Modelling of the transverse loading of filament wound pipes

E-glass/epoxy resin pipes have been examined for static and low-velocity impact loads. In order to quantify the results, two modelling methods have been employed. The first, a simple analytical solution, predicted the deflection to first failure very well. This was only slightly improved by the use of a commercially available finite element package. This also allowed good prediction of the stress states of the pipes under transverse load and provides a convenient means of assessing which layers delaminate first.     

A numerical analysis of turbulent flow in pipes

The finite element method is used to solve both fully developed and developing turbulent flow in pipes. A particular feature of the approach is the introduction of a special wall element. The purpose of the introduction of such an element is twofold. The first is to avoid using elements with extremely large aspect ratios and the second to attempt a better representation of near wall changes in velocity. The applicability of the method is illustrated by comparing with published experimental and numerical data.     

Non-Newtonian flow in pipes of non-circular cross section

Rectilinear flow through pipes of non-circular cross section in the case of elastico- viscous liquids is not possible in general and some secondary flow in the cross section of the pipe is to be expected. The present paper contains a detailed theoretical and experimental study of the problem for pipes of square and rectangular cross section. Our main concern is the form that the secondary flows take and their influence on the flow rate through the pipe.

The governing equations, which are non-linear partial differential equations, are solved numerically using finite difference methods used in conjuction with S.L.O.R. It is shown, that, for both the square and rectangular cross sections, there are eight vortices present. These have the same strength for the square cross section, but four of the eight become progressively weaker as the ratio of the sides of the rectangle is increased.

The effect of a variable (shear-dependent) viscosity on the flow rate is found to be sub- stantial but the effect of the secondary flows on the flow rate is predicted to be small unless the fluid has some rather unusual properties

The experimental results are in general agreement with the theoretical predictions.     

Viscosity effects on flows of generalized Newtonian fluids through curved pipes

This paper is concerned with the application of finite element methods to obtain solutions for steady fully developed generalized Newtonian flows in a curved pipe of circular cross-section and arbitrary curvature ratio, under a given axial pressure gradient.     

Modelling and control of a class of time-varying continuous flow processes

Models of variable parameter flow processes are derived and their control is discussed. Using a pH reactor with varying flow rate as an example a variable transformation is introduced, which makes the model equations invariant under a new time scale. For a restricted class of flow processes classical analysis and synthesis methods can then be used to design a proper controller to guarantee the system stability and performance in general. The method is illustrated by developing a time-varying PID-controller algorithm as an example. Both simulation results and pilot-plant tests are reported, to verify the performance of the controller.     

Magnetohydrodynamic flow with slippage in an annular duct for microfluidic applications

In this paper, we investigate theoretically the 3D laminar flow of an electrolyte in an annular duct driven by a Lorentz force. The duct is formed by two concentric electrically conducting cylinders limited by insulating bottom and top walls. A uniform magnetic field acts along the axial direction, while a potential difference is applied between the cylinders so that a radial electric current traverses the fluid. The interaction of the current and the magnetic field produces a Lorentz force that drives an azimuthal flow. The steady flow is solved using a Galerkin method with Bessel–Fourier series in the radial direction and trigonometric series along the vertical direction, allowing different combinations of slip conditions at the walls. The orthogonality of both series with the general boundary conditions of the third kind is used to find an analytic approximation. Velocity patterns and flow rates are explored by varying the aspect ratio of the duct and the gap between the cylinders, as well as the slippage at the walls. Results can provide useful information for optimization and design of annular microfluidic devices.     

高炉环缝洗涤器流场和阻力特性数值模拟

为预测高炉环缝洗涤器（Annular Gap Scrubber,AGS）内部流场和阻力特性,采用CFD仿真方法建立AGS的二维轴对称CAE仿真模型．实测数据检验表明该模型的仿真偏差在10％以内,可以满足工程应用需求．对高炉AGS的多工况仿真结果表明,喷水引起的压力损失增加约占总压差的40％～70％;水滴撞击环缝内锥壁面且撞击区域集中,易造成内锥磨损．CAE仿真得到的阻力特性已成功应用于国内首套自主研发的高炉AGS．     

Pipelines: Modelling a software architecture through relations

A pipeline is a popular architecture which connects computational components (filters) through connectors (pipes) so that computations are performed in a stream like fashion. The data are transported through the pipes between filters, gradually transforming inputs to outputs. This kind of stream processing has been made popular through UNIX pipes that serially connect independent components for performing a sequence of tasks. We show in this paper how to formalize this architecture in terms of monads, hereby including relational specifications as special cases. The system is given through a directed acyclic graph the nodes of which carry the computational structure by being labelled with morphisms from the monad, and the edges provide the data for these operations. It is shown how fundamental compositional operations like combining pipes and filters, and refining a system by replacing simple parts through more elaborate ones, are supported through this construction.Received: 23 September 2002 / 4 May 2003     

