Browsing by Author "Fael, Cristina Maria Sena"
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- ASHES - Advecção e difusão de sedimentos provenientes de incêndios florestais transportados em suspensão em cursos de água com margens rugosasPublication . Fael, Cristina Maria Sena; Ferreira, Rui Miguel Lage; Ricardo, Ana Margarida da Costa; Keizer, Jan Jacob; Abrantes, Nelson José CabaçosPara além das perdas de biodiversidade e recursos florestais, os incêndios são responsáveis pelo acréscimo de cinzas e material sólido transportados pelas encostas até aos cursos de água, contribuindo para a contaminação dos ecossistemas aquáticos. Para alcançar um bom estado ecológico das massas de água, exigido pela Diretiva Quadro da Água, é fundamental avaliar e controlar a quantidade de sedimentos nos sistemas fluviais. A presença de vegetação, além de contribuir para manter a biodiversidade, promove a sedimentação do material sólido transportado pelo escoamento. A gestão da vegetação nas zonas ribeirinhas pode ser uma solução para a mitigação de impactes associados à poluição causada pelos incêndios florestais. Assim, o estudo do transporte de material sólido suspenso em escoamentos em canais com vegetação é relevante para a gestão de bacias hidrográfica e conservação da biodiversidade. Estes são os motivos pelos quais se pretende: i) estudar os processos de advecção e difusão de sedimentos em suspensão (SS) em zonas com vegetação; ii) desenvolver um modelo numérico inovador capaz de modelar processos hidrodinâmicos e de qualidade da água em rios; iii) recomendar medidas de mitigação para a poluição aquática originada por incêndios florestais, contribuindo para a necessidade societal de preservar os recursos hídricos. Estes objetivos serão atingido através de uma abordagem multidisciplinar articulando trabalho de campo, laboratorial e numérico. As condições dos testes laboratoriais serão definidas pelos resultados do trabalho de campo, que prevê a monitorização da erosão na zona de transição entre uma encosta recentemente afetada por um incêndio e um curso de água. A ferramenta de modelação será desenvolvida e validada com dados experimentais, à escala da haste e do troço de rio, adquiridos em condições laboratoriais controladas, medindo simultaneamente a velocidade instantânea do escoamento e a concentração de SS. Para melhorar a visualização de escoamentos por entre elementos sólidos distribuídos aleatoriamente, simulando zonas com vegetação, prevê-se a construção de um canal que permita a realização de testes utilizando fluidos e objetos sólidos de igual índice de refratividade. Este canal e a metodologia para aquisição de dados conferem um carácter inovador ao projeto. Os resultados finais do ASHES incluem: i) uma ferramenta de simulação para modelar os processos de hidrodinâmica e de qualidade da água nos rios; ii) bases de dados curadas de velocidades do escoamento e concentrações de SS; iii) recomendações para critérios de projeto para áreas com vegetação a fim de promover a retenção de poluentes, mitigando a poluição aquática gerada por incêndios florestais. O efeito de adicionalidade do projeto também deve ser destacado: i) a ferramenta de simulação beneficiará diretamente as entidades ligadas à gestão dos recursos hídricos; ii) formação de jovens investigadores ao nível de mestrado (7) e de doutoramento (3).
- Characterization of the Skid Resistance and Mean Texture Depth in a Permeable Asphalt PavementPublication . Afonso, Márcia Isabel Lopes; Almeida, Marisa S. Dinis; Fael, Cristina Maria SenaRoad pavements need a deep characterization of the surface layer, with which the vehicles have direct contact and, therefore, must provide security to the users. The use of permeable asphalt pavements (PAP) with porous layers has provide obvious advantages in reducing runoff and the rainwater infiltration into the soil or for storage. However, the study of the interaction between the pavement surface layer and the tire rubber requires additional tests in terms of texture and friction, since they are important parameters for the design, construction, management, maintenance and roads safety. Considering the application of a PAP in a parking lot, the study objective was to characterize in the field the pavement surface in terms of mean texture depth (MTD) and skid resistance (Pendulum test value, PTV). The methods used were the volumetric technique by the patch test and the pendulum test, according to EN 13036-1 and EN 13036-4, respectively. The double layer porous asphalt (DLPA) at the surface is characterized by having a structure with high voids content that led to results of clearly rougher macrotexture and good skid resistance. The normalized limit values were met, however, a very strong correlation between MTD and PTV was not observed. A comparison was also made with porous surfaces of other studies and it was found that porous asphalt has a good behaviour at the start of construction which may tend to improve in the long term. From the study, it is concluded that the PAP presents good performance of the surface layer, providing road safety to users.
