1,446 research outputs found
Simulação numérica do comportamento de vidro reforçado com elementos metálicos embebidos
Trabalho financiado por Fundos FEDER, através do Programa Operacional Fatores de Competitividade – COMPETE, e por Fundos Nacionais, através da FCT – Fundação para a Ciência e a Tecnologia, no âmbito do projeto PTDC/ECM/116609/2010 – S-GLASS: Desempenho Estrutural e Regras de Projeto de Vigas de Vidro Reforçadas Externamente.O presente artigo descreve a simulação numérica de vigas de vidro laminado reforçadas com chapa de aço inoxidável perfurada, onde o Polivinil Butiral (PVB) e o SentryGlas (SG) são utilizados como materiais de pelÃcula intercalar. Numa fase anterior, essas vigas foram analisadas experimentalmente em ensaios realizados por Marinho [1] no Laboratório de Construção e Tecnologia da Escola de Arquitetura da Universidade do Minho. Os resultados obtidos com os modelos numéricos são calibrados com os resultados obtidos nos ensaios experimentais. Os modelos numéricos são desenvolvidos com o programa de elementos finitos ATENA.Fundação para a Ciência e a Tecnologia (FCT
Purely Elastic Flow Asymmetries
Using a numerical technique we demonstrate that the flow of the simplest differential viscoelastic fluid
model (i.e., the upper-convected Maxwell model) goes through a bifurcation to a steady asymmetric state
when flowing in a perfectly symmetric ‘‘cross-slot’’ geometry. We show that this asymmetry is purely elastic in nature and that the effect of inertia is a stabilizing one. Our results are in qualitative agreement with very recent experimental visualizations of a similar flow in the microfluidic apparatus of Arratia et al. [Phys. Rev. Lett. 96, 144502 (2006)]
On the effect of contraction ratio in viscoelastic flow through abrupt contractions
A numerical study of the creeping flow of a PTT fluid through planar sudden contractions was carried out to quantify the effect of contraction ratio upon the flow characteristics (streamlines and size and intensity of recirculation vortices). The relevant governing equations were solved with a finite volume method embodying a new high-resolution scheme (Alves et al. [Int. J. Numer. Meth. Fluids 41 (2003) 47]) for the discretisation of convection terms, which is here explained and shown to yield improved accuracy and robustness. The results of the simulations, in terms of streamline patterns, give further evidence for a lip-vortex enhancement mechanism and are in remarkable agreement with flow
visualization photographs from the literature. In addition, the results show that the variation of flow features in the vicinity of the re-entrant corner, such as lip vortex size and streamlines, are dominated by downstream quantities and scale with the common definition for the Deborah number in this flow, while flow characteristics in the salient corner region scale with that Deborah number divided by the contraction ratio
Viscoelastic flow in a 3D square/square contraction: Visualizations and simulations.
The inertialess three-dimensional (3D) flow of viscoelastic shear-thinning fluids in a 4:1 sudden square-square contraction was investigated experimentally and numerically and compared with the flow of inelastic fluids. Whereas for a Newtonian fluid the vortex length remains unchanged at low
Reynolds numbers, with the non-Newtonian fluid there is a large increase in vortex length with
fluid elasticity leading to unstable periodic flow at higher flow rates. In the steady flow regime the vortices are 3D and fluid particles enter the vortex at the middle plane, rotate towards its eye, drift sideways to the corner-plane vortex, rotate to its periphery, and exit to the downstream duct. Such
dynamic process is reverse of that observed and predicted with Newtonian fluids. Numerical predictions using a multimode Phan-Thien–Tanner viscoelastic model are found to match the visualizations accurately and in particular are able to replicate the observed flow reversal. The effect of fluid rheology on flow reversal, vortex enhancement, and entry pressure drop is investigated in detail
Homogenization on multi-materials' elements: application to printed circuit boards and warpage analysis
Multi-material domains are often found in industrial applications. Modelling them can be computationally very expensive due to meshing requirements. The finite element properties comprising different materials are hardly accurate. In this work, a new homogenization method that simplifies the computation of the homogenized Young modulus, Poisson ratio and thermal expansion coefficient is proposed, and applied to composite-like material on a printed circuit board. The results show a good properties correspondence between the homogenized domain and the real geometry simulation.This research is sponsored:
-
by the Portugal Incentive System for Research and
Technological Development. Project in co
-
promotion nº
36265/2013 (Project HMIExcel
-
2013
-
2015),
and
-
by FCT with the reference project
UID/EEA/04436/2013, by FEDER funds through the
COMPETE 2020
–
Programa Operacional
Competitividade e Internacionalização (POCI) with the
reference project POCI
-
01
-
0145
-
FEDER
-
006941info:eu-repo/semantics/publishedVersio
