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Numerical simulation of rarefied gas flow in micro and vacuum devicesRana, Anirudh Singh 22 January 2014 (has links)
It is well established that non-equilibrium flows cannot properly be
described by traditional hydrodynamics, namely, the Navier-Stokes-Fourier
(NSF) equations. Such flows occur, for example, in micro-electro-mechanical
systems (MEMS), and ultra vacuum systems, where the dimensions of the
devices are comparable to the mean free path of a gas molecule. Therefore,
the study of non-equilibrium effects in gas flows is extremely important.
The general interest of the present study is to explore boundary value
problems for moderately rarefied gas flows, with an emphasis on
numerical solutions of the regularized 13--moment equations (R13). Boundary
conditions for the moment equations are derived based on either
phenomenological principles or on microscopic gas-surface scattering models,
e.g., Maxwell's accommodation model and the isotropic scattering
model.
Using asymptotic analysis, several non-linear terms in the R13 equations are
transformed into algebraic terms. The reduced equations allow us to obtain
numerical solutions for multidimensional boundary value problems, with the
same set of boundary conditions for the linearized and fully non-linear
equations.
Some basic flow configurations are employed to investigate steady and
unsteady rarefaction effects in rarefied gas flows, namely, planar and
cylindrical Couette flow, stationary heat transfer between two plates,
unsteady and oscillatory Couette flow. A comparison with the corresponding
results obtained previously by the DSMC method is performed.
The influence of rarefaction effects in the lid driven cavity problem is
investigated. Solutions obtained from several macroscopic models, in
particular the classical NSF equations with jump and slip boundary
conditions, and the R13--moment equations are compared. The R13 results
compare well with those obtained from more costly solvers for rarefied gas
dynamics, such as the Direct Simulation Monte Carlo (DSMC) method.
Flow and heat transfer in a bottom heated square cavity in a moderately
rarefied gas are investigated using the R13 and NSF equations. The results
obtained are compared with those from the DSMC method with emphasis on
understanding thermal flow characteristics from the slip flow to the early
transition regime. The R13 theory gives satisfying results including flow
patterns in fair agreement with DSMC in the transition regime, which the
conventional Navier-Stokes-Fourier equations are not able to capture. / Graduate / 0548 / anirudh@uvic.ca
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Multiregional Computational General Equilibrium, and Spatial Interaction Trade Modelling: An Empirical Example.Schneider, Martin, Fischer, Manfred M. 07 1900 (has links) (PDF)
This paper analyses the effects of enhanced trade between Austria and its four neighbouring Central
and Eastern European countries (Czech Republic, Slovak Republic, Hungary, Slovenia) on sectoral
production and regional welfare in Austria. The analysis is based on two distinct modelling traditions
at the centre of regional science. The first model (a Fischer-Johansson Model of bilateral trade flows)
is used to predict the volume and commodity composition of future trade flows based on a long term
income scenario. The predicted long-term increases of the trade flows are huge. Exports rise by 190 %
and imports by 160 % (compared to 1995). The effects of these trade flows on sectoral production and
regional welfare in Austria are simulated by means of a multiregional computable general equilibrium
model for the Austrian economy. The model contains the 9 Federal Provinces (NUTS-II). The likely
implications of the projected trade flows are measured in terms of real income, which can be expected
to rise by 1.2 %. The welfare gains will not necesarily be shared equally by all Federal Provinces. The
results indicate a clear East-West pattern with the eastern regions of Austria gaining most. (authors' abstract) / Series: Discussion Papers of the Institute for Economic Geography and GIScience
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A entrada da Venezuela no Mercosul : uma análise de equilíbrio geral computável sobre os impactos setoriais no BrasilBueno, Eduardo Urbanski January 2013 (has links)
