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• About
• The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Stochastic computer simulations of viscous fingering

Rees, S. January 1987 (has links)
This thesis aims to develop a computer simulation of the process that occurs when one displaces a viscous fluid such as oil by a less viscous one such as water in a porous medium. Chapter 1 outlines the problem and explains why a computer simulation rather than analytical treatment is necessary for the problem. Previous computer simulations of the problem are reviewed and their respective advantages and disadvantages are considered. Chapter 2 introduces the concept of 'simulated annealing', a stochastic computational technique for solving minimisation problems with many variables and this technique is used to make a crude model of the displacement problem. The results from this are considered and the reasons for the model's failure to adequately solve the problem are discussed. In chapter 3, simulated annealing is applied to the simpler problem of the travelling salesman where one has to find the shortest route around a collection of points. The aim of this chapter is to try and find an optimum simulated annealing schedule to minimise the computer time needed to achieve a satisfactory solution. This is successfully accomplished for this particular problem by fitting the relaxation time of the system as a function of temperature to an Arrhenhius type law. But this optimisation is problem specific and it is concluded that the complicated nature of the oil displacement problem effectively precludes treatment by annealing. In chapter 4 a stochastic micro model is developed in which a pressure gradient across the system forces water into oil bearing pores. The pores have varying sizes which represent sizes which represent the varying permeability in a porous medium. A modified Gauss Seidel method is used to solve for the pressure field and an analytic expression for the saturation update is developed. The final chapter, chapter 5, develops the above model further and in particular develops a scheme whereby conservation of fluid is guaranteed. The profiles of the fingering of the water into the oil are studied and it is found that their interface fractal dimension varies monotonically with viscosity ratio.
2

Velocity measurements in a thermally convecting high prandtl number fluid

Pickles, K. January 1985 (has links)
No description available.
3

Bifurcation in physical systems

Taverner, S. January 1986 (has links)
No description available.
4

Flow of a Two-Layered Viscous Fluid Towards a Line Sink

Reid, Thomas Lewis 10 1900 (has links)
<p> The thesis contains an experimental verification of a paper by D. G. Huber dealing with a solution to the problem of the irrotational motion of two fluid strata towards a line sink. Friction was assumed negligible in the theoretical analysis and, as a result, the experimental values deviated somewhat from the theoretical expectations. The largest deviation occurred at the point of incipient drawdown where the theoretical and experimental values of the Froude number differed by 48%. The trends obtained in the experiment verify the theoretical solution. The effect of viscosity at the point of incipient drawdown for two different interface height to width ratios was determined.</p> <p> The work of Harleman et al. in submerged sluice control was extended and showed that the Froude number of the lower layer at the point of incipient drawdown with high rates of flow was much larger than expected. The reason for the change was explained using the Khafagi-Hammad relationships.</p> / Thesis / Master of Engineering (MEngr)
5

Simulação de escoamentos viscosos utilizando mapeamentos entre equações / Viscous flow simulations using diferential equation mappings

Santiago, Gustavo Fuhr January 2007 (has links)
Este trabalho faz uma nova proposta de método para solucionar a equação advectivodifusiva tridimensional que descreve os escoamentos viscosos incompressíveis. Este método usa um esquema analítico baseado em split seguido de gênese de equações diferenciais. A solução do problema é efetuada em duas etapas distintas. A primeira etapa consiste na aplicação de um split não-homogêneo sobre as Equações de Navier-Stokes, no qual uma das equações do sistema resultante contém a derivada temporal e o termo viscoso, constituindo uma equação diferencial linear não-homogênea. A solução dessa equação é obtida via mapeamento em uma equação de primeira ordem, fornecendo o formato do campo de velocidades. A partir deste se obtém o formato da função corrente para fins de gênese. Desta forma faz-se com que simulações possam ser obtidas usando computadores portáteis e, mesmo assim, requeiram tempo de processamento pequeno para a solução de problemas ditos de engenharia. Estas vantagens podem ser diretamente traduzidas em aplicações práticas de simulação como, por exemplo, a possibilidade de tomada de decisão em tempo real sobre o controle de um processo em andamento numa planta industrial, respostas transientes num escoamento turbulento ou na previsão da dispersão de poluentes em rios e mananciais críticos à saúde da população. / This work proposes a new method to solve the three-dimensional advective-diffusive equation which describes incompressible viscous flows. The proposed solution uses an analytical method based in the split of the original equation, followed by a genesis of differential equa tions. The problem is solved in two distinct steps. The first step consists of applying a nonhomogeneous split on the Navier-Stokes equations, which results in one non-homogeneous partial differential equation containing the time derivative and the viscous term. This equation is solved by mapping it into a first order equation that provides the velocity field format. Using this result we are able to obtain the stream function format, which will be used in the following genesis. This sequence allows the use of portable computers to achieve simulation results for engineering problems in small enough processing time. These advantages can be used in applications such as real- time decision making about industrial processes variables, transient turbulent flow calculations or pollution dispersion simulations in rivers or other water sources critical to the population.
6

