1,720,984 research outputs found
Relative dispersion analysis of GLAD surface drifters in the Gulf of Mexico
Full text linkRelative dispersion analysis of the Lagrangian dataset derived from the GLAD drifter campaign in the Gulf of
Mexico was computed on pairs derived from actual triplets.
The results show that an exponential growth of the relative dispersion begins and occurs within the first two days of
deployment.
The influence of inertial motions should be taken into account in order not to overestimate turbulence diffusivities
Evaluation of horizontal diffusivity in the sea surface layer
No full textIn this paper the dispersion analysis of drifter campaigns realized in two different domains, the Gulf of Mexico and the Mar Grande Basin (Italy), was carried out using both relative and absolute approach. Relative dispersion, diffusivity and velocity variance were computed identifying different growth regimes. An exponential growth of the dispersion process was detected on the initial phase of deployment and empirical laws for horizontal diffusivity were inferred. Velocity variance and integral time scale were obtained using different techniques to evaluate short-term dispersion phenomena and submesoscale turbulence. A spectral analysis realized in accordance with the Taylor's theory was used to estimate the Lagrangian time scale in domains strongly affected by inertial oscillations. The turbulence parameters inferred can be used as input data in particle Lagrangian models of dispersion providing useful tools for surface dispersion prediction in marine environmen
Simulazione della dispersione marina di petrolio in caso di sversamenti accidentali da fondo pozzo
No full textIn questo studio vengono presentate le problematiche idrauliche legate alla simulazione dei fenomeni di oil-spill e blowout. Negli esempi analizzati si utilizza l’ultima versione del modello LASEMOD (LAgrangian SEa MODel), che tiene conto anche dell’evaporazione, della dispersione naturale, del getto di risalita e delle tecniche di mitigazione con l’uso di barriere galleggianti. LASEMOD può essere accoppiato ad un qualsiasi modello idrodinamico k-epsilon, che gli fornisca i campi di velocità media, l’energia cinetica turbolenta e la diffusività turbolenta verticale. A differenza dei modelli comunemente utilizzati per l’oil-spill, utilizza un modello di traiettorie con velocità correlate per tenere conto anche delle macroscale della turbolenza, che in ambiente marino possono avere anche dimensioni rilevanti. Il mescolamento asintotico completo viene garantito con la condizione di “well mixed”. La risalita da fondo pozzo è stata simulata con una tecnica originale, che utilizza uno schema di traiettorie aleatorie di Langevin, con varianze e scale di correlazione calcolate in base alle soluzioni analitiche lagrangiane del getto galleggiante. Il modulo di simulazione della dispersione naturale serve a valutare l’effetto di rottura del film di olio sulla superficie del mare per effetto del moto ondoso e la successiva dispersione nella colonna d’acqua di goccioline d’olio di dimensioni molto piccole
Modelling of short-term dispersion in the sea surface layer
No full textThe relative dispersion of GLAD drifter campaign conducted in the northern Gulf of Mexico is investigated. The high temporal and spatial sampling of the GPS-satellite tracked drifters permits to study the short-term dispersion. The exponential regime of dispersion is detected for different groups of drifter trajectories. Experimental laws of relative horizontal diffusivity are inferred. A variable diffusivity stochastic model of dispersion, using GLAD relative diffusivity experimental laws and NCOM derived surface velocity fields, is developed and used to simulate the initial phase of dispersion of the GLAD campaign
BIM for Healthy Buildings. An Integrated Approach of Architectural Design based on IAQ Prediction
Full text linkThe relationship between users and the built environment represents a fundamental aspect of health. The factors that define the properties linked to health and well-being are increasingly becoming part of building design. In these terms, building information modelling (BIM) and BIM-based performance simulation take on a priority role. Among the key features for the design of Healthy Buildings, indoor air quality (IAQ) plays a central role. There are numerous indoor pollutants with significant health effects; volatile organic compounds (VOCs) are to be mentioned among these. The paper presents the proposal of an integrated workflow in the BIM process for the check and control of VOC emissions from building materials and their concentration in confined environments. The workflow is developed through the systematisation of IAQ parameters for the open BIM standard, the integration in the BIM process of a numerical model for the prediction of the VOCs concentration in the indoor environment, and the development of model checkers for performance verification. The results show a good adhesion between the numerical model and the implementation in BIM, providing the designer with a rapid control instrument of IAQ in the various phases of the building design. The present study is the first development focused on TVOC, but implementable concerning other aspects of IAQ, as needed for the effectiveness of performance building-based design for health and wellness issues
Automatic tag detection in multimedia survey condition
Full text linkRecently, aquatic ecosystems have captured the interest of the international scientific community, spurring the development of new instruments and methodologies to explore, monitor, and preserve these environmental systems. In this context, the detection of shapes in shallow waters (either in submerged or semi-submerged scenarios) constitutes an intriguing research topic. Our investigation is framed within the multimedia photogrammetry domain, which aims to retrieve geometric information of static objects submerged or semi-submerged in a liquid (usually water), with one or more cameras placed outside the liquid itself. Performing a photogrammetric survey of objects in shallow waters with above-water cameras remains an open research field in the domain of Optics, presenting several theoretical problems and technical bottlenecks, starting with the study of refraction behaviour. Our goal is to develop an automatically applicable methodology to estimate a priori (and correct a posteriori) the effects of refraction on camera behaviour when capturing images of submerged or semi-submerged objects under certain conditions. We therefore tested the behaviour of the cameras in a controlled environment, through different depth levels and water motion conditions, and then elaborated a mathematical model of the optical distortion phenomenon encountered. Feature extraction presents many bottlenecks, mainly due to the particular optical conditions defined by multimedia acquisition and the eventual perturbations present if the liquid is in a condition of turbulence. This paper focuses on such technical problems, presenting part of the qualitative and quantitative results obtained at this stage of our research and the approach used to resolve some detection limitations
Evaluation of ansys-fluent model against field data in the framework of the VIEPI project
Full text linkThis paper presents a CFD analysis of the wind velocity simulated in a portion of the campus of the University of Rome “La Sapienza” (Italy). One of the final goals of this study is the evaluation of the pressure field on the surfaces of the buildings in order to quantify outdoor-indoor exchanges of air mass within a street canyon adjacent to the building of interest. Numerical results concerning the wind field have been compared with in situ data collected in the framework of the VIEPI (Integrated Evaluation of Indoor Particulate Exposure) project
Estimates of turbulence parameters from satellite-tracked drifters
No full textIn this paper relative dispersion of satellite-tracked
GPS-equipped drifters of the GLAD campaign in the Gulf of
Mexico was investigated. Relative dispersion and relative velocity
variance were computed pointing out different growth regimes.
An exponential growth of the dispersion was detected and
confirmed on the initial phase of deployment. The influence of
the GPS-position error, in relation with sampling frequency, was
evaluated. The presence of inertial oscillations was observed as
well as their contribution to dispersion phenomena
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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