Relative dispersion analysis of GLAD surface drifters in the Gulf of Mexico

Relative 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

BIM for Healthy Buildings. An Integrated Approach of Architectural Design based on IAQ Prediction

The 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

Modelling VOC Emissions from Building Materials for Healthy Building Design

The profound qualitative changes of indoor air and the progressive increase in the absolute number of pollutants, combined with the scientific awareness of the health impacts deriving from spending more than 90% of one’s time inside confined spaces, have increased the attention onto the needs of well-being, hygiene, and the health of users. This scientific attention has produced studies and analyses useful for evidence-based insights into building performance. Among the main pollutants in the indoor environment, Volatile Organic Compounds (VOCs) play a central role, and the use of box-models using the mass balance approach and Computational Fluid Dynamics (CFD) models are now consolidated to study their concentrations in an indoor environment. This paper presents the use of both types of modelling for the prediction of the VOC concentration in the indoor environment and the proposal of a guide value for the Indoor Air Quality (IAQ)-oriented building design, specifically related to the indoor VOC concentration due to building materials. Methodologically, the topic is addressed through environmental sampling, the definition of the parameters necessary for the numerical models, the simulations with the box-model and the CFD, and the comparison between the results. They show a good correspondence between the modelling tools used, highlighting the central role of ventilation and allowing a discussion of the relationship between regulatory limits of emissivity of materials and Indoor Air Guide Values for the concentration of pollutants

Turbulence changes due to a tidal stream turbine operation in the Pentland Firth (Scotland, UK)

The high tidal stream resource in the Pentland Firth (Scotland, UK) has encouraged the development of commercial scale tidal farms. This work is a modelling study primarily focused on how the layout of arrays determines the extractable power and may affect physical processes in the region. Furthermore, the study provides information about submarine turbine maintenance. Tidal dynamics in the Pentland Firth and Orkney Waters (PFOW) have been reproduced by a three-dimensional FVCOM model implementation. The tidal stream turbines were represented in the model as sub grid scale objects by using a momentum sink approach. It has been explored how different turbine location, number and spacing can allow achieving very different amount of power resource, as well as degree of change to flow velocities. It has also been verified that turbulence changes can lead to an increase in bottom currents in the vicinity of the tidal turbines

Alfalfa for a sustainable ovine farming system: Proposed research for a new feeding strategy based on alfalfa and ecological leftovers in drought conditions

In the past 10 years, the average demand for meat and milk across the world has significantly increased, especially in developing countries. Therefore, to support the production of animal-derived food products, a huge quantity of feed resources is needed. This paper does not present original research, but rather provides a conceptual strategy to improve primary production in a sustainable way, in relation to forthcoming issues linked to climate change. Increases in meat and milk production could be achieved by formulating balanced diets for ovines based on alfalfa integrated with local agricultural by-products. As the central component of the diet is alfalfa, one goal of the project is increasing the yield of alfalfa in a sustainable way via inoculating seeds with symbiotic rhizobia (i.e., Sinorhizobium meliloti). Seed inoculants are already present on the market but have not been optimized for arid soils. Furthermore, a part of the project is focused on the selection of elite symbiotic strains that show increased resistance to salt stress and competitiveness. The second component of the experimental diets is bio-waste, especially that obtained from olive oil manufacturing (i.e., pomace). The addition of agro-by-products allows us to use such waste as a resource for animal feeding, and possibly, to modulate rumen metabolism, thereby increasing the nutritional quality of milk and meat

