Plane contraction flows of upper convected Maxwell and phan-ThienTanner fluids as predicted by a finite-volume method

A finite-volume (FV) procedure is applied to the prediction of two-dimensional (2-D) laminar flow through a 4 : 1 planar contraction of upper convected Maxwell (UCM) and simplified Phan-Thien±Tanner (SPTT) fluids. The method incorporates general coordinates, indirect addressing for easy mapping of complex domains, and is based on the collocated mesh arrangement. Calculations with the UCM model at a Reynolds number of 0.01 were carried out with three consecutively refined meshes which enabled the estimation of the accuracy of the predictions of the main vortex characteristics through Richardson's extrapolation. Converged solutions with the first-order upwind differencing scheme for the convective terms were obtained up to at least De à 8 in the finest mesh, but were limited to De 1, De 3 and De 5 for the fine, medium and coarse meshes, respectively, when using the second-order linear upwind scheme. The predicted flow patterns for increasing Deborah numbers with the UCM model resemble the well known lip vortex enhancement mechanism reported in the literature for constant-viscosity fluids in axisymmetric contractions and shear-thinning fluids in planar contraction, but very fine meshes were required in order to capture the described vortex activity. Predictions with the SPTT model also compared well with the behaviour reported in the literature

Uma análise crítica e comparativa de experiências de ensino do empreendedorismo baseadas na abordagem de aprendizagem por projeto

Este artigo debruça-se sobre a aplicação da abordagem de aprendizagem por projeto no ensino do empreendedorismo ou da formação empresarial em cursos de engenharia. A literatura sobre o tema é ainda escassa e persiste um debate que se tem mostrado inconclusivo sobre determinadas questões fundamentais. Neste projeto de investigação estudaram-se diversas experiências educacionais que permitem tirar ilações sobre a abordagem da aprendizagem baseada em projeto utilizada em 6 unidades curriculares de diferentes cursos de engenharia da Universidade do Minho. O período de análise compreende os últimos 10 anos, remontando a 2006 quando estas experiências foram iniciadas. A estratégia de pesquisa foi essencialmente qualitativa, de natureza descritiva e exploratória, tendo-se seguido uma metodologia iminentemente etnográfica. O artigo descreve e explora a utilização desta abordagem educacional no ensino universitário e na área da gestão empresarial ou do empreendedorismo através de um conjunto de casos que se traduzem numa diversidade de situações muito interessante. É feita uma breve descrição de cada experiência, referindo particularmente o seu contexto e a sua evolução, assim como os resultados diretos e indiretos que lhe estão subjacentes. É importante compreender a motivação que esteve na origem da implementação e na adoção da abordagem da aprendizagem baseada em projetos, as dificuldades encontradas e as alterações realizadas.Fundação para a Ciência e Tecnologia, PEst- OE/EME/UI0252/2011Algoritmi (PEst2015-2020) UID/CEC/00319/201

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

Environmental impact and comparative economic analysis among different building constructive systems used in Portugal

The choice between different materials and constructive systems can influence significantly the environmental impact and cost of construction. In this context, four constructive systems used in Portugal were studied: one conventional - composed by brick walls and steel reinforced post and beam concrete slabs; and three non-conventional - light steel framing (LSF); wood frame (WF); and insulation concrete form (ICF). Using a case study based on a contemporary Portuguese typical dwelling, some environmental impact indicators, as well as the weight and the economic cost of these solutions were evaluated

Territórios, patrimónios, regionalização: discursos sobre Leiria

Tese apresentada ao ISCTE para obtenção do grau de Doutor em Antropologia, especialidade de Museologia e Património, orientada por Jorge Freitas Branco e Ricardo Vieira.A partir de um estudo de caso sobre a região de Leiria pretende-se contribuir para a análise de processos de transformação de espaços em lugares, levados a cabo por elites regionalistas com vista à legitimação cultural e política de territórios específicos. Trabalho de campo e entrevistas a personalidades permitiram isolar dois eixos estruturantes nos discursos dessas elites: território e património. Recorrendo tanto à palavra oral como à escrita, os regionalistas leirienses circunscrevem espaços identitários. A afirmação da territorialidade leiriense não é contestada ao nível nacional. É no plano do distrito que se geram tensões. Estas assumem particular relevância no centro e no sul, suscitando instabilidade na delimitação geográfica. Se a afirmação de um território regional é uma constante nos discursos emitidos pelos meios leirienses, já a distribuição dos recursos argumentativos é matéria geradora de acesos debates. O património edificado – mosteiros de Alcobaça e da Batalha – é o elemento fundamental no processo de objectivação cultural da região. Dado que a estes monumentos havia sido anteriormente atribuída função emblematizadora à escala nacional ou mesmo europeia, intelectuais e políticos leirienses reclamam agora uma transferência de sentimentos de pertença a favor da região

