Navegando por Assunto "Finite element method"

Agora exibindo 1 - 11 de 11

Acesso aberto (Open Access)
Análise comparativa das propriedades ressonantes de nanopartículas e de nanoantenas bowtie de ouro de diferentes geometrias
(Universidade Federal do Pará, 2012-12-14) SANTOS, Thaís Lira Tavares dos; COSTA, Karlo Queiroz da; http://lattes.cnpq.br/7932708321834647; DMITRIEV, Victor Alexandrovich; http://lattes.cnpq.br/3139536479960191
This work presents a comparative analysis of the resonant properties of gold nanoparticles and gold bowtie nanoantennas with new triangular geometries. The proposed geometries are as follows: the curved side triangular ones and the triangular geometries with one corner formed by three tips. The investigated properties are the resonant responses, the spatial distributions of the electric near-field and the resonant wavelengths. The current density inside the nanostructures is also analysed for better understanding of the electric near-field enhancement. For the case of bowtie nanoantennas, the research is also focused on the study of the influence of a silicon dioxide substrate on their resonant properties and on the study of their characteristics in the far-field region (scattering cross section and radiation pattern). The numerical results are obtained in the visible and near infrared regions of the electromagnetic spectrum, simulated by the finite integration technique. For isolated nanoparticles, these results show that the suggested geometries have electric near-field intensity around 160% higher and resonant wavelength redshifted by 15%, as compared to the equilateral triangular geometry. In the case of bowtie nanoantennas, the new geometries have electric near-field intensity 90% higher and resonant wavelength blueshifted by 15%, as compared to the triangular equilateral bowtie nanoantenna. The results of this work can serve for modeling, fabrication and designing of gold nanoparticles and gold bowtie nanoantennas for different applications, for example, microscopy and optical fibre sensors.
Acesso aberto (Open Access)
Análise comparativa de nanoantenas plasmônicas no modo de recepção para a aplicação em nanocircuito óptico.
(Universidade Federal do Pará, 2020-01-30) LOPES, Patrik Coelho; COSTA, Karlo Queiroz da; http://lattes.cnpq.br/7932708321834647; https://orcid.org/0000-0003-4393-3217
In this work, a theoretical study is made for different cases of optical nanoantennas. Numerical analyzes are performed using the Finite Element Method (FEM). The first part of the analysis will be done with the isolated nanoantennas considered: dipole,dipole-loop, loop and rod-loop. Initially it is made for the transmission mode to obtain important parameters for the study of nanoantennas, such as input impedance, reflection coefficient, radiation efficiency and gain diagram. Later in reception mode, excited by a plane wave linearly polarized, varying the direction of polarization. Where the power received by charge versus frequency and the near-field electric are investigated for antennas. The results show that the case of the dipole-loop nanoantenna is the most efficient (reaching up to and er = 81.25%) in addition to a better reception band. The second part is presented the application of an optical nanocircuit, composed of the receiving loop connected to a bifilar Optical Transmission Line (OTL) with a dipole at the line end. Also investigated are the near-field and the received power for the nanocircuits analyzed separately, with a load at the terminal of the streaming. Finally, the excitation of the nanocircuit is done through an opening probe modeled by a gaussian beam, focused on the receiving loop, transferring energy to the emitting dipole, with a standing wave pattern, the electromagnetic coupling of the nanocircuit turns with the Gaussian beam, showed better results (with a maximum reached of PZC = −103 dBm) compared to the plane wave (with value maximum of PZC = −125 dBm), with the power received at the load of ZC = 50Ω.
