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Papers
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Experimental study of an onshore dual chamber oscillating water column device
A wave flume is used to study a scaled model of a stepped bottom dual-chamber Oscillating Water Column (OWC) installed onshore. Compared to traditional single-chamber OWCs, the use of dual-chambers is expected to widen the range of sea states in which the OWC is more efficient, and the step, in front of the first chamber, boosts the capturing energy capacity of the device. The Power Take-Off (PTO) system is modelled as an air opening in the pneumatic chambers. Several experiments combining regular incident waves and PTO damping conditions are performed. Results of the amplitudes of the free surface elevations inside the chambers show that the device can amplify the incident wave amplitude up to 1.57 times in chamber 2. Results of the primary efficiency show that the device is highly dependent on the PTO damping characteristics and can reach around 40% for a wide range of wave periods. Results of the reflection analysis show that the reflection coefficient is also dependent on the PTO damping characteristics but remain lower than 0.6 for all the studied cases. Sloshing phenomenon (mostly in the cross-section direction) was observed for a wavelength close to the cross-section dimension, impacting negatively on the device pneumatic performance.
Year: 2024
Number Pages:
16p..
Author(s): Gadelho, J.; REZANEJAD, K.; Guedes Soares, C.; Santos, J. A.; Anastas, G.; Fortes, C. J. E. M.
: Ocean Engineering
Editor: Elsevier
Volume:
Volume 300 (117240).
Keywords: Reflection coefficients; Efficiency improvement; Breakwater; Experiments; Oscillating water column
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Experimental study on drag coefficient of flexible vegetation under non-breaking waves
Laboratory experiments of wave propagation over rigid and flexible vegetation fields, with the same configurations, were conducted to understand the effect of vegetation flexibility on the drag coefficient (CD). The direct method and the least squares method (LSM), based on force and flow measurements, are applied to calculate the CD in the experimental conditions. The formulations of both methods are extended to estimate the CD for flexible vegetation cases. A video analysis was performed to account for the swaying motion. Typically, wave dissipation is lower for flexible than for rigid vegetation of the same configuration, under the same flow condition. Therefore, a proportional effect in the corresponding CD results, obtained from common CD calibration to wave dissipation without considering vegetation motion, is usually observed. However, the present results show that although the wave dissipation was 34% lower for flexible relative to rigid vegetation, the respective CD values were close. CD estimations considering vegetation motion and inertia suggest that CD of flexible vegetation was up to 13% higher relative to rigid vegetation. Accounting for inertia reduced the CD for rigid vegetation up to 7%, while raised the CD for flexible vegetation up to 13%.
Year: 2024
Number Pages:
14p..
Author(s): Reis, R.; Fortes, C. J. E. M.; Rodrigues, J.; HU, Z.; Suzuki , T.
: Ocean Engineering
Editor: Elsevier
Volume:
Volume 296.
Keywords: Wave dissipation; Inertia; Vegetation motion; Flexible vegetation; Drag coefficient
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Exploring Wave
Aquatic vegetation in the littoral zone plays a crucial role in attenuating wave energy andprotecting coastal communities from hazardous events. This study contributes to the developmentof numerical models aimed at designing nature-based coastal defense systems. Specifically, a novelnumerical application for simulating wave
Year: 2024
Author(s): El Rahi, J.; Martinez-Estevez, I.; Reis, R.; Tagliafierro, B.; Dominguez, J.M.; Crespo, A.J.C.; Stratigaki, V.; Suzuki, T.; Troch, P.
