Alcune soluzioni esatte delle equazioni della magnetofluidodinamica per il moto stazionario di un fluido viscoso, incomprimibile e a conducibilità elettrica finita (original) (raw)

Su un problema di diramazione riguardante i moti convettivi in un fluido viscoso

1967

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Cap. 2. Le equazioni della fluidodinamica

La formula del trasporto di Reynolds consente di portare la derivata temporale sotto il segno d'integrale. Consideriamo una generica quantità f (x, t) contenuta in un volume materiale V (t). La formula di Reynoldsè: d dt

OTTIMIZZAZIONE DI UN FRENO A FLUIDO MAGNETOREOLOGICO PER USO AUTOMOBILISTICO

Sommario Il lavoro ha come oggetto lo studio numerico di un freno a fluido magnetoreologico (MR) per uso automobilistico tramite il codice agli elementi fin iti ANSYS. In seguito ad un dimensionamento analitico preliminare del freno la realizzazione di un modello FEM magnetico permette un'accurata valutazione della distribuzione del campo magnetico nel fluido MR e la valutazione del momento frenante

Modelli idrostatici del moto da Aristotele a Galileo

TABLE OF CONTENTS: 1. ARISTOTLE’S THEORY OF MOTION 1.1 Physics as the science of motion 1.2 Motion in a medium 1.2.1 Hydrostatical origins 1.2.2 Specific weight 1.2.3 Absolute weight and lightness 1.2.4 Place 1.3 Motion in space 1.3.1 Speed 1.3.2 Vacuum 1.3.3 Philoponus 1.3.4 The horror vacui 1.3.5 Aristotle’s finalism 2. ARCHIMEDES’ HYDROSTATICS 2.1 Archimedes vs Aristotle? 2.2 Giovan Battista Benedetti 2.2.1 About weight 2.2.2 The role of the medium 2.3 Galileo’s De Motu ABSTRACT: Aristotle’s physics is defined as the science of motion. In the first part of this book we show that what Aristotle means with “motion” is very different from our current idea of motion. Indeed, motion is presently understood as the trajectory of a movable object, possibly in a (fluid) medium. Instead, Aristotle’s motion must be regarded as a relation between the movable object and its surrounding medium (§ 1.1). The mathematical model on which the current idea is grounded is a cinematic one; analogously we contend that Aristotle’s notion of motion is ultimately reducible to a hydrostatical model (§ 1.2). This notion of motion, and consequently the whole Aristotle’s physics, becomes inconsistent outside of a medium. From a hydrostatical perspective, the presence of the two Aristotelian qualities—weight and lightness—is perfectly understandable, and similarly the untenability of the notion of vacuum. Moreover, in Aristotle’s system, exactly like in a hydrostatical model, the medium has a twofold role: firstly—active role—the relation between its specific weight (or lightness) with the specific weight (or lightness) of the movable object completely determines the direction of motion. Secondly—impeding role—the relation between its density and the weight (and the shape) of the movable object determines the speed of motion. Only the latter function will survive in the Aristotelian tradition (§ 1.2.2-1.2.3). Furthermore, Aristotle’s definition of place as a limit (surface) makes sense only in a hydrostatical context: indeed, the interaction between the movable object and its surrounding medium takes place through their surface (§1.2.4). Finally the notion of natural place, which is totally extraneous to a cinematic perspective, naturally arises in a hydrostatical one: think of the natural inclination to the proper place as a tendency to restore the state of stable equilibrium of a physical system. In the case of Aristotle’s Cosmos this state is represented by the four concentric spheres of earth, water, air and fire, ordered by decreasing weight (or increasing lightness). The remaining sections of the first part of the book are devoted to investigate the reasons of the loss of the hydrostatical model by the commentators and the Aristotelian tradition (§ 1.3). In the second part of the book the revival of a hydrostatical model by Giovan Battista Benedetti (§ 2.2) and after him by Galileo (§ 2.3) is reconstructed, and the role of the rediscovering of Archimedean hydrostatic is discussed. The interpretation of Aristotle's Physics in terms of hydrostatics has been recently reproposed in C. Rovelli, Aristotle's Physics: A Physicist's Look. Journal of the American Philosophical Association, 1, pp. 23-40 (2015).

Moto di gocce di liquidi non-newtonianiindotto da vibrazioni verticali

2016

Frequenze di risonanza di modo fondamentale F (inserto) in funzione del volume V per gocce d'acqua.. .. .. .. .. .. 42 2.12 Fotograa dell'alone generato dalla vibrazione del substrato.. 44 2.13 Schermata del programma in LabVIEW per l'estrazione delle grandezze d'interesse dalle immgini delle gocce.. .. .. .. . 45 2.14 Graco estratto da una sequenza di infusione/eusione di una goccia d'acqua. .