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Mass transfer between n-butanol and water has been studied in cocurrent pipeline flow. The apparatus consisted of a feed nozzle, a glass pipe contactor and a gravity settler. Compositions were determined by refractive index measurements. The variables studied were mass input ratio, total flow rate and contactor length. Pressure drop and holdup ratio also have been determined as a function of input ratio and total flow rate. Phase NTU's, determined directly by a method proposed by Colburn and Welsh (10), were found to correlate with individual phase velocities and also were dependent on the input ratio and the contactor length. Mass transfer stage efficiencies varied from near zero to nearly one-hundred per cent. The magnitude of the end effects was estimated by measuring the amount of mass transfer that occurred with virtually zero contactor length before settling. End effects were large. The pipeline contactor was compared to other experimental liquid-liquid extraction devices described in the literature, and was found to be superior in terms of "contactor effectiveness" and energy requirements. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

The aerodynamics of a set of two-dimensional elliptic cylinders with eccentricity of 0.8 and 0.6 is studied experimentally during the organised wake condition. The dynamic calibration of the transducer used for measurement of fluctuating pressures is described in detail. The data on Strouhal number, unsteady pressures and wake geometry are presented as a function of angle of attack during static condition of the models. The effect of Reynolds number on the fluctuating pressure is also examined. The results indicate dependence of the unsteady forces on Reynolds number at zero angle of attack. Basing the Strouhal number on projected width appears to reduce its dependence on the angle of attack of the models. The existence of a large phase angle between the fluctuating pressures is of interest. The wake geometry study indicates a gradual reduction in the ratio of the lateral to the longitudinal spacing with increase in angle of attack. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

[No Abstract Available] / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

We analyze the double Hopf bifurcations which occur in two geophysical fluid dynamics models: (1) a two-layer quasigeostrophic potential vorticity model with forcing and (2) a mathematical model of the differentially heated rotating annulus experiment. The bifurcations occur at the transition between axisymmetric steady solutions and non-axisymmetric travelling waves. For both models, the results indicate that, close to the transition, there are regions in parameter space where there are multiple stable waves. Hysteresis of these waves is predicted. For each model, center manifold reduction and normal form theory are used to deduce the local behaviour of the full system of partial differential equations from a low-dimensional system of ordinary differential equations. In each case, it is not possible to compute the relevant eigenvalues and eigenfunctions analytically. Therefore, the linear part of the equations is discretized and the eigenvalues and eigenfunctions are approximated from the resulting matrix eigenvalue problem. However, the projection onto the center manifold and reduction to normal form can be done analytically. Thus, a combination of analytical and numerical methods are used to obtain numerical approximations of the normal form coefficients, from which the dynamics are deduced. The first model differs from those previously studied with bifurcation analysis since it supports a steady solution which varies nonlinearly with latitude. The results indicate that the forcing does not qualitatively change the behaviour. However, the form of the bifurcating solution is affected. The second model uses the Navier-Stokes equations in the Boussinesq approximation, in cylindrical geometry. In addition to the double Hopf bifurcation analysis, a detailed axisymmetric to non-axisymmetric transition curve is produced from the computed eigenvalues. A quantitative comparison with experimental data finds that the computed transition curve, critical wave numbers and drift rates of the bifurcating waves are reasonably accurate. This indicates that the analysis, as well as the approximations which are made, are valid. / Science, Faculty of / Mathematics, Department of / Graduate

As a young child, my father once told me that it is impossible to know and understand everything. At first I did not believe him, but as I grew up, I realised why he said it. This realisation did not, however, dawn on me overnight. During my training many textbooks and lecturers painted the picture of a world that can be described by a few simple laws. When I finished my training and started to work as a water engineer, I realised that this was only an illusion. The difference between theory and practise was bigger than I thought. I eventually came to the realisation, through the wisdom of many others, that this gap between theory and reality is not only due to the limitations of science and technology, but also to beliefs. Often these beliefs are so intertwined with science and technology that the scientists and technologists themselves are not aware of it. This study attempts to explain why differences between theory and practise exist. The modelling of water treatment process tanks is used as a vehicle to demonstrate this. In the process it is shown that scientists and technologists cannot use models in a responsible manner without also considering the broader philosophical aspects. My personal most satisfying contribution was to demonstrate the influence of philosophical views on process tank design methods. The study also makes original contributions in the field of water treatment process tank modelling. Computational Fluid Dynamic models are used in an attempt to understand water treatment process tanks better. This modelling technique applies a combination of scientific, technological and modelling concepts. An appropriate question by many technical readers will be why a significant portion of this text includes philosophical concepts if the title of the study deals with process tank modelling? First the arguments presented and the process of argumentation, can assist many scientists and engineers to develop a much broader view of science, technology and models. A second reason for this inclusion is the background it gives to where theories originated and how they were developed. Most importantly, however, the realisation of the inherent shortcomings of theories came much later and this is the third reason for its inclusion. It deals with exposing invalid assumptions and misconceptions that are held in the design of some process tanks. These misconceptions often originate from a philosophical view rather than a scientific observation. The fourth reason is to demonstrate the importance of normative aspects in the practise of science and technology. Finally, it can also benefit philosophers in the sense that they can see how philosophy can be applied to very practical problems. A need that is unsatisfied in many scientific and technical fields. / Prof. J. Haarhoff