The ALICE experiment at the CERN LHC

ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-ion detector at the CERN LHC which focuses on QCD, the strong-interaction sector of the Standard Model. It is designed to address the physics of strongly interacting matter and the quark-gluon plasma at extreme values of energy density and temperature in nucleus-nucleus collisions. Besides running with Pb ions, the physics programme includes collisions with lighter ions, lower energy running and dedicated proton-nucleus runs. ALICE will also take data with proton beams at the top LHC energy to collect reference data for the heavy-ion programme and to address several QCD topics for which ALICE is complementary to the other LHC detectors. The ALICE detector has been built by a collaboration including currently over 1000 physicists and engineers from 105 Institutes in 30 countries. Its overall dimensions are 161626 m3 with a total weight of approximately 10 000 t. The experiment consists of 18 different detector systems each with its own specific technology choice and design constraints, driven both by the physics requirements and the experimental conditions expected at LHC. The most stringent design constraint is to cope with the extreme particle multiplicity anticipated in central Pb-Pb collisions. The different subsystems were optimized to provide high-momentum resolution as well as excellent Particle Identification (PID) over a broad range in momentum, up to the highest multiplicities predicted for LHC. This will allow for comprehensive studies of hadrons, electrons, muons, and photons produced in the collision of heavy nuclei. Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception of parts of the Photon Spectrometer (PHOS), Transition Radiation Detector (TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will be completed for the high-luminosity ion run expected in 2010. This paper describes in detail the detector components as installed for the first data taking in the summer of 2008

Evaluation of horizontal diffusivity in the sea surface layer

In 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

Estimates of turbulence parameters from satellite-tracked drifters

In 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

Statistical analysis of turbulent dispersion in the sea surface layer based on satellite-tracked drifter data

This paper deals with the analysis of drifter campaigns realized in two different domains, the Gulf of Mexico and the Mar Grande Basin (Italy). Relative dispersion, diffusivity, and velocity variance were estimated, identifying different growth regimes. An exponential growth of the dispersion process was detected during the initial phase of deployment, and empirical laws for horizontal diffusivity were inferred. Velocity variance and integral time scale of the turbulence were obtained by using different techniques capable of evaluating short-term dispersion phenomena and sub-mesoscale turbulence. A spectral analysis realized in accordance with Taylor’s theory was used to estimate the Lagrangian time scale in domains strongly affected by inertial oscillations

Stima dei flussi turbolenti verticali nello strato limite superficiale marino

Lo strato superficiale del mare, il cosiddetto Ocean Surface Boundary Layer (OSBL), è la zona in cui avviene lo scambio di energia e materia tra l’atmosfera e il mare. Questo strato è caratterizzato da un elevato mescolamento causato principalmente dalle forzanti atmosferiche agenti su di esso (Moum & Smyth, 2001); qui, infatti, si vengono a formare delle strutture turbolente che trasportano e mescolano le grandezze caratteristiche sia sull’orizzontale che sulla verticale. I fenomeni che concorrono al mescolamento verticale dello strato limite superficiale sono molteplici, alcuni di questi sono ben compresi, mentre altri sono di difficile osservazione e formulazione teorica. A partire dai processi più superficiali sino a quelli più profondi, possiamo considerare i temporali, il frangimento delle onde, lo Stokes drift, lo shear, la circolazione di Langmuir, l’instabilità convettiva e per finire l’instabilità di Kelvin- Helmoltz, nella quale le onde di gravità interne agiscono principalmente all’interfaccia tra lo strato superficiale e lo strato profondo del mare. La profondità dello strato superficiale del mare è determinata dalla combinazione di tutti i fenomeni precedentemente nominati, cioè dall’agire contrastante del mescolamento turbolento e delle forze associate alla stratificazione stabile. La presenza simultanea di questi fenomeni non consente la parametrizzazione del mescolamento turbolento dell’OSBL tramite i classici modelli di circolazione oceanica (Li et al., 2019); alcuni di questi fenomeni, quindi, hanno bisogno di una parametrizzazione specifica per tenere in considerazione il loro contributo. Lo studio dell’OSBL riveste particolare importanza per la presenza al suo interno della maggior parte di organismi acquatici e degli inquinanti marini. Inoltre, è lo strato responsabile degli scambi energetici tra il mare e l’atmosfera, regolando in modo rilevante il bilancio climatologico globale. I flussi turbolenti sono le grandezze principali che quantificano questi processi e per tale motivo molti ricercatori in passato hanno ricavato schemi analitici e parametrizzazioni per la loro determinazione (Niiler & Kraus, 1977; Large et al. 1994; Burchard et al., 2008; Reichl & Hallberg, 2018). In questo lavoro, dopo aver accennato in modo qualitativo ai vari fenomeni che caratterizzano il mescolamento dello strato superficiale del mare, si presentano in modo sintetico alcune tecniche di parametrizzazione di questi fenomeni, che sembrano essere più promettenti per l’uso congiunto con modelli di dispersione di inquinanti in ambiente marino