O presente trabalho tem o objetivo de avaliar o impacto que a adesão da Venezuela ao Mercosul terá sobre o bloco em termos de criação/desvio de comércio e de bem-estar. Mais especificamente, pretende-se quantificar os impactos estáticos dos choques tarifários que este processo pode gerar sobre setores da economia brasileira. Busca-se testar a hipótese de que o resultado líquido (em termos de criação de comércio e de bem-estar) dessa ampliação do bloco será positivo. Para atingir tal objetivo, o trabalho utilizará o modelo de Equilíbrio Geral Computável Global Trade Analysis Project (GTAP, V.8). A hipótese é confirmada, havendo resultados particularmente positivos para as indústrias automobilística, de bens de capital e têxtil brasileiras. / This study aims to evaluate the impact that the accession of Venezuela to Mercosur will have on the block in terms of trade creation/diversion and of welfare. More specifically, it intends to quantify the static impacts of tariff shocks that this process can generate on sectors of the Brazilian economy. The article seeks to test the hypothesis that the net result (in terms of trade creation and welfare) of this regional agreement will be positive. To achieve this goal, the work uses the Computable General Equilibrium Model of the Global Trade Analysis Project (GTAP, V.8). The hypothesis is confirmed, with particularly positive results for the Brazilian automobile, capital goods and textile industries. / Este estudio tiene como objetivo evaluar el impacto que la adhesión de Venezuela al Mercosur tendrá en el bloque en términos de creación/desviación de comercio y de bienestar. Más concretamente, se pretende cuantificar los impactos estáticos de los shocks arancelarios que este proceso puede generar sobre los sectores de la economía brasileña. Tratamos de probar la hipótesis de que el resultado neto (en términos de creación de comercio y bienestar) de este acuerdo regional será positivo. Para lograr este objetivo, el trabajo utiliza el modelo de Equilibrio General Computable del Global Trade Analysis Project (GTAP, V.8). La hipótesis se confirma, con resultados especialmente positivos para las industrias automotriz, de bienes de capital e textil brasileñas.
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A entrada da Venezuela no Mercosul : uma análise de equilíbrio geral computável sobre os impactos setoriais no BrasilBueno, Eduardo Urbanski January 2013 (has links)
O presente trabalho tem o objetivo de avaliar o impacto que a adesão da Venezuela ao Mercosul terá sobre o bloco em termos de criação/desvio de comércio e de bem-estar. Mais especificamente, pretende-se quantificar os impactos estáticos dos choques tarifários que este processo pode gerar sobre setores da economia brasileira. Busca-se testar a hipótese de que o resultado líquido (em termos de criação de comércio e de bem-estar) dessa ampliação do bloco será positivo. Para atingir tal objetivo, o trabalho utilizará o modelo de Equilíbrio Geral Computável Global Trade Analysis Project (GTAP, V.8). A hipótese é confirmada, havendo resultados particularmente positivos para as indústrias automobilística, de bens de capital e têxtil brasileiras. / This study aims to evaluate the impact that the accession of Venezuela to Mercosur will have on the block in terms of trade creation/diversion and of welfare. More specifically, it intends to quantify the static impacts of tariff shocks that this process can generate on sectors of the Brazilian economy. The article seeks to test the hypothesis that the net result (in terms of trade creation and welfare) of this regional agreement will be positive. To achieve this goal, the work uses the Computable General Equilibrium Model of the Global Trade Analysis Project (GTAP, V.8). The hypothesis is confirmed, with particularly positive results for the Brazilian automobile, capital goods and textile industries. / Este estudio tiene como objetivo evaluar el impacto que la adhesión de Venezuela al Mercosur tendrá en el bloque en términos de creación/desviación de comercio y de bienestar. Más concretamente, se pretende cuantificar los impactos estáticos de los shocks arancelarios que este proceso puede generar sobre los sectores de la economía brasileña. Tratamos de probar la hipótesis de que el resultado neto (en términos de creación de comercio y bienestar) de este acuerdo regional será positivo. Para lograr este objetivo, el trabajo utiliza el modelo de Equilibrio General Computable del Global Trade Analysis Project (GTAP, V.8). La hipótesis se confirma, con resultados especialmente positivos para las industrias automotriz, de bienes de capital e textil brasileñas.
