Le opere dei sei giorni: aritmetica e esegesi secundum physicam in Teodorico di Chartres

L'elaborato si concentra sul Tractatus de sex dierum operibus di Teodorico di Chartre. Si è quindi analizzata la tipologia esegetica dell'autore: da una parte vi è un metodo naturalistico - in base al quale la Genesi è letta secondo categorie fisiche - dall'altra un metodo aritmetico - che rilegge la creazione biblica secondo parametri quadriviali

The interaction of droplet dynamics and turbulence cascade

The dynamics of droplet fragmentation in turbulence is described by the Kolmogorov-Hinze framework. Yet, a quantitative theory is lacking at higher concentrations when strong interactions between the phases and coalescence become relevant, which is common in most flows. Here, we address this issue through a fully-coupled numerical study of the droplet dynamics in a turbulent flow at R-lambda & AP; 140, the highest attained up to now. By means of time-space spectral statistics, not currently accessible to experiments, we demonstrate that the characteristic scale of the process, the Hinze scale, can be precisely identified as the scale at which the net energy exchange due to capillarity is zero. Droplets larger than this scale preferentially break up absorbing energy from the flow; smaller droplets, instead, undergo rapid oscillations and tend to coalesce releasing energy to the flow. Further, we link the droplet-size distribution with the probability distribution of the turbulent dissipation. This shows that key in the fragmentation process is the local flux of energy which dominates the process at large scales, vindicating its locality

I ministeri nei complessi conventuali di Roma capitale:atteggiamenti dottrinari, normativa e realizzazioni a confronto