Simulação de escoamentos viscosos utilizando mapeamentos entre equações / Viscous flow simulations using diferential equation mappings

Santiago, Gustavo Fuhr January 2007 (has links)
Este trabalho faz uma nova proposta de método para solucionar a equação advectivodifusiva tridimensional que descreve os escoamentos viscosos incompressíveis. Este método usa um esquema analítico baseado em split seguido de gênese de equações diferenciais. A solução do problema é efetuada em duas etapas distintas. A primeira etapa consiste na aplicação de um split não-homogêneo sobre as Equações de Navier-Stokes, no qual uma das equações do sistema resultante contém a derivada temporal e o termo viscoso, constituindo uma equação diferencial linear não-homogênea. A solução dessa equação é obtida via mapeamento em uma equação de primeira ordem, fornecendo o formato do campo de velocidades. A partir deste se obtém o formato da função corrente para fins de gênese. Desta forma faz-se com que simulações possam ser obtidas usando computadores portáteis e, mesmo assim, requeiram tempo de processamento pequeno para a solução de problemas ditos de engenharia. Estas vantagens podem ser diretamente traduzidas em aplicações práticas de simulação como, por exemplo, a possibilidade de tomada de decisão em tempo real sobre o controle de um processo em andamento numa planta industrial, respostas transientes num escoamento turbulento ou na previsão da dispersão de poluentes em rios e mananciais críticos à saúde da população. / This work proposes a new method to solve the three-dimensional advective-diffusive equation which describes incompressible viscous flows. The proposed solution uses an analytical method based in the split of the original equation, followed by a genesis of differential equa tions. The problem is solved in two distinct steps. The first step consists of applying a nonhomogeneous split on the Navier-Stokes equations, which results in one non-homogeneous partial differential equation containing the time derivative and the viscous term. This equation is solved by mapping it into a first order equation that provides the velocity field format. Using this result we are able to obtain the stream function format, which will be used in the following genesis. This sequence allows the use of portable computers to achieve simulation results for engineering problems in small enough processing time. These advantages can be used in applications such as real- time decision making about industrial processes variables, transient turbulent flow calculations or pollution dispersion simulations in rivers or other water sources critical to the population.
7

Simulação de escoamentos viscosos utilizando mapeamentos entre equações / Viscous flow simulations using diferential equation mappings

Santiago, Gustavo Fuhr January 2007 (has links)
Este trabalho faz uma nova proposta de método para solucionar a equação advectivodifusiva tridimensional que descreve os escoamentos viscosos incompressíveis. Este método usa um esquema analítico baseado em split seguido de gênese de equações diferenciais. A solução do problema é efetuada em duas etapas distintas. A primeira etapa consiste na aplicação de um split não-homogêneo sobre as Equações de Navier-Stokes, no qual uma das equações do sistema resultante contém a derivada temporal e o termo viscoso, constituindo uma equação diferencial linear não-homogênea. A solução dessa equação é obtida via mapeamento em uma equação de primeira ordem, fornecendo o formato do campo de velocidades. A partir deste se obtém o formato da função corrente para fins de gênese. Desta forma faz-se com que simulações possam ser obtidas usando computadores portáteis e, mesmo assim, requeiram tempo de processamento pequeno para a solução de problemas ditos de engenharia. Estas vantagens podem ser diretamente traduzidas em aplicações práticas de simulação como, por exemplo, a possibilidade de tomada de decisão em tempo real sobre o controle de um processo em andamento numa planta industrial, respostas transientes num escoamento turbulento ou na previsão da dispersão de poluentes em rios e mananciais críticos à saúde da população. / This work proposes a new method to solve the three-dimensional advective-diffusive equation which describes incompressible viscous flows. The proposed solution uses an analytical method based in the split of the original equation, followed by a genesis of differential equa tions. The problem is solved in two distinct steps. The first step consists of applying a nonhomogeneous split on the Navier-Stokes equations, which results in one non-homogeneous partial differential equation containing the time derivative and the viscous term. This equation is solved by mapping it into a first order equation that provides the velocity field format. Using this result we are able to obtain the stream function format, which will be used in the following genesis. This sequence allows the use of portable computers to achieve simulation results for engineering problems in small enough processing time. These advantages can be used in applications such as real- time decision making about industrial processes variables, transient turbulent flow calculations or pollution dispersion simulations in rivers or other water sources critical to the population.
8

