of selective CO oxidation in a hydrogen-rich stream

In this study, carbon monoxide removal by preferential oxidation in a hydrogen-rich stream is simulated between two parallel infinite plates of 150 μm distance. A three-step kinetic is considered that includes carbon monoxide oxidation, hydrogen oxidation and water–gas shift reaction. The walls temperature is in the range of 80–120 °C. The function of this microreactor is to reduce carbon monoxide content from about 2% to below 10 ppm, suitable for use in a PEM fuel cell. Based on the problem conditions, the flow is in the continuum regime and application of the Navier–Stokes equations is admissible. In order to simulate the reacting flow, continuity, conservations of x- & y-momentum, conservation of energy, conservation of species, state equation and reaction rates are simultaneously solved through SIMPLE algorithm by utilizing power-law scheme. Effects of important parameters including walls temperature, steam content, CO content and O₂/CO are assessed. It is observed that increasing walls temperature or oxygen content will increase both CO selectivity and conversion. It is also found that by steam addition, CO conversion is improved without significant change of CO selectivity. These results are in good agreement with previous published data.     

Solution of transport equations on unstructured meshes with cell-centered colocated variables. Part II: Applications

This paper describes applications of the discretization procedure presented in the companion paper [A.W. Date, Solution of transport equations on unstructured meshes with cell-centered colocated variables. Part I. Discretization, Companion Paper, this volume]. Six problems having different domain complexities, presence of body and surface forces and, boundary conditions are solved. Where possible, the solutions are compared with published experimental or numerical data.     

A MODIFIED SIMPLE ALGORITHM FOR 2-D FLOW IN OPEN CHANNEL

1.　INTRODUCTIONSince the SIMPLE[1 ] algorithm was set up,it has been used to numerically simulateincompressible flow successfully.And later on,the improved algorithms such as SIMPLERalgorithm[2 ] and SIMPLEC algorithm[3] have been presented in succession.For all thealgorithms stated above,only when velocity field varies linearly with water pressure(i.e.,pressure flow) ,owing to the coefficients of the velocity correction formulae beingindependent of pressure,do the velocity corre…