La ricerca, dopo aver approfondito le motivazioni che hanno spinto il costituendo Regno d’Italia a espropriare numerosi complessi conventuali in tutto il territorio nazionale, ha focalizzato l’attenzione sul caso degli organismi religiosi riservati quali sedi di dicasteri per la nuova capitale. All’indomani del 20 settembre 1870, in vista del trasferimento della capitale da Firenze a Roma, da attuarsi in tempi molto rapidi, il problema degli spazi da destinare all’apparato statale si presenta pressante e complicato. L’amministrazione pontificia, diversa per impostazione e per dimensioni, era concentrata in pochi edifici, del tutto inadeguati e insufficienti per soddisfare le necessità del nuovo Stato, anche perchè la maggior parte di essi non passa al Demanio e non è, quindi, utilizzabile. L’urgenza di trovare spazi idonei in tempi brevi, la difficile situazione finanziaria, che rende sconsigliabile intraprendere nuove realizzazioni, e la preoccupazione per l’enorme potere che le istituzioni ecclesiastiche esercitano sulla popolazione, in una situazione politica nazionale e internazionale tutt’altro che definita, fanno ricadere la scelta della localizzazione dei principali uffici governativi proprio sui complessi conventuali. La vicenda appare di singolare importanza, ponendosi come cardine nella trasformazione di Roma da capoluogo pontificio a capitale del Regno d’Italia: tali complessi architettonici, in precedenza punto di riferimento di una ristretta comunità locale, vengono investiti della responsabilità di rappresentare il volto ufficiale della nuova nazione, assumendo una posizione di rilievo nella città. Gli interventi di trasformazione e adattamento a sedi degli uffici governativi si inseriscono nell’ambito delle diverse realizzazioni con cui lo Stato cerca di trovare una propria tangibile affermazione, esprimere le proprie aspirazioni e celebrare i traguardi raggiunti. Nella peculiare situazione italiana, che ha portato all’unificazione di realtà locali e amministrative molto diverse, appare particolarmente importante definire uno “stile nazionale” in cui tante realtà locali possano riconoscersi. Questo tentativo si esprime attraverso la ripresa di linguaggi del passato, in particolare dell’architettura rinascimentale, ideale estetico apprezzato anche nel resto d’Europa, come testimoniano i numerosi rilievi di palazzi rinascimentali italiani pubblicati nella prima metà del XIX secolo e l'adozione di tale modello per molti edifici pubblici in diverse città europee, in un momento storico in cui vari stati affrontano il delicato tema della definizione architettonica da dare alle costruzioni rappresentative. In particolare, a Roma si opta per il modello sangallesco, riferimento “stilistico” adottato per molte sedi istituzionali. La parte centrale dello studio approfondisce alcuni casi esemplari di complessi conventuali, particolarmente significativi perché oggetto di profonde modificazioni: il complesso di S. Silvestro in Capite, selezionato per ospitare il Ministero dei Lavori Pubblici, e quello di S. Maria sopra Minerva, riservato a sede dei ministeri dell’Istruzione Pubblica e, in via temporanea, delle Finanze. Questi organismi, dopo essere stati oggetto di diversificati interventi di adattamento, pur mantenendo sostanzialmente inalterata la propria compagine strutturale, hanno subito profonde trasformazioni della loro configurazione architettonica. Anche altri complessi vengono “accomodati” per accogliere uffici ministeriali; tra questi, i conventi di S. Agostino e dei SS. Apostoli, che danno alloggio ai dicasteri della Marina e della Guerra, sono interessati da interventi di carattere prettamente funzionale, mentre i due contigui conventi di S. Teresa e dell’Incarnazione, destinati a sede definitiva del Ministero della Guerra, subiscono interventi radicali, che si traducono nella demolizione e ricostruzione di ampie porzioni dei fabbricati. Dal punto di vista strettamente architettonico, i diversi esempi analizzati, pur mostrando peculiarità derivanti dalle situazioni contingenti, risultano tuttavia caratterizzati da approcci e modalità operative comuni. Gli interventi, che si inseriscono nell’ambito delle tendenze eclettiche e dei revivals stilistici della seconda metà dell’Ottocento, interpretano, con diverse varianti, lo stile neocinquecentesco, anche se non mancano particolari soluzioni eclettiche, come il palazzo delle Poste in piazza S. Silvestro. Si manifesta con chiarezza il tentativo di conferire alle preesistenti strutture un’apparente conformazione simmetrica, soprattutto attraverso l’elaborazione di “aggiornati” prospetti richiesti, oltre che dal nuovo ruolo assunto dall’organismo architettonico, anche dalle recenti trasformazioni urbane che hanno alterato le consolidate relazioni instauratesi, nel tempo, con l’intorno. Un altro elemento che accomuna i diversi esempi analizzati è legato alla necessità di elaborare nuove facciate, anche quando l’intervento è improntato a una certa economicità e l’adeguamento interno mostra un carattere espressamente funzionale; in alcuni casi, invece, le sistemazioni interne presentano un maggior respiro grazie alla creazione di inediti rapporti con il contesto urbano, alla radicale ridefinizione delle strutture preesistenti e alla realizzazione di nuovi apparati decorativi. Tali esperienze, prevalentemente affidate ai tecnici dei Genio Civile o Militare, innescano un vivace e articolato dibattito che costituirà un passo significativo nella definizione del sistema di tutela del patrimonio storico-artistico del nuovo Stato e nell’impostazione delle competenze e della formazione professionale dei tecnici chiamati ad operare sulle preesistenze architettoniche e monumentali. In queste circostanze, inoltre, comincia a maturare la convinzione dell’opportunità di indire concorsi pubblici per la progettazione di opere statali così importanti, competizioni considerate essenziale momento di incontro e confronto tra le diverse tendenze artistiche e architettoniche presenti nel Paese

A momentum-conserving, consistent, Volume-of-Fluid method for incompressible flow on staggered grids

The computation of flows with large density contrasts is notoriously difficult. To alleviate the difficulty we consider a consistent mass and momentum-conserving discretization of the Navier-Stokes equation. Incompressible flow with capillary forces is modelled and the discretization is performed on a staggered grid of Marker and Cell type. The Volume-of-Fluid method is used to track the interface and a Height-Function method is used to compute surface tension. The advection of the volume fraction is performed using either the Lagrangian-Explicit / CIAM (Calcul d'Interface Affine par Morceaux) method or the Weymouth and Yue (WY) Eulerian-Implicit method. The WY method conserves fluid mass to machine accuracy provided incompressiblity is satisfied which leads to a method that is both momentum and mass-conserving. To improve the stability of these methods momentum fluxes are advected in a manner "consistent" with the volume-fraction fluxes, that is a discontinuity of the momentum is advected at the same speed as a discontinuity of the density. To find the density on the staggered cells on which the velocity is centered, an auxiliary reconstruction of the density is performed. The method is tested for a droplet without surface tension in uniform flow, for a droplet suddenly accelerated in a carrying gas at rest at very large density ratio without viscosity or surface tension, for the Kelvin-Helmholtz instability, for a falling raindrop and for an atomizing flow in air-water conditions

