Simulação computacional da interação fluido-estrutura em bombas de cavidades progressivas

The pumping through progressing cavities system has been more and more employed in the petroleum industry. This occurs because of its capacity of elevation of highly viscous oils or fluids with great concentration of sand or other solid particles. A Progressing Cavity Pump (PCP) consists, basically, of a rotor - a metallic device similar to an eccentric screw, and a stator - a steel tube internally covered by a double helix, which may be rigid or deformable/elastomeric. In general, it is submitted to a combination of well pressure with the pressure generated by the pumping process itself. In elastomeric PCPs, this combined effort compresses the stator and generates, or enlarges, the clearance existing between the rotor and the stator, thus reducing the closing effect between their cavities. Such opening of the sealing region produces what is known as fluid slip or slippage, reducing the efficiency of the PCP pumping system. Therefore, this research aims to develop a transient three-dimensional computational model that, based on single-lobe PCP kinematics, is able to simulate the fluid-structure interaction that occurs in the interior of metallic and elastomeric PCPs. The main goal is to evaluate the dynamic characteristics of PCP s efficiency based on detailed and instantaneous information of velocity, pressure and deformation fields in their interior. To reach these goals (development and use of the model), it was also necessary the development of a methodology for generation of dynamic, mobile and deformable, computational meshes representing fluid and structural regions of a PCP. This additional intermediary step has been characterized as the biggest challenge for the elaboration and running of the computational model due to the complex kinematic and critical geometry of this type of pump (different helix angles between rotor and stator as well as large length scale aspect ratios). The processes of dynamic generation of meshes and of simultaneous evaluation of the deformations suffered by the elastomer are fulfilled through subroutines written in Fortan 90 language that dynamically interact with the CFX/ANSYS fluid dynamic software. Since a structural elastic linear model is employed to evaluate elastomer deformations, it is not necessary to use any CAE package for structural analysis. However, an initial proposal for dynamic simulation using hyperelastic models through ANSYS software is also presented in this research. Validation of the results produced with the present methodology (mesh generation, flow simulation in metallic PCPs and simulation of fluid-structure interaction in elastomeric PCPs) is obtained through comparison with experimental results reported by the literature. It is expected that the development and application of such a computational model may provide better details of the dynamics of the flow within metallic and elastomeric PCPs, so that better control systems may be implemented in the artificial elevation area by PCP

Avaliação da dispersão de efluente líquido de refinaria de petróleo

Neste trabalho são apresentadas duas técnicas para a avaliação da dispersão, num corpo d'água receptor, do efluente líquido de uma refinaria de petróleo. Assim, a pluma de dispersão foi caracterizada por medidas em campo de condutividade elétrica e por simulação computacional (simulador Cormix). Como caso de estudo, escolheu-se uma refinaria de petróleo cujo efluente é lançado no rio Atibaia (Paulínia/SP). O comportamento do efluente foi avaliado em um trecho de 1000 m após o ponto de lançamento. Os resultados demonstraram que a medição da condutividade elétrica é uma técnica adequada para a avaliação da dispersão de efluentes líquidos de refinaria de petróleo, pois apresentam alta condutividade elétrica e, com isso, há um forte contraste entre os valores do efluente e do rio. Além disso, outros parâmetros de qualidade da água do rio seguiram comportamento de dispersão semelhante ao da condutividade. A pluma de dispersão gerada pelo simulador computacional apresentou uma elevada concordância com os dados obtidos em campo. Nesse sentido, a simulação computacional pode ser uma ferramenta útil para a avaliação da dispersão do efluente considerando-se cenários hipotéticos, e para projetos de emissários.

Transient stability indices from a hybrid approach

This paper deals with hybrid method for transient stability analysis combining time domain simulation and a direct method. Nowadays, the step-by-step simulation is the best available tool for allowing the uses of detailed models and for providing reliable results. The main limitation of this approach involves the large time of computational simulations and the absence of stability margin. On the other hand, direct methods, that demand less CPU time, did not show ample reliability and applicability yet. The best way seems to be using hybrid solutions, in which a direct method is incorporated in a time domain simulation tool. This work has studied a direct method using the transient potential and kinetic energy of the critical machine only. In this paper the critical machine is identified by a fast and efficient method, and the proposal is new for using to get stability margins from hybrid approaches. Results from systems, like 16-machine, show stability indices to dynamic security assessment. © 2001 IEEE.

Effects in the population inversion of3H4 level in Tm, Tm-Tb and Tm-Eu doped germanate glasses for amplifiers applications

The population inversion of the Tm3+ in GLKZ glass involved in the 1470 nm emission (3H4 → 3F 4) as a function of Tb (or Eu) concentration was calculated by computational simulation for a CW laser pumping at 792 nm. These calculations were performed using the experimental Tm→Tb an Tm→Eu transfer rates and the spectroscopic parameters of the Tm (0.1 mol %) system. The result shows that 0.2 mol % (Tb3+) and 0.4 mol % of Eu3+ ions propitiate best population inversion of Tm3+ (0.1 mol %) maximizing the amplification coefficient of germanate (GLKZ) glass when operating as laser intensity amplification at 1470 nm. Besides the effective deactivation of the 3F4 level, the presence of Tb3+ or Eu 3+ ions introduce a depopulation of the 3H4 emitting level by means of a cross relaxation process with Tm3+ ions. In spite of this, the whole effect is verified to be benefic for using Tm-doped GLKZ glass codoped with Tb3+ or Eu3+ as a suitable material for confectioning optical amplifiers that operates in the S-band for telecommunication.