Editor: MDPI
Keywords: Project chrono; DualSPHysics; SPH-FEA coupling; Fluid
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Global and local geometrical imperfections of pultruded GFRP profiles based on a modal approach
ABSTRACT - The ultimate capacity of pultruded glass fibre reinforced polymer (pGFRP) profiles depends significantly on geometrical imperfections (GIs), given their sensitivity to buckling phenomena arising from both thin walls and low elastic moduli. However, GIs are not yet comprehensively addressed in design guidance. This paper proposes a new approach to characterize the initial GIs of pGFRP profiles based on a modal approach. Given the lack of comprehensive knowledge in this area, this study presents a highly accurate and robust methodology to measure GIs and dimensional deviations (DDs) in pGFRP profiles using a 3D contact coordinate measurement machine (CMM). The modal approach encompasses the measurement of dimensional parameters and a point cloud transformation that enables the assessment of GIs associated with pure buckling modes of pGFRP profiles. This procedure allows the quantification of three types of global GIs associated to (i) minor-axis (weak axis), (ii) major-axis (strong axis) bending, and (iii) twist. Additionally, the procedure also includes the assessment of local GIs, considering the wall (plate-like) imperfections. The separation of GIs into these four types (shape and amplitude) is of major relevance as its paves the way to the development of analytical design formulas for the strength prediction of pGFRP members. The approach described in this paper also serves two important purposes: (i) the statistical analysis of DDs and GIs of pGFRP members, and (ii) the identification of distinct shapes and amplitudes of GIs that form the basis for reliable design considerations of pGFRP members.
Year: 2024
Number Pages:
18p..
Author(s): Silvestre, N.; Correia, J.; Pinheiro, A.; Ribeiro, A.; Lages Martins, L.; Lazzari, J.
: Construction and Building Materials
Editor: ELSEVIER
Volume:
412 (2024) 134813.
Keywords: Modal decomposition; Geometrical imperfections; Dimensional deviation; 3D contact measurements; Pultruded profiles; Glass fibre reinforced polymer (GFRP)
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Hygroscopicity and Morphology of Bio-Based Boards
The internal structures and the hygroscopicity of bio-based boards consisting of giantreed (Arundo donax L.) and hazelnut shells as bio-aggregates, and a sodium silicate solution asthe adhesive, were investigated. The aim was to evaluate the influence of each material (the bio-aggregates and adhesive) and their distributions in the boards on the final performance. By carrying out X-ray computed tomography, the internal structures and the porosities of the boards were determined, allowing important considerations of their hygroscopicity. The voids
Year: 2024
Number Pages:
22p..
Author(s): Cintura, E.; Lina Nunes; Molari, L.; Bettuzzi, M.; Morigi, M.; Brancaccio, R.; Faria, P.
: Applied Sciences
Editor: MDPI
Volume:
14, 873.
Keywords: Tomography; Sodium silicate; Moisture buffering; Hygroscopicity; Hazelnut shel; Giant reed; Bio-resource; Bio-aggregate; Arundo donax; Agro-industrial waste
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Hygrothermal behaviour of external thermal insulation composite systems (ETICS) to withstand biological colonisation
ETICS are multilayer building solutions applied to the building external walls to provide animproved thermal performance to the building envelope. However, several questions have beenraised concerning the durability of ETICS, namely related to biological colonisation phenomena.Considering the high susceptibility of ETICS to bio-colonisation, the following research questions arise: (i) what is the impact of surface temperature (ST) and surface relative humidity (SRH)fuctuation on mould growth in ETICS facades? (ii) is it possible to predict mould growth onETICS under fuctuating conditions considering favourable and unfavourable growth conditions?This study aims to investigate the infuence of the hygrothermal behaviour of five different ETICS(with thermal mortars and insulation boards) on mould growth. ETICS were exposed for one yearat an urban site in Lisbon, Portugal, facing North, during which the ST and the SRH weremonitored. Concurrently, numerical simulations were performed to evaluate the hygrothermalbehaviour of the ETICS. Three theoretical indices were applied, using numerically and experimmentally obtained values of ST and SRH as input to provide an indication of the risk of mould growth. The results were complemented and validated by assessing the bio-colonisation, water performance and aesthetic properties of the ETICS. Index 1 (percentage of time with SRH
Year: 2024
Number Pages:
25.
