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Comportamento Aerodinâmico de Estrutura de Ponte com Seção Alterada pela Presença de Veículos.
No full textStructures of flexible bridges are often susceptible to dynamic action
wind, presenting the so-called aeroelastic phenomena caused by the interaction between
elastic inertial and aerodynamic forces. The occurrence of this type of oscillation can generate
structural damage and discomfort to users. Traditionally, the study of the effects
dynamic wind on structures was done only through experiments in tunnels
wind. Currently tests are also used in numerical models by
computational fluid dynamics (CFD - Computational Fluid Dynamics). using a
computational fluid dynamics tool, it is intended, in this work,
evaluate the effects of wind on the aerodynamic behavior of the Rio-Niterói bridge, when
this is not your aerodynamic profile altered by the presence of large vehicles.
Records show that the presence of large vehicles change your profile making
more intense rhythmic oscillation induced vortex shedding bridge. the
Results are expressed in terms of the aerodynamic force coefficients and
Strouhal number for the section of the bridge and the vehicles and the bridge joint section
More vehicle.: Estruturas de pontes flexíveis são freqüentemente suscetíveis a ação dinâmica do
vento, apresentando os chamados fenômenos aeroelásticos causados pela interação entre as
forças inerciais elásticas e as aerodinâmicas. A ocorrência desse tipo de oscilação pode gerar
danos estruturais e desconforto aos usuários. Tradicionalmente, o estudo dos efeitos
dinâmicos do vento em estruturas era feito apenas através de experimentos em túneis de
vento. Atualmente utilizam-se também análises em modelos numéricos por meio da
fluidodinâmica computacional (CFD – Computational Fluid Dynamics). Utilizando uma
ferramenta computacional em dinâmica dos fluidos, pretende-se, no presente trabalho,
avaliar os efeitos do vento no comportamento aerodinâmico da ponte Rio-Niterói, quando
esta tem seu perfil não aerodinâmico alterado pela presença de veículos de grande porte.
Registros mostram que a presença de veículos de grande porte altera o seu perfil tornando
mais intensa a oscilação da ponte induzida pelo desprendimento cadenciado de vórtices. Os
resultados são apresentados em termos dos coeficientes aerodinâmicos de força e do
número de Strouhal, para a seção da ponte e dos veículos e para a seção conjunta ponte
mais veículo
Repair Welding Effects on the Bending Fatigue Strength of AISI 4130 Aeronautical Steel used in a Critical to the Flight-Safety Structure
No full textApplication of Nanofiltration to the Treatment of Acid mine Drainage Waters
Get PDFThis study investigated the separation of uranium and other elements in high concentrations from acid mine
waters at Caldas Uranium Mining, in the southeast of Brazil, using nanofiltration membranes. Nanofiltrarion is
widely used in water treatment due to the lower energy requirements and higher yields than reverse osmosis. Separation characteristics are dependent on both the molecular size and charge of the dissolved species in the feed solution as well as membrane properties. In this investigation the potential of nanofiltration to removed dissolved species like uranium from acid mine water drainage was measured. Two composite aromatic polyamide commercially membranes of FilmTec/Dow were tested and it found that uranium rejections of greater than 90% and also showed potential for the separation of aluminum and manganese
Radiological practices using dosimetric films and electronic dosimeters in F-18 production at cyclotron complex center at IEN/CNEN
Get PDFThe aim of this work is to evaluate, guide and correct radiological practices based on dose rate values
obtained from dosimetric films and electronic dosimeters used by technicians involved in Fluorine-18
production facilities at IEN/CNEN. Standard statistical methods have been used to analyze and to
evaluate these results. The comparison between these results is the first step to orient decisions
concerning radiological practices. Besides, radiometric routine surveys are under evaluation in order to
improve radiological control in these facility areas. The electronic dosimeters provide the technicians
immediate reading and this help them take protective action immediately. So the comparison between
dosimetric film and electronic dosimeters data will provide information about how the recently employed
electronic dosimeters are being used and what corrections in their practical use are necessary in order to
achieve correct practices. In addition the results and observations obtained will be very important to
implement possible changes in radiological routine practices in order to optimize them and keep
occupationally exposed individuals radiological dose rates, as low as reasonably achievable, according to
ALARA principle
Performance ao a thermal neutron radiographic system using imaging plates
Get PDFA performance evaluation of a neutron radiographic system equipped with a thermal neutron sensitive imaging
plate has been undertaken. It includes the assessment of spatial resolution, linearity, dynamic range and the
response to exposure time, as well as a comparison of these parameters with the equivalent ones for neutron