Modelagem do escoamento monofásico em bomba centrífuga submersa operando com fluidos viscosos / On the influence of viscosity upon electrical submersible pumping performance

Amaral, Gilmar Dutra Leite do 16 August 2018 (has links)
Orientador: Fernando de Almeida França / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-16T21:15:02Z (GMT). No. of bitstreams: 1 Amaral_GilmarDutraLeitedo_M.pdf: 4129101 bytes, checksum: 158cb95f0e4fa9111e692d4f3c9571dc (MD5) Previous issue date: 2007 / Resumo: Na indústria do petróleo, quando o bombeamento centrífugo submerso (BCS) é considerado como método de elevação artificial, existe a necessidade de determinar seu desempenho operando com óleos de média e alta viscosidades. O presente trabalho mostra uma proposta de criação de modelo de previsão de desempenho e comparação com dados experimentais, relativos ao desempenho de bombas centrífugas convencional e do tipo submersa, operando com fluidos viscosos. Para a construção do modelo, partiu-se das equações diferenciais da conservação da massa e quantidade de movimento para o escoamento no interior dos canais do rotor, usando abordagem unidimensional. Com o auxílio de dados experimentais, a transferência e transformação de energia no rotor, no difusor e outros elementos constituintes das bombas foram quantificadas e modeladas, compondo todo processo que ocorre em um estágio do equipamento. Para ajustar e validar o modelo teórico, foi construído um aparato laboratorial para realização de testes específicos em uma bomba centrífuga radial convencional e em dois diferentes modelos de BCSs, modelos GN 7000 e J350N, operando com água e glicerina como fluidos de trabalho. Foram adquiridos cerca de seiscentos pontos operacionais (vazão, pressão, rotação, torque e temperatura). Os testes abrangeram o seguinte universo de aplicação para as BCSs: rotação entre 1800 a 3500 rpm, vazões entre zero e 14.000 bbl/d, viscosidades de 1 cP, 60 cP, 270 cP, 720 cP e 1020 cP. Os resultados do modelo foram comparados com os valores medidos em laboratório nas três bombas testadas. Finalmente, foram comparadas também as curvas de desempenho das BCSs, obtidas no laboratório, com as curvas geradas a partir dos fatores de correção obtidos no ábaco do Hydraulics Institute-USA / Abstract: In the oil industry, when artificial lift using Electrical Submersible Pumps (ESP) is considered, there is a need to determine their performance for displacing oils of medium to high viscosity. This work proposes a model that is able to predict the performance of conventional centrifugal pumps and ESPs when pumping heavier oils (meaning oils of high viscosities). Data from experiments carried with conventional centrifugal pumps and ESPs displacing fluids of viscosity ranging from 1 cP to 1020 cP, model results and results provided by other researchers and commonly used in design procedures, were taken into account for comparisons and to provide insights for the model development. In some cases, specific and detailed measurements of pressure at different positions along the pump, from the inlet eye to the discharge section, were taken. They contributed to the model development and to understand the mechanics of the energy transfer and the conversion processes that the flow undergoes along a pump single stage or throughout the entire equipment. To obtain the experimental data a set-up was built, where one conventional centrifugal pump and two ESPs were tested. The test fluids were water (1 cP) and glycerin in different temperatures to vary the viscosity from 60 cP to 1020 cP. A heat pump and a heat exchanger were connected to the pumping system for that. The experimental results, data found in the literature and the benchmark results published by the manufacturers for pumps operating with water were compared with results calculated by the proposed model to validate it. Finally, a comparison between the experimental results and the data calculated using the procedures of the Hydraulic Institute - USA, to calculate centrifugal pump performance for viscous fluids, is presented / Mestrado / Explotação / Mestre em Ciências e Engenharia de Petróleo
9