GDQR法用于输流曲管的流致振动研究

将广义微分求积法(GDQR)用于分析输流曲管的流致振动问题,这是一个新的尝试．基于输流曲管的面内振动微分方程,利用GDQR法使曲管系统在空间域上得以离散化,从而获得了输流曲管的动力学方程组．数值算例中,计算得到了输流曲管在几种典型边界条件下的固有频率以及曲管发生失稳的临界流速等,这些计算结果与前人的解析解结果吻合较好．此外,还给出了两端固定输流曲管典型的动力响应行为．研究表明,GDQR法极易处理输流曲管这一类动力学模型,精度令人满意,进一步的研究可望推广到输流管道的非线性振动分析中．     

Characteristics of annular impinging jets with/without swirling flow by short guide vanes

Annular jets impinging on a uniformly heated flat plate with or without swirling flow by short guide vanes are experimentally characterized. With the Reynolds number fixed at a relatively low value, the variation of jet flow structures with impinging distance is characterized using the technique of particle image velocimetry (PIV). Correspondingly, the distributions of wall pressure and heat transfer on the plate are measured. At sufficiently large impinging distances, without swirling flow, the obtained fl...     

High-fidelity simulations of unsteady flow through turbopumps and flowliners

High-fidelity computations were carried out to analyze the orbiter liquid hydrogen (LH₂) feedline flowliner and the low-pressure-fuel-turbopump (LPFTP). Computations were performed on the Columbia platform which is a 10,240-processor supercluster consisting of 20 Altix nodes with 512 processors each. Various computational models were used to characterize the unsteady flow features in the turbopump, including the orbiter LPFTP inducer, the orbiter manifold and an experimental test article used to represent the manifold. Unsteady flow originating from the orbiter LPFTP inducer is one of the major contributors to the high-frequency cyclic loading that results in high cycle fatigue damage to the gimbal flowliners just upstream of the LPFTP. The flowfields for the orbiter manifold and representative test article are computed and analyzed for similarities and differences. An incompressible Navier–Stokes flow solver INS3D, based on the artificial compressibility method, was used to compute the flow of liquid hydrogen in each test article.     

System monitoring through element flow reasoning

Whether a manufacturing plant is operating “healthily” or not can be identified by the characteristics of how elements (e.g., components or products, etc.) are moving in it. The technique presented in this paper can be regarded as a generic system approach as it aims at monitoring a system regardless of the nature. This concept is different from the approaches of constructing dedicated models to watch facilities; it aims at monitoring a system by employing simple counting devices to capture the element flowing characteristics. Also, a mathematical model to identify some typical problems in production such as Blocking, Slowdown, Overflow, etc. has also been provided. Simulated experimental works were conducted, which showed that the proposed technique is able to assist in the diagnostic operation in the case of a problem occurring.     

Liquid flow through a diverging microchannel

In this work, experiments and three-dimensional numerical calculations of fluid flow through diverging microchannels were carried out with the aim of bringing out differences between flow in uniform and nonuniform passages. Deionized water was used as the working fluid in the experiments where the effects of mass flow rate (8.33 × 10^?6 to 8.33 × 10^?5 kg/s), microchannel hydraulic diameter (118–177 µm), length (10–30 mm) and divergence angle (4°–16°) on pressure drop were studied. The results are analyzed in detail with the help of numerical data. The pressure drop exhibits a linear dependence on the mass flow rate, whereas it is inversely proportional to the divergence angle and square of the hydraulic diameter. The pressure drop increases anomalously at 16°, suggesting that flow reversal occurs between 12° and 16°, which agrees with the corresponding value at the conventional scale. For the purpose of predicting pressure drop using straight microchannel theory, an equivalent hydraulic diameter was defined. It is observed that the equivalent hydraulic diameter, located at one-third of the diverging microchannel length from the inlet, becomes mostly independent of the mass flow rate, microchannel hydraulic diameter, length and divergence angle. The pressure drop for a diverging microchannel becomes equal to an equivalent hydraulic diameter uniform cross-section microchannel, suggesting that conventional correlations for straight microchannels can also be applied to diverging microchannels. The data presented in this work are of fundamental importance and can help in optimization of diffuser design used for example in valveless micropumps.     

Simulation of the flow through woven fabrics

Filament-level three-dimensional simulations of the flow through single layer woven fabrics were done using FLUENT^TM. For screen Reynolds numbers, Re_s, between 50 and 300, CFD simulations reproduce experimental measurements of wind tunnel screen pressure drops to within ±10%. Simulations of woven fabrics with geometric non-uniformities have also been undertaken. In these simulations one or more strands of the fabric is shifted laterally relative to its undisturbed location. If the filament displacement, normalized by the centre-to-centre separation between filaments, is ε, the enhancement in the flow rate through the enlarged opening in the fabric is given by approximately 2ε. A very simplified model of the geometry is consistent with this enhanced flow rate. The findings of this research are relevant to both wind tunnel and papermachine forming fabric design.     

