1,720,974 research outputs found
An efficient method to identify cross-sea states from wave measurements
No full textThis paper is aimed at describing a simple and efficient method to identify cross-sea states from directional wave measurements. The method is based on a new parameter named "Cross-Sea Index" (CSI), which is defined as the difference between two distinct definitions of the overall mean wave direction: the classic one introduced by Longuet-Higgins and the more recent one suggested by De Girolamo. In the following, the theoretical basis of the method is firstly outlined. The influence of the directional spectrum characteristics on the Cross-Sea Index is then discussed. Afterwards, the results of two Monte Carlo simulations are shown. These simulations were aimed at testing the new method and at comparing its outcomes with those of three other existing criteria. Finally, the new method is applied to the directional wave measurements, which were recorded by the Italian Sea Wave monitoring Network (SWaN) during the storm on 26th December 1993. All the achieved results clearly show the efficiency of the herein-proposed method. (C) 2004 Elsevier B.V. All rights reserved
Continuous hydrologic modelling for design simulation in small and ungauged basins: a step forward and some tests for its practical use
No full textThe design hydrograph estimation in small and ungauged basins represents one of the most common practices and, yet, a challenging open research topic for hydrologists. When discharge observations are not available, the practitioner is compelled to apply empirical approaches. The rational formula is slowly disappearing, while event-based approaches are more and more widespread. A step forward is represented by continuous models that have the potential to address the major drawbacks of event-based approaches. In this work we applied a continuous model specifically designed for ungauged basins (COSMO4SUB) and tested its use in conditions where typically the rational formula and the event-based approaches are applied. Results confirm that the continuous modelling is suitable for rapid and effective design simulations supporting flood hazard modelling and mapping studies
Validation of the three-wave quasi-kineticapproximation for the spectral evolution inshallow water
No full textThis paper aims at validating the three-wave quasi-kinetic approximation for the spectral evolution of weakly nonlinear gravity waves in shallow water. The problem is investigated using a one-dimensional numerical wave propagation model, formulated in the spectral representation. This model includes both a nonlinear triad interactions term and a wave breaking dissipation term. Some numerical tests were carried out in order to show the importance of using the triad nonlinear term in wave propagation spectral models, particularly to describe both behavior of the spectral integral parameters and of the spectral shape evolution in shallow water depth. Furthermore; a comparison against different set of experimental observations was carried out. Comparing the numerical results with the experimental observations made it possible to show the modeling efficiency of the three-wave quasi-kinetic approximation
Fluid–particle flow simulation by averaged continuous model
No full textIn this paper we present a numerical method for fluid–particle flow simulation. The mathematical model is based on the averaged continuum. The presence of particles is taken into account in terms of effective viscosity, which is defined by means of both Newtonian and non-Newtonian (Bingham plastic) models. The dispersed phase equation closure is based on particle buoyancy as well as on shear-induced self-diffusion effects. The proposed approach allows us to study sediment transport problems and the related evolution of bed forms, without requiring the generation of curvilinear coordinate systems and time-consuming step-by-step regridding. In fact, the present model describes the bottom shape in terms of a density contour surface, rather than a moving boundary of the fluid domain. Simple two-dimensional numerical tests have been performed: (i) Bingham flow in a driven cavity and (ii) particle settling in a pure Couette flow. Finally, preliminary results concerning (iii) two-dimensional scour below pipelines in steady flow have been presented and discussed
Misure strumentali di moto ondoso della Rete Ondametrica Nazionale: analisi statistica aggiornata degli eventi estremi
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Ottimizzazione della disposizione planimetrica delle dighe frangiflutti portuali per contenere i problemi di sedimentazione
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