- Clear-water scour at submerged pile groupsPublication . Galán, Álvaro; Simarro, Gonzalo; Fael, Cristina Maria Sena; Cardoso, António HelenoAccurate estimates of the scour depth around submerged pile groups are important in river engineering for a number of reasons, however, the literature on this issue is scarce. This study introduced an experimental campaign of 48 long-duration clear water experiments at submerged and skewed pile groups composed of cylindrical elements under steady flow. The effects of the skew angle, submergence ratio and pile group configuration on the equilibrium scour depth were investigated. The experimental scour depths were compared with the results from the HEC-18 empirical method and a modification of it to take into account a wide range of submergence ratios was proposed. Further, a new formulation to estimate the equilibrium scour depth at submerged pile groups was introduced with good agreement for the tests under consideration. Some considerations about the most employed characteristic lengths used to normalize the equilibrium scour depth were made.
- Development of the Concept vs Prototyping: Implementation of a real scale Water-Energy Integrated SystemPublication . Silva, Ana Rita; Santos, Fernando Charrua; Espírito Santo, António; Páscoa, J. C.; Fael, Cristina Maria SenaCurrently, the concept of smart cities and renewable energy are more consolidated and developed. With each passing day, new technological advances are emerging within both themes. At the same time, the water sector has becoming increasingly demanding in terms of quality and compliance with all existing legislation. That said, it is understandable that both sectors and their management entities come together in search of more sustainable operations that go against the reduction of greenhouse gas emissions, decentralization of energy production and the improvement of efficiency, quality and use of resources. It is important to understand the synergies between water and energy to contradict what has been said so far about the increasing demand for energy, its exponential trend and the negative repercussions on freshwater resources. As such, this article aims to address the interconnection between both sectors to promote alternative scientific and technological improvements to the management and development of Integrated Water-Energy systems, while studying the dynamics between the theoretical development of the problem and the challenges of prototyping of such complex systems in real and urban context.
- Effect of Debris on the Local Scour at Bridge PiersPublication . Dias, Ana Josefa; Fael, Cristina Maria Sena; Núñez-González, FranciscoScour is one of the most recurrent causes of failure of bridge structures in alluvial rivers. There is a variety of formulas for the assessment of bridge scour characteristics and for the design of suitable protection. Nevertheless, current approaches neglect the effect of debris carried by natural streams during floods, even when the accumulation of debris can extremely amplify the action of scouring processes. Until now, very limited efforts have been conducted to systematically investigate these effects. The present study focuses on the effect of debris on the maximum clear-water scour depth at cylindrical piers inserted in uniform, fully-developed turbulent flows in wide rectangular channels with flatbed composed of uniform, non-ripple forming sand. For these purposes, an experimental campaign was carried out by performing 17 long-duration (td = 7 days) experiments. The experimental tests were performed in the hydraulic structures channel at the University of Beira Interior. The channel was 0.83 m wide, 12.0 m long and 1.0 m deep. In the central reach of the flume, a 3.0 m long and 0.30 m deep recess exists where scour is free to develop. The experiments were carried out with a cylindrical pier with 0.05 m diameter and two boxes, each with debris of different dimensions, either of triangular or rectangular shape. The tests were carried out with constant approach flow depth, d = 0.15 m, and average approach flow velocity, U, approximately equal to the average approach flow velocity for the threshold condition of sediment entrainment, Uc ∼ 0.31 m/s. For this velocity, the scour depth can be expected to be maximal. The experiments will give a special focus to the development of scour hole as the accumulated debris increase. Moreover, the experimental results will be compared with a reference experimental run without debris, so that the increments on scour depth due to the single debris clusters of different characteristics will be obtained and discussed. The following conclusions were obtained: i) The shape and position of the debris accumulation have a strong influence on the final scour depth. Debris placed on the bottom, upstream of the bridge pier, with a triangular shape, does not induce any increase in scour depths, the values are practically the same as the one obtained for the reference pier (without debris); ii) The method suggested by [3], as modified by [6], performed well, replicating the main trends observed in the experiments; and the influence of the relative submerged ratio of the debris on the scour depth, followed the trend observed previously by [8], with an increasing scour depth up to a critical value of the ratio, and then decreasing scour for ratios higher than this critical value.
