Experimental investigation and CFD modelling of flow, sedimentation, and solids separation in a combined sewer detention tank

The lack of knowledge about particle behavior in combined sewer detention tanks remains a significant difficulty for the design of these works. In this paper, the use of 3D computational fluid dynamics (CFD) is investigated for studying flow, sedimentation, and solids separation in a tank equipped with one inlet pipe and two outlets (outlet pipe and overflow weir). Twenty-three experiments have been carried out. The Fluent^® CFD code is used for simulating the flow field. Sedimentation and solids separation are calculated using the particle tracking facility of the software. Bed shear stress (BSS) and bed turbulent kinetic energy (BTKE) boundary conditions are investigated. The time scale constant of the random walk model has been set to the unexpected value of 0.5-1. The simulated mass percentages and deposit locations are in good agreement with measurements. The sensitivity to the BTKE threshold and particle density is studied.     

基于SPH方法的弹性体贮箱内液体晃动特性分析

采用Abaqus中的光滑粒子流体动力学(Smoothed Particle Hydrodynamics,SPH)求解器分析贮箱液体晃动.通过理论解验证SPH算法分析液体晃动的可行性;考察贮箱模型分别为弹性体和刚体时的压力变化,可知刚体贮箱的峰值压力比弹性体的大且其峰值出现更早;考虑贮箱为弹性体,研究在各因素下充液贮箱的晃动特性,包括充液量、晃动转角、液体材料属性和周期等.当贮箱充液量为2/3左右时,贮箱受液体晃动影响最明显;随着晃动转角的增大或周期减小,贮箱结构变形显著增大;液体材料属性对贮箱的影响有限.     

带球形底的圆柱容器中液体小幅晃动的实验研究和有限元分析

晃动阻尼比的计算一直是航天器控制系统建模中很难把握的问题,本文进行了带球形底的圆柱容器中液体小幅晃动模态的固有频率和阻尼的实验研究,并将其与作者提出的有限元计算得到的结果进行了对比分析．频率的计算值与实验值吻合得很好,按洁净液面情况算得的阻尼值比实验值偏小．如果将液面污染耗散带来的阻尼乘以一定的因子引入阻尼的计算,则可得到与实验结果接近的阻尼计算值．这种形状容器在卫星上常用,本文结果对工程具有很好的指导意义．     

An investigation into the modelling of virtual objects with sound vibration properties

In order to increase the power of virtual environments, several different attempts have been made to incorporate sound interactivity in some form. For example, several implementations of virtual environments permit the playing of a previously recorded soundfile upon the triggering of an associated event. The user may then, for instance, perceive the sound of a creaky door when one is opened. However, a relatively more effective system for entertaining joint audio and visual response may be derived by using physical modelling techniques. We have undertaken a pilot investigation in which virtual objects are implemented in a manner such that they implicitly possess vibration properties analogous to that of the real world. Consequently these objects are able to vibrate in response to stimulus. The vibrations may be visually perceived as, for example, wave patterns on the surface of an object, and acoustically perceived by mapping values representative of surface displacement to a loudspeaker. This paper discusses the current state of the project.     

发电列车车下燃油箱保温性能CFD仿真

基于CFD理论,应用STAR-CCM+仿真某发电列车车下燃油箱在给定高寒工况下的保温性能.在考虑列车运行时车外流场影响的基础上,耦合分析箱体、保温材料和燃油等的温度分布特性,找出燃油可能发生结蜡的区域.给出相关分析结论和改进建议,为保证燃油箱拥有稳定的工作性能提供可靠的设计参考.     

Nonlinear modelling and control of the flow over aerofoils using CFD simulations

A simulation based approach for nonlinear dynamical modelling and feedback control of the drag to lift ratio for aerofoils is investigated through case studies involving NACA 23012, ag13 and b737a aerofoils. The flow around the aerofoils is studied via numerical solutions of the 2D Navier–Stokes (NS) equations. A standard computational fluid dynamics (CFD) solver is extended to be able to measure desired feedback values and to apply a control input to the flow field. The proposed modelling and control approach is based on first determining the measurement points and injection points on the aerofoil for the control input. Then, to estimate the dynamical model, some input–output data are collected by injecting a chirp input flow to the field and saving the measurement data. Next a Hammerstein–Wiener (HW) type nonlinear dynamical model of the flow field is estimated using system identification. For control design, the nonlinear part of the model is eliminated by means of inverse functions, followed by the application of automated tuning methods to the linear part to obtain the closed-loop system. The results show that the designed feedback control system can reduce the drag to lift ratio considerably as compared to the unactuated case.     