Acesso aberto (Open Access)
Análise de esforços eletromagneto-mecânicos nos enrolamentos de um transformador sob condições de correntes de inrush
(Universidade Federal do Pará, 2016-04-27) FONSECA, Wellington da Silva; SOEIRO, Newton Sure; http://lattes.cnpq.br/7303174583088137; NUNES, Marcus Vinícius Alves; http://lattes.cnpq.br/9533143193581447
This thesis presents an analysis of the effect of electromagnetic origin forces on structural deformation, stress and safety factor in power transformers when they are subjected to inrush currents. The methodology adopted is based on a magneto-mechanical assessment of the transformer using the finite element method (FEM). In this sense, the operating condition of its transformer energization is considered to accurately estimate the magnetic field density in the ferromagnetic structure and to find the values of mechanical stresses or forces in the axial and radial directions on the windings. These components are distributed over energized the high-voltage windings for observing the mechanical loading, which are more susceptible to such current actions. With this goal, it is implemented two- dimensional (2D) and threedimensional (3D) modeling of the discretized transformer structures in consolidated software, which are based on the Finite Elements Method, intended so to obtain more precise results in calculating the variables described. Comparisons between the results from the numerical method with those obtained by analytical methods are made, demonstrating that the FEM provides more precise distribution of stresses along the windings of the transformers when subjected to operating limits conditions as under currents inrush. It is also presented the magnetic flux distribution in the transformer, with high currents circulating in concentric winding of this. It modifies the flux path, causing in a significant increase in the leakage field and consequently on radial and axial forces. The results obtained for the structural behavior of the windings during inrush currents were also seen that the ends of the windings, where the spacers are located, producing high structural weakness due to the axial electromagnetic forces. This also implies a reduction in the safety factor at the ends windings ends and should be considered on the design of power transformers.
Acesso aberto (Open Access)
Análise magnética e mecânica em transformadores sob correntes de energização e energização solidária
(Universidade Federal do Pará, 2019-10-01) LIMA, Diorge de Souza; BEZERRA, Ubiratan Holanda; http://lattes.cnpq.br/6542769654042813
The power transformer is one of the most important equipment in the electric power system, allowing the feasibility of connecting the generating centers to the consumer centers, even over long distances. Reliable and continuous operation is of fundamental importance for service maintenance and is subject to various types of disturbances that can lead to failures. In this perspective, studies of the dynamic behavior of transformer windings through computer simulations have been widely used to safely and accurately evaluate their operation. Therefore, this paper presents the methodology for research on a 50 MVA power transformer using the finite element method for static and time domain analysis. Thus, the study was performed by means of magnetic-mechanical couplings. In the first analysis (circuit study), the ATPDraw software was used to obtain the behavior of the inrush current and solidarity energization during the transformer bank energization. Therefore, in the ANSYS MAXWELL software magnetic studies were performed. For this, a real 3D model was used (taking into account the characteristics of the lamination core and windings, being in disc). Thus, the results of the behavior of magnetic induction and magnetic forces in the windings of the equipment are presented. Finally, in the ANSYS STRUCTURAL software, structural (mechanical) studies were performed. Also, as before, a close-to-real 3D model was used, presenting as results the behavior of the total deformation in the winding, the mechanical stress suffered and the degree of safety during the occurrence of energization. The static studies were considered three operating conditions: nominal condition, sympathetic inrush and inrush current. For the nominal condition, the equipment's plate data was used, for the energizing condition (sympathetic inrush and inrush current) the largest amplitude obtained during the simulation was used. It is noteworthy that for the time domain analysis, only the condition of the inrush current was analyzed, both for the high computational cost required and for being the worst condition in the static analysis.
Acesso aberto (Open Access)
Construção de um modelo de dispersão de poluentes na Baía do Guajará
(Universidade Federal do Pará, 2005-12-19) BATISTA, Adriano Gomes; SENA, Manoel José dos Santos; http://lattes.cnpq.br/2349287816857909; MESQUITA, André Luiz Amarante; http://lattes.cnpq.br/1331279630816662
The sea and coastal environment of Brazil have suffered a process of considerable environmental degradation in the last years. This degradation was caused by the growing environmental pressure on the sea and the continental natural resources that have overwhelmed the limited capacity of the ecosystems to absorb the impacts. In the specific case of the Bay of Guajará, located in the Estuaries Guajará, in the area delimited by the Bay of Marajó and for the rivers Pará and Guamá, these risks are associated mainly to the pollution originating from of the city of Belém and the petroleum derived pollution caused by transport operations. In the case of the Bay of Guajará, it is known that there are sewer spillings periodically caused by the tide. Because this pollution is caused by the tide, there is little that can be done to correct or soften the effects of this problem. The numeric models consider the complexity of the physical phenomena that govern the operation of the coastal environment, and have been used as tools in hydrodynamic simulation with recognized importance in coastal administration. This application can support several studies: the understanding of the dispersing processes of pollutants; the implantation of systems of monitoring of water quality; the plan of action in cases of a oil spillage; and the effects of alterations in the geometry of channels and bays and estuaries. The objective of this work is to explain these subjects and to describe the necessary stages for the construction of a numeric model of dispersion in the Bay of Guajará using the tools of the Systems of Geographical Information and the Method of Finite Elements.
