Impact of Sodium Chloride Crystallization on Saliva Droplets Spreading

It is well known that SARS–CoV–2, can be transmitted through airborne diffusion of saliva droplets which travels into atmospheric air through a thermo-fluid dynamic interaction with it. In order to limit SARS-CoV-2 spread, social distancing is crucial. However, in this context is really important to emphasize that available knowledge is largely inadequate to make predictions on the airborne spreading of infectious droplets emitted during a cough and/or sneezing. The main aim of our research activity is to provide a contribution to thermo-fluid dyamic modeling of saliva droplets diffusion produced by coughing. In particular in this paper, several efforts were devoted to the analysis of impact of saliva chemical composition on the their spreading in space

Progettazione fluidodinamica e realizzazione di destratificatori per applicazioni industriali e prime valutazioni per sistemi a pala flessibile

La ventilazione di grandi ambienti industriali riveste un ruolo fondamentale nell'eliminare la stratificazione dell'aria, promuovendo un rimescolamento continuo e un'omogeneizzazione della temperatura interna dell'edificio e riducendo le perdite di calore verso l'esterno e i consumi energetici dell'edificio. In quest'ottica lo studio di nuovi sistemi per la ventilazione e l'efficientamento di quelli esistenti assume grande importanza. La ricerca presentata in questa tesi è volta alla progettazione fluidodinamica di due categorie di destratificatori largamente utilizzati in questo campo: gli HVLS fan e i ventilatori assiali intubati. Per entrambi i prodotti è stato seguito l'intero processo produttivo, dalla progettazione alla realizzazione e commercializzazione del prodotto. Nel primo caso è stata sviluppata una nuova pala in estruso di alluminio ad alta efficienza con l'obiettivo di ridurre i consumi elettrici e migliorare l'efflusso di aria dalla girante, utilizzando un codice della BEM per elica spingente per la progettazione e una verifica sperimentale del prototipo. Per quanto riguarda il ventilatore assiale, la progettazione si è concentrata sul convogliatore, con profilo aerodinamico, per garantire una maggiore portata elaborata dalla girante e una maggiore velocità in uscita. Oltre ciò, la ricerca si è concentrata sullo studio di ali flessibili e deformabili come possibile applicazione per gli HVLS fan. Queste ali, infatti, hanno il vantaggio di essere estremamente leggere e di avere un importante impatto estetico che potrebbe essere richiesto in alcuni ambienti come centri commerciali, palestre, biblioteche o altri edifici aperti al pubblico. Lo studio quindi, ha lo scopo di caratterizzare queste ali da un punto di vista aerodinamico mediante test in galleria del vento, al fine di comprenderne il funzionamento e le prestazioni. I risultati sperimentali ottenuti saranno utilizzati per valutarne l'applicabilità ai destratificatori.Large industrial environments ventilation plays a fundamental role in removing air stratification. It promotes a continuous mixing and homogenization of building internal temperature so to reduce heat losses towards the outside and energy consumption of the building itself. From this point of view, the study of new ventilation systems and increasing efficiency of existing ones is an issue of great importance. The research presented in this thesis is aimed at the fluid dynamics design of two categories of destratifiers, widely used in this field: on one side the HVLS fans and on the other the axial ducted fans. The entire production process was followed for both products, from design to realization and marketing of the product. For what concern to the HVLS fan, a new highly efficient extruded aluminium blade was developed with the aim of reducing electricity consumption and improving the flow of air from the impeller. The design process involved the use of a BEM code for propeller; than an experimental verification of the prototype was made in order to characterize the performance of the product. For the axial fan, the design was concentrated on the propeller duct, characterized by an aerodynamic profile, to guarantee a greater flow rate going through the impeller and a greater output speed. Beyond that, the research focused on the study of flexible and deformable wings as a possible application for HVLS fans. These wings, indeed, have the advantage of being extremely light and of having an important aesthetic impact that could be required in some environments such as shopping centers, gyms, libraries or other buildings open to the public. The study therefore aims to characterize these wings from an aerodynamic point of view by wind tunnel tests, in order to understand their operation and performance. The experimental results obtained will be used to evaluate their applicability to destratifiers

Thermal Behaviour of a Cylindrical Li-Ion Battery

This paper presents an experimental evaluation of thermal and electrical performances of a 26650 cylindrical Lithium Iron Phosphate/graphite battery cell. Thermal management of Lithium batteries is a fundamental issue of electric mobility, where batteries are subjected to severe operating conditions. Therefore, battery heat generation is a very important characteristic to be studied. In this work cell performances were assessed during battery discharge at ambient temperature over a wide range of discharge rates. The cell surface temperature was measured both with thermocouples and infrared thermography. Furthermore, also the open circuit potential and entropic heat coefficient were experimentally measured. Based on this experimental data, a simplified battery thermal model was used to evaluate the battery heat generation. The results show a substantial increase of battery surface temperature especially at high discharge rates. During discharge, the heat generated is greater at low battery state of charge due to the sudden decrease of cell potential. The contributions to heat generation are also carefully evaluated

A Multi-Scale Approach for Modelling Airborne Transport of Mucosalivary Fluid

COVID-19 pandemic promoted a lot of research activities in relation to mucosalivary fluid airborne transport. Indeed, infection mechanisms are the result of mucosalivary fluid droplets exchange and the knowledge in this area is still largely inadequate. One of the main challenges concerns the modelling of mucosalivary fluid complex nature. Specifically, this is a key element to predict small diameters dry nuclei formation which are highly relevant from the transmission risk point of view. For this reason, in this paper we present and discuss the development of a new multi-scale modelling technique which incorporates the Population Balance Equation into a standard particle-source-in-cell method. Thus, the effectiveness of the aforementioned technique in droplet nuclei generation modelling is showed and discussed. Also the impact of velocity boundary conditions at the mouth print is assessed as well as the effect of the correlations for mass transfer showing that their neglect causes an underestimation in distance reached by the droplets

A low—storage Runge—Kutta OpenFOAM solver for compressible low—Mach number flows: aeroacoustic and thermo—fluid dynamic applications

A solver for compressible Navier–Stokes equations is presented in this paper. Low-storage RungeKutta schemes were adopted for time integration; on the other hand the finite volume approach available within OpenFOAM library has been adopted for space discretization. Kurganov-Noelle-Petrova approach was used for convective terms, while central schemes for diffusive ones. The aforementioned techniques were selected and tested in order to allow the possibility of solving a broad range of physical phenomena with particular emphasis to aeroacoustic and thermo-fluid dynamic problems. Indeed, that standard OpenFOAM solution techniques produce an unacceptable dissipation for acoustic phenomena computations. Non–reflective boundary treatment was also considered to avoid spurious numerical reflections. The reliability and the robustness of the solver is proved by computing several benchmarks. Lastly, the impact of the thermal boundary conditions on the sound propagation was analyzed