Výpočtová analýza dynamických vlastností axiálních ložisek / Computational analysis of the dynamic behavior of the thrust bearings

Žatko, Miroslav January 2010 (has links)
This master´s thesis solves the problem of stationary viscous flow of incompressible fluids in thin layers of fluid film lubrication in fixed pad thrust bearings. The parametric computational model of oil domain was created for investigation the distribution of pressure, velocity and thermal fields together with the determination of the basic parameters as axial force, heating up and friction loss. Subsequently this model was applied for investigation influence of uneven bearing clearance. The problem task was solved by final volume method in Ansys CFX 12.0 software.
10

Reforzamiento estructural para mejorar el nivel de desempeño del Hospital Santa Rosa, implementando el diseño apropiado de amortiguadores fluido viscoso

Cáceres Pérez, Gladys, Pichihua Alata, Natali Sheyla 10 June 2020 (has links)
Movimientos telúricos ocurridos en distintas partes del mundo han originado considerables pérdidas económicas y humanas. Es importante mencionar también que, durante estos últimos años, en los principales países desarrollados tales como Taiwán, Japón y Estados Unidos se ha venido implementando nuevas tecnologías para mejorar el desempeño en las estructuras frente a acciones sísmicas como son los sistemas de protección sísmica. Uno de estos avances son los disipadores de energía fluido viscoso cuya implementación muestra resultados óptimos para el incremento del amortiguamiento y reducción de desplazamientos laterales. Para cumplir con el objetivo principal de la investigación, se evaluó el diseño estructural del bloque A2 del Hospital Santa Rosa, una edificación esencial ubicada en el distrito de Pueblo Libre, Lima. Se realizó el modelo y análisis sísmico de la estructura existente, cuyos resultados muestras derivas ( ∆=5.98%o ) mayores al límite establecido en la Norma E.030 ( ∆=5%o ). Además, presenta efectos de columna corta que originan el agrietamiento de las unidades de albañilería, hecho que los hace vulnerables. Frente a los resultados presentados se realiza una nueva modelación y análisis sísmico del bloque en estudio, considerando como reforzamiento los disipadores de fluido viscoso. Para ello, se analiza nuevamente la estructura a través de un análisis tiempo historia tomando distintas consideraciones como el sismo de diseño y las propiedades de los disipadores fluido viscoso en donde las derivas máximas se han reducido de 5.98%o a 3.30 %o. Adicionalmente, se analiza la estructura con una técnica de reforzamiento tradicional como son las placas de concreto armado, con el objetivo de evaluar la viabilidad de la primera propuesta. Los resultados indican que, con un reforzamiento de muros de concreto se obtiene una deriva de ∆=3.36%o y ∆=3.30%o empleando los disipadores viscosos, lo cual demuestra la viabilidad de la propuesta en respuestas estructurales. / Telluric movements in different parts of the world have caused considerable economic and human losses. It is also important to mention that, in recent years, in the main developed countries such as Taiwan, Japan and the United States, new technologies have been implemented to improve the performance of structures against seismic actions such as seismic protection systems. One of these advances are the viscous fluid energy dissipators whose implementation shows optimal results for increasing damping and reducing displacement. In order to comply with the main objective of the research, the structural design of block A2 of the Santa Rosa Hospital, an essential building located in the Pueblo Libre district, Lima, was evaluated. The seismic analysis and model of the existing structure was carried out, whose results show drifts ( ∆=5.98%o ) greater than the limit established in Standard E.030 ( ∆=5%o ). In addition, it presents short column effects that cause cracking of the masonry units, a fact that makes them vulnerable. In front of the presented results, a new modeling and seismic analysis of the block under study is performed, considering viscous fluid dissipators as reinforcement. For this, the structure is analyzed again through a time-history analysis taking different considerations such as the design earthquake and the properties of the viscous fluid heatsinks where the maximum drifts have been reduced from 5.98%o to 3 .30%o Additionally, the structure is analyzed with a traditional reinforcement technique such as reinforced concrete plates, with the aim of evaluating the feasibility of the first proposal. The results indicate that, with a reinforcement of concrete walls, a drift of ∆=3.36%o and ∆=3.30 is obtained using viscous heatsinks, which demonstrates the viability of the proposal in structural responses. / Tesis

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