Acesso aberto (Open Access)
Desenvolvimento de um modelo via MEF para análise da dispersão de poluentes em rios, lagos e estuários
(Universidade Federal do Pará, 2012-03) LIMA, Rômulo Correa; BLANCO, Claudio José Cavalcante; http://lattes.cnpq.br/8319326553139808; MESQUITA, André Luiz Amarante; http://lattes.cnpq.br/1331279630816662
Freshwater of good quality is a pre-requisite for social and economic development of a given region. Paradoxically, this same development is normally responsible for the pollution of their water sources, through domestic or industrial waste dumping without treatment, or through agricultural activities. In this way, the monitoring and the management of that sources are extremely important for the wellbeing of the people living in that region. Among the possible tools to auxiliary this management is the computational simulation of pollutant transport in the hydro medium. In this context, this work presents a computational procedure for the solution of the 2D advectiondiffusion- reaction equation, which is the basis for all the mass transport models. This process consists in the union of the finite elements and finite difference methods in the discretization of the spatial and temporal components, respectively. This methodology was evaluated with the help of tests with synthetic and real data. First one considered the case of mass transport by pure advection to ensure its stability in cases where the classical formulations fail. Second test simulated the transport of a hypothetical pollutant in a piece of a river and showed the correct effect of the drag due to advection and spreading due to diffusion. The last test evaluated the transport of total phosphorus in Agua Preta Lake from the pumped water of the Guama river and point sources located at the margins of the reservoir. The result of the simulation showed the potential of the algorithm to deal with cases closer to the reality.
Acesso aberto (Open Access)
Diagnóstico numérico em embarcações de atendimento de atendimento médico-hospitalar visando à otimização vibro-acústica
(Universidade Federal do Pará, 2017-11-10) FERREIRA, Aracelli Suzane Andrade; SOEIRO, Newton Sure; http://lattes.cnpq.br/7303174583088137; https://orcid.org/0000-0003-4224-767X
The use of vessels for hospital care has been one of the main means used by some prefectures belonging to the states of the Legal Amazon to take medical and dental care to communities located in distant locations. These vessels were named by the Ministry of Health of Basic Units of Fluvial Health (UBSF). The design of these units, however, is differentiated in many ways, since it provides for the installation of equipment not present in other conventional vessels. In addition, the service performed in these units requires satisfactory acoustic-vibro-conditions so that health professionals can perform the procedures correctly. This work aims to perform a numerical analysis through the Finite Element Method to evaluate the modal and acoustic properties of the medical service vessel. The work contemplated two analyzes: modal and acoustic. In the modal analysis, the axis, propeller and the structure of the UBSF were considered as objects of study, as these are the main sources of excitation. The acoustic analysis sought to ascertain the main sources of noise emission and its propagation within the UBSF. In this second analysis, it was possible to predict the overall sound pressure level and octave bands inside the vessel. The Ansys and Comsol softwares were used for the modal and acoustic analysis, respectively. After the analyzes, the data obtained with the main national and international standards related to the subject were compared. The results found in this study demonstrated that the reference model proposed by the Ministry of Health did not meet the criteria established by the norms. It is proposed, therefore, as solutions to attenuate the undesired effects from the acoustic-acoustic phenomena, the use of materials with absorptive properties and increase in the structural rigidity of the vessel. Such measures would allow users and crew members to improve the comfort and conditions of basic health care services.
Acesso aberto (Open Access)
Estudo de vibrações eólicas em linhas de transmissão de energia elétrica de alta tensão
(Universidade Federal do Pará, 2008-10-30) SANTOS, Alexandre Sá dos; SOEIRO, Newton Sure; http://lattes.cnpq.br/7303174583088137
The increasing demand for electrical energy has stimulated the technological advance of the equipment associated to its transport, generating a situation in which one has to operate under ever increasing nominal voltages, mainly due to economical reasons. This fact has a direct implication on the diameter of the conductors, elevating their cost, as well as that of the supporting structures. In order to overcome this problem, without cost elevation of the electrical transmission line project, the idea is to use more than one conductor per phase, in a parallel assembly with small distances between cables, which can be achieved through the insertion of spacers at regular intervals between the supporting towers. However, operational mechanical problems may arise such as, for example, total or partial rupture of cables and/or spacers due to dynamical wind excitations. Thus, this work investigates the dynamical behavior of a bundle of cables of electrical transmission lines, using a finite element model, which reproduces the coupling between cables and the transmission lines’ spacers-dampers and the fixing structures, considering non-linear geometrical effects due to huge cable displacements, and line continuity, i.e., the adjacent vain, which is taken into account by the model as an equivalent stiffness. Wind load is modeled through a non-deterministic process, from its statistical properties, such that two parts are considered: an average load, statistically analyzed, and a variable load, analyzed as a transient. Results show that the variable load part conduces to a dynamic response of the model, which could represent a dominant behavior. Therefore, the traditional methodology of assuming wind load as a static excitation could lead, in some cases, to disastrous consequences.