An improved numerical solution of multiphase flow analysis in soil

The present paper is concerned with a numerical solution for the analysis of coupled water, a non-aqueous phase liquid, and gas and heat flow in unsaturated and saturated soil. First, it briefly presents all the problem governing equations and then concentrates on the development of a robust numerical solution algorithm. It improves the solution procedure by extending the primary variable switching scheme so that it can also be used for multiphase flow analysis and by developing a method for reducing the usual numerical oscillations. Finally, a sample numerical analysis of a spill of diesel fuel in a box filled with partially water-saturated soil is presented.     

Physical modelling and control of lateral web position for wallpaper making processes

This paper presents a modelling and control algorithm for the lateral movement of web using a pivoting guider, where an accurate lateral positioning is important for web conveyor systems so as to achieve a high productivity and improve the product quality. The process considered is the hot embosser for the polyvinyl chloride-based materials where a steering guide is used for the in-register embossing. A new theoretical model is developed by regarding a moving web as a beam with a very small, but finite thickness. This leads to a transfer function that has four complex poles and two zeros with a time delay. This model has been validated through real experiments. The design of a Smith predictive control scheme has been made that shows, from a number of real-time applications, a high potential in speeding up the response of the pivoting guider and reducing the lateral variations of the moving web.     

An investigation of stability limits while holding a load

The objective of this study was to investigate the effects of load height and foot placement on the functional base of support (FBOS) limits and the postures that participants used when they reached their FBOS limits. Twelve young male participants were tested while holding a 12-kg load at reach (above their heads), at shoulder and knuckle height, and unladen under both wide and narrow foot placements. The FBOS limits and the centre of pressure (COP) excursion length were calculated based on data from a force platform. Postural angles when participants reached their FBOS limits were calculated from records of a 2-D motion analysis system. The results showed that the load height had greater effect on the posterior FBOS limit. As the load height decreased, the COP excursion length decreased. Participants were prone to using a hip strategy to maintain postural balance when reaching their FBOS limits. Quantitative data of FBOS limits and postural control while participants hold a load at various heights when reaching their FBOS limits is of value for designing a safe materials handling workplace.     

An investigation of stability limits while holding a load

The objective of this study was to investigate the effects of load height and foot placement on the functional base of support (FBOS) limits and the postures that participants used when they reached their FBOS limits. Twelve young male participants were tested while holding a 12-kg load at reach (above their heads), at shoulder and knuckle height, and unladen under both wide and narrow foot placements. The FBOS limits and the centre of pressure (COP) excursion length were calculated based on data from a force platform. Postural angles when participants reached their FBOS limits were calculated from records of a 2-D motion analysis system. The results showed that the load height had greater effect on the posterior FBOS limit. As the load height decreased, the COP excursion length decreased. Participants were prone to using a hip strategy to maintain postural balance when reaching their FBOS limits. Quantitative data of FBOS limits and postural control while participants hold a load at various heights when reaching their FBOS limits is of value for designing a safe materials handling workplace.     

Statistical process monitoring of a multiphase flow facility

Industrial needs are evolving fast towards more flexible manufacture schemes. As a consequence, it is often required to adapt the plant production to the demand, which can be volatile depending on the application. This is why it is important to develop tools that can monitor the condition of the process working under varying operational conditions. Canonical Variate Analysis (CVA) is a multivariate data driven methodology which has been demonstrated to be superior to other methods, particularly under dynamically changing operational conditions. These comparative studies normally use computer simulated data in benchmark case studies such as the Tennessee Eastman Process Plant (Ricker, N.L. Tennessee Eastman Challenge Archive, Available at 〈http://depts.washington.edu/control/LARRY/TE/download.html〉 Accessed 21.03.2014).The aim of this work is to provide a benchmark case to demonstrate the ability of different monitoring techniques to detect and diagnose artificially seeded faults in an industrial scale multiphase flow experimental rig. The changing operational conditions, the size and complexity of the test rig make this case study an ideal candidate for a benchmark case that provides a test bed for the evaluation of novel multivariate process monitoring techniques performance using real experimental data. In this paper, the capabilities of CVA to detect and diagnose faults in a real system working under changing operating conditions are assessed and compared with other methodologies. The results obtained demonstrate that CVA can be effectively applied for the detection and diagnosis of faults in real complex systems, and reinforce the idea that the performance of CVA is superior to other algorithms.     

