Study of bubbly flows in an open-source software
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Journal Title
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Insinööritieteiden korkeakoulu |
Master's thesis
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Authors
Date
2018-06-11
Department
Major/Subject
Mcode
ENG21
Degree programme
Master's Programme in Energy Technology (EEN)
Language
en
Pages
72+2
Series
Abstract
Bubbly flows occur everywhere in nature and engineering. The study of such flows can be done theoretically, experimentally or computationally. In the present thesis, latter option was chosen and multiphase computational fluid dynamics (M-CFD) simulation methods are tested for simulation of a specific situation of such flows. All the simulations done under this thesis are about an initially spherical bubble starting from rest in quiescent water. In order to accurately assess the dynamics of that bubble an open-source M-CFD software was used, OpenFOAM. The dynamics of the bubble was set by means of the study of three characteristics: rise velocity, trajectory and shape. Here, a Matlab algorithm was developed to get the rise velocity of the bubble. Two cases have been simulated based on Krishna et al. (1999) experimental, simulated and numerical data base, one in two dimensions and the other in three dimensions, both were computed to a range of bubble between 4 and 12 millimeters in diameter. The simulations were carried out using a geometric Volume-Of-Fluid (VOF) method, IsoAdvector which utilizes iso-surfaces in the subcell interface reconstruction step. This algorithm provides results that are close agreement with the experimental, simulated and numerical data already named, and also in close agreement with the experimental rise velocities of Haberman et al. (1953) investigation. Furthermore, the rise velocity equation proposed by Jamialahmadi et al. (1994) and the bubble shapes shown in Kumar Tripathi et al. (2015) simulations match with the simulations of the present study. Therefore, these results verify the capability of OpenFOAM simulations with IsoAdvector algorithm, which are powerful tools for a priori determination of the morphology and rise characteristics of an initially spherical bubble starting from rest in quiescent water and yield on the same level as ANSYS-CFX commercial software.Description
Supervisor
Vuorinen, VilleThesis advisor
Laurila, ErkkiKeywords
open-source, rise velocity, trajectory, bubble shape, IsoAdvector, M-CFD