Acesso aberto (Open Access)
Identificação de sistemas multiforças a partir de dados de vibração e técnicas de aprendizado de máquinas
(Universidade Federal do Pará, 2024-11-07) PINHEIRO, Giovanni de Souza; NUNES, Marcus Vinícius Alves; http://lattes.cnpq.br/9533143193581447
The emergence of defects in dynamic components tends to produce changes in the forces generated, which can be detected through alterations in the vibration response spectrum of the equipment. Understanding the forces acting on a structure is extremely important, especially in cases where measurement points are limited or inaccessible, as it allows for assessing, among other things, whether the component's lifespan is compromised by the current condition of the machine. In such cases, an inverse problem needs to be solved. Machine Learning techniques have been standing out as a powerful tool for prediction among the solutions developed for this type of problem, being increasingly applied to engineering problems. Therefore, this work aims to evaluate different machine learning models for the identification of a system, composed of a suspended plate with one or more applied forces, based on measured vibration data. In this regard, a computational model was generated and calibrated using vibration responses measured in the laboratory. A robust database was created using Response Surface Methodology together with the Design of Experiment (DOE) and then used to assess the ability of machine learning models to predict the location, excitation frequency, magnitude, and number of forces acting on the structure. Among the six machine learning models evaluated, k-NN was able to predict with an error of 0.013%, and random forests showed a maximum error of 0.2%. Finally, a database, containing a line of experimental data, was used to evaluate the k-NN and Random Forest models, obtaining a score of 0.96 and 0.93, respectively. The innovation of the study lies in the application of the proposed method for parameter identification in multiforce systems.
Acesso aberto (Open Access)
Modelagem numérica bidimensional de dados CSAMT com fonte dipolar elétrica usando elementos finitos
(Universidade Federal do Pará, 2016-08-20) PEREZ, Jarol David Garcia; SILVA, Valdelírio da Silva e; http://lattes.cnpq.br/9701131346395521; RÉGIS, Cícero Roberto Teixeira; http://lattes.cnpq.br/7340569532034401
This work presents the application of a 2,5D numerical modelling scheme to simulate data of the CSAMT (Controlled Source Audio MagnetoTellurics) electromagnetic method using the Finite Element method. We have applied the technique of separating the total electromagnetic field into two parts: the so called primary and secondary fields. The set of equations that govern the system has to be expressed in the spectral domain of the Fourier Transform. The solution is obtained as a composition of 2D solutions. In the first part of the dissertation, we present a validation of the answer generated for primary fields and a comparison of the 1D responses with those from the MT method. The second part of the text presents a validation of the 2,5D responses, as well as an analysis of the results, in terms of apparent resistivity and the measured electrical field related to an isolated body in a homogeneous half-space. We analyze the changes in the results resulting from changes in model parameters like the contrast of resistividade between the half-space and the anomalous body, the depth of the body and the frequency. The code developed is able to simulate with good precision the measurements of the CSAMT method in any survey configuration.
Acesso aberto (Open Access)
Modelagem numérica de dados MCSEM 2.5-D
(Universidade Federal do Pará, 2012-04-20) SILVA, Hilton Farias da; SILVA, Marcos Welby Correa; http://lattes.cnpq.br/3213216758254128
This work deals with the implementation of numerical 2.5-D Marine Controlled Source Electromagnetic (MCSEM) modeling applied to hydrocarbon exploration in stratified environment. In the mathematical formulation the fields were assumed to have two parts: the primary and the secondary ones. The first uses of Schelkunoff potentials in its formulation and they were employed in both (x; ky; z; !) and (x; y; z; !) domains. The secondary fields are solved in the frequency domain space (x; ky; z) by finite element method. With a Inverse Fourier transform, the secondary fields were taken in the domain (x; y; z). From the total field, we can show the influence of an oil reservoir in a stratified environment and its sensitivity to the lateral extension of a hydrocarbon reservoir.