On a purely lagrangian formulation of sloshing and fluid-induced vibrations of tanks

A general variational principle for fluid-structure interactions is obtained from a purely Lagrangian point of view, thus avoiding any difficulty at the fluid-structure interaction. This rather general variational principle is shown to degenerate, when suitable restrictions are made, in two known formulations, whose range of applicability is defined with the aid of three nondimensional numbers.     

An investigation of data entry methods with a personal computer

The features of three methods of data entry were investigated and a trial of them was carried out using operators with differing amounts of keyboard experience. The first method was a simple system of character entry using a word processing package, and the second and third systems were written in a commercial data base language; one was designed to possess limited intelligence, the other moderate intelligence. The amount of time and computing expertise required to set up each method increased in parallel with its sophistication. The most sophisticated method offered theoretical advantages of reduced error rates and increased keying rates but these were not realized in practice. The limited intelligence method, in which data were entered into a screen image of the record form, was fastest overall and was most popular with all users. This method together with verification by dual keying will provide a convenient, rapid, and high fidelity method of data entry. The simplest method was found to be adequate for short forms but incurred high error rates with longer forms.     

An investigation of the microcomputer as a mathematics teaching aid

Three short computer programs are being developed to aid the teaching of elementary graph interpretation in the first years of the secondary school. They run on a microcomputer which is used as a teaching aid and which supplements rather than replaces existing teaching methods. The programs exploit a variety of effective graphics including animation. A long term aim is to prepare the pupil more adequately for graphs in the real world by shifting the teaching emphasis from graph plotting to graph interpretation, and by greater use of graphs which depict data rather than mathematical functions. Classroom trials suggest that the programs are useful for class teaching and with small remedial groups. However, it is argued that the success of computer-based teaching material can only be accurately assessed when it is available to a substantial number of schools.     

Experimental investigation and finite element modelling of the effects of flow velocities on a skewed integral bridge

This paper presents finite element modelling of the effects of different flow velocities on the structural behaviour of a skewed integral bridge. Flow velocities affect the scour depths at the piles of a bridge and thus affect its structural behaviour. Laboratory tests on a scaled-down hydraulic model along with numerical modelling were performed to simulate the structural behaviour of the scoured integral bridge. A finite element package was used for the numerical modelling work, and the displacements and strains corresponding to the measured locations on the physical model were extracted. The experimental and numerical results for the case of maximum scour depths were compared.     

An empirical investigation of a modified technology acceptance model of IPTV

This study explores the factors influencing the adoption of IPTV, and tests the applicability of the technology acceptance model (TAM) in a new convergent technology. The behavioural constructs from TAM were tested for predicting user acceptance of IPTV. Structural equation modelling was used to analyse data and to design a theoretical model predicting the individual's intention to adopt IPTV. A modified TAM for IPTV proposes that new constructs determine user-perceived usefulness and enjoyment of using IPTV. Although this study confirms the impact of information quality and system quality on consumers' technology experience, it specifically shows that the perceived quality of content and system were found to have a significant effect on users' perceived usefulness and perceived enjoyment. In addition, social influences had a positive effect on the intention to use IPTV. These findings suggest an extension of the TAM model for convergence technologies. This research advances theory and contributes to the foundation for future research aimed at improving the understanding of users' adoption behaviour of convergence technologies. Implications of these findings for practice and research are examined.     

An attempt to reconstruct the cerebral bloodvessels from a lateral and a frontal angiogram

We prove that, contrary to expectation, no part of any bloodvessel of the brain can be reconstructed if only two orthogonal subtraction angiograms are given and a priori knowledge is not used.We further discuss other possible approaches to reconstruct the cerebral vessels.     

An application of knowledge based modelling using scripts

Knowledge management (KM) takes an increasingly significant place in the companies. The field of the KM aims to answer the problems of memory within companies by proposing methodologies to formalise know-how during the different steps of production. The KM is a domain with many ramifications and applications. One of them, so called Knowledge Based Engineering, search how to record knowledge from experts to put them in CAD software. Our study relates to the possibility of using the knowledge of an expert in modelling and, more particularly, on the automatic modelling of filling systems in foundry.