Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2006. / Cyrus K. Aidun, Committee Member ; Farrokh Mistree, Committee Member ; Yves H. Berthelot, Committee Member ; Philip J. W. Roberts, Committee Member. Includes bibliographical references.

Typescript. Includes bibliographical references (leaves 124-126).

Master of Technology: Civil Engineering In the Faculty of Engineering At the Cape Peninsula University of Technology 2014 / Notches, particularly rectangular and V shaped are the cheapest and most common devices used to measure the flow rate of water in open channels. However, they have not been used to measure the flow rate of non-Newtonian fluids. These viscous fluids behave differently from water. It is difficult to predict the flow rate of such fluids during transportation in open channels due to their complex viscous properties. The aim of this work was to explore the possibility of extending the application of especially rectangular and V-shaped notches to non-Newtonian fluids. The tests reported in this document were carried out in the Flow Process and Rheology Centre laboratory. Notches fitted to the entrance of a 10 m flume and an in-line tube viscometer were calibrated using water. The in-line tube viscometer with 13 and 28 mm diameter tubes was used to determine the fluid rheology. Flow depth was determined using digital depth gauges and flow rate measurements using magnetic flow meters. Three different non-Newtonian fluids, namely, aqueous solutions of Carboxymethyl Cellulose (CMC) and water-based suspensions of kaolin and bentonite were used as model non-Newtonian test fluids. From these the coefficient of discharge (Cd) values and appropriate non-Newtonian Reynolds numbers for each fluid and concentration were calculated. The experimental values of the coefficient of discharge (Cd) were plotted against three different definitions of the Reynolds number. Under laminar flow conditions, the discharge coefficient exhibited a typical dependence on the Reynolds number with slopes of ~0.43-0.44 for rectangular and V notches respectively. The discharge coefficient was nearly constant in the turbulent flow regime. Single composite power-law functions were used to correlate the Cd-Re relationship for each of the two notch shapes used. Using these correlations, the Cd values could be predicted to within ±5% for the rectangular and V notches. This is the first time that such a prediction has been done for a range of non-Newtonian fluids through sharp crested notches. The research will benefit the mining and food processing industries where high concentrations of non-Newtonian fluids are transported to either disposal sites or during processing.

O objetivo deste trabalho foi a análise do movimento do fluido dentro de um segmento de vórtice em anel gerado através da ação magnetohidrodinâmica e o monitoramento do seu movimento resultante, de modo a oferecer condições de visualização usando velocimetria a laser com técnica de processamento de imagens de partículas envolvidas na circulação. O objetivo final desta linha de pesquisa é que através de análises de dados como as velocidades envolvidas na circulação obtida, possa modelar corpos em movimento em fluidos, de forma que o arrasto devido ao seu deslocamento possa ser reduzido. O movimento circulatório a que foi submetido o fluido sem meios mecânicos, ou seja, por meio de uma força resultante da ação de campos conjugados, teve a função de criar campos de baixa pressão tendo, para isso, acelerado o fluido em um circuito fechado restrito pela atuação da força e das paredes da célula de ensaio. O movimento do fluido, com a leitura da variação de velocidades em pontos diferentes do circuito teve o auxílio de um equipamento ótico que forneceu todas as variações, mesmo as mínimas, mostrando que tal aparato pode ser desenvolvido para a obtenção de melhores resultados. / The aim of this work involves the analysis of fluid flow, using sea water stimulated by localised magnetohydrodynamic induction within an experimental glass sided receptacle. The above mentioned apparatus simulated one segment of a three dimensional apparatus capable of creating a flow pattern very similar to that of a vortex ring. Particle Image Velocimetry techniques using a copper vapour laser with computerised image and data acquisition system were used to analyse the flow in the experimental segment. The final aim of this line of research is to be able to eventually model the shape of bodies in movement within a fluid when combined with the use of a magnetohydrodynamically induced flow field in such a way as to significantly reduce fluid drag forces on the body. Circulatory movement was induced in the fluid within the confines of the experimental tank using a locally applied Lorentz field force between electrodes to accelerate the fluid. Both the electrical and magnetic fields were controlled independently using separate external rectified a.c. circuits. The aim of the fluid movement described above was to induce low static pressure over a specific surface area. The analysis of the fluid movement, including the measurement of velocities in different points of the circuit was attained using specialised optical equipment linked to a computerised data acquisition and analysis system. The results, which included exceptionally low velocity readings, showed thatsuch equipment possesses the potential for developed for the attainment of better results in the future.

