1,720,996 research outputs found
Wave and tidal current effects on a lagoon inlet
No full textA method for studying the dynamics of lagoon inlets is presented. The HISWA model was used to propagate the offshore wave conditions towards the coastal zone, while the current field inside the lagoon and close to the inlets was computed through a 2D model that solves the vertically integraded momentum and continuity equations for shallow water free surface flows
Physical and numerical modelling of wave transformations in the Venice Lagoon
No full textAim of the study is to assess the capability of a numerical model to reproduce the wave modification when propagating in a very shallow water environment crossed by small canals. This is a typical situation within the Venice Lagoon, and it does appear that the wave transformation due to the cutting canals can be responsible of bank erosion and of other important phenomena (e.g. reflection and set-up/down).
A suitable wave model was therefore applied to the “academic case” of a rectangular trough of finite width, and compared with the results obtained through the laboratory tests, specifically performed in a wave flume. The applied model, SWAN, is an advanced third generation model, specifically developed for shallow waters. The model is based on the wave action balance equation with sources and sinks terms. Being the wave action conserved for a wave propagating in non-homogeneous media, the SWAN model seems to fit the requirements to correctly reproduce the wave evolution over a trough.
Once validated with the laboratory data, the wave model could be applied to the convoluted bathymetry of the lagoon and used to get an estimate of the energy dissipation on the canals’ edges and eventually an estimate of the slopes erosion
Model tests for evaluating beach nourishment behaviour
No full textAfter having shortly discussed about the nourishment fundamentals, focussing the attention on the benefits and on the factors promoting the beach fills, some specific questions on fill design, on related processes and on the temporal aspects of such beach-protecting intervention were addressed and tentatively answered. In the second part, the physical-model tool, as a way for answering to the suggested questions is presented and three different case studies are discussed
Rapid evolution of shoreline after a beach nourishment downdrift of a groin and at an embayed beach: theory vs. observation
Full text linkThis paper describes the evolving shoreline over a 3,5 years period after an important nourishment, approx. 100 m3/m, made by submarine sand carried out in Lido di Dante beach, Italy. The focus is made on the evolution of an embayed beach of Lido di Dante and of the rapid evolution of the shoreline located down drift a groin. Different behaviors were observed downdrift the groin and in the embayed beach: in the unprotected zone, downdrift the groin system, a seasonal variation is evident. The shoreline retreated very fast after the nourishment and the evolution has been modeled by the classic Pelnard Considere equation. At the embayed beach no evident seasonal variation was observed. Main changes are due to beach rotation, dependent on the wave direction
Investigating the impact of surface wave breaking on modeling the trajectories of drifters in the northern Adriatic Sea during a wind-storm event
No full textAn accurate numerical prediction of the oceanic upper layer velocity is a demanding requirement for
many applications at sea and is a function of several near-surface processes that need to be incorporated
in a numerical model. Among them, we assess the effects of vertical resolution, different vertical mixing
parameterization (the so-called Generic Length Scale –GLS– set of k–e, k–x, gen, and the Mellor–Yamada),
and surface roughness values on turbulent kinetic energy (k) injection from breaking waves.
First, we modified the GLS turbulence closure formulation in the Regional Ocean Modeling System
(ROMS) to incorporate the surface flux of turbulent kinetic energy due to wave breaking. Then, we
applied the model to idealized test cases, exploring the sensitivity to the above mentioned factors. Last,
the model was applied to a realistic situation in the Adriatic Sea driven by numerical meteorological forcings
and river discharges. In this case, numerical drifters were released during an intense episode of Bora
winds that occurred in mid-February 2003, and their trajectories compared to the displacement of satellite-
tracked drifters deployed during the ADRIA02-03 sea-truth campaign.
Results indicted that the inclusion of the wave breaking process helps improve the accuracy of the
numerical simulations, subject to an increase in the typical value of the surface roughness z0. Specifically,
the best performance was obtained using aCH = 56,000 in the Charnok formula, the wave breaking parameterization
activated, k–e as the turbulence closure model. With these options, the relative error with
respect to the average distance of the drifter was about 25% (5.5 km/day). The most sensitive factors in
the model were found to be the value of aCH enhanced with respect to a standard value, followed by
the adoption of wave breaking parameterization and the particular turbulence closure model selected.Published225-2393.7. Dinamica del clima e dell'oceanoJCR Journalrestricte
Modelli numerici integrati in aree costiere: un esempio di applicazione nel nord Adriatico
No full textRecent decades have witnessed considerable developments in the field of integrated numerical models used for simulating dynamic processes in coastal areas, that can now provide quantitative support to decision makers for questions such as erosion and coastal vulnerability.
Improvements in various theoretical formulations and an on-going increase in computing power (alongside the growing availability of long-term observations and numerical output from meteorological and sea-state models) allow the implementation of high-resolution and long-term applications.
However, the efficient use of these numerical tools is a function of their capacity to describe a variety of physical processes that are ‘integrated’ amongst themselves correctly. Indeed, from the air-sea interface to the turbulent mixing of water masses and the water-sediment interaction, integrated numerical modelling has to face a series of scientific and practical challenges still open. Examples include the non-linear interaction of waves and currents, the problem of turbulence, the modelling of resuspension and sediment-transport processes, the role of long-period waves in generating beach and dune erosion. Dealing with these using numerical models is necessary for a variety of reasons, from protecting the coast to search-and-rescue activities and support for marine construction work of all types
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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