Longo, Carmelina (2017) Numerical simulations of a dosing jet: impact of compressibility on an induced breakup. [Tesi di dottorato]


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Item Type: Tesi di dottorato
Lingua: English
Title: Numerical simulations of a dosing jet: impact of compressibility on an induced breakup
Longo, Carmelinacarmelina.longo@unina.it
Date: 11 December 2017
Number of Pages: 107
Institution: Università degli Studi di Napoli Federico II
Department: dep08
Dottorato: phd038
Ciclo di dottorato: 30
Coordinatore del Corso di dottorato:
Mensitieri, Giuseppegiuseppe.mensitieri@unina.it
Maffettone, Pier LucaUNSPECIFIED
Date: 11 December 2017
Number of Pages: 107
Uncontrolled Keywords: Numerical simulations, breakup, compressible flow
Settori scientifico-disciplinari del MIUR: Area 09 - Ingegneria industriale e dell'informazione > ING-IND/26 - Teoria dello sviluppo dei processi chimici
Date Deposited: 06 Jan 2018 03:14
Last Modified: 19 Mar 2019 12:06
URI: http://www.fedoa.unina.it/id/eprint/12203


Filling operations, i.e., dosing a fixed amount of liquid in a bottle, are relevant in many industrial fields. A key aspect is a precise control of the breakup of the stream exiting a nozzle, avoiding events like dripping (falling down of drops) and stringing (formation of filament and threads). Breakup phenomena have been widely studied under constant flow rate conditions and different regimes of filament thinning have been identified. In this work, we analyze the effects of liquid properties and time-varying operating conditions on the breakup dynamics of a Newtonian liquid through Volume-of-Fluid numerical simulations and experiments. This thesis is divided in two main parts. In the first part, we study the dynamics of different classes of Newtonian liquids subjected to flow rates that linearly decrease in time. We find that the operating conditions only partially alter the thinning dynamics and, once a critical dimension of the filament has been reached, the dynamics is fairly described by scaling laws derived for steady-state operating conditions. In the second part, we address the filament breakup problem of a real dosing system. Experiments show the presence of air entrapped in the liquid phase during the process that significantly alters the breakup dynamics. The effect of entrapped air is accounted for in numerical simulations by defining and implementing a new model that adequately describes the compressibility effects induced by the coexistence of the two phases. The dissolved air delays the onset of the thinning phase and determines a slowdown of thinning dynamics. A good quantitative agreement between experiments and simulations in terms of time evolution of the filament radius at a fixed distance from the nozzle is found.


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