A computationally efficient method for simulating fluid flow in elastic pipes in three dimensions

We propose a new method for carrying out lattice-Boltzmann simulations of pulsatile fluid flow in three-dimensional elastic pipes. It is based on estimating the distances from sites at the edge of the simulation box to the wall along the lattice directions from the displacement of the closest point on the wall and the curvature there, followed by application of a nonequilibrium extrapolation method. Viscous flow in an elastic pipe is studied in three dimensions at a wall displacement of 5% of the radius of the pipe, which is realistic for blood flow through large cerebral arteries. The numerical results for the pressure difference, wall displacement and flow velocity agree well with the analytical predictions. At all sites, the calculation depends only on information from nearest neighbours, so the method proposed is suitable for efficient computation on multicore machines. Compared to simulations with rigid walls, simulations with elastic walls require only 13% more computational effort at the parameters chosen in this study.     

Understanding fire and smoke flow through modeling and visualization

Computer modeling and visualization are important tools for understanding the processes of fire behavior. Fire models range in complexity from simple correlations for predicting quantities such as flame heights or flow velocities to moderately complex zone fire models for predicting time-dependent smoke layer temperatures and heights. Zone fire model calculations can run on today's computers within minutes because they solve only four differential equations per room. Zone models approximate the entire upper layer with just one temperature. This approximation works remarkably well but breaks down for complicated flows or geometries. For such cases, computational fluid dynamics (CFD) techniques are required.     

Traffic simulation of two adjacent unsignalized T-junctions during rush hours using Arena software

In this paper, the focus is on simulating the traffic of two adjacent T-junctions during rush hours located at Jalan Universiti in the city of Skudai, Johor, Malaysia. This study was conducted with the objective of simulating the traffic on the network in order to understand and analyze its bottlenecks and propose solutions to improve it. The simulation model was developed with ARENA software, and the initial result shows that there is a substantial queue in one of the routes, arm C. A model with traffic light was proposed to tackle the problem. Results obtained from the improved model revealed that the average waiting time in arm C declined by 67%. Furthermore, the average waiting time of the queues in the entire system decreased by 53%. In addition, in this paper, it was shown how Arena software can be adopted to simulate traffic problems effectively. The method in this research can be applied to investigate various traffic scenarios and their consequences before implementing them in reality.     

Modelling of a new solar air heater through least-squares support vector machines

This paper reports on a modelling study of new solar air heater (SAH) system efficiency by using least-squares support vector machine (LS-SVM) method. In this study, a device for inserting an absorbing plate made of aluminium cans into the double-pass channel in a flat-plate SAH. A SAH system is a multi-variable system that is hard to model by conventional methods. As regards the LS-SVM, it has a superior capability for generalization, and this capability is independent on the dimensionality of the input data. In this study, a LS-SVM based method was intended to adopt SAH system for efficient modelling. For modelling, different mass flow rates in flow duct and collector types are used and then for obtaining the optimum LS-SVM parameters, such as regularization parameter, and optimum kernel function and parameters, several tests have been carried out. The performance of the proposed methodology was evaluated by using several statistical validation parameters. It is found that root mean squared error (RMSE) value is 0.0024, the coefficient of multiple determinations (R²) value is 0.9997 and coefficient of variation (cov) value is 2.1194 for the proposed radial basis function (RBF)-kernel LS-SVM method at 0.03 kg/s air mass flow rate. It is found that RMSE value is 0.0135, R² value is 0.9991 and cov value is 2.9868 for the proposed RBF-kernel LS-SVM method at 0.05 kg/s air mass flow rate. Comparison between predicted and experimental results indicates that the proposed LS-SVM model can be used for estimating the efficiency of SAHs with reasonable accuracy.     

Healthcare Modelling through Role Activity Diagrams for Process-Based Information Systems Development

The aim of this paper is to introduce the socio-technical Role Activity Diagram modelling language to National Health Service (NHS) information systems requirements engineering using a process approach. Most requirements engineering in the NHS is done using data-driven methods such as data flow diagrams. Role Activity Diagrams provide not only a socio-technical method for analysing a particular systems development problem, but they also offer a process-based approach for capturing workflows and their associated information flows, and facilitate communication between analysts and users in an intuitive fashion. In particular, they elicit the important roles in a process and the interaction and collaboration required to achieve the goals of the process. The process approach has been applied in business information systems development. It is introduced here as a potential for systems development in the NHS.     

Inter-organizational relationships and the flow of information through value chains

I developed a framework that can identify types of inter-organizational relationships. Various kinds of information exchanged between trading partners were grouped into two broad types: transactional and managerial. I then examined the effects of inter-organizational information systems (IOS) and traditional communication media (TCM) on the amount of information exchanged. Stepwise regression analyses showed that the use of value chains was the most significant factor influencing the exchange of both types of information. In examining the impact of the information exchanged to improve production performance, it appeared that different kinds of information influenced different aspects. Depending on the usage level of the media and the types of information exchanged, four categories of inter-organizational relationships and their particular characteristics were defined: traditional links for coordination, strategic alliances, electronic links for coordination, and virtual organizations.