O objetivo deste trabalho foi a análise do movimento do fluido dentro de um segmento de vórtice em anel gerado através da ação magnetohidrodinâmica e o monitoramento do seu movimento resultante, de modo a oferecer condições de visualização usando velocimetria a laser com técnica de processamento de imagens de partículas envolvidas na circulação. O objetivo final desta linha de pesquisa é que através de análises de dados como as velocidades envolvidas na circulação obtida, possa modelar corpos em movimento em fluidos, de forma que o arrasto devido ao seu deslocamento possa ser reduzido. O movimento circulatório a que foi submetido o fluido sem meios mecânicos, ou seja, por meio de uma força resultante da ação de campos conjugados, teve a função de criar campos de baixa pressão tendo, para isso, acelerado o fluido em um circuito fechado restrito pela atuação da força e das paredes da célula de ensaio. O movimento do fluido, com a leitura da variação de velocidades em pontos diferentes do circuito teve o auxílio de um equipamento ótico que forneceu todas as variações, mesmo as mínimas, mostrando que tal aparato pode ser desenvolvido para a obtenção de melhores resultados. / The aim of this work involves the analysis of fluid flow, using sea water stimulated by localised magnetohydrodynamic induction within an experimental glass sided receptacle. The above mentioned apparatus simulated one segment of a three dimensional apparatus capable of creating a flow pattern very similar to that of a vortex ring. Particle Image Velocimetry techniques using a copper vapour laser with computerised image and data acquisition system were used to analyse the flow in the experimental segment. The final aim of this line of research is to be able to eventually model the shape of bodies in movement within a fluid when combined with the use of a magnetohydrodynamically induced flow field in such a way as to significantly reduce fluid drag forces on the body. Circulatory movement was induced in the fluid within the confines of the experimental tank using a locally applied Lorentz field force between electrodes to accelerate the fluid. Both the electrical and magnetic fields were controlled independently using separate external rectified a.c. circuits. The aim of the fluid movement described above was to induce low static pressure over a specific surface area. The analysis of the fluid movement, including the measurement of velocities in different points of the circuit was attained using specialised optical equipment linked to a computerised data acquisition and analysis system. The results, which included exceptionally low velocity readings, showed thatsuch equipment possesses the potential for developed for the attainment of better results in the future.

