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An efficient computational model for water wave propagation in coastal regions
An efficient numerical model of the mild-slope equation, describing water wave propagation (combined refraction-diffraction), based on robust iterative methods is presented. The elliptic formulation (boundary value problem) of the governing equation is selected for numerical treatment because it is particularly suited to complex wave fields like those encountered inside harbours. The requirement that the computational model be capable of dealing with large problem domains is addressed by implementing and testing two iterative solvers, both belonging to the family of Krylov subspace methods. The two solvers are based on the Stabilised Bi-Conjugate Gradient Method (Bi-CGSTAB) and the Generalised Minimum Residual (GMRES) method. The performance characteristics of the solvers are established using results for two standard test cases widely used as benchmarks in coastal modelling. It is shown that the Bi-CGSTAB algorithm has a considerably better convergence rate than the GMRES algorithm and, moreover, it is faster and more efficient than other published methods for the same problem.
Year: 1998
Number Pages:
263-271.
Author(s): Oliveira, F. S. B. F.; Anastasiou, K.
Editor: Applied Ocean Research
Volume:
vol. 20/5.
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Assessment of Pollution Hazards in the Estarreja Aquifer (Portugal).
N/A
Year: 1998
Number Pages:
21 pp.
Author(s): Lobo Ferreira, J. P. C.; Leitão, T. E.; Pássaro, D.
Editor: ******
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Caracterização dinâmica de estruturas de pontes com base em ensaios de vibrações ambiente
Neste artigo apresentam-se inicialmente algumas considerações sobre ensaios dinâmicos in situ de estruturas, focando-se em especial a utilização de ensaios de vibrações ambiente para a avaliação das características dinâmicas de estruturas de pontes. São referidos vários trabalhos onde foram utilizados ensaios deste tipo. Descrevem-se em seguida dois estudos recentemente realizados pelo LNEC com vista à caracterização dinâmica da ponte da Arrábida na cidade do Porto e da ponte da Figueira da foz, apresentando-se o equipamento utilizado, as técnicas de ensaio e análise adotadas e os resultados obtidos.
Year: 1998
Number Pages:
35-50pp.
Author(s): Rodrigues, J.; Campos Costa, A.
: RPEE
Editor: LNEC
Volume:
Série I, nº 44.
Keywords: Pontes; Ensaio dinâmico in-situ
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Morfodinâmica de margens estuarinas: evolução da restinga do Alfeite nos últimos 150 anos (estuário do Tejo)
N/A
Year: 1998
Number Pages:
c-59-c-62.
Author(s): Freire, P.; Andrade, C.
Editor: Comunicações do Inst. Geológico e Mineiro
Volume:
tomo 84, fascículo 1.
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NON LINEAR DESIGN OF TAPERED ELEMENTS
N/A
Year: 1998
Number Pages:
3pp.
Author(s): Baptista, A. M.; Muzeau, J. P.
: Journal of Constructional Steel Research
Editor: Elsevier
Volume:
Nº11-3.
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On the role of tracking on Eulerian-Lagragian solutions of the transport equation
We investigate the effect of tracking errors on the accuracy and stability of Eulerian-Lagrangian methods (ELMs) for the solution of the transport equation. A combination of formal analysis and numerical experimentation demonstrates that the effect is severe. Even moderate tracking errors substantially affect the preservation of the zeroth, first and second moments of concentration ( mass, phase and diffusion) and may lead to the instability of otherwise stable and very accurate ELMs. The use of accurate tracking algorithms is strongly recommended for Eulerian-Lagrangian simulations involving complex flows. Key Words: Transport equation. Eulerian-Lagrangian methods. Tracking methods. Mass conservation. Numerical experimentation. Accuracy
Year: 1998
Number Pages:
539-554.
Author(s): Oliveira, A.; Melo Baptista, A.
Editor: Advances in Water Resources
Volume:
vol. 21/7.
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A Centrifugadora geotécnica do LNEC
O Laboratório Nacional de Engenharia Civil (LNEC) dispõe desde 1995 de umacentrifugadora geotécnica. A centrifugadora, uma Acutronic modelo 661, tem uma capacidade de 40g--ton e um raio de 1,80 m à plataforma giratória. O artigo descreve o desenvolvimento da instalação,incluindo as características gerais do equipamento e sistemas eléctricos, ópticos e mecânicosassociados. Perspectivam-se as possibilidades de modelação física no âmbito da geotecnia.
Year: 1997
Number Pages:
18p.
Author(s): Portugal, J. C.; L. Aguilar Madeira; Santos, Carlos
: Revista da Sociedade Portuguesa de Geotecnia
Editor: Sociedade Portuguesa de Geotecnia
Volume:
1/3.
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A nova centrifugadora portuguesa
O Laboratório Nacional de Engenharia Civil (LNEC) dispõe desde 1995 de umacentrifugadora geotécnica. A centrifugadora, uma Acutronic modelo 661, tem uma capacidade de 40gtone um raio de 1,80 m à plataforma giratória. O artigo descreve o desenvolvimento da instalação,incluindo as características gerais do equipamento e sistemas eléctricos, ópticos e mecânicos associados
Year: 1997
Number Pages:
14p.
Author(s): Portugal, J. C.; L. Aguilar Madeira; Silva, M.; Santos, C.; Maranha das Neves, E.; Correia, R.
: Revista da Sociedade Portuguesa de Geotecnia
Editor: Sociedade Portuguesa de Geotecnia
Volume:
81.
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A three-dimensional model of tidal currents in the mouth of Tagus estuary
Three-dimensional simulations of barotropic tides are used to investigate the complex circulation at the mouth of the Tagus estuary. Comparison with field data shows that elevations are well represented in the main area of interest, but velocities are slightly over-predicted due to a simplified treatment of intertidal flats. Model results show the existence of strong velocity phase lags (up to 1.75 hours for the semi-diurnal constituents) between the shallow areas and the deep channel. These phase lags are partially responsible for the generation by advective accelerations of a strong residual velocity field (velocities reach 0.5 m/s -1) with well defined eddies. The interaction between the residual and tidal velocity fields in turn generates strong chaotic stirring.Localized sigma coordinates (LSC), a recently proposed method which allows the number of nodes per vertical to vary horizontally, are used for the first time in a three-dimensional application. A previously proposed criterion for the horizontal distribution of the total number of vertical nodes is shown to be inadequate when advective accelerations are important. However, with an alternative criterion, the use of LSC reduces maximum errors by a factor of two relative to traditional sigma coordinates.
Year: 1997
Number Pages:
17/14: 1689-1714.
Author(s): Fortunato, A. B.; Baptista, A. M.; LUETTICH, R.
Editor: Continental Shelf Research
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Assessment of Legislation Concerning Geographical Zoning for Groundwater Protection. Application to a Portuguese Case-Study
N/A
Year: 1997
Number Pages:
315-323.
Author(s): Lobo Ferreira, J. P. C.; Ciabatti, P.
Editor: Operational Water Managment, Refsgaard &Karalis (eds) 1997
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