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A entrada da Venezuela no Mercosul : uma análise de equilíbrio geral computável sobre os impactos setoriais no BrasilBueno, Eduardo Urbanski January 2013 (has links)
O presente trabalho tem o objetivo de avaliar o impacto que a adesão da Venezuela ao Mercosul terá sobre o bloco em termos de criação/desvio de comércio e de bem-estar. Mais especificamente, pretende-se quantificar os impactos estáticos dos choques tarifários que este processo pode gerar sobre setores da economia brasileira. Busca-se testar a hipótese de que o resultado líquido (em termos de criação de comércio e de bem-estar) dessa ampliação do bloco será positivo. Para atingir tal objetivo, o trabalho utilizará o modelo de Equilíbrio Geral Computável Global Trade Analysis Project (GTAP, V.8). A hipótese é confirmada, havendo resultados particularmente positivos para as indústrias automobilística, de bens de capital e têxtil brasileiras. / This study aims to evaluate the impact that the accession of Venezuela to Mercosur will have on the block in terms of trade creation/diversion and of welfare. More specifically, it intends to quantify the static impacts of tariff shocks that this process can generate on sectors of the Brazilian economy. The article seeks to test the hypothesis that the net result (in terms of trade creation and welfare) of this regional agreement will be positive. To achieve this goal, the work uses the Computable General Equilibrium Model of the Global Trade Analysis Project (GTAP, V.8). The hypothesis is confirmed, with particularly positive results for the Brazilian automobile, capital goods and textile industries. / Este estudio tiene como objetivo evaluar el impacto que la adhesión de Venezuela al Mercosur tendrá en el bloque en términos de creación/desviación de comercio y de bienestar. Más concretamente, se pretende cuantificar los impactos estáticos de los shocks arancelarios que este proceso puede generar sobre los sectores de la economía brasileña. Tratamos de probar la hipótesis de que el resultado neto (en términos de creación de comercio y bienestar) de este acuerdo regional será positivo. Para lograr este objetivo, el trabajo utiliza el modelo de Equilibrio General Computable del Global Trade Analysis Project (GTAP, V.8). La hipótesis se confirma, con resultados especialmente positivos para las industrias automotriz, de bienes de capital e textil brasileñas.
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Macroscopic description of rarefied gas flows in the transition regimeTaheri Bonab, Peyman 01 September 2010 (has links)
The fast-paced growth in microelectromechanical systems (MEMS), microfluidic fabrication, porous media applications, biomedical assemblies, space propulsion, and vacuum technology demands accurate and practical transport equations for rarefied gas flows. It is well-known that in rarefied situations, due to strong deviations from the continuum regime, traditional fluid models such as Navier-Stokes-Fourier (NSF) fail. The shortcoming of continuum models is rooted in nonequilibrium behavior of gas particles in miniaturized and/or low-pressure devices, where the Knudsen number (Kn) is sufficiently large.
Since kinetic solutions are computationally very expensive, there has been a great desire to develop macroscopic transport equations for dilute gas flows, and as a result, several sets of extended equations are proposed for gas flow in nonequilibrium states. However, applications of many of these extended equations are limited due to their instabilities and/or the absence of suitable boundary conditions.
In this work, we concentrate on regularized 13-moment (R13) equations, which are a set of macroscopic transport equations for flows in the transition regime, i.e., Kn≤1. The R13 system provides a stable set of equations in Super-Burnett order, with a great potential to be a powerful CFD tool for rarefied flow simulations at moderate Knudsen numbers.
The goal of this research is to implement the R13 equations for problems of practical interest in arbitrary geometries. This is done by transformation of the R13 equations and boundary conditions into general curvilinear coordinate systems. Next steps include adaptation of the transformed equations in order to solve some of the popular test cases, i.e., shear-driven, force-driven, and temperature-driven flows in both planar and curved flow passages. It is shown that inexpensive analytical solutions of the R13 equations for the considered problems are comparable to expensive numerical solutions of the Boltzmann equation. The new results present a wide range of linear and nonlinear rarefaction effects which alter the classical flow patterns both in the bulk and near boundary regions. Among these, multiple Knudsen boundary layers (mechanocaloric heat flows) and their influence on mass and energy transfer must be highlighted. Furthermore, the phenomenon of temperature dip and Knudsen paradox in Poiseuille flow; Onsager's reciprocity relation, two-way flow pattern, and thermomolecular pressure difference in simultaneous Poiseuille and transpiration flows are described theoretically. Through comparisons it is shown that for Knudsen numbers up to 0.5 the compact R13 solutions exhibit a good agreement with expensive solutions of the Boltzmann equation.
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