Analysis of primary atomization in sprays using Direct Numerical Simulation

[ES] La comprensión de los fenómenos físicos que acontecen en la región densa (también conocida como campo cercano) durante la atomización de los sprays ha sido una de las mayores incógnitas a la hora de estudiar sus aplicaciones. En el sector industrial, el rango de interés abarca desde toberas en aplicaciones propulsivas a sprays en aplicaciones médicas, agrícolas o culinarias. Esta evidente falta de conocimiento obliga a realizar simplificaciones en la modelización, provocando resultados poco precisos y la necesidad de grandes caracterizaciones experimentales en la fase de diseño. De esta manera, los procesos de rotura del spray y atomización primaria se consideran problemas físicos fundamentales, cuya complejidad viene dada como resultado de un flujo multifásico en un régimen altamente turbulento, originando escenarios caóticos. El análisis de este problema es extremadamente complejo debido a la ausencia sustancial de teorías validadas referentes a los fenómenos físicos involucrados como son la turbulencia y la atomización. Además, la combinación de la naturaleza multifásica del flujo y su comportamiento turbulento resultan en una gran dificultad para afrontar el problema. Durante los últimos 10 años, las técnicas experimentales han sido finalmente capaces de visualizar la región densa, pero la confianza, análisis y efectividad de dichos experimentos en esta región del spray todavía requiere de mejoras sustanciales. En este contexto, esta tesis trata de contribuir al entendimiento de estos procesos físicos y de proporcionar herramientas de análisis para estos flujos tan complejos. Para ello, mediante Direct Numerical Simulations se ha afrontado el problema resolviendo las escalas de movimiento más pequeñas, y capturando todas las escalas de turbulencia y eventos de rotura. Uno de los objetivos de la tesis ha sido evaluar la influencia de las condiciones de contorno del flujo entrante en la atomización primaria y en el comportamiento turbulento del spray. Para ello, se han empleado dos condiciones de contorno diferentes. En primer lugar se ha empleado una condición de contorno sintética para producir turbulencia homogenea a la entrada, simulando el comporamiento de la tobera. Una de las características más interesantes de este método es la posibilidad de retocar los parámetros dentro del algoritmo. En particular, la escala de longitud integral se ha variado para evaluar la influencia de las estructuras mas grandes de la tobera en la atomización primaria. El análisis de la condición de contorno sintética también ha permitido el diseño óptimo de simulaciones de las cuales se han derivado estadísticas turbulentas significativas. En este escenario, se han llevado a cabo estudios más profundos sobre la influencia de propiedades de las estructuras turbulentas como la homogeneidad y la anisotropía tanto en el espectro de los flujos como en las estadísticas de las gotas. Para tal fin, se han desarrollado metodologías novedosas para computar el análisis espectral y la estadística de las gotas Entre los resultados de este análisis destaca la independencia de la condición de contorno de entrada en las estadísticas de las gotas, mientras que por otra parte, recalca que las características turbulentas desarrolladas en el interior de la tobera afectan a la cantidad total de masa atomizada. Estas consideraciones se encuentran respaldadas por el análisis espectral realizado, mediante el cuál se concluye que la turbulencia multifásica comparte el comportamiento universal descrito por las teorías de Kolmogorov.[CA] La comprensió dels fenòmens físics que succeïxen en la regió densa (també coneguda com a camp pròxim) durant l'atomització dels sprays ha sigut una de les majors incògnites a l'hora d'estudiar les seues aplicacions. En el sector industrial, el rang d'interés comprén des de toveres en aplicacions propulsives a sprays en aplicacions mèdiques, agrícoles o culinàries. Esta evident falta de coneixement obliga a realitzar simplificacions en la modelització, provocant resultats poc precisos i la necessitat de grans caracteritzacions experimentals en la fase de disseny. D'esta manera, els processos de ruptura del spray i atomització primària es consideren problemes físics fonamentals, la complexitat dels quals ve donada com resultat d'un flux multifàsic en un règim altament turbulent, originant escenaris caòtics. L'anàlisi d'este problema és extremadament complex a causa de l'absència substancial de teories validades dels fenòmens físics involucrats com són la turbulència i l'atomització. A més, la combinació de la naturalesa multifàsica del flux i el seu comportament turbulent resulten en una gran dificultat per a afrontar el problema. Durant els últims 10 anys les tècniques experimentals han sigut finalment capaces de visualitzar la regió densa, però la confiança, anàlisi i efectivitat dels experiments en esta regió del spray encara requerix de millores substancials. En este context, esta tesi tracta de contribuir en l'enteniment d'estos processos físics i de proporcionar ferramentes d'anàlisi per a estos fluxos tan complexos. Per a això, per mitjà de Direct Numerical Simulations s'ha afrontat el problema resolent les escales de moviment més menudes, al mateix temps que es