Territórios, patrimónios, regionalização: discursos sobre Leiria

A partir de um estudo de caso sobre a região de Leiria pretende-se contribuir para a análise de processos de transformação de espaços em lugares, levados a cabo por elites regionalistas com vista à legitimação cultural e política de territórios específicos. Trabalho de campo e entrevistas a personalidades permitiram isolar dois eixos estruturantes nos discursos dessas elites: território e património. Recorrendo tanto à palavra oral como à escrita, os regionalistas leirienses circunscrevem espaços identitários. A afirmação da territorialidade leiriense não é contestada ao nível nacional. É no plano do distrito que se geram tensões. Estas assumem particular relevância no centro e no sul, suscitando instabilidade na delimitação geográfica. Se a afirmação de um território regional é uma constante nos discursos emitidos pelos meios leirienses, já a distribuição dos recursos argumentativos é matéria geradora de acesos debates. O património edificado – mosteiros de Alcobaça e da Batalha – é o elemento fundamental no processo de objectivação cultural da região. Dado que a estes monumentos havia sido anteriormente atribuída função emblematizadora à escala nacional ou mesmo europeia, intelectuais e políticos leirienses reclamam agora uma transferência de sentimentos de pertença a favor da região.Using the Leiria region as a study case, it was analysed the transformation processes of spaces into places, promoted by regional elites with the purpose of cultural and political legitimacy of specific territories. Fieldwork and interviews carried with some personalities enabled us to identify two structural axes in those elites’ discourses referred their: territory and heritage. Helped by the use of the written and spoken word Leiria’s regionalists describe identity places. The affirmation of Leiria’s territoriality is not tension’s object at national level. It is at provincial level where those are created. These tensions are specially felt in the centre and south of the region, causing some instability in its geographic delimitation. Even when the affirmation of a region is a constant among discourses delivered by Leiria’s means, also the argumentative resources´ distribution generates warm debates. The monumental heritage as Alcobaça and Batalha’s monasteries is elemental in the cultural objectification process belonging to this region. Due to these monuments had previously been given an emblematic function at national, or even, European level, Leiria’s intellectuals and politicians claim, nowadays, for enhancing of belonging feelings in favour of the region

Integration of e-portfolios in learning management systems

The LMS plays a decisive role in most eLearning environments. Although they integrate many useful tools for managing eLearning activities, they must also be effectively integrated with other specialized systems typically found in an educational environment such as Repositories of Learning Objects or ePortfolio Systems. Both types of systems evolved separately but in recent years the trend is to combine them, allowing the LMS to benefit from using the ePortfolio assessment features. This paper details the most common strategies for integrating an ePortfolio system into an LMS: the data, the API and the tool integration strategies. It presents a comparative study of strategies based on the technical skills, degree of coupling, security features, batch integration, development effort, status and standardization. This study is validated through the integration of two of the most representative systems on each category - respectively Mahara and Moodle

Steady and unsteady laminar flows of newtonian and generalized newtonian fluids in a planar T-junction

An investigation of laminar steady and unsteady flows in a two-dimensional T-junction was carried out for Newtonian and a non-Newtonian fluid analogue to blood. The flow conditions considered are of relevance to hemodynamical applications and the localization of coronary diseases, and the main objective was to quantify the accuracy of the predictions and to provide benchmark data that are missing for this prototypical geometry. Under steady flow, calculations were performed for a wide range of Reynolds numbers and extraction flow rate ratios, and accurate data for the recirculation sizes were obtained and are tabulated. The two recirculation zones increased with Reynolds number, but the behaviour was non-monotonic with the flow rate ratio. For the pulsating flows a periodic instability was found, which manifests itself by the breakdown of the main vortex into two pieces and the subsequent advection of one of them, while the secondary vortex in the main duct was absent for a sixth of the oscillating period. Shear stress maxima were found on the walls opposite the recirculations, where the main fluid streams impinge onto the walls. For the blood analogue fluid, the recirculations were found to be 10% longer but also short lived than the corresponding Newtonian eddies, and the wall shear stresses are also significantly different especially in the branch duct