A statistical equilibrium theory in two-dimensional turbulence is used to study the emergence of coherent structures. Macroscopic states are described by a local probability measure on the fluctuating vorticity field. The most probable macroscopic state is characterized by maximizing entropy subject to a family of constraints derived from the conserved quantities of the incompressible Euler equations. Coherent structures are identified with such macrostates. Attention is focused on the special case of enstrophy-moments and a doubly periodic domain. The algorithm of Turkington and Whitaker is applied to this special case. The convergence properties of the algorithm are derived from the optimization structure of the constraint maximization problem. The algorithm produces an entropy increasing sequence. The trivial case of conserving energy and enstrophy serves as the starting equilibrium state when implementing the algorithm. The probability density of the energy-enstrophy model is Gaussian and we perturb away from the trivial case by imposing higher enstrophy moments. Perturbing away from the trivial case forces the model to become nonlinear. It is found that the preferred statistical equilibrium state of the maximum entropy problem is determined by kurtosis. For high kurtosis a dipole is preferred and for low kurtosis a shear-layer is preferred. Several local solutions are found which converge to the maximum entropy state for high energy.

This dissertation presents a theoretical study of a variety of charged polymer systems: Critical conditions are determined for adsorption of a charged polymer chain in an electrolyte solution by a curved, charged surface; the scaling behavior and density profiles of a polyelectrolyte brush is examined; the stretch-colapse transition of a charged, grafted polymer layers in a poor solvent is analyzed; and, the sequence dependence of heteropolymer configurations is calculated. These problems are studied theoretically using standard techniques of statistical mechanics.

The quasi-steady state-space models generally used to simulate the dynamics of underwater vehicles perform well in most steady flow scenarios, and are therefore acceptable for modeling today\'s fleet of endurance-focused autonomous underwater vehicles (AUVs). However, with their usage of numerous assumptions and simplifications, these models are not well suited to certain unsteady flow situations and for use in the development of AUVs capable of performing more extreme maneuvers. In the interest of better serving efforts to design a new generation of more maneuverable AUVs, a tool for simulating vehicle maneuvering within computational fluid dynamics (CFD) based environments has been developed. Unsteady Reynolds-averaged Navier-Stokes (URANS) simulations are used in conjunction with a 6-degree-of-freedom (6-DoF) rigid-body kinematic model to provide a numerical test basin for vehicle maneuvering simulations. The accuracy of this approach is characterized through comparison with experimental measurements and quasi-steady state-space models. Three state-space models are considered: one model obtained from semi-empirical database regression (this is the method most commonly used in application) and two models populated with coefficients determined from the results of prescribed motion CFD simulations. CFD analyses focused on supporting the design of a general purpose AUV are also presented. / Ph. D.

This thesis seeks to investigate the predictive capabilities of Advanced turbulence models in the wake region of a wall-mounted cube. Dynamic Hybrid RANS/LES (DHRL), Hybrid RANS/LES (HRL) models, Nonlinear Explicit Algebraic Reynolds Stress Model (NEARSM), One- and Two-equation models, and numerical flux schemes will be compared against Direct Numerical Simulation (DNS) results to determine which model, or combination of models, produce the closest replication. The simulations were ran in Loci-Chem using both built-in features and modular code additions. The simulation results show the Shear Stress Transport (SST) model ran with NEARSM and Optimized Gradient REconstruction (OGRE) scheme gives better results than all other RANS and HRL models investigated herein. This result is matched only by SST with DHRL and OGRE. The best results were achieved using SST with NEARSM, DHRL, and OGRE. Thus, the NEARSM model shows potential to improve simulation results compared to simpler linear eddy-viscosity models.