The target of this work is to contribute to the enhancement of numerical methods for the simulation of complex thermal systems. Frequently, the factor that limits the accuracy of the simulations is the computing power: accurate simulations of complex devices require fine three-dimensional discretizations and the solution of large linear equation systems.Their efficient solution is one of the central aspects of this work. Low-cost parallel computers, for instance, PC clusters, are used to do so. The main bottle-neck of these computers is the notwork, that is too slow compared with their floating-point performance.Before considering linear solution algorithms, an overview of the mathematical models used and discretization techniques in staggered cartesian and cylindrical meshes is provided. The governing Navier-Stokes equations are solved using an implicit finite control volume method. Pressure-velocity coupling is solved with segregated approaches such as SIMPLEC.Different algorithms for the solution of the linear equation systems are reviewed: from incomplete factorizations such as MSIP, Krylov solvers such as BICGSTAB and GMRESR to acceleration techniques such as the Algebraic Multi Grid and the Multi Resolution Analysis with wavelts. Special attention is paid to preconditioned Krylov solvers for their application to parallel CFD problems.The fundamentals of parallel computing in distributed memory computers as well as implemetation details of these algorithms in combination with the domain decomposition method are given. Two different distributed memory computers, a Cray T3E and a PC cluster are used for several performance measures, including network throughput, performance of algebraic subroutines that affect to the overall efficiency of algorithms, and the solver performance. These measures are addressed to show the capabilities and drawbacks of parallel solvers for several processors and their partitioning configurations for a problem model.Finally, in order to illustrate the potential of the different techniques presented, a three-dimensional CFD problem is solved using a PC cluster. The numerical results obtained are validated by comparison with other authors. The speedup up to 12 processors is measured. An analysis of the computing time shows that, as expected, most of the computational effort is due to the pressure-correction equation,here solved with BiCGSTAB. The computing time algorithm , for different problem sizes, is compared with Schur-Complement and Multigrid. / El trabajo de tesis se centra en la solución numérica de las ecuaciones de navier-Stokes en regimen transitorio, tridimensional y laminar. Los algoritmos utilizados son del tipo segregado (SIMPLEC)y se basan en el uso de técnicas de volumenes finitos, con mallas estructurales del tipo staggered y discretizaciones temporales implícitas. En este contexto, el pricipal, problema son los elevados tiempos de cálculo de las simulaciones, que en buena parte se deben a la solución de los sistemas de ecuaciones lineales. Se hace una revisión de diferentes métodos utilizados típicamente en ordenadores secuenciales: GMRES, BICGSTAB, ACM, MSPIP. A fin de reducir los tiempos de cálculo se emplean ordenadores paralelos de memoria distribuida, basados en la agrupacion de ordenadores personales convencionales (PC clusters). Por lo que respecta a la potencia de cálculo por procesador, estos sistemas son comparables a los ordenadores paralelos de memoria distribuida convencionales (como el Cray T3E) siendo, su principal problema la baja capacidad de comunicación (elevada latencia, bajo ancho de banda). Este punto condiciona toda la estrategia computacional, obligando a reducir al máximo el número y el tamaño de los mensajes intercambiados. Este aspecto se cuantifica detalladamente en la tesis, realizando medidas de tiempos de cálculo en ambos ordenadores para diversas operaciones críticas para los algoritmos lineales. Tambien se miden y comparan los tiempos de cálculo y speed ups obtenidos en la solución de los sistemas lineales con diferentes algoritmos paralelos (Jacobi, MSIP, GMRES, BICGSTAB) y para diferentes tamaños de malla. Finalmente, se utilizan las técnicas anteriores para resolver el caso denominado driven cavity, en situacionies tridimensionales y con numeros de Reynolds de hasta 8000. Los resultados obtenidos se utilizan para validar los códigos desarrollados, en base a resultados de otros códigos y también se basa en la comparación con resultados experimentales procedentes de la bibliografía. Se utilizan hasta 12 procesadores, obteniendose spped ups de hasta 9.7 en el cluster de PCs. Se analizan los tiempos de cálculo de cada fase del código, señalandose areas para futuras mejoras. Se comparan los tiempos de cálculo con los algoritmos implementados en otros trabajos. La conclusión final es que los clusters de PCs son una plataforma de gran potencia en los cálculos de dinámica de fluidos computacional.

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Thesis (M.S. in Aeronautical Engineering)--Naval Postgraduate School, June 2003. / Thesis advisor(s): Kevin D. Jones, Max F. Platzer. Includes bibliographical references (p. 89). Also available online.

Electrospray ionization (ESI) has been an invaluable technique to mass spectrometry (MS) especially for analyzing large bio-molecules with unparalleled sensitivity, robustness, and simplicity. Great effort in the development of ESI technique has been devoted in the emitter design, as its shape and geometry have proved pivotal to the electrospray performance and further MS detection. Intrinsic problems for the traditional single-hole emitters including clogging and low throughput limit the applicability of the technique. To address this issue, the current project is focused on developing multiple electrospray (MES) emitters for improved ESI-MS analysis. In this thesis, joint work of both computational fluid dynamic (CFD) simulations for electrospray and offline electrospray experiments for spray current measurement were performed. Numerical simulations were used to test the effect of various emitter designs on electrospray performance and the laboratory results serve as a guide and validation. The CFD code was based on Taylor-Melcher leaky dielectric model (LDM) and the transient electrospray process was successfully simulated. The method was first validated via a 750 μm inner diameter (i.d.) emitter and further applied to a 20 μm i.d. model. Different stages of the electrospray process were visually demonstrated and the quantitative investigations for the change of spray current under various applied electric fields and flow rates share good agreement with previous simulations and measurements. Based on the single-aperture prototype, MES simulations were performed with 2-hole and 3-hole emitters. Simulation predictions compared favorably with the experimental results. Evidence from this work has proved that CFD simulation can be used as an effective numerical tool to test emitter designs for MES. The benchmarking result on the successful simulation of a microscale emitter electrospray achieved in this work is believed to be the smallest scale of the dynamic simulation for electrospray published to date. / Thesis (Master, Chemistry) -- Queen's University, 2011-12-23 13:36:08.754

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