capturen totes les escales de turbulència i esdeveniments de ruptura. Un dels objectius de la tesi ha sigut avaluar la influència que les condicions de contorn del flux entrant tenen en l'atomització primària i en el comportament turbulent del spray. Per a això, s'han empleat dos condicions de contorn diferents. En primer lloc s'ha empleat una condició de contorn sintètica per a produir turbulència homogènia a l'entrada, simulant el comportament de la tovera. Una de les característiques més interessants d'este mètod és la possibilitat de retocar els paràmetres dins de l'algoritme. En particular, l'escala de longitud integral s'ha variat per a avaluar la influència de les estructures mes grans de la tovera en l'atomització primària. L'anàlisi de la condició de contorn sintètica també ha permés el disseny òptim de simulacions de les quals s'han derivat estadístiques turbulentes significatives. En este escenari, s'han dut a terme estudis més profunds sobre la influència de propietats de les estructures turbulentes com l'homogeneïtat i l'anisotropia tant en l'espectre dels fluxos com en les estadístiques de les gotes. Per a tal fi, s'han desenrotllat metodologies noves per a computar l'anàlisi espectral i l'estadística de les gotes. Entre els resultats d'esta anàlisi destaca la independència de la condició de contorn d'entrada en les estadístiques de les gotes, mentres que d'altra banda, es recalca que les característiques turbulentes desenrotllades en l'interior de la tovera afecten a la quantitat total de massa atomitzada. Estes consideracions es troben recolzades per l'anàlisi espectral realitzat, per mitjà del qual es conclou que la turbulència multifásica compartix el comportament universal descrit per les teories de Kolmogorov.[EN] The understanding of the physical phenomena occurring in the dense region (also known as near field) of atomizing sprays has been long seen as one of the biggest unknown when studying sprays applications. The industrial range of interest goes from nozzles in combustion and propulsion applications to medical sprays, agricultural and food process applications. This substantial lack of knowledge is responsible for some important simplification in modeling, that often result to be inaccurate or simply partial, leading to the evident need of large experimental characterization during the design phase. In fact, the spray breakup and primary atomization processes are indeed fundamental problems of physics, which complexity results from the combination of a multiphase flow in a highly turbulent regime that leads to chaotic scenarios. The analysis of this problem is extremely problematic, due to a substantial lack of definitive theories about the physical phenomena involved, namely turbulence and atomization. Furthermore, the combination of the multiphase nature of the flow and its turbulent behavior makes substantially difficult to address the problem. Only within the last 10 years, experimental techniques have been capable of visualizing the dense region, but the experiments reliability, analysis and effectiveness in this region still requires vast improvements. In this scenario, this thesis aims to contribute in the understanding of these physical process and to provide analysis tools for these complex flows. In order to do so, Direct Numerical Simulations have been used for addressing the problem at its smallest scale of motion, while reliably capturing all turbulence scales and breakup events. The multiphase nature of the flow is accounted for by using the Volume of Fluid method. One of the goal of the thesis was to assess the influence of the inflow boundary conditions on the primary atomization and on the spray's turbulence behavior. In order to do so, two different boundary conditions were used. In a first place, a synthetic inflow boundary condition was used in order to produce a homogeneous turbulence inflow, simulating the nozzle behavior. One of the interesting features of this method was the possibility of tweaking the parameters within the algorithm. In particular, the integral length scale was varied in order to assess the influence of nozzle larger turbulent structures on the primary atomization. The analysis on the synthetic boundary condition also allowed to optimally design simulations from which derive meaningful turbulence statistics. On this framework, further studies were carried over on the influence of turbulent structures properties, namely homogeneity and anisotropy, on both the flows spectra and droplets statistics. In order to achieve this goal, novel procedures for both computing the flow spectra and analyzing droplets were developed and are carefully addressed in the thesis. The results of the analysis highlight the independence of droplets statistics from the inflow boundary condition, while, on the other hand, remarking how the total quantity of atomized mass is significantly affected by the turbulence features developed within the nozzle. This considerations are supported by the spectrum analysis performed, which also highlighted how multiphase turbulence shares the universal features described in Kolmogorov theories.Crialesi Esposito, M. (2019). Analysis of primary atomization in sprays using Direct Numerical Simulation [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/133975TESI