Author(s): Parracha, J.; Veiga, M. R.; Flores-Colen, I.; Lina Nunes
: Journal of Building Engineering
Editor: Elsevier Ltd.
Volume:
86 e 108932.
Keywords: Numerical simulation; Onsite monitoring; Mould growth; Moisture; Temperature; Thermal insulation materials
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Integrating Uncertainty in Performance Assessment of Water Distribution Networks by Scenario Building
This paper presents and demonstrates a novel scenario-building methodology that integrates contextual and future time uncertainty into the performance assessment of water distribution networks (WDNs). A three-step approach is proposed: (i) System context analysis, identifying the main key factors that impact the WDN performance; (ii) Scenario definition, identifying the implicated WDN variables, describing its possible evolution, and conjugating them to further establish the reference scenario and the two most relevant and opposite ones; and (iii) Scenario modelling, simulating the WDN behaviour for those scenarios. The obtained spatial and temporal hydraulic results are further used to calculate performance metrics. The methodology is applied to a real WDN to assess resilience performance considering infrastructure asset robustness (real water loss performance indicator), service reliability (minimum pressure index), and service flexibility (network resilience index). A new formulation to assess the metric evolution over time is proposed, deducting the further-away performance results by using an uncertainty weight. The results demonstrate that the increase in metric amplitude for the opposite scenarios over time highlights future uncertainty, reflecting context uncertainty, and the comparison of metric spatial distribution (i.e., at the pipe/node levels) highlights critical areas with higher associated uncertainty.
Year: 2024
Number Pages:
18p..
Author(s): Carneiro, J.; Loureiro, D.; Cabral , M.; Covas, D.
: Water
Editor: MDPI
Volume:
Volume 16, Issue 7.
Keywords: Resilience metrics; Scenario modelling; Scenario planning; Aleatory uncertainty; Drinking water networks
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Metrological quality of the excitation force in forced vibration test of concrete dams
Abstract. This paper describes the study of the metrological quality of the excitation force in the context of force vibration test of concrete dams. For this purpose, a measurement uncertainty evaluation was performed, based on available probabilistic information about the input quantities
Year: 2024
Author(s): Lages Martins, L.; Gomes, J. P.; Ribeiro, A.
: Journal of Physics
Editor: IOP Publishing
Volume:
vol. 2647.
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Moving from classical towards machine learning stances for bus passengers
Passenger alighting estimation is a critical task in public transport (PT) management, especially for entry-only Automatic Fare Collection (AFC) transport systems where passenger alighting are not recorded. Effective estimation methods are necessary for trip analysis and route planning, offering valuable insights into passengers
Year: 2024
Author(s): Cerqueira, S.; Arsénio, E.; Barateiro, J.; Henriques, R.
Editor: Elsevier
Keywords: Origin-destination matrices; Transport planning; Sustainable mobility; Public transport; Non-commuting patterns; Density-based clustering; Trip-chaining; Alighting estimation
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Numerical analysis of 3D hydrodynamics and performance of an array of oscillating water column wave energy converters integrated into a vertical breakwater
Performance and hydrodynamics of an array of Oscillating Water Column (OWC) Wave Energy Converter (WEC) integrated into a vertical breakwater is studied. The FLUENT® software, in which the numerical model is based on the Reynolds-Averaged Navier-Stokes equations and the Volume of Fluid method for free surface flow modeling, is used in a 3D numerical wave tank. Three vertical breakwater configurations subject to the action of incident regular waves with periods from 6 to 12 s are studied: normal breakwater, with vertical walls parallel to the direction along the breakwater length; and two novel breakwater geometries, partially and fully convergent breakwaters, whose converging vertical walls are inclined
Year: 2024
Number Pages:
20p..
Author(s): Didier, E.; Teixeira, P.
: Revista Renewable Energy
Editor: Elsevier
Volume:
Vol. 225 (120297).
Keywords: 3D RANS-VoF numerical wave tank; Efficiency; Vertical breakwater; Oscillating water column; Array of wave energy converters
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