- Estudo do desempenho de misturas betuminosas com incorporação de fibras celulósicasPublication . Afonso, Márcia Isabel Lopes; Maia, Maria; Almeida, Marisa S. Dinis; Martinho, Fernando; Fael, Cristina Maria SenaAs administrações de estradas em todo o mundo têm tomado consciência da importância do estudo das misturas betuminosas a aplicar nas camadas superficiais dos pavimentos rodoviários, face à necessidade de aumentar a durabilidade e o desempenho mecânico e funcional dos pavimentos. O principal objetivo deste estudo é avaliar o comportamento de quatro tipos de misturas, duas misturas drenantes e duas misturas densas. Foi, ainda, avaliada a influência da incorporação de fibras celulósicas aditivadas, com vista a melhorar a adesividade entre os agregados e o ligante. As fibras, de dois tipos distintos, irão contribuir para evitar a perda de ligante por escorrência, aumentar a afinidade entre agregado e betume e aumentar a resistência à deformação permanente.
- Flow-3D Modelling of the Debris Effect on Maximum Scour Hole Depth at Bridge PiersPublication . Mendonça, Inês Sofia Pereira; Canilho, Hugo Daniel Leitão; Fael, Cristina Maria SenaBridge foundations are frequently inserted in riverbeds constituted by alluvial material, being, therefore, subjected to scouring processes. Such phenomenon is aggravated during flood events due to the increase of water flow or due to the increase of the debris carried by the flow that can pile up along the bridge structural elements. The debris can partially obstruct bridge spans and accumulate near bridge piers and abutments, which will have consequences in terms of reduction of flow capacity and an increment of the maximum scour depth. The dimensions, shape and its location are characteristics that must be considered when predicting the scour depth. The present study aims at analyzing the effect of the debris on the maximum clear-water scour depth at cylindrical piers inserted in uniform sand, non-ripple forming sand, fully-developed turbulent flows in wide rectangular channel, using computational fluid dynamics software, Flow-3D. For this purpose, debris with a triangular and rectangular shape, floating and on the sand bed, were tested, using the k-ε RNG turbulence model and the numerical results were compared with those obtained experimentally. It was possible to verify that the floating debris gives greater scour hole depth and the debris on sand bed behave as scour countermeasure reducing the scour hole depth. Also, rectangular shaped debris seems to cause more scour near the structures than the triangular shaped ones, which also seemed beneficial to the scour hole, by reducing it. However, the results obtained computationally are significantly lower than those obtained experimentally.