Analysis of mechanical behavior in bending of polymer composites using the finite elements method

The use of composite materials has increased in the recent decades, mainly in the aeronautics and automotives industries. In the present study is elaborated a computational simulation program of the bending test using the finite elements method, in the commercial software ANSYS. This simulation has the objective of analyze the mechanical behavior in bending of two composites with polymeric matrix reinforced with carbon fibers. Also are realized bending tests of the 3 points to obtain the resistances of the materials. Data from simulation and tests are used to make a comparison between two failures criteria, Tsai-Wu and Hashin criterion. Copyright © 2009 SAE International.

Decay of photo-induced conductivity in Sb-doped SnO2 thin films, using monochromatic light of about bandgap energy

Doping tin dioxide (SnO2) with pentavalent Sb5+ ions leads to an enhancement in the electrical conductivity of this material, because Sb5+ substitutes Sn4+ in the matrix, promoting an electronic density increase in the conduction band, due to the donor-like nature of the doping atom. Results of computational simulation, based on the Density Functional Theory (DFT), of SnO2:4%Sb and SnO2:8%Sb show that the bandgap magnitude is strongly affected by the doping concentration, because the energy value found for 4 at%Sb and 8 at%Sb was 3.27 eV and 3.13 eV, respectively, whereas the well known value for undoped SnO2 is about 3.6 eV. Sb-doped SnO2 thin films were obtained by the sol-gel-dip-coating technique. The samples were submitted to excitation with below theoretical bandgap light (450 nm), as well as above bandgap light (266 nm) at low temperature, and a temperature-dependent increase in the conductivity is observed. Besides, an unusual temperature and time dependent decay when the illumination is removed is also observed, where the decay time is slower for higher temperatures. This decay is modeled by considering thermally activated cross section of trapping centers, and the hypothesis of grain boundary scattering as the dominant mechanism for electronic mobility. © 2012 Elsevier B.V. All rights reserved.

Análise e implementação de técnicas de medição de microvibrações utilizando interferometria óptica e processadores digitais de sinais

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Estudo da teoria de potência conservativa para análise de sistemas elétricos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Comportamento do pedestre e ambiente térmico urbano

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Modelo do bulbo olfativo baseado em redes neurais recorrentes

Pós-graduação em Física - IGCE

O cálculo variacional e o problema da braquistócrona

Pós-graduação em Matemática Universitária - IGCE

Simulação numérica da clipagem arterial utilizando interação fluido-estrutura através do método de elementos finitos

Pós-graduação em Engenharia Mecânica - FEIS

Estudo de N-metilformamida em meio aquoso e não aquoso (THF)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Modelagem em simulação computacional do cristal e superfícies do BaZr'O IND. 3' e SrZrO IND. 3': propriedades eletrônicas e estruturais

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Proposta de um algoritmo híbrido de agendamento de grants baseado na priorização de filas para gerenciamento de recursos em WDM-PONs

As Redes Ópticas Passivas (Passive Optical Networks - PONs) vêm experimentando um sólido crescimento nas últimas décadas por terem sido concebidas como uma excelente alternativa para a solução de um dos maiores problemas para as redes de telecomunicações: o gargalo nas redes de acesso. A próxima geração desta tecnologia, as chamadas Next Genaration PONs (NG-PON), surgem como consequência da evolução das tecnologias ópticas e oferecem suporte aos serviços de próxima geração, melhorando os parâmetros de desempenho das TDM-PONs e inclusive aumentando a área de cobertura destas redes. Esta expansão geográfica beneficia as empresas de telecomunicações que passam a focar seus esforços na simplificação de suas infra-estruturas através da unificação das redes metropolitanas, de acesso e de backhaul, reduzindo a quantidade de nós e, consequentemente, de custos operacionais e financeiros. Trata-se de uma significativa mudança no cenário das redes de acesso que passam a ter grandes distâncias entre as Optical Network Units (ONUs) e o Central Office (CO) e uma imensa variedade de serviços, tornando fundamental a presença de algoritmos de agendamento capazes de gerenciar todos os recursos compartilhados de forma eficiente, ao mesmo tempo que garantem controle e justeza na alocação dinâmica dos tráfegos upstream e downstream. É a partir deste contexto que esta dissertação tem como objetivo geral apresentar a proposta de um algoritmo híbrido de agendamento de grants baseado na priorização de filas (Hybrid Grant Scheduler based on Priority Queuing – HGSPQ), que além de gerenciar todos os recursos em WDM-PONs, busca oferecer eficiência e controle ao Optical Line Terminal (OLT) no agendamento dinâmico dos tráfegos. Os resultados apresentados foram extraídos de cenários desenvolvidos em ambiente de simulação computacional e se baseiam nas métricas de atraso e vazão para avaliação de seu desempenho. Também será avaliado como a quantidade de recursos no OLT interfere nestas métricas.