Is Namalycastis abiuma (Grube, 1871) (Annelida: Nereididae) restricted to its type-locality? Evidence from morphological and molecular data
Namalycastis abiuma has been recorded as a worldwide distributed species, found in most tropical and subtropicalmangroves and estuarine environments. However, this status has been questioned in several publications, whichindicate that several distinct species are being identified under the name N. abiuma. In this study, we performa morphological analysis, along with a series of species delimitation tests and a phylogenetic analysis—usingthe molecular marker 16S—to evaluate whether analyzed populations previously identified as Namalycastisabiuma belong to the same species. We used sequences from the GenBank database in the analysis, as well assix newly sequenced specimens collected from the coast of Brazil, two of them from the N. abiuma type-locality.For species delimitation, we applied the Generalized Mixed Yule Coalescent (GMYC), the Assemble Speciesby Automatic Partitioning (ASAP), and the Multi-rate Poisson Tree Processes (mPTP) tests. Results from GMYCand ASAP suggest that Namalycastis abiuma may be endemic to the type-locality and that all other populationsstudied represent a second distinct species. However, mPTP indicates that all Namalycastis species includedshould be grouped into one single species. The mPTP results seem to be biased due to data limitation as it showedpoor statistical support. Our morphological data, especially on the shape and dentition of the sub-neuroacicularfalciger blades, support the GMYC and ASAP results, suggesting restricted endemism for Namalycastis abiuma.Based on these results, we conclude that N. abiuma is restricted to its type-locality and we provide a descriptionof a new species, Namalycastis lanai sp. nov. occurring in Brazilian waters from 22°S to 27°S, including, at itssouthern range, an overlap with N. abiuma at Florianópolis. Finally, we provide a key to all Namalycastis speciesfound in Brazil
Modelação estatÃstica dos Ãndices de sinistralidade, aplicados ao setor da construção
Face ao quadro problemático das estatÃsticas de sinistralidade e considerando a Segurança na construção uma missão vital e de primordial significado para a sociedade, pretendeu-se com o presente estudo desenvolver modelos matemáticos, com capacidade explicativa do comportamento dos Ãndices de sinistralidade em função de variáveis setoriais e globais como a taxa de desemprego e a taxa de crescimento do PIB de Portugal. Foram utilizados dados oficiais relativos a uma amostra de conveniência composta por 58 empresas do setor da construção, referente ao perÃodo de 6 anos. Foi efetuado o tratamento estatÃstico dos dados e desenhados modelos com base em regressões lineares. No final, dois dos modelos desenvolvidos apresentaram capacidade explicativa. Sendo que nestes aparecem como variáveis relevantes, a taxa de desemprego e os custos de formação por trabalhador. Apesar da capacidade explicativa dos modelos e da possibilidade da sua utilização pelas empresas do setor, como ferramenta potenciadora da Prevenção dos acidentes ocupacionais, é ainda questionada a eventual falta de consistência dos dados e a qualidade da formação ministrada nas empresas
Varietal flavour compounds of four grape varieties producing Madeira wines
Boal, Malvasia, Sercial and Verdelho are the main white grape varieties used in Madeira wine production. To estimate the free fraction of varietal aroma compounds of these varieties, 39 samples of musts were analysed to determine their content of monoterpenols and C13 norisoprenoids (terpenoids), using dynamic headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry. The r-values for linearity studies of the analytical method used, varied between 0.977 (nerolidol) and 0.999 (linalool). The repeatability for each compound varied between 2.5% (citronellol) and 11.8% (β-ionone).
The mean values from three vintages (1998, 1999 and 2000) confirmed that these musts have differentiated contents of terpenoids. In opposition to Verdelho musts, Malvasia showed the highest free terpenoids content. In order to establish relations between the compounds and the varieties under investigation, principal component analysis and linear discriminant analysis were applied to the data, revealing a good separation and classification power between the four groups as a function of varietal origin
The role of poroelasticity on the biomechanics of the intervertebral disc : a finite element study
The major goal for the present work is to evaluate a biomimetic Finite Element (FE) model of the Intervertebral Disc (IVD). Recent studies have emphasized the importance of an accurate biomechanical modeling of the IVD, which is a highly complex biphasic medium. A novel biphasic poroelastic model was implemented and coupled with Wilson’s model (2005) for biphasic osmotic swelling behavior. Numerical tests were devoted to the analysis of the time- dependent behavior of the IVD. The results show good agreement with literature experimental data (Heuer et al., 2007 or O’Connell et al., 2011) and also with other numerical studies (Galbusera et al., 2011). In brief, this in-development IVD FE model aims to be a valuable tool to study the biomechanics of the IVD and its pathways for degeneration.Fundação para a Ciência e a Tecnologia (FCT
- …