Artigos de Revista

Mechanical constraints have a non-negligible influence in the motion of oscillating wave surge converter (OWSC) devices. The key novelty of this paper is a numerical simulation tool for OWSCs that does not neglect or significantly compromise mechanical constraints such as hydraulic power take-off (PTO) system, revolute joints and frictional contacts among components. The paper is aimed at presenting the key components of the numerical simulation tool and at validating it with laboratory data featuring an OWSC with mechanical constraints under regular and irregular waves. It is based on the implementation of the multibody solver of Project Chrono under the Smoothed Particle Hydrodynamics (SPH) model of DualSPHysics, where the SPH solver resolves the interaction between wave and flap and the multibody solver resolves the interaction between flap and mechanical constraints. Comparison between numerical results and experimental data show that the numerical simulation tool properly predicts the dynamics of the OWSC. Furthermore, in what concerns hydrodynamics of the near-flap flow, the computed and measured free-surface elevations and phase-averaged flow field show reasonable agreement. Once properly validated, the numerical simulation tool is then applied to study the influence of several mechanical constraints, PTO damping characteristics and flap inertia on the hydrodynamic of the OWSC. The viability of OWSC design solutions based on the developed numerical simulation tool is emphasised, in view of its performance in the test cases to which it was subjected.

A reflexão discute e propõe uma abordagem do ato de caminhar como método integrado e interdisciplinar para captar a experiência territorial das pessoas e, no campo do urbanismo, perspetivar a cidade. Atenta aos amplos benefícios do uso caminhado da cidade, às virtualidades do incrementar espaços caminháveis, ao caminhar como ato de resistência e assimilação estético-sensorial da cidade, o objetivo aqui é, todavia, abordar o caminhar como recurso metodológico de apreensão compreensiva, cocriativa e mais responsiva da cidade. A acuidade do caminhar advém aqui, por um lado, de um percurso etnográfico de investigação que, por outro lado, tem colaborado para insinuar sobre o interesse de uma maior ingerência didático-pedagógico que, em defesa de que se caminhe mais antes de intervir na cidade, assuma efetivamente o caminhar como um potencial método cocriativo do captar e fazer o espaço urbano.

O presente artigo, alicerçado nos Projetos de investigação CyberParks e C3Places, examina como as tecnologias digitais podem envolver os utilizadores na cocriação de um espaço público aberto que responda às suas necessidades, explorando o papel mediador das Tecnologias da Informação e da Comunicação (TIC) nesse processo. Partindo de resultados preliminares dos dois projetos, será explorado mais especificamente o uso do espaço público por adolescentes e discutida a necessidade de repensar o espaço público através de uma perspetiva mais participada.

Nowadays, humanity is consuming unsustainably the planet’s resources. In the scope of energy resource consumption, e.g., the intense use of fossil fuels has contributed to the acceleration of climate changes on the planet, and the overriding need to increase energy efficiency in all sectors is now widely recognized, aiming to reduce greenhouse gases (GHG) emissions by 69% in 2030. Largely due to climate changes,water has also become a critical resource on the planet and hydric stress risk will rise significantly in the coming decades. Accordingly, several countries will have to apply measures to increase water efficiency in all sectors, including at the building level. These measures, in addition to reducing water consumption, will contribute to the increase of energy efficiency and to the decrease of GHG emissions, especially of CO2. Therefore, the nexus water energy in buildings is relevant because the application of water efficiency measures can result in a significant contribution to improve buildings’ energy efficiency and the urban water cycle (namely in abstraction, treatment, and pumping). For Mediterranean climate, there are few studies to assess the extent and impact of this nexus. This study presents the assessment of water-energy nexus performed in a university building located in a mainland Portugal central region. The main goals are to present the results of the water and energy efficiency measures implemented and to assess the consequent reduction of water, above 37%, and energy (30%) consumption, obtained because of the application of water-efficient devices and highly efficient light systems in the building. The water efficiency increase at the building level represents at the urban level an energy saving in the water supply system of 406 kWh/ year, nearly 0.5% of the building energy consumption, with a consequent increase in the energy efficiency and in the reduction of GHG emissions. Complementarily, other energy-efficient measures were implemented to reduce the energy consumption. As the building under study has a small demand of domestic hot water with no hydro pressure pumps and has a small water-energy nexus, it was concluded that the significant reduction of the building energy consumption did not influence the indoor comfort.