Study of turbulence in atomizing liquid jets

[EN] Among the many unknowns in the study of atomizing sprays, defining an unambiguous way to analyze turbulence is, perhaps, one of the most limiting ones. The lack of proper tools for the analysis of the turbulence field (e.g. specific one/two-point statistics, spectrum, structure functions) limits the understanding of the overall phenomenon occurring, impeding the correct estimation of motion scales (from the Kolmogorov one to the integral one). The present work proposes a methodology to analyze the turbulence in atomizing jets using a pseudo-fluid method. The many challenges presented in these types of flows (such as temporal fluid properties uncertainties, strong anisotropy and lack of a priori chance of determining the motion scales) can be simplified by such a method, as it will be clearly shown by the smooth results obtained. Finally, the method is tested against the one-phase flows turbulent data available in the literature for the Kolmogorov scaling of the one-dimension energy spectra, showing how a pseudo-fluid method could provide a reliable tool to analyze multiphase turbulence, especially in spray's primary atomization.This research has been partially funded by Spanish Ministerio de Economia y Competitividad through project RTI2018-099706-B-100, "Estudio de la atomizacion primaria mediante simulaciones DNS y tecnicas opticas de muy alta resolucion". Additionally, the authors thankfully acknowledge the computer resources at MareNostrum 4 (Barcelona Supercomputing Center) and their technical support provided by FI-2017-2-0035 and TITAN (Oak Ridge Leadership Computing Facility) in the frame of the project TUR124.Torregrosa, AJ.; Payri, R.; Salvador, FJ.; Crialesi-Esposito, M. (2020). Study of turbulence in atomizing liquid jets. 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A criterion for when an emulsion drop undergoing turbulent deformation has reached a critically deformed state

Turbulent breakup in emulsification devices is a dynamic process. Small viscous drops undergo a sequence of oscillations before entering the monotonic deformation phase leading to breakup. The turbulence-interface interactions prior to reaching critical deformation are therefore essential for understanding and modeling breakup. This contribution uses numerical experiments to characterize the critically deformed state (defined as a state from which breakup will follow deterministically, even if no further external stresses would act on the drop). Critical deformation does not coincide with a threshold maximum surface area, as previously suggested. A drop is critically deformed when a neck has formed locally with a curvature such that the Laplace pressure exceeds that of the smallest of the bulbs connected by the neck. This corresponds to a destabilizing internal flow, further thinning the neck. Assuming that the deformation leads to two spherical bulbs linked by a cylindrical neck, the critical deformation is achieved when the neck diameter becomes smaller than the radius of the smallest bulb. The role of emulsifiers is also discussed

Analysis on the efects of turbulent inflow conditions on spray primary atomization in the near-field by direct numerical simulation

[EN] It is widely acknowledged that the development of sprays in the near-field is of primary importance for the spray formation downstream, as it affects both the spray angle, as well as the intact core length. In this frame, the present work aims to study the effects of turbulence inlet boundary condition on the spray formation by means of Direct Numerical Simulations on a real condition at low Reynolds number. To this extent, the code Paris-Simulator has been used, while a digital filter-based algorithm was used in order to generate synthetic turbulence at the inlet boundary condition. The influence of turbulence intensity and lengthscale on the atomization process has been studied and analyzed through 3 simulation for which these parameters have been varied. The results clearly highlight how the atomization is heavily affected by the inlet turbulence configuration. An analysis of the different atomizing conditions has been conducted, aiming to understand how the variation introduced by the inlet boundary condition on the velocity field is affecting the local atomization dynamics.This work was partly sponsored by "Ministerio de Economia y Competitividad", of the Spanish Government, in the frame of the Project "Estudio de la interaccion chorro-pared en condiciones realistas de motor", Reference TRA2015-67679-c2-1-R. The author thankfully acknowledges the computer resources at MareNostrum (BSC) and the technical support provided by FI-2016-3-0031.Salvador, FJ.; Ruiz, S.; Crialesi Esposito, M.; Blanquer Espert, I. (2018). Analysis on the efects of turbulent inflow conditions on spray primary atomization in the near-field by direct numerical simulation. International Journal of Multiphase Flow. 102:49-63. https://doi.org/10.1016/j.ijmultiphaseflow.2018.01.019S496310