radiography employing conventional films and a gadolinium foil as converter. The evaluation and comparison
between the radiographic systems have been performed at the Instituto de Engenharia Nuclear - CNEN, using
the Argonauta Reactor as source of thermal neutrons and a commercially available imaging plate reade
Particle trajectory tracing for electrostatic and magnetostatic fields
Get PDFThis work reports a numerical method for single charged particle trajectories computation in 2D electrostatic
and magnetostatic stationary fields, in other words, fields that do not change in time. This is approached by
the finite element method domain discretisation, and numerical computation of particle trajectory, calculated
by the two step centred in time method, which calculates the particle position on the next step using a dummy
step in order to increase the accuracy for the same step size. Given particle's coordinates, the finite element
that contains that particle is found based on Lohner's algorithm. The examples used to test the method are a
electric deflector for the electric case and cyclotron for the magnetic case. Both are very important devices to
science and technology, being used in a variety of domestic and industrial appliances and in several scientific
and technologic researches. Other particle optics devices can benefit of the method proposed in this paper, as
beam bending devices and spectrometers, among others. This method can be easily extended for particle
trajectories computation in 3D domains, can be extended also for dynamic fields and for the relativistic case,
which is ideal for the typical speed involved when working with particles near the atomic level
Methodology for studies of natural circulation in closed circuits
Get PDFThis work presents an analysis of stability of the phenomenon of natural circulation for onedimension
single-phase flow in a closed loop. The computer program uses a stabilized finite
element formulation for the solution of the Navier-Stokes and energy equations in cartesian
coordinates. The formulation has been developed and tested in a computer code developed at
the Nuclear Engineering Institute (IEN-CNEN) and is now available either for future analysis
or design of nuclear system
Propagation speed of 18F y-Radiation 511 ke V in air
No full textPropagation speed of 18F-isotope γ-radiation 511 keV was measured in air; result comparable to the same parameter measured with 22Na-isotope
A reliable method to count tracks from solid state nuclear track detectors in the measurement of radon concentration
Get PDFRadon is an alpha emitter that accounts for about 50% of internal dose for man and is an important cause of
death by lung cancer. For this reason, reliable methods to measure the radon concentration in the air are of great
concern to the area of radiological protection. From the radiological point of view, the 222Rn is more relevant
than the 220Rn because the latter has a shorter half-life and thus is less likely to reach the human body. This
paper describes the method used at the Instituto de Engenharia Nuclear (IEN) to measure the 222Rn
concentration (Bq.m-3) in occupational and domestic environments. This method is based on the well-known
track etch technique and the detector employed is the LEXAN plastic. It is described the electrochemical
process used to reveal the tracks generated at the detector surface by the incidence of the alpha particles from
radon and its progeny decay. In order to count the tracks, a program based on image processing techniques was
developed at the IEN. This program processes the grey-scale images that are obtained by scanning the revealed
detectors. The counting uncertainty of this program was estimated by comparing its results with those found by
manual counting. As will be seen, this program gives reliable results even if the tracks overlap and the
electrochemical revelation process provides tracks with high shape distortion. Other issues relating to the
performance of this program are also discussed
A methodological framework applied to the choice of the best method in replacement of nuclear systems
No full textThe economic equipment replacement problem is a central question in Nuclear Engineering. On the one hand,
new equipments are more attractive given their best performance, better reliability, lower maintenance cost etc.
New equipments, however, require a higher initial investment. On the other hand, old equipments represent the
other way around, with lower performance, lower reliability and specially higher maintenance costs, but in
contrast having lower financial and insurance costs. The weighting of all these costs can be made with
deterministic and probabilistic methods applied to the study of equipment replacement. Two types of distinct
problems will be examined, substitution imposed by the wearing and substitution imposed by the failures. In
order to solve the problem of nuclear system substitution imposed by wearing, deterministic methods are
discussed. In order to solve the problem of nuclear system substitution imposed by failures, probabilistic
methods are discussed. The aim of this paper is to present a methodological framework to the choice of the most useful method applied in the problem of nuclear system substitution