No 14º Encontro Internacional de Modelação Numérica em Barragens, organizado pela ICOLD, foi proposta a análise numérica de uma barragem de betão em arco localizada na Suécia sujeita a gradientes térmicos significativos ao longo do ano. Neste artigo apresentam-se os resultados numéricos obtidos com base numa discretização mais refinada do corpo da barragem, quando comparada com o modelo adotado no encontro internacional. Os resultados da análise mecânica realizada com um modelo de fenda discreta são comparados com as observações in situ. Verifica--se que o modelo estrutural mais refinado permite obter resultados mais próximos dos observados, nomeadamente a distribuição de fendilhação no paramento de jusante e o campo de deslocamentos. Analisa-se ainda o efeito das armaduras distribuídas colocadas junto ao paramento de montante e ao paramento de jusante no controlo de deformação e fendilhação.

Tidal inlets connect the ocean to inner water bodies and are present worldwide. Shallow inlets display fast morphological changes, due to complex interactions between tides, waves, and shallow depths. Their closure is commonly observed under storm waves, but the underlying processes remain only partly understood. Here, we present new field evidence that infragravity waves contribute to the closure of shallow inlets. The analysis of new field data collected at a shallow inlet under storm waves reveals that infragravity waves up to 0.4 m high can propagate inside the lagoon during flood but are blocked by opposing currents during ebb. At the passage of an infragravity wave crest, currents peak over 2.5 m/s and increase instantaneous sand fluxes by 2 orders of magnitude. Large accumulations of sand at the lagoon entrance damp tidal propagation until full inlet closure. This mechanism provides a new explanation for the closure of shallow inlets observed worldwide.

Sheds roof is a natural ventilation strategy that presents roof openings working as air collectors or extractors. A detailed review of the literature indicates a lack of research analyzing the impact of different sheds roof shapes and roof configurations on natural ventilation potential. his paper aims to evaluate the impact of changes in distance and alignment between wind catcher and leeward sheds roof. The methodology was Computational Fluid Dynamics (FCD) simulation. tests were performed in a atmospheric boundary layer wind tunnel on a 1:15 scale model to evaluate the accuracy of CFD simulations in different design configurations of sheds roof. The analysis showed that CFD simulations are generaly in good agreement with the wind tunnel tests. The difference between the most o the monitored points in the two tools used had errors below 10%. besides this, the results show that changes in alignment of the sheds and increasing distance between them decrease and increase the internal airflow to the leeward and windward sheds of the roof, respectively. In the first case it is due to the reduction in the sheds openings area. In the second these changes turn the sheds more effective in the air capture.

Está em curso um projeto de geminação a cargo de um consórcio franco-português, ao abrigo do Acordo de Associação Argélia-UE, que tem por objetivo prestar apoio ao "Organisme National de Contrôle Technique des Travaux Publics" (CTTP) argelino na implementação de um sistema de suporte à decisão para a gestão da rede de estradas e das obras de arte rodoviárias. Neste artigo pretende-se dar a conhecer sumariamente os principais aspetos desta interessante cooperação científica e técnica internacional, em que Portugal é representado pelo Laboratório Nacional de Engenharia Civil (LNEC).

This paper describes a methodology to determine the optimal size of a Wells turbine to be used in an OWC device taking into account hydro-aerodynamic coupling, performance curves of the turbine and air pressure control by a relief valve. The proposed model, named turbine diameter optimization (TDO) model, considers the movement of the water surface inside the OWC chamber as a piston movement in response to the hydrodynamic forces from the incoming waves. The aerodynamic is based on the first law of thermodynamics applied to the air column of the chamber. The power-pressure curve of the turbine and the air pressure control by relief valve are implemented in the model to determine the turbine power output for several regular incident waves. The TDO model is initially calibrated by a numerical model based on Reynolds-Average-Navier-Stokes (RANS) equations for each wave component of an expected sea state distribution. Thereafter, the power output generated by turbines of several sizes is calculated with lower computational cost (few minutes) in comparison with RANS based models (thousands of hours) in a personal computer. This developed methodology is an important support to the process of turbine sizing for an OWC device for an expected sea state distribution.

This paper analyses the possibility of using air curtains to prevent smoke flow from fire compartments. Full size experiments have been carried out and several relevant conditions to assess smoke-tightness have been tested. The smoke temperature during the tests was ranging from 182ºC to 351ºC, the angle measured between the curtain axis and the vertical plane was ranging from 18º and 26º, the nozzle thickness was ranging from 0.017 m to 0.045 m and the velocity at the nozzle was ranging from 8.3 m/s to 19.9 m/s. During the tests, the air curtain’s nozzle was positioned horizontally at the top of a permanent opening (door). With this configuration, we obtained an approximately vertical downward jet through the used opening. This paper includes the final results of the tests and develops an analytical tool for predicting the performance of air curtains. It was concluded that it is possible to achieve smoke-tightness, provided that the adequate plane jet parameters and the compartment’s smoke exhaust are correctly adjusted. According to this analysis, the smoke-tightness limit corresponds to equation B=??P?_a???P?_s =-0.30 u_a?u_(a_min) +1.25 (with 1.30? u_a?u_(a_min) ?1.67).