- Hydraulic Conductivity of the Permeable Asphalt Pavement – Laboratory vs In Situ TestPublication . Afonso, Márcia Isabel Lopes; Santos, Tiago Silva; Fael, Cristina Maria Sena; Almeida, Marisa S.DinisPermeable asphalt pavements (PAP) are a key measure for mitigating the climate change effects in urban areas. Cities are becoming increasingly dense and have large areas of waterproofing due to the excessive construction of buildings and highways that prevent the rainwater drainage into the soil. Recently, the PAP study with a double layer porous asphalt (DLPA) has been an alternative to the use of a porous asphalt single layer (PA), with recognized advantages in increasing water infiltration and, consequently, in decreasing surface runoff. It was developed in field a PAP of small dimensions to assess its capacity to respond to floods. The purpose of this study is to evaluate the hydraulic conductivity (K) of the DLPA applied on the PAP, both in laboratory conditions and in field conditions, and verify the representativeness of the laboratory results in relation to the results obtained in situ. In laboratory terms, the LCS permeameter was used, which evaluates the vertical and horizontal hydraulic conductivity, both in specimens produced in the laboratory and in cores extracted in situ. In the field, the LCS permeameter and the falling head permeameter were used to measure the hydraulic conductivity and the relative hydraulic conductivity (HC), respectively. The laboratory tests were performed according to Standards EN 12697-19 and NLT 327 and the in situ tests according to Standards EN 12697-40 and NLT 327. It was verified that the specimens produced in the laboratory of the two porous layers showed values of K (vertical and horizontal) lower than those obtained in the field cores, both for the individual layers PA and for the DLPA. Thus, it was found that the study in controlled environment differs in terms of results. This divergence justified the need to perform a field study in order to perceive the actual performance of the PAP surface layer. This study was characterized by the values of K (m/s) and HC (s-1), from which it was not possible to obtain a relation. From this study it was concluded that the measuring methods of the hydraulic conductivity in the laboratory were close to the behaviour of the same in situ, however its evaluation under real conditions is always essential.
- Influence of a Bubble Curtain Device on Microplastics DynamicsPublication . Santos, César Augusto Vaz; Camacho, E. A. R.; Silva, André; Fael, Cristina Maria SenaAir bubble curtains have been applied to a wide range of situations, from the attenuation of underwater noise, debris control, and containment of suspended sediment to the reduction in saltwater intrusion. This work conducts a preliminary numerical study on the influence of a bubble curtain device on microplastic dynamics. Simulations are conducted with a two-phase unsteady model, and the trajectories of the microplastic particles are computed with the Discrete Phase Model (DPM). Particles are injected upstream of the bubble curtain, and their transport is analyzed under different flow conditions. Results show that the ratio between the water velocity and the air injection velocity can significantly impact the efficiency of the device in directing the particles toward the surface. Furthermore, a higher degree of turbulent mixing is seen for lower water velocities. This study highlights the intricate flow behavior, and the need for a deeper understanding of other variables such as the microplastic size and concentration and the geometry of the air injection system.
- Influence of clogging on the hydrologic performance of a double layer porous asphaltPublication . Afonso, Márcia Isabel Lopes; Fael, Cristina Maria Sena; Almeida, Marisa S. DinisNowadays, the increasing urbanisation and the effect of climate change in cities has been a constant concern. In particular, the floods cause a significant increase in surface runoff, mostly on roads and parking areas. As an alternative to asphalt pavements, usually used in these areas, permeable pavements have been developed with Porous Asphalt (PA). These pavements allow the infiltration of water from the surface to the ground due to the high void content of the PA, thus reducing the surface runoff and increasing recharge of groundwater. Over the years, the infiltration capacity of the mixtures decreases with the clogging by sediments from the vehicles themselves and/or from the local environment. In order to mitigate this effect, a Double Layer Porous Asphalt (DLPA) was developed. This research intends to deepen the knowledge about the influence of the clogging of a DLPA, with respect to the infiltration capacity, since it is an essential theme in the pavements lifespan and that needs to be developed. This study considered different evaluation phases of the infiltration capacity with two clogging cycles (500 and 1000 g/m2). The materials used were: sand, region soil, and rubber waste. The infiltration capacity test was performed in different phases after a rainfall event of 100 mm/h with a rainfall simulator developed for this purpose. Furthermore, the permeability test with the falling head permeameter was carried out in parallel, obtaining outflow times for each clogging phase and subsequent maintenance phase. The research concluded that DLPA has a high infiltration capacity after the first clogging cycle in both performed tests. In the second clogging cycle, the results show that the infiltration decreased due to the partial filling of the pores, mainly, for the rubber-filled DLPA. The type of clogging material influences the infiltration capacity, nevertheless partially recovered after simple maintenance was performed.
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